Family Law Essay Example | Topics and Well Written Essays - 1000 words - 2

Family Law - Essay Example Thus, the clause most applicable in this case is one of â€Å"unreasonable behaviour† on part of James. (Family Law Act 1996) It is important to note that the reason for divorce has very little bearing on how the court decides the award of maintenance amount, property ownership/share, etc (Cook 2006). Similarly, decisions regarding the children are made independent of property issues and spouse maintenance issues. Even though the Victorian house is inherited by James, there is no guarantee that he will retain his complete ownership of the house after divorce. Though Susan has not contributed financially to the home or the bills during the marriage, she still has a right to make a claim, for she has â€Å"contributed in kind†. Her complete care for the children allowed James to concentrate on his career. Thus, Susan has a â€Å"beneficial interest† on the property and the court will consider the house as â€Å"Matrimonial Property† (www.dca.gov.uk). The court even has the power to transfer ownership, if need be. Before deciding on how to share the property, the court will take into account the length of the marriage, the parties’ age, their lifestyle needs, their earning capacity and the children’s needs. (Family Law Act 1996) Essentially, when a couple seek divorce, a court can, and quite often does, divide up the matrimonial assets, his, hers and theirs, in any way it sees fit. The resolution of financial disputes in a divorce case is also known as â€Å"ancillary relief†. Regardless of who owns the property, the court may have it transferred to the other and this applies to all property owned either by James or Susan as well as the jointly owned ones. (Watson-Lee 2006) Ownership and Tenancy are two different things. Susan had indicated her wish to continue living in the house along with the children. Susan is being reasonable in making this claim. Given the previous case histories of divorce cases, it could be

A Short story Essay Example | Topics and Well Written Essays - 1250 words

A Short story - Essay Example Based on his dad interest in driving and education, Tom used to be driven to the school every day in the morning and in the evening. His father, though a good driver who emulated the road signs and rules was a tough driver who drove with a high speed unless there was a traffic jam. During his trip to the school, Tom used to ask his father many questions as to why he was driving in that high speed and go between cars yet the car was not involved in an accident. His father did not lie to him but informed Tom that diligent and confident is the major aspect that a good driver is supposed to follow. This made Tom to have an interest in driving. Tom’s dad was a person who wanted his children to develop their career at their early ages. During the holidays, Tom used most of his free time driving with James, his father. In this way, Tom closely interacted with his father and he was in a better position to ask all the disturbing questions that he was asking as they were driving to and from the school. His father on the other hand, allowed Tom to drive in flat areas where there were no cars in order to avoid accidents. Most notably, the father taught Tom on all the aspects of driving including the physical parts of a motor vehicle and the road signs. When being taught by his father Tom used to disturb him with all sought of questions. Being eager to know how to drive and become an excellent driver, Tom loved the way his father drove the family and this inspired him. Whenever the car could get a puncture, James would repair the puncture and the journey would continue without delay. The basic mechanic process that Tom†™s dad used to undertake any time the car experienced problems inspired Tom since he would look at his father going down the car and try to make things work in the right manner. Though Tom’s dad used to allow Tom to drive in lowlands and where their were no vehicles, his father one day as they were driving from school 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 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

William Shakespeare, :: essays research papers

William Shakespeare, April 23 of 1564 the beginning to the path of great literature and performance, the birth of William Shakespeare, whose creations have affected everyone for generations. |He was born and raised in Stratford-upon-Avon. William was the third child out of eight from John and Mary Shakespeare. The names of the other seven children are Joan, Margaret, Gilbert, Joan, Ann, Richard and Edmund. William’s grandfather, Richard Shakespeare was a whittawer and a dealer in agricultural commodities. Richard died 52 days after the birth of William.   Ã‚  Ã‚  Ã‚  Ã‚  William attended the Stratford Grammar School. Even though the record-of- attendance have been lost it is no doubt that he truly attended the school, since the school was built and maintained expressly for the purpose of education the sons of prominent citizens. Because William attended church, the other obvious education is the exposer to either the Geneva Bible or the Bishops’ Bible or King James. It also brings him to the influence of The Book of Common Prayer. No one knows exactly how long William remained at the Stratford Grammar School but it is believed that an assistant of John Shakespeare forced him to withdraw William from thence. His later education must be the ways of business he would have learned around his father’s shop. Spectators said they have seen William give speeches to the calf before slaughtering them for his father’s leather work.   Ã‚  Ã‚  Ã‚  Ã‚  William married Ann Hathwey in 1582. She was also from Stratford where William was born. Even though she was eight years older than he, their marriage was a success. Ann was three months in pregnancy when they were wed. Their first born Susanna was born in May 26, 1583. After that they had twins named after life time friends, Hamnet and Judeth Sadler. There wasn’t much talk from William about his marriage except some of his literature showed apparent resemblance of him and his wife. It seemed he was regarding him and his wife in some plays.   Ã‚  Ã‚  Ã‚  Ã‚  There were no records of Shakespeare’s activities after the birth of his twins. We called it the lost years. It was believed that at those periods he was on refuge from a sort of crime. There wasn’t any hard evidence on his activities but there were many theories to fill in the time of activity.   Ã‚  Ã‚  Ã‚  Ã‚  The mark of William Shakespeare’s rise in London theater world in 1592 on a famous literary by Robert Greene which clearly refers to William Shakespeare.

Anorexia VS. Bulimia Essay

The amount of pressure for an adolescence to be skinny these days, is outrageous. Most eating disorders, like anorexia and bulimia, are onset between mid to late adolescence. 0. 5 percent of womben suffer from anorexia, and one to three percent from bulimia. These are both serious psychiatric disorders that are mistaken for one another all the time. Admittedly, they do have many similarities, but very distinct differences. Anorexia and bulimia show many similar symptoms, which is one reason they get mistaken so often. Some of the symptoms are weakness and dizziness, tooth decay, obsession over food, constipation, irregular heartbeat, and swelling of the hands, feet, arms, and legs. One of the most distinct differences is that bulimia is categorized as a complex emotional issue, while anorexia is a combination of biological, psychiatric, and environmental issues. Although both are worried about their weight, they approach food situations very differently. Physical signs of bulimia are harder to recognize, unless on a very personal level. Usually, there are no obvious signs of weight loss. This is because during an average eating binge, one may consume from three thousand to five thousand calories in an hour. Afterwards one feels a great since of guilt, making the decision to purge to make themselves feel better. What one doesn’t realize is, vomiting after a meal will only eliminate fifty percent of the calories ingested. Resulting in that person staying at a normal weight. However, the physical signs of anorexia are much more obvious. This is a disorder that causes people to obsess about their weight and the food they eat. They will pretend to eat or lie about how much food they’ve actually ate. They will attempt to maintain a weight that is far below normal, starve themselves and exercise excessively. The thoughts of dieting, food, and their body take up most of their day. Resulting in rapid weight loss. For a person that suffers with bulimia overeating is more like a compulsion. A person begins to feel increasingly out of control. Although they may try, it is difficult to regain control without help. Anorexia, on the other hand, makes a person feel in control, over atleast one aspect in their life. When a person suffers with anorexia they may lose the ability to see their true self. This means that, no matter how skinny a person gets, it’s never enough to them. They developed strange or secretive food rituials and become very fixated with their body image, to the point that it causes major health risks. POWERED BY TCPDF (WWW. TCPDF. ORG).

Do the Writings of Clausewitz have contemporary relevance? Essay

Carl Von Clausewitz has long been considered one of the most important writers in the field of military strategy and tactics. Born in 1780 he first saw action in 1793 when he was a Lance Corporal in the Prussian Army.1 He was to serve throughout the Napoleonic wars working for both the Prussians and the Russians. However: â€Å"throughout his military career he never held a command and was probably unsuited for such. He was essentially a student of war†¦Ã¢â‚¬ 2 However, despite this lack of command, Clausewitz had certainly gained enough experience during the Napoleonic wars to have a fairly comprehensive idea about what war was: â€Å"Before he was forty, he had taken part in some of the greatest battles in the history of warfare and had seen the armies of Napoleon storm their way across Europe to Moscow†¦ Alls this had been the result of military operations, but it was clear to Clausewitz as a young man that the explanation for the success or failure of these operations was not to be sought on the battlefield alone†.3 As a result of this, during his career he came up with many ideas of views on the nature and conduct of war, writing literally thousands of pages of manuscripts on a wide range of areas ranging from politics to tactics.4 After the wars end, he set about trying to write a comprehensive eight part ‘guide’ on his ideas. This collection of essays and manuscripts became known as â€Å"Vom Kriege† (On War). Clausewitz died in 1831 having only completed six of the eight parts.5 Indeed it is important to realise that despite the importance of his work, it is still unfinished and does not cover a number of areas: â€Å"On War contains a comprehensive analysis of the strategy operations and tactics of Napoleonic War, and of their 18th Century background. Left out of the account are most technological, administrative and organisational factors†¦ On War deals almost entirely with the ultimate issues as Clausewitz saw them: Political and strategic planning and the conduct of hostilities†6 Since his death, Clausewitz’s work has come to be regarded as probably one of the most important works on military thinking ever written. Bernard Brodie once wrote that: â€Å"His is not simply the greatest, but the only great book about war†7 Although Clausewitz is still seen as one of the greatest thinkers on war, the question remains – is he still relevant today? Given the immense changes in not only the way we conduct war, but also our attitudes towards war, does his thinking still have any relevance in an era of information warfare and peacekeeping missions? Also given the dramatic changes in the conduct of warfare are his works still important: â€Å"As one US army general has (said) â€Å"the digitisation of the battlefield means the end of Clausewitz†8 Given the large size of Clausewitz’s work it is impossible look at the whole of On War for its continuing relevance. Instead for this essay I have chosen to examine a number of ideas in detail including the idea of war as part of policy, the notion of decisive battle and also his idea of a ‘centre of gravity’. Due to lack of space I have decided not focus on other areas such as the trinity between the politicians, the people and the armed forces, as well as looking at other areas. At it’s simplest Clausewitz’s first book attempts to understand what war actually is and what it does. At it’s simplest he defined it as: â€Å"War is an act of force to compel an enemy to do our will†9 This seems to be true, even today it is hard to imagine a nation state going to war without a rational reason to do so – be it to regain territory or to right a wrong. More recently the growth of Peace enforcement operations such as the war in Kosovo is a classic example of forcing a nation state to bow to the will of others. As such it seems that Clausewitz’s most simple definition still rings true today Clausewitz’s next statement is far more controversial though: â€Å"Kind hearted people might of course think there was some ingenious way to disarm or defeat an enemy without too much bloodshed, and might imagine this is the true goal of the art of war. Pleasant as it sounds, it is a fallacy that must be exposed: War is such a dangerous business that the mistakes which come from kindness are the very worst†10 The above paragraph seems to be aimed at those who have studied the writings of Sun Tzu – the Chinese strategist to which Clausewitz is frequently compared. Sun Tzu felt that war was not about bloodshed – instead he felt that: â€Å"all warfare is based on deception†¦Ã¢â‚¬ 11 Michael Handle wrote that â€Å"Sun Tzu devotes considerable attention to the actions that precede war†¦ for him diplomacy is the best means of achieving his ideal of victory without fighting or bloodshed†.12 It seems that Sun Tzu’s theory of warfare is based more on the notion of avoidance of war rather than the fighting of war itself, whereas Clausewitz feels that war occurs once all other policy choices have been exhausted: â€Å"War is merely the continuation of policy by other means†13 This seems to suggest that in Clausewitz’s mind, War should be seen as merely as a logical progression in policy once other policies such as diplomacy have failed – essentially war is pursued in order to further a States national interest. However some question whether this is still the case: â€Å"Future war will be fought not to pursue national interests, but to kill enemy leaders, to convert opponents to one’s religion, to obtain booty, or sometimes for simple entertainment. Thus the core of Clausewitz’s .philosophy of war – that states wage war using armies in pursuit of political objectives will disappear. Others have maintained that nuclear weaponry, trans-national constabulary warfare, counter-terrorism, counter-narcotrafficking†¦ have rendered obsolete Clausewitz’s definition of war as an act of policy†.14 I believe though that his views are still relevant, in that once a war has begun it should be fought aggressively until its logical conclusion, however unlike in Clausewitz’s time, today the conditions required for victory may be very different and as such it may be harder to achieve a logical conclusion.15 Clausewitz seems more focussed on the idea that the only means of resolving a war is bloodshed (the so called idea of decisive battle) â€Å"The destruction of the enemies forces in war must always be the dominant consideration†16 While this may have been the ideal way of winning wars in the 19th Century it is arguable that in today’s world this view is obsolete for a variety of reasons. Firstly in the 19th Century the only real way of waging war was through lining up two opposing armies and fighting it out until one side one. This procedure was repeated until one country won the war. In today’s world the methods available to fight wars have changed – in place of armies, generals can use precision strikes with guided missiles fired from thousands of miles away to eliminate enemy units with minimal casualties. Special forces units can be used to eliminate key figures and deprive armies of leadership at critical times17. However the main reason why Clausewitz’s views of the objectives in warfare could be seen as obsolete is due to the changing nature of warfare itself. When On War was written, war was a two dimensional affair – fought primarily on land and sea.18 In 2001 though war can be fought on land, sea, air, space and also in cyberspace. In addition there are a wide variety of unconventional types of wars to be fought. As James Adams notes: â€Å"Today we are at war on several fronts. The fights against terrorism, organized crime, economic espionage and weapons proliferation are permanent conflicts that are likely to confront us through the next century†¦ In this new world the soldier will be the young geek in uniform who can insert a virus into Tehran’s electricity supply to plunge the city into darkness†19 There have been suggestions that since 1990 the world (or at least the West) has undergone a so called Revolution in Military Affairs – i.e. a total change in the way that war is fought. Given this, is the idea of decisive battle still relevant? Some institutions clearly feel that it is not – especially as the types of wars that will be fought are so different: â€Å"ironically the dominance that the US will gain from the RMA†¦ will be such that the nature of future conflict will force competitors to deliver asymmetric strategies, including weapons of mass destruction, to counter the US superiority.20 In these new types of conflicts, the search for Clausewitzian decisive victory will be far more elusive and far less relevant than in conventional conflicts†.21 Despite the above quote, I believe that the idea is still relevant – but that the methods that can be used to bring about a decisive victory have changed. As has been seen an enemy can be defeated without using conventional ground troops at all – instead a wide range of different assets could be used. Indeed one view of future warfare suggests that victory (but not necessarily destruction) over an enemy force could be achieved without the use of weapons: â€Å"First a computer virus is inserted into the aggressors telephone switching stations, bringing about a total failure of the phone system. Next computer logic bombs set to activate at certain times, destroy the electronic routers that control rail lines and military convoys†¦ meanwhile enemy field officers obey the orders they receive over the radios unaware that the commands are phoney†¦ US planes, specially outfitted for psychological operations, then jam the enemy’s TV broadcasts with propaganda messages that turn the populace against the ruler. When the despot boots up his PC, he finds that millions of dollars he has hoarded in his Swiss bank account have been zeroed out. Zapped. All without firing a shot†22 This example is quite interesting as it simultaneously supports the relevance of Clausewitz, while at the same time proving how his writings have become dated in places It supports the notion of decisive victory in that it shows how a country can conclusively defeat an enemy – thus supporting his idea of decisive victory. But at the same time it shows clearly that not all of Clausewitz is still relevant. For example Clausewitz seemed cynical about the idea of achieving victory without much (or any) violence: â€Å"How are we to counter the highly sophisticated theory that supposes it is possible for a particularly ingenious method of inflicting minor direct damage on the enemy’s forces to lead to major indirect destruction; or that claims to produce by means of limited but skilfully applied blows, such paralysis of the enemy’s forces and control of his willpower as to constitute a significant shortcut to victory†23 This argument clearly shows that not all of Clausewitz has aged well – obviously during the Napoleonic era the idea of information warfare did not exist – so it would have been next to impossible to win a war using non violent means – however as has been shown in this age it is at least technically possible to achieve such a victory. It suggests that some parts of Clausewitz’s work should perhaps be seen as less relevant to certain situations than others. One area which appears to still be relevant is Clausewitz’s comments on the application of force. In the West today public opinion seems to favour engagements with minimal casualties – the public seem to want intervention when scenes of suffering are on TV (the so called CNN effect), but at the same time seem unwilling to tolerate the idea of people dying to stop the suffering24. This is a situation where Clausewitz noted that: â€Å"If one side uses force without compunction, undeterred by the bloodshed it involves while the other side refrain, the first will gain the upper hand†.25 This idea seems to have been taken onboard by a number of third world leaders who have engaged in some form of conflict with Western Countries (primarily the USA). A good example of this is the conflicts in Somalia – when the USA sent in troops to help restore order to the country they were hampered by restrictive rules of engagement and limited amounts of equipment – for example tanks as these were felt inappropriate. 26On the other hand, the opposition led by self styled Warlord General Aideed had no such restrictions – and it showed – he was repeatedly able to gain the upper hand and when US/UN troops attempted to capture him he was able to ambush and kill literally dozens of them.27 The images of American bodies being abused were enough to force an immediate and humiliating withdrawal from Somalia – a classic Clausewitzian example of one side using force when the other was unwilling and gaining the advantage – in this case over the strongest power in the world. This lesson illustrates an area where Clausewitz’s views on war are still highly relevant – indeed it appears that other countries learnt from this experience – in Haiti for example when the US sent a landing ship into the country to enforce a UN brokered peace agreement in 1994 they were met by a bunch of thugs who: â€Å"shook their fists, waved placards and shouted threats at the US ship. They were hooligans who would have dispersed at the first sign of well armed troops. But among their slogans was one in particular â€Å"we are going to turn this place into another Somalia†. News of the ‘Welcome Party’ and its curses were flashed to Washington where it provoked a panic†¦. The Clinton administration immediately ordered the (USS) Harlan County to withdraw from Haitian waters and to sail back to the USA†28 Again this is another good example of how even the threat to employ violence against a country which is not prepared to do so can have a major influence out of all proportion to the size of the protestors. It also demonstrates the continuing influence of Clausewitzian ideas. The example used above of the American experience in Somalia and Haiti is also relevant to Clausewitz’s ideas on ‘The centre of gravity’ – an idea which Clausewitz defined as follows: â€Å"What the theorist has to say here is this: one must keep the dominant characteristics of both belligerents in mind. Out of those characteristics a certain centre of gravity develops, the hub of all power and movement on which everything depends. That is the point at which all our energies should be directed†29 Furthermore Clausewitz identified three key components of this idea: â€Å"The Opponents army, his capital and, if he had a stronger protector the army of his ally. Since all of these were vulnerable to attack, said Clausewitz, ‘the defeat and destruction of his fighting force remains the best way to begin, and will in any case be a very significant feature of the campaign'†30 A good example of this would be the case of the Royal Navy during the Falklands War – Argentina identified the carriers as the centre of gravity for the UK operation and spent a good deal of time trying to sink them. As the commander of the Task Force noted: â€Å"If they hit Hermes or Invincible the Royal Navy will somehow be publicly disgraced†¦Worse yet, the British military will become the laughing stock of the world, limping home in defeat. John Bull humbled at last. At sea.†31 Although Clausewitz did not write on maritime warfare this is a clear example of how important the destruction of a naval fighting component can be to the success of a war. Other good examples of a country identifying and targeting the centre of gravity include Iraq’s use of Scud missiles against Israel during the Gulf war – had Israel responded militarily then it is likely that the coalition against Iraq would have collapsed as it seems doubtful that Arab powers such as Egypt and Syria would willingly fight on the same side as Israel. This supports Clausewitz’s ideas of attacking the armies (or at least cities) of allies to win the war. 32 For the coalition however attacking and destroying the Iraqi army (primarily the Republican Guard) was of vital importance – not only as knocking it out would win the war – but also destroying the Republican Guard would remove Saddam Hussein’s power base and hopefully make it impossible for him to remain as leader of Iraq. The Gulf War is a good example then of Clausewitz’s ideas continuing to be highly relevant to the planning of a military campaign. However some commentators (QUOTE!!) feel that the Gulf War was probably the last large conventional war to be fought by the West and that the nature of war in the future has changed. I believe then that the centre of gravity idea is still highly relevant – however I feel that it has become more refined since Clausewitz’s time. Although Clausewitz feels that there are only three key areas to which it applies, I feel that today the centre of gravity can be practically anything. For example in Somalia and Haiti – the use of force and the threat to use force proved the Americans centre – when faced with even the possibility of casualties, the Americans withdrew. This suggests that today the centre of gravity can be anything from a capital city to a single infantryman – who if killed could cause a change in policy. Another change is that Clausewitz assumed that the centre of gravity would be identical for both sides – whereas today that is not the case – a good example is that of the asymmetric warfare that is being waged between the USA and the terrorist Osama Bin Laden – he recognised the Pentagon and World Trade Centre as key examples of American power and prestige and saw them as their centre of gravity in any terrorist action. The Americans on the other hand see Bin Laden as the key centre of gravity – The most powerful country on earth is fighting a war, with a single man as their key target. This is a dramatic change from the days of mass warfare which Clausewitz was used to, and demonstrates not only the rapidly changing nature of warfare, but also illustrates the way that Clausewitz’s ideas can continue to be adapted to look at warfare in the present day. During this essay I have looked at a number of Clausewitz’s ideas in an attempt to see whether they have continuing relevance in a world where warfare is very different from the time when On War was written. By and large I feel that Clausewitz’s ideas are still relevant – or at least able to be adapted into the present day. Where he is not so relevant is more due to the development of weapons and styles of warfare that he could not have possibly been aware of, rather than through any fault of his own. I feel that the following quote sums up nicely the relevance of Clausewitz to this day: â€Å"Of course not all of Clausewitz’s military thought has remained relevant. His vision of war did not include its economic, air, sea and space dimensions for example. But his concept of war†¦will remain valid as long as states, drug lords, warrior clans and terrorist groups have mind to wage it†33 1 Information taken from On War, p5, Carl Von Clausewitz, (edited by Michael Howard & Peter Paret), 1984, Princeton University Press. 2 The Conduct of War 1789-1961, Chapter 4, p59. Major General J.F.C.Fuller, 1972 Methuen 3 Clausewitz, Michael Howard, p11, 1983, Oxford University Press. 4 Information taken from On War, p5, Carl Von Clausewitz, (edited by Michael Howard & Peter Paret), 1984, Princeton University Press 5 Indeed there is evidence to suggest that by 1827 he considered only the first chapter of book one to be complete – the remainder needing revision. Source The Conduct of War 1789-1961, Chapter 4, p59. Major General J.F.C.Fuller, 1972 Methuen 6 Makers of Modern Strategy, p208, Oxford University Press, 2000 edition. 7 Clausewitz, Michael Howard, p01, 1983, Oxford University Press. 8 Quote taken from www.gov.au/lwsc/publications/CA%eEssays/RMA 9 On War, p75, Carl Von Clausewitz, (edited by Michael Howard & Peter Paret), 1984, Princeton University Press 10 On War, p75, Carl Von Clausewitz, (edited by Michael Howard & Peter Paret), 1984, Princeton University Press 11 Sun Tzu’s art of War, The modern Chinese interpretation, p95 General Tao Hanzhang, 1987, David and Charles 12 Masters of War, Sun Tzu, Clausewitz and Jomini, p32, Michael I.Handel 1992, Frank Cass 13 On War, p87, Carl Von Clausewitz, (edited by Michael Howard & Peter Paret), 1984, Princeton University Press 14 Quote taken from www.Clausewitz.com, however text is from an article originally published in Joint Forces Quarterly, Winter 1995-1996 which is reproduced on the website. 15 For example – what are the current victory objectives in the campaign in Afghanistan and how will we know when victory has been achieved? 16 On War, p230, Carl Von Clausewitz, (edited by Michael Howard & Peter Paret), 1984, Princeton University Press 17 For example the possible attempts at the time of writing by US/UK special forces to capture or eliminate Osama Bin Laden. 18 Even then Clausewitz did not attempt to write on maritime operations – concentrating solely on land warfare. 19 The Next World War,p14, James Adams, 1998 Hutchinson. 20 A good example of this prediction was seen with the terrorist attack on the 11th of September. 21 Quote taken from www.gov.au/lwsc/publications/CA%eEssays/RMA 22 Flashpoint World War Three, p153-154, Andrew Murray, 1997, Pluto Press 23 On War, p228, Carl Von Clausewitz, (edited by Michael Howard & Peter Paret), 1984, Princeton University Press 24 Given the current situation in the USA it will be interesting to see whether the so called ‘body bag’ syndrome has ended or whether once US troops are killed, public opinion will change to demand a more peaceful solution. 25 On War, p75-76, Carl Von Clausewitz, (edited by Michael Howard & Peter Paret), 1984, Princeton University Press 26 Information taken from Deliver us From Evil, (Chapter 4), William Shawcross,2000, Bloomsbury. 27 Total American losses in Somalia were 30 dead, 175 wounded, the UN lost 72 killed and 87 wounded (Source World Conflicts, Patrick Brogan, 1998, Bloomsbury) 28 Deliver us from evil, p103, William Shawcross, 2000 Bloomsbury. 29 On War, p596, Carl Von Clausewitz, (edited by Michael Howard & Peter Paret), 1984, Princeton University Press 30 Clausewitz, Michael Howard, p39, 1983, Oxford University Press. (Professor Howard incorporates a quote from On War, p596, Carl Von Clausewitz, (edited by Michael Howard & Peter Paret), 1984, Princeton University Press) 31 One Hundred Days, p100, Admiral Sandy Woodward, 1992, Harper Collins 32 However – given the overwhelming amount of Western military power in the region and the political willpower to fight the war, it seems likely that Iraq would still have lost the war – whether Israel was a centre of gravity in the sense that it could remove the coalition from the war seems dubious. 33 Quote taken from www.Clausewitz.com, however text is from an article originally published in Joint Forces Quarterly, Winter 1995-1996 which is reproduced on the website.

The Dragon essays

The Dragon essays In Raffels translation of Beowulf the dragon protects the men from what can deceive them, but takes away the one thing they have been deceived by. The Dragon plays a very important role in the epic. He is not like other dragons from the medieval time and protects a virgin up in a tower. What was the motive for a dragon supposedly protecting a virgin from getting rescued? The dragon that is depicted in this novel does not protect a virgin, but he protects a whole hoard of gold. In the end of this epic a slave steals a cup, and the dragon takes revenge on the Geat land. Beowulf, although young, still has the obligation to protect his people from the Dragon. Beowulf fights the dragon and is slain, some may view the dragon as destroyer, others as a protector. In reality, which one does the dragon truly seem to be? The dragon is a destroyer but a protector as well. In Beowulfs time gold is a very valuable commodity to have. Gold was used for money, trading, and to just show signs of pure wealth. The dragon protected this gold not only to have use for himself, but also to protect men from their own greedy souls. The dragon does not consciously protect this gold, but in doing so he protects not only the power of the king, but the certain civil unrest of the community in which the gold could have been found. A slave comes to the dragons lair and steals a cup from the dragon to take back to his master to be excepted back to the community for his wrongdoing. Upon, the dragon noticing this he suddenly becomes enraged that someone dares to steal from the lair of the dragon. And evening came and wild with anger; It could fly burning across the land, killing and destroying everything with its breath. The sun was gone, and its heart was glad: glowing with rage; It left the tower, impatient to repay his enemies. From this passage in the book a reader can see that the dragon is no longer a protec ...

Endoscopy essays

Endoscopy essays The procedures that I had the opportunity to watch in the Endoscopy department were: Bone marrow aspiration and Colonoscopy. The impression I had before about bone marrow aspiration was that this procedure is one of the most painful I have seen in my experience working in hospital. But after this one, I believe that bone marrow aspiration doesnt have to be painful, if the patient is well sedated and pain is under control. Then for the colonoscopy I watched, the patient was well sedated and in any moment he showed any discomfort. I am going to start by describing the bone marrow aspiration. This procedure was performed to a seventeen year-old Caucasian male, who was admitted to the hospital with complain of lower GI pain. In the lab work performed on him, the platelets count result was lower than normal, so the doctor order BMA to find out was is going on, since the patient denies any hematologic problem in the past. The procedure was performed in the posterior superior iliac spine, which is the preferred site. The site of puncture was cleansed with betadine solution, and a local anesthetic was given at the area. Also, the patient was on conscious sedation med with Versed 2mg and 3 minutes later 1mg was given, total of 3mg of Versed. Demerol 75mg for pain was given. Then, a thin aspiration needle was inserted, and a small sample of the bone marrow fluid was withdrawn. The fluid was placed in a three different lab tubes for examination. There may be some risk for bleeding at the puncture site; th e patient had to stay in bed for two hours. The incision site was covered with 4X4 gauze and taped. This test is used to diagnose leukemia and other disorders that affect the blood. It may help determine if cancer is metastasized. It is also helpful in diagnosing some types of anemia and infections. For this procedure no special preparation is necessary, but it is recommended to skip the meal before the procedu ...