On the Implant Communication and MAC Protocols for a WBAN

On the Implant Communication and MAC Protocols for a WBAN Abstract Recent advances in micro-electro-mechanical systems (MEMS), wireless communication, low-power intelligent sensors, and semiconductor technologies have allowed the realization of a wireless body area network (WBAN). A WBAN provides unobtrusive health monitoring for a long period of time with real-time updates to the physician. It is widely used for ubiquitous healthcare, entertainment, and military applications. The implantable and wearable medical devices have several critical requirements such as power consumption, data rate, size, and low-power medium access control (MAC) protocols. This article consists of two parts: body implant communication, which is concerned with the communication to and from a human body using RF technology, and WBAN MAC protocols, which presents several low-power MAC protocols for a WBAN with useful guidelines. In body implant communication, the in-body radio frequency (RF) performance is affected considerably by the implants depth inside the human body as well as by the muscle and fat. We observe best performance at a depth of 3cm and not close to the human skin. Furthermore, the study of low-power MAC protocols highlights the most important aspects of developing a single, a low-power, and a reliable MAC protocol for a WBAN. Keywords: In-body, on-body, RF communication, Implant, WBAN 1. Introduction Cardiovascular diseases are the foremost cause of deaths in the United States and Europe since 1900. More than ten million people are affected in Europe, one million in the US, and twenty two million people in the world [1]. The number is projected to be triple by 2020, resulting in an expenditure of around 20% of the gross domestic product (GDP). The ratio is 17% in South Korea and 39% in the UK [2]. The healthcare expenditure in the US is expected to be increased from $2.9 trillion in 2009 to $4 trillion US dollars in 2015 [3]. The impending health crisis attracts researchers, industrialists, and economists towards optimal and quick health solutions. The non-intrusive and ambulatory health monitoring of patients vital signs with real time updates of medical records via internet provide economical solutions to the health care systems. A wireless body area network (WBAN) is becoming increasingly important for healthcare systems, sporting activities, and members of emergency as well as military services. WBAN is an integration of in-body (implants) and on-body (wearable) sensors that allow inexpensive, unobtrusive, and long-term health monitoring of a patient during normal daily activities for prolonged periods of time. In-body radio frequency (RF) communications have the potential to dramatically change the future of healthcare. For example, they allow an implanted pacemaker to regularly transmit performance data and the patients health status to the physician. However, the human body poses many wireless transmission challenges. This is partially conductive and consists of materials having different dielectric constants and characteristics impedance. The interface of muscles and fats may reflect the RF wave rather than transmitting it. The key elements of an RF-linked implant are the in-body antenna and the communi cation link performance. Also, in the case of many implants and wearable sensors, a low-power MAC protocol is required to accommodate the heterogeneous traffic in a power-efficient manner. This article is divided into two parts: body implant communication and WBAN MAC protocols. In the body implant communication part, we look at the RF communication link performance at various depths inside a human (artificial) body. In the MAC part, we review the existing low-power MAC protocols and discuss their pros and cons in the context of a WBAN. We further provide alternative MAC solutions for in-body and on-body communication systems. The rest of the article is divided into three sections. In section 2, we present a discussion on body implant communication including in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. Section 3 discusses several low-power MAC protocols and realizes a need for a new, a low-power, and a reliable MAC protocol for a WBAN. The final section concludes our work. 2. Body Implant Communication There are several ways to communicate with an implant that includes the use of electromagnetic induction and RF technology. Both are wireless and their use depends on the application requirements. Further, the key elements of an RF-linked implant are the in-body antenna and the communication link performance. The following part discusses in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. 2.1. In-body Electromagnetic Induction Several applications still use electromagnetic coupling to provide a communication link to an implant device. In this scheme, an external coil is held very close to the body that couples to a coil implanted just below the skin surface. The implant is powered by the coupled magnetic field and requires no battery for communication. Data is transferred from the implant by altering the impedance of the implanted loop that is detected by the external coil and electronics. This type of communication is commonly used to identify animals that have been injected with an electronic tag. Electromagnetic induction is used when continuous, long-term communication is required. The base band for electromagnetic communication is typically 13.56 MHz or 28 MHz, with other frequencies also available. The choice of a particular band is subject to regulation for maximum specific absorption rate (SAR). The inductive coupling achieves best power transfer efficiency when uses large transmit and receive coil s. It, however, becomes less efficient when the space is an issue of the device is implanted deep inside the human body. Furthermore, inductive coupling technique does not support a very high data rate and cannot initiate a communication session from inside of the body. 2.2. In-body RF Communication Compared with the electromagnetic induction, RF communication dramatically increases bandwidth and supports a two-way data communication. The band designated for the in-body RF communication is medical implant communication service (MICS) band and is around 403 to 405 MHz. This band has a power limit of 25  µW in the air and is usually split into ten channels of 300 kHz bandwidth each. The human body is a medium that poses numerous wireless transmission challenges. It consists of various components that are not predictable and will change as the patient ages, gains or losses weight, or even changes posture. Values of dielectric constant (ÃŽ µr), conductivity (ÏÆ') and characteristic impedance (Zo) for some body tissue are given in table 1 [4]. This demonstrates that these two tissue types are very different. Also, the dielectric constant affects the wavelength of a signal. At 403 MHz, the wavelength in the air is 744mm, but in muscle with ÃŽ µr = 50 the wavelength reduces to 105mm, which helps in designing implanted antennas. 2.3. In-body Antenna Design A modern in-body antenna should be tuneable by using an intelligent transceiver and software routine. This enables the antenna coupling circuit to be optimised. Due to the frequency, and available volume, a non-resonant antenna is commonly used. It has a lower gain than a resonant antenna. This makes design of the antenna coupling circuit very important. Antenna options are dictated by the location of the implant. A patch antenna can be used when the implant is flat. Patch antennas are comprised of a flat insulating substrate coated on both sides with a conductor. The substrate is a body compatible material with a platinum or a platinum/iridium conductor. The upper surface is the active face and is connected to the transceiver. The connection to the transceiver needs to pass through the case where the hermetic seal is maintained, requiring a feed-through. The feed-through must have no filter capacitors present; these are common on other devices. An implanted patch antenna is electrically larger than its physical size because it is immersed in a high (ÃŽ µr) medium. It can be much larger electrically if the substrate is of higher (ÃŽ µr), such as titania or zirconia. A loop antenna can also be attached to the implant. This antenna operates mostly by the magnetic field, whereas the patch operates mostly by the electric field. The loop antenna delivers performance comparable to that of a dipole, but with a considerably smaller size. In addition, the magnetic permeability of muscle or fat is very similar to that of an air, unlike the dielectric constant that varies considerably. This property enables an antenna to be built and used with much less need for retuning. A loop antenna can be mounted on the case in a biocompatible structure. 2.4. In-body Link Performance The demonstration system consists of a base-station, an implant, antennas, and a controlling laptop. The base-station contains a printed circuit board (PCB) with a wakeup RF circuit, a Zarlink ZL70101 IC, and a micro-controller. It sends a wakeup signal on industrial, scientific, and medical (ISM) 2.4 GHz band to power up the implant to communicate. It also supports communication within the MICS band. The implant contains a Zarlink ZL70101 IC, a micro-controller, and a battery. The power limits of the wakeup signal for ISM and MICS bands transmitters are 100mW and 25  µW respectively. Experiments that measure the performance of an implant inside a living body are difficult to arrange. The alternative is to use 3D simulation software or a body phantom defined in [5]. The use of 3D simulation software is time consuming and hence practically not valuable. Therefore, measurements are generally performed using the body phantom and immersing a battery-powered implant into it [6]. Since no additional cables are attached to the test implant, the interference errors in the measurements are minimal. The body phantom is filled with a liquid that mimics the electrical properties of the human body tissues. The test environment is an anechoic chamber that includes a screened room. The interior walls of the room have sound-absorbent cones to minimize any reflections from walls or the floor that could distort the results. In real life, however, the results will be affected by the reflections from walls, desks, and other equipment and hardware. The body phantom is mounted on a woo den stand (non-conductive). The distance from the body phantom to the base-station is 3m. The MICS base-station dipole antenna is mounted on a stand. 1(a) shows the anechoic chamber with a body phantom (on the wooden stand), a log periodic test antenna (foreground), and a base-station dipole (right). The log periodic antenna is used to calculate the power radiated from the body phantom. A depth is defined as the horizontal distance between the outer skin of the phantom and the test implant. Vertical polarization of the implant is the case when the long side of the box and the patch antenna is vertical. The link performance is measured once the communication link is established. The measurements include the effective radiated power (ERP) from the implant, the received signal at the implant from the base-station, and the link quality. Measurements are made over a set distance with all the combinations of implant and test antenna polarisations, i.e., vertical-vertical (V-V), horizontal-vertical (H-V), vertical-horizontal (V-H), and horizontal-horizontal (H-H) polarisations. Typical results are shown in 1(b) where the ERP is calculated from the received signal power and the antenna characteristics. The measurement of the signal levels is done with the log periodic antenna and the spectrum analyzer. It can be seen in the that there is a significant difference in signal levels with polarisation combinations and depths. For a V-V polarisation, the ERP increases from a 1cm depth to a maximum between 2 and 7 cm, and then it decreases. The gradual increase is due to the simulated body acti ng as a parasitic antenna. The also shows how the signal level is affected by the depth with different polarisation. Such a test needs to be done with the antenna that is to be used in the final product. To measure the received signal at the implant, the Zarlink ZL70101 has an inbuilt receive signal strength indication (RSSI) function that gives a measure of the signal level detected. RSSI is a relative measurement with no calibration. The implant receives and measures a continuous wave signal transmitted by the base-station. In this case, the implant and the base-station antennas are vertically polarised. 1(c) shows an increase in the signal level at a depth between 3 and 4cm for a 15dec power. The power settings refer to the base-station and are cond to set the ERP to 25  µW. Signal levels are not valuable unless they are related to data transmission. One way to maintain the link quality is to measure the number of times the error correction is invoked during the transmission of 100 blocks of data. Two types of error correction codes, i.e., error correction code (ECC) and cyclic redundancy code (CRC) are invoked to maintain data integrity and reliability. The fewer ECC and CRC invocations result in better link quality. In 1(d), the error correction is lowest at a depth between 3 and 5 cm. A sample of ECC data collected at a 3cm implant depth is given in Table 2. The Count indicates the number of data blocks, the Time (ms) indicates the block transmission time, and the ECC indicates the number of times it is invoked. During the transmission of 100 blocks of data at a 3cm depth, the ECC is invoked 368 times, which is further equivalent to an average 3.68 times (as given in 1(d)). 2.5. Discussion The ERP, RSSI, as well as the ECC and CRC plots show that the implant demonstrates the best performance at a depth between 3 and 5 cm. The depth and position of an implant is not chosen for engineering performance but for the best clinical reasons. The implant designer must be aware of the possible losses through the human body. The attenuation and the parasitic antenna effects vary from patient to patient, with the position of the implant and with the time as the patient gains, or looses weight. Therefore, these factors need to be built into the link budget. 3. WBAN MAC Protocols Some of the common objectives in a WBAN are to achieve maximum throughput, minimum delay, and to maximize the network lifetime by controlling the main sources of energy waste, i.e., collision, idle listening, overhearing, and control packet overhead. A collision occurs when more than one packet transmits data at the same time. The collided packets have to be retransmitted, which consumes extra energy. The second source of energy waste is idle listening, meaning that a node listens to an idle channel to receive data. The third source is overhearing, i.e., to receive packets that are destined to other nodes. The last source is control packet overhead, meaning that control information area added to the payload. Minimal number of control packets should be used for data transmission. Generally MAC protocols are grouped into contention-based and schedule-based MAC protocols. In contention-based MAC protocols such as carrier sense multiple access/collision avoidance (CSMA/CA) protocols, nodes contend for the channel to transmit data. If the channel is busy, the node defers its transmission until it becomes idle. These protocols are scalable with no strict time synchronization constraint. However, they incur significant protocol overhead. In schedule-based protocols such as time division multiple access (TDMA) protocols, the channel is divided into time slots of fixed or variable duration. These slots are assigned to nodes and each node transmits during its slot period. These protocols are energy conserving protocols. Since the duty cycle of radio is reduced, there is no contention, idle listening and overhearing problems. But these protocols require frequent synchronization. Table 3 compares CSMA/CA and TDMA protocols. 3.1. WBAN MAC Requirements The most important attribute of a good MAC protocol for a WBAN is energy efficiency. In some applications, the device should support a battery life of months or years without interventions, while others may require a battery life of tens of hours due to the nature of the applications. For example, cardiac defibrillators and pacemakers should have a lifetime of more than 5 years, while swallowable camera pills have a lifetime of 12 hours. Power-efficient and flexible duty cycling techniques are required to minimize the idle listening, overhearing, packet collisions and control packet overhead. Furthermore, low duty cycle nodes should not receive frequent synchronization and control information (beacon frames) if they have no data to send or receive. The WBAN MAC should also support simultaneous operation on in-body (MICS) and on-body channels (ISM or UWB) at the same time. In other words, it should support multiple physical layer (Multi-PHYs) communication or MAC transparency. Other important factors are scalability and adaptability to changes in the network, delay, throughput, and bandwidth utilization. Changes in the network topology, the position of the human body, and the node density should be handled rapidly and successfully. The MAC protocol for a WBAN should consider the electrical properties of the human body and the diverse traffic nature of in-body and on-body nodes. For example, the data rate of in-body nodes varies, ranging from few kbps in pacemaker to several Mbps in capsular endoscope. In the following sections, we discuss proposed MAC protocols for a WBAN with useful guidelines. We also present a case study of IEEE 802.15.4, PB-TDMA, and S-MAC protocols for a WBAN using NS2 simulator. 3.2. Proposed MAC Protocols for a WBAN In this section, we study proposed MAC protocols for a WBAN followed by useful suggestions/comments. Many of the proposed MAC protocols are the extension of existing MAC protocols originally proposed for wireless sensor networks (WSNs). 3.2.1. IEEE 802.15.4 IEEE 802.15.4 has remained the main focus of many researchers during the past few years. Some of the main reasons of selecting IEEE 802.15.4 for a WBAN were low-power communication and support of low data rate WBAN applications. Nicolas et.al investigated the performance of a non-beacon IEEE 802.15.4 in [7], where low upload/download rates (mostly per hour) are considered. They concluded that the non-beacon IEEE 802.15.4 results in 10 to 15 years sensor lifetime for low data rate and asymmetric WBAN traffic. However, their work considers data transmission on the basis of periodic intervals which is not a perfect scenario in a real WBAN. Furthermore, the data rate of in-body and on-body nodes are not always low, i.e., it ranges from 10 Kbps to 10 Mbps, and hence reduces the lifetime of the sensor nodes. Li et.al studied the behavior of slotted and unslotted CSMA/CA mechanisms and concluded that the unslotted mechanism performs better than the slotted one in terms of throughput and lat ency but with high cost of power consumption [8]. Intel Corporation conducted a series of experiments to analyze the performance of IEEE 802.15.4 for a WBAN [9]. They deployed a number of Intel Mote 2 [10] nodes on chest, waist, and the right ankle. Table 4 shows the throughput at a 0dBm transmit power when a person is standing and sitting on a chair. The connection between ankle and waist cannot be established, even for a short distance of 1.5m. All other connections show favourable performance. Dave et al. studied the energy efficiency and QoS performance of IEEE 802.15.4 and IEEE 802.11e [11] MAC protocols under two generic applications: a wave-form real time stream and a real-time parameter measurement stream [12]. Table 5 shows the throughput and the Power (in mW) for both applications. The AC_BE and AC_VO represent the access categories voice and best-effort in the IEEE 802.11e. Since the IEEE 802.15.4 operates in the 2.4 GHz unlicensed band, the possibilities of interference from other devices such as IEEE 802.11 and microwave are inevitable. A series of experiments to evaluate the impact of IEEE 802.11 and microwave ovens on the IEEE 802.15.4 transmission are carried out in [13]. The authors considered XBee 802.15.4 development kit that has two XBee modules. Table 6 shows the affects of microwave oven on the XBee remote module. When the microwave oven is ON, the packet success rate and the standard deviation is degraded to 96.85% and 3.22% respectively. However, there is no loss when the XBee modules are taken 2 meters away from the microwave oven. 3.2.2. Heartbeat Driven MAC Protocol (H-MAC) A Heartbeat Driven MAC protocol (H-MAC) [14] is a TDMA-based protocol originally proposed for a star topology WBAN. The energy efficiency is improved by exploiting heartbeat rhythm information in order to synchronize the nodes. The nodes do not need to receive periodic information to perform synchronization. The heartbeat rhythm can be extracted from the sensory data and hence all the rhythms represented by peak sequences are naturally synchronized. The H-MAC protocol assigns dedicated time slots to each node to guarantee collision-free transmission. In addition, this protocol is supported by an active synchronization recovery scheme where two resynchronization schemes are implemented. Although H-MAC protocol reduces the extra energy cost required for synchronization, it does not support sporadic events. Since the TDMA slots are dedicated and not traffic adaptive, H-MAC protocol encounters low spectral/bandwidth efficiency in case of a low traffic. For example, a blood pressure node may not need a dedicated time slot while an endoscope pill may require a number of dedicated time slots when deployed in a WBAN. But the slots should be released when the endoscope pill is expelled. The heartbeat rhythm information varies depending on the patient condition. It may not reveal valid information for synchronization all the time. One of the solutions is to assign the time slots based on the nodes traffic information and to receive synchronization packets when required, i.e., when a node has data to transmit/receive. 3.2.3. Reservation-based Dynamic TDMA Protocol (DTDMA) A Reservation-based Dynamic TDMA Protocol (DTDMA) [15] is originally proposed for a normal (periodic) WBAN traffic where slots are allocated to the nodes which have buffered packets and are released to other nodes when the data transmission/reception is completed. The channel is bounded by superframe structures. Each superframe consists of a beacon used to carry control information including slot allocation information, a CFP period a configurable period used for data transmission, a CAP period a fixed period used for short command packets using slotted aloha protocol, and a configurable inactive period used to save energy. Unlike a beacon-enabled IEEE 802.15.4 superframe structure where the CAP duration is followed by CFP duration, in DTDMA protocol the CFP duration is followed by CAP duration in order to enable the nodes to send CFP traffic earlier than CAP traffic. In addition, the duration of inactive period is configurable based on the CFP slot duration. If there is no CFP t raffic, the inactive period will be increased. The DTDMA superframe structure is given in 2(a). It has been shown that for a normal (periodic) traffic, the DTDMA protocol provides more dependability in terms of low packet dropping rate and low energy consumption when compared with IEEE 802.15.4. However, it does not support emergency and on-demand traffic. Although the slot allocation based on the traffic information is a good approach, the DTDMA protocol has several limitations when considered for the MICS band. The MICS band has ten channels where each channel has 300 Kbps bandwidth. The DTDMA protocol is valid only for one channel and cannot operate on ten channels simultaneously. In addition, the DTDMA protocol does not support the channel allocation mechanism in the MICS band. This protocol can be further investigated for the MICS band by integrating the channel information in the beacon frame. The new concept may be called Frequency-based DTDMA (F-DTDMA), i.e., the coordinator first selects one of the channels in the MICS band and then divides the selected channel in TDMA superframe (s) according to the DTDMA protocol. However the FCC has imposed several restrictions on the channel selection/allocation mechanism in the MICS band, which further creates problems for the MAC designers. 3.2.4. BodyMAC Protocol A BodyMAC protocol is a TDMA-based protocol where the channel is bounded by TDMA superframe structures with downlink and uplink subframes as given in 2(b) [16]. The downlink frame is used to accommodate the on-demand traffic and the uplink frame is used to accommodate the normal traffic. There is no proper mechanism to handle the emergency traffic. The uplink frame is further divided into CAP and CFP periods. The CAP period is used to transmit small size MAC packets. The CFP period is used to transmit the normal data in a TDMA slot. The duration of the downlink and uplink superframes are defined by the coordinator. The advantage of the BodyMAC protocol is that it accommodates the on-demand traffic using the downlink subframe. However, in case of low-power implants (which should not receive beacons periodically), the coordinator has to wake up the implant first and then send synchronization packets. After synchronization, the coordinator can request/send data in the downlink subframe. The wake up procedure for low-power implants is not defined in the BodyMAC protocol. One of the solutions is to use a wakeup radio in order to wake up low-power implants before using the downlink subframe. In addition the wakeup packets can be used to carry control information such as channel (MICS band) and slot allocation information from the coordinator to the nodes. Finally, the BodyMAC protocol uses the CSMA/CA protocol in the CAP period which is not reliable for a WBAN. This should be replaced by slotted-ALOHA as done in DTDMA. Further details on low-power MAC protocols (originally proposed for WSNs) for a WBAN are given in Appendix I. 3.3. Case Study: IEEE 802.15.4, PB-TDMA, and SMAC Protocols for a WBAN In this section, we investigate the performance of a beacon-enabled IEEE 802.15.4, preamble-based TDMA [17], and SMAC protocols for an on-body communication system. Our analysis is verified by extensive simulations using NS-2. The wireless physical parameters are considered according to a low-power Nordic nRF2401 transceiver (Chipcon CC2420 radio [18] is considered in case of IEEE 802.15.4) [19]. This radio transceiver operates in the 2.4-2.5 GHz band with an optimum transmission power of -5dBm. We use the shadowing propagation model throughout the simulations. We consider a total of 7 nodes firmly placed on a human body. The nodes are connected to the coordinator in a star topology. The distribution of the nodes and the coordinator is given in 3(a). The initial nodes energy is 5 Joules. The packet size is 120 bytes. The average data transmission rate of ECG, EEG, and EMG is 10, 70, and 100 kbps. The transport agent is a user datagram protocol (UDP). Since the traffic is an uplink t raffic, the buffer size at the coordinator is considered unlimited. In a real WBAN, the buffer size should be configurable based on the application requirements. For energy calculation, we use the existing energy model defined in NS-2. The simulation area is 33 meter and each node generates constant bit rate (CBR) traffic. The CBR traffic is an ideal model for some of the medical applications, where the nodes send data based on pre-defined traffic patterns. However, most of the nodes in a WBAN have heterogeneous traffic characteristics and they generate periodic and aperiodic traffic. In this case, they will have many traffic models operating at the same time, ranging from CBR to variable bit rate (VBR). 3(b) shows the throughput of the IEEE 802.15.4, PB-TDMA, and S-MAC protocols. The performance of the IEEE 802.15.4, when cond in a beacon-enabled mode, outperforms PB-TDMA and S-MAC protocols. The efficiency of a MAC protocol depends on the traffic pattern. In this case, S-MAC protocol results poor performance because the traffic scenario that we generated is not an ideal scenario for the S-MAC. 3(c) shows the residual energy at various nodes during simulation time. When nodes finish their transmission, they go into sleep mode, as indicated by the horizontal line. The coordinator has a considerable energy loss because it always listens to the other nodes. However, the energy consumption of the coordinator is not a critical issue in a WBAN. We further analyze the residual energy at the ECG node for different transmission powers. There is a minor change in energy loss for three different transmission powers as given in 3(d). This concludes that reducing the transmission power only d oes not save energy unless supported by an efficient power management scheme. The IEEE 802.15.4 can be considered for certain on-body medical applications, but it does not achieve the level of power required for in-body nodes. It is not sufficient for high data rate medical and non-medical applications due to its limitations to 250 kbps. Furthermore, it uses slotted or unslotted CSMA/CA where the nodes are required to sense the channel before transmission. However, the channel sensing is not guaranteed in MICS band because the path loss inside the human body due to tissue heating is much higher than in free space. Bin et.al studied the clear channel assessment (CCA) range of in-body nodes which is only 0.5 meters [20]. This unreliability in CCA indicates that CSMA/CA is not an ideal technique for the in-body communication system. An alternative approach is to use a TDMA-based protocol that contains a beacon, a configurable contention access period (CCAP), and a contention free period (CFP) [21]. Unlike the IEEE 802.15.4, this protocol is required to use a slot ted-ALOHA protocol in the CCAP instead of CSMA/CA. The CCAP period should contain few slots (3 or 4) of equal duration and can be used for short data transmission and a guaranteed time slot (GTS) allocation. To enable a logical connection between the in-body and the on-body communication systems, a method called bridging function can be used as discussed in [21]. The bridging function can integrate in-body and on-body nodes into a WBAN, thus satisfying the MAC transparency requirement. Further details about bridging function are given in [22]. 3.4. Discussion Since the CSMA/CA is not suitable due to unreliable CCA and heavy collision problems, it can be seen that the most reliable power-efficient protocol is a TDMA-based protocol. Many protocols have been proposed for a WBAN and most of them are based on a TDMA-based mechanism. However, all of them have pros and cons for a real WBAN system that should operate on Multi-PHYs (MICS, ISM, and UWB) simultaneously. The MAC transparency has been a hot topic for the MAC designers since different bands have different characteristics in terms of data rate, number of channels in a particular frequency band, and data prioritization. A good MAC protocol should enable reliable operation on MICS, ISM, and UWB etc bands simultaneously. The main problems are related to MICS band due to FCC restrictions [23]. According to FCC, â€Å"Within 5 seconds prior to initiating a communications session, circuitry associated with a medical implant programmer/control transmitter must monitor the channel or channels the MICS system devices intend to occupy for a minimum of 10 milliseconds per channel.† In other words, the coordinator must perform Listen-before-talking (LBT) criteria prior to a MICS communication sessions. The implants are not allowed to On the Implant Communication and MAC Protocols for a WBAN On the Implant Communication and MAC Protocols for a WBAN Abstract Recent advances in micro-electro-mechanical systems (MEMS), wireless communication, low-power intelligent sensors, and semiconductor technologies have allowed the realization of a wireless body area network (WBAN). A WBAN provides unobtrusive health monitoring for a long period of time with real-time updates to the physician. It is widely used for ubiquitous healthcare, entertainment, and military applications. The implantable and wearable medical devices have several critical requirements such as power consumption, data rate, size, and low-power medium access control (MAC) protocols. This article consists of two parts: body implant communication, which is concerned with the communication to and from a human body using RF technology, and WBAN MAC protocols, which presents several low-power MAC protocols for a WBAN with useful guidelines. In body implant communication, the in-body radio frequency (RF) performance is affected considerably by the implants depth inside the human body as well as by the muscle and fat. We observe best performance at a depth of 3cm and not close to the human skin. Furthermore, the study of low-power MAC protocols highlights the most important aspects of developing a single, a low-power, and a reliable MAC protocol for a WBAN. Keywords: In-body, on-body, RF communication, Implant, WBAN 1. Introduction Cardiovascular diseases are the foremost cause of deaths in the United States and Europe since 1900. More than ten million people are affected in Europe, one million in the US, and twenty two million people in the world [1]. The number is projected to be triple by 2020, resulting in an expenditure of around 20% of the gross domestic product (GDP). The ratio is 17% in South Korea and 39% in the UK [2]. The healthcare expenditure in the US is expected to be increased from $2.9 trillion in 2009 to $4 trillion US dollars in 2015 [3]. The impending health crisis attracts researchers, industrialists, and economists towards optimal and quick health solutions. The non-intrusive and ambulatory health monitoring of patients vital signs with real time updates of medical records via internet provide economical solutions to the health care systems. A wireless body area network (WBAN) is becoming increasingly important for healthcare systems, sporting activities, and members of emergency as well as military services. WBAN is an integration of in-body (implants) and on-body (wearable) sensors that allow inexpensive, unobtrusive, and long-term health monitoring of a patient during normal daily activities for prolonged periods of time. In-body radio frequency (RF) communications have the potential to dramatically change the future of healthcare. For example, they allow an implanted pacemaker to regularly transmit performance data and the patients health status to the physician. However, the human body poses many wireless transmission challenges. This is partially conductive and consists of materials having different dielectric constants and characteristics impedance. The interface of muscles and fats may reflect the RF wave rather than transmitting it. The key elements of an RF-linked implant are the in-body antenna and the communi cation link performance. Also, in the case of many implants and wearable sensors, a low-power MAC protocol is required to accommodate the heterogeneous traffic in a power-efficient manner. This article is divided into two parts: body implant communication and WBAN MAC protocols. In the body implant communication part, we look at the RF communication link performance at various depths inside a human (artificial) body. In the MAC part, we review the existing low-power MAC protocols and discuss their pros and cons in the context of a WBAN. We further provide alternative MAC solutions for in-body and on-body communication systems. The rest of the article is divided into three sections. In section 2, we present a discussion on body implant communication including in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. Section 3 discusses several low-power MAC protocols and realizes a need for a new, a low-power, and a reliable MAC protocol for a WBAN. The final section concludes our work. 2. Body Implant Communication There are several ways to communicate with an implant that includes the use of electromagnetic induction and RF technology. Both are wireless and their use depends on the application requirements. Further, the key elements of an RF-linked implant are the in-body antenna and the communication link performance. The following part discusses in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. 2.1. In-body Electromagnetic Induction Several applications still use electromagnetic coupling to provide a communication link to an implant device. In this scheme, an external coil is held very close to the body that couples to a coil implanted just below the skin surface. The implant is powered by the coupled magnetic field and requires no battery for communication. Data is transferred from the implant by altering the impedance of the implanted loop that is detected by the external coil and electronics. This type of communication is commonly used to identify animals that have been injected with an electronic tag. Electromagnetic induction is used when continuous, long-term communication is required. The base band for electromagnetic communication is typically 13.56 MHz or 28 MHz, with other frequencies also available. The choice of a particular band is subject to regulation for maximum specific absorption rate (SAR). The inductive coupling achieves best power transfer efficiency when uses large transmit and receive coil s. It, however, becomes less efficient when the space is an issue of the device is implanted deep inside the human body. Furthermore, inductive coupling technique does not support a very high data rate and cannot initiate a communication session from inside of the body. 2.2. In-body RF Communication Compared with the electromagnetic induction, RF communication dramatically increases bandwidth and supports a two-way data communication. The band designated for the in-body RF communication is medical implant communication service (MICS) band and is around 403 to 405 MHz. This band has a power limit of 25  µW in the air and is usually split into ten channels of 300 kHz bandwidth each. The human body is a medium that poses numerous wireless transmission challenges. It consists of various components that are not predictable and will change as the patient ages, gains or losses weight, or even changes posture. Values of dielectric constant (ÃŽ µr), conductivity (ÏÆ') and characteristic impedance (Zo) for some body tissue are given in table 1 [4]. This demonstrates that these two tissue types are very different. Also, the dielectric constant affects the wavelength of a signal. At 403 MHz, the wavelength in the air is 744mm, but in muscle with ÃŽ µr = 50 the wavelength reduces to 105mm, which helps in designing implanted antennas. 2.3. In-body Antenna Design A modern in-body antenna should be tuneable by using an intelligent transceiver and software routine. This enables the antenna coupling circuit to be optimised. Due to the frequency, and available volume, a non-resonant antenna is commonly used. It has a lower gain than a resonant antenna. This makes design of the antenna coupling circuit very important. Antenna options are dictated by the location of the implant. A patch antenna can be used when the implant is flat. Patch antennas are comprised of a flat insulating substrate coated on both sides with a conductor. The substrate is a body compatible material with a platinum or a platinum/iridium conductor. The upper surface is the active face and is connected to the transceiver. The connection to the transceiver needs to pass through the case where the hermetic seal is maintained, requiring a feed-through. The feed-through must have no filter capacitors present; these are common on other devices. An implanted patch antenna is electrically larger than its physical size because it is immersed in a high (ÃŽ µr) medium. It can be much larger electrically if the substrate is of higher (ÃŽ µr), such as titania or zirconia. A loop antenna can also be attached to the implant. This antenna operates mostly by the magnetic field, whereas the patch operates mostly by the electric field. The loop antenna delivers performance comparable to that of a dipole, but with a considerably smaller size. In addition, the magnetic permeability of muscle or fat is very similar to that of an air, unlike the dielectric constant that varies considerably. This property enables an antenna to be built and used with much less need for retuning. A loop antenna can be mounted on the case in a biocompatible structure. 2.4. In-body Link Performance The demonstration system consists of a base-station, an implant, antennas, and a controlling laptop. The base-station contains a printed circuit board (PCB) with a wakeup RF circuit, a Zarlink ZL70101 IC, and a micro-controller. It sends a wakeup signal on industrial, scientific, and medical (ISM) 2.4 GHz band to power up the implant to communicate. It also supports communication within the MICS band. The implant contains a Zarlink ZL70101 IC, a micro-controller, and a battery. The power limits of the wakeup signal for ISM and MICS bands transmitters are 100mW and 25  µW respectively. Experiments that measure the performance of an implant inside a living body are difficult to arrange. The alternative is to use 3D simulation software or a body phantom defined in [5]. The use of 3D simulation software is time consuming and hence practically not valuable. Therefore, measurements are generally performed using the body phantom and immersing a battery-powered implant into it [6]. Since no additional cables are attached to the test implant, the interference errors in the measurements are minimal. The body phantom is filled with a liquid that mimics the electrical properties of the human body tissues. The test environment is an anechoic chamber that includes a screened room. The interior walls of the room have sound-absorbent cones to minimize any reflections from walls or the floor that could distort the results. In real life, however, the results will be affected by the reflections from walls, desks, and other equipment and hardware. The body phantom is mounted on a woo den stand (non-conductive). The distance from the body phantom to the base-station is 3m. The MICS base-station dipole antenna is mounted on a stand. 1(a) shows the anechoic chamber with a body phantom (on the wooden stand), a log periodic test antenna (foreground), and a base-station dipole (right). The log periodic antenna is used to calculate the power radiated from the body phantom. A depth is defined as the horizontal distance between the outer skin of the phantom and the test implant. Vertical polarization of the implant is the case when the long side of the box and the patch antenna is vertical. The link performance is measured once the communication link is established. The measurements include the effective radiated power (ERP) from the implant, the received signal at the implant from the base-station, and the link quality. Measurements are made over a set distance with all the combinations of implant and test antenna polarisations, i.e., vertical-vertical (V-V), horizontal-vertical (H-V), vertical-horizontal (V-H), and horizontal-horizontal (H-H) polarisations. Typical results are shown in 1(b) where the ERP is calculated from the received signal power and the antenna characteristics. The measurement of the signal levels is done with the log periodic antenna and the spectrum analyzer. It can be seen in the that there is a significant difference in signal levels with polarisation combinations and depths. For a V-V polarisation, the ERP increases from a 1cm depth to a maximum between 2 and 7 cm, and then it decreases. The gradual increase is due to the simulated body acti ng as a parasitic antenna. The also shows how the signal level is affected by the depth with different polarisation. Such a test needs to be done with the antenna that is to be used in the final product. To measure the received signal at the implant, the Zarlink ZL70101 has an inbuilt receive signal strength indication (RSSI) function that gives a measure of the signal level detected. RSSI is a relative measurement with no calibration. The implant receives and measures a continuous wave signal transmitted by the base-station. In this case, the implant and the base-station antennas are vertically polarised. 1(c) shows an increase in the signal level at a depth between 3 and 4cm for a 15dec power. The power settings refer to the base-station and are cond to set the ERP to 25  µW. Signal levels are not valuable unless they are related to data transmission. One way to maintain the link quality is to measure the number of times the error correction is invoked during the transmission of 100 blocks of data. Two types of error correction codes, i.e., error correction code (ECC) and cyclic redundancy code (CRC) are invoked to maintain data integrity and reliability. The fewer ECC and CRC invocations result in better link quality. In 1(d), the error correction is lowest at a depth between 3 and 5 cm. A sample of ECC data collected at a 3cm implant depth is given in Table 2. The Count indicates the number of data blocks, the Time (ms) indicates the block transmission time, and the ECC indicates the number of times it is invoked. During the transmission of 100 blocks of data at a 3cm depth, the ECC is invoked 368 times, which is further equivalent to an average 3.68 times (as given in 1(d)). 2.5. Discussion The ERP, RSSI, as well as the ECC and CRC plots show that the implant demonstrates the best performance at a depth between 3 and 5 cm. The depth and position of an implant is not chosen for engineering performance but for the best clinical reasons. The implant designer must be aware of the possible losses through the human body. The attenuation and the parasitic antenna effects vary from patient to patient, with the position of the implant and with the time as the patient gains, or looses weight. Therefore, these factors need to be built into the link budget. 3. WBAN MAC Protocols Some of the common objectives in a WBAN are to achieve maximum throughput, minimum delay, and to maximize the network lifetime by controlling the main sources of energy waste, i.e., collision, idle listening, overhearing, and control packet overhead. A collision occurs when more than one packet transmits data at the same time. The collided packets have to be retransmitted, which consumes extra energy. The second source of energy waste is idle listening, meaning that a node listens to an idle channel to receive data. The third source is overhearing, i.e., to receive packets that are destined to other nodes. The last source is control packet overhead, meaning that control information area added to the payload. Minimal number of control packets should be used for data transmission. Generally MAC protocols are grouped into contention-based and schedule-based MAC protocols. In contention-based MAC protocols such as carrier sense multiple access/collision avoidance (CSMA/CA) protocols, nodes contend for the channel to transmit data. If the channel is busy, the node defers its transmission until it becomes idle. These protocols are scalable with no strict time synchronization constraint. However, they incur significant protocol overhead. In schedule-based protocols such as time division multiple access (TDMA) protocols, the channel is divided into time slots of fixed or variable duration. These slots are assigned to nodes and each node transmits during its slot period. These protocols are energy conserving protocols. Since the duty cycle of radio is reduced, there is no contention, idle listening and overhearing problems. But these protocols require frequent synchronization. Table 3 compares CSMA/CA and TDMA protocols. 3.1. WBAN MAC Requirements The most important attribute of a good MAC protocol for a WBAN is energy efficiency. In some applications, the device should support a battery life of months or years without interventions, while others may require a battery life of tens of hours due to the nature of the applications. For example, cardiac defibrillators and pacemakers should have a lifetime of more than 5 years, while swallowable camera pills have a lifetime of 12 hours. Power-efficient and flexible duty cycling techniques are required to minimize the idle listening, overhearing, packet collisions and control packet overhead. Furthermore, low duty cycle nodes should not receive frequent synchronization and control information (beacon frames) if they have no data to send or receive. The WBAN MAC should also support simultaneous operation on in-body (MICS) and on-body channels (ISM or UWB) at the same time. In other words, it should support multiple physical layer (Multi-PHYs) communication or MAC transparency. Other important factors are scalability and adaptability to changes in the network, delay, throughput, and bandwidth utilization. Changes in the network topology, the position of the human body, and the node density should be handled rapidly and successfully. The MAC protocol for a WBAN should consider the electrical properties of the human body and the diverse traffic nature of in-body and on-body nodes. For example, the data rate of in-body nodes varies, ranging from few kbps in pacemaker to several Mbps in capsular endoscope. In the following sections, we discuss proposed MAC protocols for a WBAN with useful guidelines. We also present a case study of IEEE 802.15.4, PB-TDMA, and S-MAC protocols for a WBAN using NS2 simulator. 3.2. Proposed MAC Protocols for a WBAN In this section, we study proposed MAC protocols for a WBAN followed by useful suggestions/comments. Many of the proposed MAC protocols are the extension of existing MAC protocols originally proposed for wireless sensor networks (WSNs). 3.2.1. IEEE 802.15.4 IEEE 802.15.4 has remained the main focus of many researchers during the past few years. Some of the main reasons of selecting IEEE 802.15.4 for a WBAN were low-power communication and support of low data rate WBAN applications. Nicolas et.al investigated the performance of a non-beacon IEEE 802.15.4 in [7], where low upload/download rates (mostly per hour) are considered. They concluded that the non-beacon IEEE 802.15.4 results in 10 to 15 years sensor lifetime for low data rate and asymmetric WBAN traffic. However, their work considers data transmission on the basis of periodic intervals which is not a perfect scenario in a real WBAN. Furthermore, the data rate of in-body and on-body nodes are not always low, i.e., it ranges from 10 Kbps to 10 Mbps, and hence reduces the lifetime of the sensor nodes. Li et.al studied the behavior of slotted and unslotted CSMA/CA mechanisms and concluded that the unslotted mechanism performs better than the slotted one in terms of throughput and lat ency but with high cost of power consumption [8]. Intel Corporation conducted a series of experiments to analyze the performance of IEEE 802.15.4 for a WBAN [9]. They deployed a number of Intel Mote 2 [10] nodes on chest, waist, and the right ankle. Table 4 shows the throughput at a 0dBm transmit power when a person is standing and sitting on a chair. The connection between ankle and waist cannot be established, even for a short distance of 1.5m. All other connections show favourable performance. Dave et al. studied the energy efficiency and QoS performance of IEEE 802.15.4 and IEEE 802.11e [11] MAC protocols under two generic applications: a wave-form real time stream and a real-time parameter measurement stream [12]. Table 5 shows the throughput and the Power (in mW) for both applications. The AC_BE and AC_VO represent the access categories voice and best-effort in the IEEE 802.11e. Since the IEEE 802.15.4 operates in the 2.4 GHz unlicensed band, the possibilities of interference from other devices such as IEEE 802.11 and microwave are inevitable. A series of experiments to evaluate the impact of IEEE 802.11 and microwave ovens on the IEEE 802.15.4 transmission are carried out in [13]. The authors considered XBee 802.15.4 development kit that has two XBee modules. Table 6 shows the affects of microwave oven on the XBee remote module. When the microwave oven is ON, the packet success rate and the standard deviation is degraded to 96.85% and 3.22% respectively. However, there is no loss when the XBee modules are taken 2 meters away from the microwave oven. 3.2.2. Heartbeat Driven MAC Protocol (H-MAC) A Heartbeat Driven MAC protocol (H-MAC) [14] is a TDMA-based protocol originally proposed for a star topology WBAN. The energy efficiency is improved by exploiting heartbeat rhythm information in order to synchronize the nodes. The nodes do not need to receive periodic information to perform synchronization. The heartbeat rhythm can be extracted from the sensory data and hence all the rhythms represented by peak sequences are naturally synchronized. The H-MAC protocol assigns dedicated time slots to each node to guarantee collision-free transmission. In addition, this protocol is supported by an active synchronization recovery scheme where two resynchronization schemes are implemented. Although H-MAC protocol reduces the extra energy cost required for synchronization, it does not support sporadic events. Since the TDMA slots are dedicated and not traffic adaptive, H-MAC protocol encounters low spectral/bandwidth efficiency in case of a low traffic. For example, a blood pressure node may not need a dedicated time slot while an endoscope pill may require a number of dedicated time slots when deployed in a WBAN. But the slots should be released when the endoscope pill is expelled. The heartbeat rhythm information varies depending on the patient condition. It may not reveal valid information for synchronization all the time. One of the solutions is to assign the time slots based on the nodes traffic information and to receive synchronization packets when required, i.e., when a node has data to transmit/receive. 3.2.3. Reservation-based Dynamic TDMA Protocol (DTDMA) A Reservation-based Dynamic TDMA Protocol (DTDMA) [15] is originally proposed for a normal (periodic) WBAN traffic where slots are allocated to the nodes which have buffered packets and are released to other nodes when the data transmission/reception is completed. The channel is bounded by superframe structures. Each superframe consists of a beacon used to carry control information including slot allocation information, a CFP period a configurable period used for data transmission, a CAP period a fixed period used for short command packets using slotted aloha protocol, and a configurable inactive period used to save energy. Unlike a beacon-enabled IEEE 802.15.4 superframe structure where the CAP duration is followed by CFP duration, in DTDMA protocol the CFP duration is followed by CAP duration in order to enable the nodes to send CFP traffic earlier than CAP traffic. In addition, the duration of inactive period is configurable based on the CFP slot duration. If there is no CFP t raffic, the inactive period will be increased. The DTDMA superframe structure is given in 2(a). It has been shown that for a normal (periodic) traffic, the DTDMA protocol provides more dependability in terms of low packet dropping rate and low energy consumption when compared with IEEE 802.15.4. However, it does not support emergency and on-demand traffic. Although the slot allocation based on the traffic information is a good approach, the DTDMA protocol has several limitations when considered for the MICS band. The MICS band has ten channels where each channel has 300 Kbps bandwidth. The DTDMA protocol is valid only for one channel and cannot operate on ten channels simultaneously. In addition, the DTDMA protocol does not support the channel allocation mechanism in the MICS band. This protocol can be further investigated for the MICS band by integrating the channel information in the beacon frame. The new concept may be called Frequency-based DTDMA (F-DTDMA), i.e., the coordinator first selects one of the channels in the MICS band and then divides the selected channel in TDMA superframe (s) according to the DTDMA protocol. However the FCC has imposed several restrictions on the channel selection/allocation mechanism in the MICS band, which further creates problems for the MAC designers. 3.2.4. BodyMAC Protocol A BodyMAC protocol is a TDMA-based protocol where the channel is bounded by TDMA superframe structures with downlink and uplink subframes as given in 2(b) [16]. The downlink frame is used to accommodate the on-demand traffic and the uplink frame is used to accommodate the normal traffic. There is no proper mechanism to handle the emergency traffic. The uplink frame is further divided into CAP and CFP periods. The CAP period is used to transmit small size MAC packets. The CFP period is used to transmit the normal data in a TDMA slot. The duration of the downlink and uplink superframes are defined by the coordinator. The advantage of the BodyMAC protocol is that it accommodates the on-demand traffic using the downlink subframe. However, in case of low-power implants (which should not receive beacons periodically), the coordinator has to wake up the implant first and then send synchronization packets. After synchronization, the coordinator can request/send data in the downlink subframe. The wake up procedure for low-power implants is not defined in the BodyMAC protocol. One of the solutions is to use a wakeup radio in order to wake up low-power implants before using the downlink subframe. In addition the wakeup packets can be used to carry control information such as channel (MICS band) and slot allocation information from the coordinator to the nodes. Finally, the BodyMAC protocol uses the CSMA/CA protocol in the CAP period which is not reliable for a WBAN. This should be replaced by slotted-ALOHA as done in DTDMA. Further details on low-power MAC protocols (originally proposed for WSNs) for a WBAN are given in Appendix I. 3.3. Case Study: IEEE 802.15.4, PB-TDMA, and SMAC Protocols for a WBAN In this section, we investigate the performance of a beacon-enabled IEEE 802.15.4, preamble-based TDMA [17], and SMAC protocols for an on-body communication system. Our analysis is verified by extensive simulations using NS-2. The wireless physical parameters are considered according to a low-power Nordic nRF2401 transceiver (Chipcon CC2420 radio [18] is considered in case of IEEE 802.15.4) [19]. This radio transceiver operates in the 2.4-2.5 GHz band with an optimum transmission power of -5dBm. We use the shadowing propagation model throughout the simulations. We consider a total of 7 nodes firmly placed on a human body. The nodes are connected to the coordinator in a star topology. The distribution of the nodes and the coordinator is given in 3(a). The initial nodes energy is 5 Joules. The packet size is 120 bytes. The average data transmission rate of ECG, EEG, and EMG is 10, 70, and 100 kbps. The transport agent is a user datagram protocol (UDP). Since the traffic is an uplink t raffic, the buffer size at the coordinator is considered unlimited. In a real WBAN, the buffer size should be configurable based on the application requirements. For energy calculation, we use the existing energy model defined in NS-2. The simulation area is 33 meter and each node generates constant bit rate (CBR) traffic. The CBR traffic is an ideal model for some of the medical applications, where the nodes send data based on pre-defined traffic patterns. However, most of the nodes in a WBAN have heterogeneous traffic characteristics and they generate periodic and aperiodic traffic. In this case, they will have many traffic models operating at the same time, ranging from CBR to variable bit rate (VBR). 3(b) shows the throughput of the IEEE 802.15.4, PB-TDMA, and S-MAC protocols. The performance of the IEEE 802.15.4, when cond in a beacon-enabled mode, outperforms PB-TDMA and S-MAC protocols. The efficiency of a MAC protocol depends on the traffic pattern. In this case, S-MAC protocol results poor performance because the traffic scenario that we generated is not an ideal scenario for the S-MAC. 3(c) shows the residual energy at various nodes during simulation time. When nodes finish their transmission, they go into sleep mode, as indicated by the horizontal line. The coordinator has a considerable energy loss because it always listens to the other nodes. However, the energy consumption of the coordinator is not a critical issue in a WBAN. We further analyze the residual energy at the ECG node for different transmission powers. There is a minor change in energy loss for three different transmission powers as given in 3(d). This concludes that reducing the transmission power only d oes not save energy unless supported by an efficient power management scheme. The IEEE 802.15.4 can be considered for certain on-body medical applications, but it does not achieve the level of power required for in-body nodes. It is not sufficient for high data rate medical and non-medical applications due to its limitations to 250 kbps. Furthermore, it uses slotted or unslotted CSMA/CA where the nodes are required to sense the channel before transmission. However, the channel sensing is not guaranteed in MICS band because the path loss inside the human body due to tissue heating is much higher than in free space. Bin et.al studied the clear channel assessment (CCA) range of in-body nodes which is only 0.5 meters [20]. This unreliability in CCA indicates that CSMA/CA is not an ideal technique for the in-body communication system. An alternative approach is to use a TDMA-based protocol that contains a beacon, a configurable contention access period (CCAP), and a contention free period (CFP) [21]. Unlike the IEEE 802.15.4, this protocol is required to use a slot ted-ALOHA protocol in the CCAP instead of CSMA/CA. The CCAP period should contain few slots (3 or 4) of equal duration and can be used for short data transmission and a guaranteed time slot (GTS) allocation. To enable a logical connection between the in-body and the on-body communication systems, a method called bridging function can be used as discussed in [21]. The bridging function can integrate in-body and on-body nodes into a WBAN, thus satisfying the MAC transparency requirement. Further details about bridging function are given in [22]. 3.4. Discussion Since the CSMA/CA is not suitable due to unreliable CCA and heavy collision problems, it can be seen that the most reliable power-efficient protocol is a TDMA-based protocol. Many protocols have been proposed for a WBAN and most of them are based on a TDMA-based mechanism. However, all of them have pros and cons for a real WBAN system that should operate on Multi-PHYs (MICS, ISM, and UWB) simultaneously. The MAC transparency has been a hot topic for the MAC designers since different bands have different characteristics in terms of data rate, number of channels in a particular frequency band, and data prioritization. A good MAC protocol should enable reliable operation on MICS, ISM, and UWB etc bands simultaneously. The main problems are related to MICS band due to FCC restrictions [23]. According to FCC, â€Å"Within 5 seconds prior to initiating a communications session, circuitry associated with a medical implant programmer/control transmitter must monitor the channel or channels the MICS system devices intend to occupy for a minimum of 10 milliseconds per channel.† In other words, the coordinator must perform Listen-before-talking (LBT) criteria prior to a MICS communication sessions. The implants are not allowed to

Civil Rights and African American Baseball Players

Civil Rights and African American Baseball Players How African Americans in Baseball Affected the Civil Rights Movement. 8th hour Segregation was the main core of what prevented African Americans from pursuing their dreams of being baseball players, up until a few very recognizable players influenced others to step in and help win freedom for playing baseball. All American baseball teams were consisting of mainly whites but some teams allowed African Americans into their teams up until 1890 when the National Association of Baseball rejected blacks from playing. This caused an uproar in the black community and lead to the creations of all black teams that would travel and play other all black teams and sometimes an all white team, like in 1888 when the Cuban Giants defeated the all white New Yorks 4 games of of a five game series. After many years of overwhelming segregation in the south many blacks moved up into the North where they sought the opportunity of creating their own league. In 1920, Rube Foster the owner of the Chicago American Giants brought other midwest teams together and created the first all bla ck league called the Negro Leagues.( Feature African-American Baseball. PBS. PBS, 2003. Web. 21 Apr. 2014.) The Negro Leagues had a very significant impact in the the entrance of blacks into the majors. After the first all black team was organized and the league was set up this opened up an opportunity for players to really show what they got. Before teams knew it they were winning championships. The first all African American league was starting to piece together. And with all this going on, one player had a goal set and that was to be the first black player in a white league. And that player is Jackie Robinson. In 1945 Jackie was the first black player to sign a formal contract with a white team. He took a big step into what led to the allowance of any black player to be in the majors. With the civil rights movement going on he endured hardships that no person could imagine, according to Duke Snider, He (Jackie Robinson) knew that the future of blacks in baseball depended on it. The pressure was enormous, overwhelming, and unbearable at times. I dont know how he held up. I know I never c ould have. By the end of his rookie career as a Dodger he was named rookie of the year, and as time went on all of his success of breaking the color barrier and becoming the first African American to get into the majors and accomplish many records. Even though Jackie is not around to see how the hardships he faced have made life on people today more easy, he is still remembered as the player who paved a path for our nation. The impact of not only Robinson but also Doby and Campy gave inspiration to Martin Luther King Jr. About a week before King died he stated, Youll never know how easy you and Jackie and Doby and Campy made it for me to do my job by what you did on the baseball field. Baseball was integrated before the army, before schools, and before many other things. It all happened without Jackie but someone had to be the first to step up and take a chance, and that was just what he did. (Bio.com. AE Networks Television, n.d. Web. 28 Apr. 2014.†) A few years before World War II, Max Manning had been pitching for the Newark Eagles as a phenomenal side armer. He never thought there would be a chance for him to go and become a pitcher on a white team. His thoughts change for a while when he was approached by an unfamiliar face, the coach of the Detroit Tigers. They were offering a tryout spot for pitching, but that changed when the rest of the team found out he was black. His Negro leagues career was interrupted as he was called into service during World War II. He then returned to pitch the final Negro Leagues World series where his team won. With all this going on Max never gave up and never really cared about what people cared about his color, he only cared about playing ball. After his baseball life was over he went back to school and decided to become a sixth grade teacher up until his death in in June of 2003. Feature African-American Baseball. PBS. PBS, n.d. Web. 29 Apr. 2014.) Before Jackie Robinson broke the color barrier, ball players in Oklahoma had been playing in sandlot leagues and excelling in the sport. Willie Wells played in the sandlot â€Å"blackball† leagues all the way through his teen years in highschool as a shortstop. When he finally came up to the Negro leagues he became the best shortstop in the league. In 1997 he joined the Baseball hall of Fame. Along with Willie there were many other black players that had showed they were worthy of being in Baseballs Hall of Fame. In all there are about 18 players from the Negro Leagues in the Hall of Fame, and most had not been recognized till the 80s, all the way up to about 2002. The reason it took so long is because nobody really cared about blacks in baseball because they â€Å"never compared† to whites. After many years of segregation many white people started to gain respect for him, As Mickey Mantle said after one of the games BASEBALL, AFRICAN AMERICAN. BASEBALL, AFRICAN AMERICAN. N.p., n.d. Web. 07 Mar. 2014 : After the game, Jackie Robinson came into our clubhouse and shook my hand. He said, Youre a helluva ballplayer and youve got a great future. I thought that was a classy gesture, one I wasnt then capable of making. I was a bad loser. What meant even more was what Jackie told the press, Mantle beat us. He was the difference between the two teams. They didnt miss DiMaggio . I have to admit, I became a Jackie Robinson fan on the spot. And when I think of that world Series, his gesture is what comes to mind. Here was a player who had without doubt suffered more abuse and more taunts and more hatred than any player in the history of the game. And he had made a special effort to compliment and encourage a young white kid from Oklahoma.(Jackie Robinson Quotes. Jackie Robinson Quotes. N.p., n.d. Web. 02 May 2014.) As time progressed more and more people started to show respect for Jackie and others that helped integrate baseball and this gave a boost too other players, according to a statement by Hank Aaron In baseball, there is something electrifying about the big leagues. I had read so much about (Stan) Musial,(Ted) Williams and (Jackie) Robinson. I had put those guys on a pedestal. They were something special. I really thought they put their pants on different, rather than one leg at a time.(Hank Aaron Quotes. Hank Aaron Quotes. N.p., n.d. Web. 04 May 2014.) Near the end of World War II the attendance at Negro leagues took a major decline as the best players were called up into interleague which is the step right below major. With that happening the Negro leagues took a dip and fell apart. This lead to integration of blacks into baseball. What caused this greater decline was the focus of the fans only on the major players like Robinson and Doby. To gain more support teams called female players to stand at the gates just to attract more fans but in the end the players just kept on going to white teams. (Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 05 May 2014.) When people think about integration of baseball, they think Jackie Robinson, but thats not all of it. It took a whole community, a whole league just to earn a chance on an all white team. This was a team effort, the biggest step in baseball history started with one big contract to Jackie and the rest took off. Baseball was never the same, and today it isnt a struggle. Without this happening, today baseball probably wouldnt be what it is.

Pearl Harbor not a surprise Essay -- essays research papers

Introduction – Pearl Harbor was vulnerable to attack because of the obstruction of defense and warning. I. Signs of Japan’s intent to attack II. Politics involvement A. War support B. Eight-step plan III. Neglected warning signs near Pearl Harbor soon before the attack A. Midget subs B. Radar detecting The attack on Pearl Harbor has been known to be a complete surprise. Whenever one thinks about it, they consider that it was. They may think that it was a total surprise except for a few small warning signs that our government seems to have ignored. Children are taught that Pearl Harbor is the "Surprise Attack on Pearl Harbor" in school. It has gone into history as this. Even the president, Franklin D. Roosevelt, said in a speech soon after the attacks it was, but he was lying. Franklin D. Roosevelt, in fact, and a few select top armed forces advisors working closely with him are directly responsible for the â€Å"surprise† of the attack on Pearl Harbor. Many opportunities to prevent and defend the attacks upon Pearl Harbor were never taken. The United States government knew well of Japan’s intent to attack Pearl Harbor well before the occurred. The attack may have been a surprise to Pearl Harbor, but it sure wasn’t to Franklin D. Roosevelt and few select top armed forces advisors of his. An investigation after the attack revealed that the intercepting station received at least forty-three different decoded messages that had clues to the attack. The president had at least four intelligence officers under direct orders from Roosevelt. They had decoded the Japanese code and had been monitoring their communications before the attack. They knew all about news of the planned attack. In 48 hours before the attack, LTC Clifford M. Andrew, was told to burn forty file cabinets of top secret information on Pearl Harbor so no investigation could seek out the truth which was labeled top secret and destroyed. Why did Franklin D. Roosevelt hinder any warnings to go though to Pearl Harbor? He knew that most of American society before the Pearl Harbor bombing believed in the idea of isolationism. The only wa... ...he attack started, many soldiers thought it was a drill and nobody took action right away. There may have been a positive side to the attack. Overall, Roosevelt did many things considered wrong and abusive to his right of presidency. However, had he not, the United States may never have entered the war. And certainly we would not have been as united in our stand against evil, for the surprise attack on Pearl Harbor made Americans sympathetic for our striped men and women, causing more help from the mass majority of Americans, eventually leading to victory in World War II. Had Nazi Germany won, no one knows the extent of evil that would have been caused. Even though Franklin Delano Roosevelt did many wrong things, his reasoning was good, and we were victorious. Yes, in its self, December 7th 1941 was known mostly to be a day that will â€Å"live in infamy,† for the destruction of part of America’s military power, many lives lost, and the start of the war for the U.S. To sum this report up, December 7, 1941 should be better known for the day that will â€Å"live in infamy† because of the obstruction of warning or basic defense that would have certainly saved many lives and military property.

Social Status and Feminism in The Great Gatsby Essay -- Feminism Femin

F. Scott Fitzgerald's novel, The Great Gatsby may appear to be a simple tragic romance; however, within the text, Fitzgerald identifies and defines social gaps and importance of wealth. He also presents women within a very separate space as the men. The Great Gatsby allows the reader to enter into the world of wealth and experience the joys and tragedies of being within this certain class as well as allowing the reader to interpret the position of gender inside the class. "Whenever you feel like criticizing anyone,' he [my father] told me, "just remember that all the people in this world haven't had the advantages that you've had" (Gatsby 1). This quote was possibly the backbone of the narrator's actions and character. Through out the novel, the characters that he came into contact with were immediately associated with their money and their association with their given level of wealth. The irony of this opening line is that the poor, or less wealthy, were never really even seen by the narrator. The only people that the narrator saw, according to the reader, are the more wealthy and upper class that were associated with Gatsby's parties. What is even more ironic than the overall absence of the lower classes within the novel is where this neglected level of wealth actually did become part of the novel. Ironically, the only character that lower wealth was associated with was Gatsby. In his past, he was of lower class, but in the actual time when the novel was written, Gatsby was not only representative of wealth, but he seemed to have had the most wealth of all the characters. He was the most prestigious when compared to all of the other characters, yet was the only to have the absence of money in his past. The quote in the p... ...lar practices and thoughts, or he completely redefined them. By doing so, the novel takes on a new identity separate from its tragic romantic cover. Social status and feminism tower over the lost and found love that encompasses this novel.    Works Cited and Consulted: Bewley, Marius. â€Å"Scott Fitzgerald’s Criticism of America.† In Modern Critical Interpretations: The Great Gatsby. edited by Harold Bloom. New York: Chelsea House Publishers. 1986. 11-27. Fetterley, Judith. The Resisting Reader: A Feminist Approach to American Fiction. Bloomington: Indiana UP, 1978. Fryer, Sarah Beebe. Fitzgerald's New Women: Harbingers of Change. Ann Arbor, MI: UMI Research P, 1988. McAdams, Tony. â€Å"Ethics in Gatsby: An Examination of American Values.† In Readings on The Great Gatsby. edited by Katie de Koster. San Diego, California: Greenhaven Press. 1998. 111-120. Social Status and Feminism in The Great Gatsby Essay -- Feminism Femin F. Scott Fitzgerald's novel, The Great Gatsby may appear to be a simple tragic romance; however, within the text, Fitzgerald identifies and defines social gaps and importance of wealth. He also presents women within a very separate space as the men. The Great Gatsby allows the reader to enter into the world of wealth and experience the joys and tragedies of being within this certain class as well as allowing the reader to interpret the position of gender inside the class. "Whenever you feel like criticizing anyone,' he [my father] told me, "just remember that all the people in this world haven't had the advantages that you've had" (Gatsby 1). This quote was possibly the backbone of the narrator's actions and character. Through out the novel, the characters that he came into contact with were immediately associated with their money and their association with their given level of wealth. The irony of this opening line is that the poor, or less wealthy, were never really even seen by the narrator. The only people that the narrator saw, according to the reader, are the more wealthy and upper class that were associated with Gatsby's parties. What is even more ironic than the overall absence of the lower classes within the novel is where this neglected level of wealth actually did become part of the novel. Ironically, the only character that lower wealth was associated with was Gatsby. In his past, he was of lower class, but in the actual time when the novel was written, Gatsby was not only representative of wealth, but he seemed to have had the most wealth of all the characters. He was the most prestigious when compared to all of the other characters, yet was the only to have the absence of money in his past. The quote in the p... ...lar practices and thoughts, or he completely redefined them. By doing so, the novel takes on a new identity separate from its tragic romantic cover. Social status and feminism tower over the lost and found love that encompasses this novel.    Works Cited and Consulted: Bewley, Marius. â€Å"Scott Fitzgerald’s Criticism of America.† In Modern Critical Interpretations: The Great Gatsby. edited by Harold Bloom. New York: Chelsea House Publishers. 1986. 11-27. Fetterley, Judith. The Resisting Reader: A Feminist Approach to American Fiction. Bloomington: Indiana UP, 1978. Fryer, Sarah Beebe. Fitzgerald's New Women: Harbingers of Change. Ann Arbor, MI: UMI Research P, 1988. McAdams, Tony. â€Å"Ethics in Gatsby: An Examination of American Values.† In Readings on The Great Gatsby. edited by Katie de Koster. San Diego, California: Greenhaven Press. 1998. 111-120.

Succubus Blues CHAPTER 26

â€Å"Why so blue, Kincaid?† I looked up from the information desk's computer screen to see Doug leaning lazily over the counter's edge. â€Å"Am I?† â€Å"Sure. You have the saddest look on your face I've ever seen. It's breaking my heart.† â€Å"Oh. Sorry. Just tired, I guess.† â€Å"Well, then, get out of here. Your shift's over.† Glancing down, I read the time on the computer. Five-oh-seven. â€Å"I guess it is.† He eyed me askance as I rose listlessly from the chair and made my way out from behind the desk. â€Å"You sure you're okay?† â€Å"Yeah. Like I said, just tired. I'll see you around.† I started to walk away. â€Å"Oh, hey, Kincaid?† â€Å"Yeah?† â€Å"You're friendly with Mortensen, aren't you?† â€Å"Sort of,† I conceded cautiously. â€Å"Do you know what happened to him? He used to be here, like, every day, and now he's been gone all week. It's freaking Paige out. She thinks we offended him or something. â€Å" â€Å"I don't know. We're not that friendly. Sorry.† I shrugged. â€Å"Maybe he's sick. Or out of town.† â€Å"Maybe.† I left the store, stepping out into the dark autumn evening. Friday in Queen Anne brought people in droves, drawn by the area's assortment of activities and nightlife. Ignoring them, lost in my own thoughts, I walked over to my car, parked a block away. Immediately, a vulture in a red Honda slowed down and put her signal on, realizing my spot was about to be vacated. â€Å"You ready for this?† Carter asked me, materializing in the passenger seat. I fastened my seatbelt. â€Å"Ready as I'll ever be.† We drove up to the University District in silence, a hundred questions on my mind. Since removing Seth from my apartment last week, the angel had told me not to worry, that he would see to the writer's recovery. I'd still worried anyway, of course, about both Seth and the deal I'd made with Jerome. I was about to become the single greatest source of chaos and temptation in Seattle; even Hugh's stellar track record wouldn't look so good†¦ er, bad, anymore. I would be more than the slave Helena had claimed I was. The very thought made me ill. â€Å"I'll be with you,† Carter told me soothingly as we approached Seth's door minutes later. The angel flickered briefly in my vision, and I realized he'd gone invisible to mortal eyes, though not to mine. â€Å"What does he know?† â€Å"Not much. He's been awake more and more these last couple of days, and I've told him a little, but really†¦ I think he's been waiting for you.† Sighing, I nodded and stared at the door. Suddenly I felt unable to move. â€Å"You can do this,† Carter said gently. Nodding again, I turned the door handle and stepped inside. Seth's condo looked much the same as when I'd last been here, the kitchen still bright and cheery, the living room lined with boxes of unpacked books. Faint music drifted from the bedroom. I thought it was U2, but I didn't recognize the song. Moving toward the sounds, I reached Seth's bedroom, pausing in the doorway, afraid to cross the threshold. He was in bed, half sitting up, propped up by pillows. In his hands he held The Green Fairy Book, looking to be about a third of the way through it. He looked up at my approach, and I nearly sagged in relief to see how much better he looked. His color was back, his eyes bright and alert. Only that facial hair looked ragged and unkempt, the result of no shaving for a week, I guessed. That answered my question about whether or not Seth had maintained the thin, neat beard on purpose. He reached for a remote on the bedside table and turned the music off. â€Å"Hey.† â€Å"Hey.† I took a few more steps into the room, afraid to get any closer. â€Å"Do you want to sit?† he asked. â€Å"Sure.† Cady and O'Neill's faces scrutinized me from the bulletin board as I brought a chair alongside Seth. I sat down, looked at him, and then looked away, unable to handle the depth of those amber-brown eyes after seeing into his mind. Our old silence fell between us, the progress we'd made in conversation banished to the winds. Seth would not take the lead this time. As Carter had observed, the writer was waiting for me. I looked back up, forcing myself to meet his eyes. I had to do this. I had to do the explaining here, but I balked at it. It was ironic, I thought. Me, who half the time didn't know when to shut up. Me, famed for always having some catchy quip at the ready. Knowing it would never get any easier, I took a deep breath and let it all out, conscious of the weight of heaven at my back and the hell I'd just consented to stretching out before me. â€Å"The truth is†¦ the truth is, I don't really work in a bookstore. I mean, I do, but that's not really why I'm here, what my purpose is. The truth is that I'm a succubus, and I know you've probably heard of us before – or think you've heard of us before, but I doubt what you've heard is correct†¦Ã¢â‚¬  On I went. I told him. I told him everything. The rules of the succubus lifestyle, my dissatisfaction with it, why I wouldn't date people I liked. I told him about other immortals, angels and demons walking among us. I even explained about nephilim, hinting that Roman's presence in my apartment had been part of a lure on my part, but mostly skimming over the embarrassing circumstances Seth had found us in. On and on, I talked, not even knowing what I said half the time. I only knew I had to keep talking, keep trying to explain to Seth that which defied explanation. I finally reached the end, my stream of discourse exhausted. â€Å"So. So, I guess that's it. You can believe it or not, but the forces of good and evil – as humans perceive them, at least – are alive and well in the world, and I'm one of them. This city is filled with supernatural agents and entities; humans just don't realize it. It's probably just as well, really. Otherwise, if they knew too much about us, they might find out how pathetic and fucked up our lives actually are.† I shut up, thinking if Seth hadn't seen what he had already seen, he probably would have thought I was crazy. Hell, even after it all, he still probably thought I was crazy. He would be justified. Those brown eyes weighed me and my words in silence, and an annoying wetness welled up in my own eyes. I looked away to hide it, blinking rapidly, because while succubi might be accused of doing all sorts of bizarre things around mortal men, I was pretty sure crying wasn't one of them. â€Å"You said†¦ you said you used to be human.† He spoke the words awkwardly, no doubt trying to grasp the whole concept of mortal and immortal. â€Å"How then†¦ how did you become a succubus?† I looked back up at him. I could refuse him nothing in that moment, no matter how painful. â€Å"I made a bargain. I told you before that I was married†¦ that I had cheated on my husband. The consequences of that were†¦ not pleasant. I traded away my life – becoming a succubus – in order to repair the damage I had caused.† â€Å"You gave away eternity to fix one mistake?† Seth frowned. â€Å"That doesn't seem equitable.† I shrugged, highly uncomfortable with the topic. I had never spoken of it to anyone. â€Å"I don't know. It's done.† â€Å"Okay.† He shifted slightly in bed, the soft swishing of fabric the only sound between us. â€Å"Well. Thanks for telling me.† I recognized a dismissal when I heard one, and it dug into me like a blade. That was it. Done. Seth was through with me. We were finished. After everything I had told him, there was no way things could return to how they'd been, but really, wasn't that for the best? I hurriedly stood up, suddenly not wanting to be there any longer. â€Å"Yeah. Okay.† I moved toward the door, suddenly pausing to look back at him. â€Å"Seth?† â€Å"Yeah?† â€Å"Do you understand? Why I do what I do? Why we can't – why we have to – † I couldn't finish the thought. â€Å"It's impossible. I wish it were different†¦Ã¢â‚¬  â€Å"Yeah,† he said quietly. Turning, I fled his condo for my car. When I got into it, I buried my face into the steering wheel, sobbing uncontrollably. After a few minutes, gentle arms wrapped around me, and I turned toward Carter, crying into his chest. I'd heard reports of people who had angelic encounters, witnesses talking about the peace and beauty experienced by such moments. I'd never given any of it much thought, but as minutes passed, the terrible pain in my chest abated, and I grew calmer, finally lifting my head up to look at the angel. â€Å"He hates me,† I choked out. â€Å"Seth hates me now.† â€Å"Why do you say that?† â€Å"After everything I just told him†¦Ã¢â‚¬  â€Å"I suspect he's troubled and confused, yes, but I don't think he hates you. Love like that doesn't turn to hate quite so easily, though I'll admit the two intertwine sometimes.† I sniffled. â€Å"Did you feel it? His love?† â€Å"Not like you did. I sensed it, though.† â€Å"I've never felt anything like it. I can't match that. I like him†¦ like him so much. Maybe I even love him too, but not in the same way he loves me. I'm not worthy of that love.† Carter made a soft, chastising click. â€Å"No one is beyond being loved.† â€Å"Not even someone who just agreed to spend the next century hurting humans, corrupting souls, and leading them to temptation and despair? You must hate me for that. Even I hate me for that.† The angel watched me, expression steady and calm. â€Å"Why did you agree then?† I leaned my head back against the seat. â€Å"Because I couldn't stand the thought of me†¦ of that love being wiped out of his head†¦ of not being remembered.† â€Å"Ironic, huh?† I turned toward him, hardly surprised at anything anymore. â€Å"How much do you know about me?† â€Å"Enough. I know what you got for becoming a succubus.† â€Å"I thought it was the right thing then†¦Ã¢â‚¬  I murmured, my mind's eye turning to a faraway time and place, another man. â€Å"He was so sad and so angry at me†¦ he couldn't go on, knowing what I'd done. I just wanted to be blotted from his mind forever. I thought it would be better if he – if everyone – forgot about me. Forgot I'd ever existed.† â€Å"And now you don't agree?† I shook my head. â€Å"I saw him†¦ years later, when he was an old man. I shape-shifted to the form he'd known me in – that was the last time I've worn that face, actually – and approached him. He looked right past me, though. Didn't know me at all. The time we'd had together. The love he'd had for me. All gone. Gone forever. It killed me. I felt like one of the walking dead after that. â€Å"I couldn't let that happen. Not again. Not with Seth, after experiencing what he felt for me. Even if that love is ruined†¦ marred by what he thinks of me now. Even if he never speaks to me again. It's still better than that love never having existed at all.† â€Å"Love is rarely flawless,† Carter pointed out. â€Å"Humans delude themselves by thinking it has to be. It is the imperfection that makes love perfect.† â€Å"No riddles, please,† I told him, suddenly feeling tired. â€Å"I just lost the one person I might have loved again after all these years. Really, truly loved too. Not just pure excitement either, like with Roman. Seth†¦ Seth had it all. Passion. Commitment. Friendship. â€Å"Not only that, but I've agreed to go on ‘active duty' again as a succubus.† I closed my eyes, swallowing the bile in my throat. I thought of all the nice guys in the world, men like Doug and Bruce. I did not want to be their downfall. â€Å"I really do hate it, Carter. You have no idea how much I hate it, no idea how much I don't want to do this anymore. But it's worth it. Worth it if Seth can keep his memories.† I looked over at the angel uncertainly. â€Å"He can, can't he?† Carter nodded, and I exhaled with relief. â€Å"Good. At least there's one spot of hope in all of this.† â€Å"Of course there is. There's always hope.† â€Å"Not for me.† â€Å"There's always hope,† he repeated more firmly, a commanding note in his voice that startled me. â€Å"No one is beyond hope.† I could feel tears coming to my eyes again. Lord. I seemed to be crying all the time lately. â€Å"What about a succubus?† â€Å"Especially a succubus.† He put his arms around me again, and I gave way to my sobs once more, a damned soul taking momentary respite in the embrace of a heavenly creature. I wondered if what he said was true, if it was possible that there was still hope for me, but then I remembered something that made me half laugh and half choke all at once. Angels never lied.

Assess the Significance of the Role of Individuals in Reducing Racial Discrimination in the Period 1877-1981

Assess the significance of the role of individuals in reducing racial discrimination in the period 1877-1981. The post-civil war era of American history could be argued as one with great promise for African Americans. With the North winning the Civil War and Lincoln granting the Emancipation Proclamation in 1863, surely the seeds had been sown for equality for all in America; blacks and whites included?Despite the foundations having been laid for equality, it may not be surprising that only small progress was made when Lincoln- the â€Å"saviour† of Blacks- had little interest in abolishing slavery in the first place; â€Å"if I could save the Union without freeing any slave, I would do it†. However, it cannot be disputed that, whatever his intentions had been, Lincoln's Emancipation Proclamation did provide just a glimpse of hope for African Americans; De Jure, the African Americans throughout America had freedom and were able to leave the slavery of Southern plantatio n owners.Why is it then, that De Facto, the years following the Civil War failed to provide this ‘new hope' for Blacks and that racism & discrimination continued for many years to come? The idea of Blacks developing the mind set they needed in order to fight for their freedom can be categorised as their ‘developing consciousness'. Throughout the 19th and 20th century, it was evident that Blacks had begun to realise that they too had rights and were entitled to the same as the Whites.Through the work of organisations such as the NAACP (National Association for the Advancement of Coloured People) and the Harlem Renaissance as well as individuals such as William Edward Burghardt (W. E. B) Du Bois; Blacks in American began developing their identity as a group and using this to fight back against the oppression of Whites. Du Bois was known as a vocal critic of Booker T Washington, being an educated Black- graduating from Fisk University in 1885 and studying history at Harvard University- he became the first African-American to receive a Ph.D. From Harvard. In order to develop Black Consciousness, Du Bois joined forces with the like minded activists of the NAACP. The NAACP's main focal points were: The abolition of segregation; equal voting rights; educational opportunities for black people; the enforcement of the Fourteenth and Fifteenth Amendments. Despite the main focuses of the NAACPs campaigns, it could be argued that the main thing they did for the progress of Black Equality was the uniting of Blacks under one force; by 1918 there were around 43,994 members in the NAACP.This gathering of Blacks under one organisation cannot be ignored, for the first time the African-Americans of America were joining together in order to fight for their freedom. One key event which argues against the idea that individuals were significant in reducing racial discrimination is that of WWI; argued by Sander's- â€Å"The First World War generated jobs and gave blacks s oldiers a glimpse of greater equality†. The treatment of Blacks abroad- particularly France- showed the African-Americans that the treatment they were receiving at home was unfair and that they were indeed in a situation which needed to change.It is a hard task indeed to decide whether or Black Consciousness increased due to the work solely of individuals such as Du Bois, organisations like the NAACP or events like WWI. Many would argue that it was not a single one of these factors which led to the increase of Black's realisation of potential. One argument however is that surely without individuals behind the organisations, the work and impact of the organisation is nothing? Individuals are able to lead, organise and even inspire; something that events and organisations are unable to do.The process of increased black nationalism is certainly one which cannot be overlooked; indeed it may not have achieved solid changes in law, and some go as far to say that it may have even hin dered the advancement of Black Civil Rights. Despite this one could argue that the development of black nationalism catalysed the civil rights movement for many African Americans; installing a sense of pride inside the hearts of many which was drastically needed at the time. Before trying to pin any credible progress on the black nationalism movement it is first important to attempt to define ‘Black Nationalism'.A simple definition of it would be that it was an ideology which stresses the desire for separatism of the black race; â€Å"unity as a people, pride in African heritage, the creation of autonomous institutions and the search for a territory to build a nation† (Cone, 1991, 122). However the ideology of black nationalists varies greatly between individuals; a perfect example of this is Malcolm X and Martin Luther King. The two vary drastically between their methods in raising black nationalism.The methods and effectiveness of Malcolm X's campaign for the improved lives of black Americans are up for questioning by many. Indeed his tactics were more radicalised than his non-violent counterpart Dr King: Malcolm X even stated in Washington, 1964 that â€Å"I'm here to remind the white man of the alternative to Dr King†. This statement could be seen to sum up the purpose of Malcolm X; due to the lack of credible change attached to him, one has to question whether his purpose was merely just to show what could happen (increased radicalisation and violence) if the demands of Dr King were not met.This lack of credible, positive actions and change by Malcolm X and his current organisation the Nation Of Islam is an idea which can be- and has been- argued in depth. One could argue that, in terms of De Jure, Malcolm X did not achieve anything significant and indeed many considered him to be irresponsible and negative; Thurgood Marshall even went as far as to say that the NOI was â€Å"run by a bunch of thugs†. Despite this, De Facto, one cannot simply ignore the fact that Malcolm X did indeed draw early attention to the awful conditions in the ghettos and according to the FBI, he was â€Å"The most successful recruiter for the Black Muslims†.This can be credited to Malcolm X being a Zeitgeist; he was able to tap into the spirit of the time and the feelings of the people, using this to draw the huge amounts of support he did for the Nation of Islam. Indeed it may be seen that a radical, passionate individual like Malcolm X was needed at that specific time for the black nationalism movement; it cannot be ignored that Martin Luther King was not at his most successful stage and the fire of black civil rights and nationalism which had been burning brightly was indeed beginning to burn dimmer or some might even say had gone out at the time.After looking at the impact in which individuals had on the civil rights movement and the contrast of events, one can still come back to the fundamentals of the debate; without a n individual to start an organisation or instigate an event surely no progress at all would have been made? If one is able to look at the larger picture of the progress made in reducing racial discrimination in the years Assess the Significance of the Role of Individuals in Reducing Racial Discrimination in the Period 1877-1981 Assess the significance of the role of individuals in reducing racial discrimination in the period 1877-1981. The post-civil war era of American history could be argued as one with great promise for African Americans. With the North winning the Civil War and Lincoln granting the Emancipation Proclamation in 1863, surely the seeds had been sown for equality for all in America; blacks and whites included?Despite the foundations having been laid for equality, it may not be surprising that only small progress was made when Lincoln- the â€Å"saviour† of Blacks- had little interest in abolishing slavery in the first place; â€Å"if I could save the Union without freeing any slave, I would do it†. However, it cannot be disputed that, whatever his intentions had been, Lincoln's Emancipation Proclamation did provide just a glimpse of hope for African Americans; De Jure, the African Americans throughout America had freedom and were able to leave the slavery of Southern plantatio n owners.Why is it then, that De Facto, the years following the Civil War failed to provide this ‘new hope' for Blacks and that racism & discrimination continued for many years to come? The idea of Blacks developing the mind set they needed in order to fight for their freedom can be categorised as their ‘developing consciousness'. Throughout the 19th and 20th century, it was evident that Blacks had begun to realise that they too had rights and were entitled to the same as the Whites.Through the work of organisations such as the NAACP (National Association for the Advancement of Coloured People) and the Harlem Renaissance as well as individuals such as William Edward Burghardt (W. E. B) Du Bois; Blacks in American began developing their identity as a group and using this to fight back against the oppression of Whites. Du Bois was known as a vocal critic of Booker T Washington, being an educated Black- graduating from Fisk University in 1885 and studying history at Harvard University- he became the first African-American to receive a Ph.D. From Harvard. In order to develop Black Consciousness, Du Bois joined forces with the like minded activists of the NAACP. The NAACP's main focal points were: The abolition of segregation; equal voting rights; educational opportunities for black people; the enforcement of the Fourteenth and Fifteenth Amendments. Despite the main focuses of the NAACPs campaigns, it could be argued that the main thing they did for the progress of Black Equality was the uniting of Blacks under one force; by 1918 there were around 43,994 members in the NAACP.This gathering of Blacks under one organisation cannot be ignored, for the first time the African-Americans of America were joining together in order to fight for their freedom. One key event which argues against the idea that individuals were significant in reducing racial discrimination is that of WWI; argued by Sander's- â€Å"The First World War generated jobs and gave blacks s oldiers a glimpse of greater equality†. The treatment of Blacks abroad- particularly France- showed the African-Americans that the treatment they were receiving at home was unfair and that they were indeed in a situation which needed to change.It is a hard task indeed to decide whether or Black Consciousness increased due to the work solely of individuals such as Du Bois, organisations like the NAACP or events like WWI. Many would argue that it was not a single one of these factors which led to the increase of Black's realisation of potential. One argument however is that surely without individuals behind the organisations, the work and impact of the organisation is nothing? Individuals are able to lead, organise and even inspire; something that events and organisations are unable to do.The process of increased black nationalism is certainly one which cannot be overlooked; indeed it may not have achieved solid changes in law, and some go as far to say that it may have even hin dered the advancement of Black Civil Rights. Despite this one could argue that the development of black nationalism catalysed the civil rights movement for many African Americans; installing a sense of pride inside the hearts of many which was drastically needed at the time. Before trying to pin any credible progress on the black nationalism movement it is first important to attempt to define ‘Black Nationalism'.A simple definition of it would be that it was an ideology which stresses the desire for separatism of the black race; â€Å"unity as a people, pride in African heritage, the creation of autonomous institutions and the search for a territory to build a nation† (Cone, 1991, 122). However the ideology of black nationalists varies greatly between individuals; a perfect example of this is Malcolm X and Martin Luther King. The two vary drastically between their methods in raising black nationalism.The methods and effectiveness of Malcolm X's campaign for the improved lives of black Americans are up for questioning by many. Indeed his tactics were more radicalised than his non-violent counterpart Dr King: Malcolm X even stated in Washington, 1964 that â€Å"I'm here to remind the white man of the alternative to Dr King†. This statement could be seen to sum up the purpose of Malcolm X; due to the lack of credible change attached to him, one has to question whether his purpose was merely just to show what could happen (increased radicalisation and violence) if the demands of Dr King were not met.This lack of credible, positive actions and change by Malcolm X and his current organisation the Nation Of Islam is an idea which can be- and has been- argued in depth. One could argue that, in terms of De Jure, Malcolm X did not achieve anything significant and indeed many considered him to be irresponsible and negative; Thurgood Marshall even went as far as to say that the NOI was â€Å"run by a bunch of thugs†. Despite this, De Facto, one cannot simply ignore the fact that Malcolm X did indeed draw early attention to the awful conditions in the ghettos and according to the FBI, he was â€Å"The most successful recruiter for the Black Muslims†.This can be credited to Malcolm X being a Zeitgeist; he was able to tap into the spirit of the time and the feelings of the people, using this to draw the huge amounts of support he did for the Nation of Islam. Indeed it may be seen that a radical, passionate individual like Malcolm X was needed at that specific time for the black nationalism movement; it cannot be ignored that Martin Luther King was not at his most successful stage and the fire of black civil rights and nationalism which had been burning brightly was indeed beginning to burn dimmer or some might even say had gone out at the time.After looking at the impact in which individuals had on the civil rights movement and the contrast of events, one can still come back to the fundamentals of the debate; without a n individual to start an organisation or instigate an event surely no progress at all would have been made? If one is able to look at the larger picture of the progress made in reducing racial discrimination in the years