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A Review of Mac Protocols for Wireless Body Area Networks

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Abstract

This paper represents broad study of MAC protocols built-up for wireless body area networks. In Today's world data is constantly evolving to process larger data sets and maintain higher degree of connectivity. At same time, advances in efficiency allow for amplified mobility and openness. Body Area Networks signify the liable union among connectivity and smartness. A Body Area Network (BAN) is defined officially as a scheme of devices in close proximity to a person's body that collaborate for the benefit of the user. The enhancement in average lifetime and fitness cost in many developed nations are the main reasons for innovation in health care. Various applications and requirements of the WBAN are discussed in his paper. Also, the strengths and weakness of the protocols have been discussed.

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Table.1. Classification of MAC Protocols VI. Existing / Proposed Mac Protocols For Wbans tang i ei i aad The most challenging task is to design and implement the low power Mac protocols for WBAN. Ir humans nodes can be accommodated on body and in body, where the signal propagations are affected by the electrical properties of the body. Mac is a sub layer of data link layer of OSI model and provides the mediun access protocol, which is a channel access control mechanism. Mac layer also add and remove frames from th network. ET pee gongs St SN ERS I a NEE Nodes periodically listens the channel. Channel is periodically sensed by the sensor nodes. Nodes go to sleep mode if it is sensed idle, or keep the transceivers in active mode to receive all the data packets. This is called as polling. Time interval is divided into idle and wake up interval [16]. As the idle interval nodes wakes up to listen the long preamble transmitted by the network coordinator. The network attains the address of the polled node. As the node receives the preamble with its address, either it transmits the data packet or null packet indicating that the buffer of the node is empty [9]. Ex: Wise-Mac.
Table.1. Classification of MAC Protocols VI. Existing / Proposed Mac Protocols For Wbans tang i ei i aad The most challenging task is to design and implement the low power Mac protocols for WBAN. Ir humans nodes can be accommodated on body and in body, where the signal propagations are affected by the electrical properties of the body. Mac is a sub layer of data link layer of OSI model and provides the mediun access protocol, which is a channel access control mechanism. Mac layer also add and remove frames from th network. ET pee gongs St SN ERS I a NEE Nodes periodically listens the channel. Channel is periodically sensed by the sensor nodes. Nodes go to sleep mode if it is sensed idle, or keep the transceivers in active mode to receive all the data packets. This is called as polling. Time interval is divided into idle and wake up interval [16]. As the idle interval nodes wakes up to listen the long preamble transmitted by the network coordinator. The network attains the address of the polled node. As the node receives the preamble with its address, either it transmits the data packet or null packet indicating that the buffer of the node is empty [9]. Ex: Wise-Mac.
Here message is divided into fragments and is transmitted in burst. For transmitting the entire fragments one RTS packet and one CTS packet is reserved over the medium. Sender waits for an ACK from the receiver when data fragment is transmitted. only one of the intended receiver. Due to overhearing contention-based protocols less effectual in energy thar TDMA protocols. In SMAC overhearing is avoided by making nodes go to sleep which causes interference [10].
Here message is divided into fragments and is transmitted in burst. For transmitting the entire fragments one RTS packet and one CTS packet is reserved over the medium. Sender waits for an ACK from the receiver when data fragment is transmitted. only one of the intended receiver. Due to overhearing contention-based protocols less effectual in energy thar TDMA protocols. In SMAC overhearing is avoided by making nodes go to sleep which causes interference [10].
When node is in active period it will keep listening and transmitting. When no activation period occur for a time TA the active period ends. Node will get in the sleep mode if it is not in an active period. Hence,T / determines the least amount of idle listening per frame[11]. TMAC is an improvement on SMAC by introducing adaptive duty cycle that can adapt to different traffic patterns and avoid useless wakeups. Node wakes up periodically to communicate with its neighbors and then go to sleep again until the next frame arrives. In the intervening time, new messages are queued. Nodes interact with each other using a Request-To-Send (RTS), Clear-To-Send (CTS), and Data, Acknowledgement (ACK) scheme, which grant both collision avoidance and reliable transmission.
When node is in active period it will keep listening and transmitting. When no activation period occur for a time TA the active period ends. Node will get in the sleep mode if it is not in an active period. Hence,T / determines the least amount of idle listening per frame[11]. TMAC is an improvement on SMAC by introducing adaptive duty cycle that can adapt to different traffic patterns and avoid useless wakeups. Node wakes up periodically to communicate with its neighbors and then go to sleep again until the next frame arrives. In the intervening time, new messages are queued. Nodes interact with each other using a Request-To-Send (RTS), Clear-To-Send (CTS), and Data, Acknowledgement (ACK) scheme, which grant both collision avoidance and reliable transmission.
Extra time slot depend upon targeted packet error rate, packet drop and number of sensor nodes. Guard band time is inserted between two consecutive time slots to avoid collision/overlapping of packets transmission. Two types of MN can be used in this protocol one which is having single transceivers and the other one which is having two transceivers. The protocol consumes energy in case of communication data rates as well as for short burst of data. As, for periodic synchronization this protocol uses a Network Control (NC) packet after N number of time frames due to which extra energy is consumed [1]. It has fixed frame structure which is based on pure TDMA, and for on-demand traffic no CAP is provided to accommodate small burst of data. Tt eens ee FP ede SE SS eels NTE BS SI a a Static nature of BAN and TDMA approach are being utilized efficiently to maximize the network lif Body nodes send data to master nodes which communicate with a monitoring station (MS). Data received analyses by MS while the on- body network communication and synchronization is being performed by M1 Frame is divided into multiple time slots. Time slot S1 to Sn are allocated to sensor nodes while time slots RS1 1 RS2 are reserved and are assigned when requested.
Extra time slot depend upon targeted packet error rate, packet drop and number of sensor nodes. Guard band time is inserted between two consecutive time slots to avoid collision/overlapping of packets transmission. Two types of MN can be used in this protocol one which is having single transceivers and the other one which is having two transceivers. The protocol consumes energy in case of communication data rates as well as for short burst of data. As, for periodic synchronization this protocol uses a Network Control (NC) packet after N number of time frames due to which extra energy is consumed [1]. It has fixed frame structure which is based on pure TDMA, and for on-demand traffic no CAP is provided to accommodate small burst of data. Tt eens ee FP ede SE SS eels NTE BS SI a a Static nature of BAN and TDMA approach are being utilized efficiently to maximize the network lif Body nodes send data to master nodes which communicate with a monitoring station (MS). Data received analyses by MS while the on- body network communication and synchronization is being performed by M1 Frame is divided into multiple time slots. Time slot S1 to Sn are allocated to sensor nodes while time slots RS1 1 RS2 are reserved and are assigned when requested.
Fig.9. Super frame structure of priority guaranteed MAC protocol ee ee. TO nee eee A Oe AR ee Senta ee ee A super frame structure is used by this protocol. There are five parts of active period; a beacon, Contro hannel AC1, Control Channel AC2, Time Slot Reserved for Bursty (TSRB) traffic, Time Slot Reserved fo ariodic (TSRP) traffic [22].
Fig.9. Super frame structure of priority guaranteed MAC protocol ee ee. TO nee eee A Oe AR ee Senta ee ee A super frame structure is used by this protocol. There are five parts of active period; a beacon, Contro hannel AC1, Control Channel AC2, Time Slot Reserved for Bursty (TSRB) traffic, Time Slot Reserved fo ariodic (TSRP) traffic [22].
For reliable transmission two wakeup mechanisms are defined: For normal traffic transmission traffic- based wakeup mechanism is used and for emergency/on-demand data transmission wakeup radio mechanism is used [16]. To monitor routine physiological parameters normal traffic is generated by the sensor nodes. To monitor emergency situation initiates unpredictable emergency traffic is initiated by on-body sensor nodes. Time axis of super frame structure is divided into three parts: a beacon message, to accommodate short burst of data Configurable Contention Access Period (CCAP) and a Contention Free Period (CFP) where Guaranteed Time Slots (GTS) are assigned to end nodes for collision free communication. Slotted ALOHA is used by the proposed protocol in CCAP.
For reliable transmission two wakeup mechanisms are defined: For normal traffic transmission traffic- based wakeup mechanism is used and for emergency/on-demand data transmission wakeup radio mechanism is used [16]. To monitor routine physiological parameters normal traffic is generated by the sensor nodes. To monitor emergency situation initiates unpredictable emergency traffic is initiated by on-body sensor nodes. Time axis of super frame structure is divided into three parts: a beacon message, to accommodate short burst of data Configurable Contention Access Period (CCAP) and a Contention Free Period (CFP) where Guaranteed Time Slots (GTS) are assigned to end nodes for collision free communication. Slotted ALOHA is used by the proposed protocol in CCAP.
Berkely MAC uses adaptive duty cycling mechanism to reduce duty cycle and minimize idle listening and is an asynchronous MAC protocol. It employs an enhanced filtering method to enlarge the reliability of channel assessment. BMAC employs an adaptive preamble sampling scheme to achieve low power operation. Nodes periodically wake up for a short time interval in each duty cycle to check for preamble. For channel arbitration, link layer acknowledgments for reliability, and low power listening (LPL) B-MAC uses clear channel assessment (CCA) and packet back offs. To optimize throughput, power consumption, latency, fairness, reliability [18]
Berkely MAC uses adaptive duty cycling mechanism to reduce duty cycle and minimize idle listening and is an asynchronous MAC protocol. It employs an enhanced filtering method to enlarge the reliability of channel assessment. BMAC employs an adaptive preamble sampling scheme to achieve low power operation. Nodes periodically wake up for a short time interval in each duty cycle to check for preamble. For channel arbitration, link layer acknowledgments for reliability, and low power listening (LPL) B-MAC uses clear channel assessment (CCA) and packet back offs. To optimize throughput, power consumption, latency, fairness, reliability [18]
Sa ee To avoid collision due to clocks drift AGBA maintain synchronization of devices. Guard band time is inserted between two consecutive time slots using AGBA[7]. The guard band time is based on clock drift of devices and is adjustable. Guard band is supervised by Drift Adjustment Factor (DAF) to avoid waste of bandwidth using extra guard bands. GTS is used to avoid collision [18]. Med MAC takes low data traffic into significance which is not suited in WBANs where date rates for wearable and implanted sensors may be high. errr H-MAC is heartbeat driven TDMA based MAC protocol. Traffic collision is one of the most important features of BSN’s. The main task of the sensors is to collect all kind of psychological parameters. For ex: - When a person walks very fast or his temperature rises, the heartbeat rate blood pressure rate also roses with the rate of breathing. A single physiological fluctuation may wake up numerous radio sensors and incur a series of medium access request. H-MAC is a TDMA-based MAC protocol which is energy efficient and is designed for star- topology BSNs, in which an external network coordinator exists which is powerful. The coordinator could be a smart cell phone, a wrist worn pulse monitoring watch, or a PDA. Since the outer device can be re-energized easily, it could be served as gateway to other networks and may possess more computing resources. H-MAC assigns devoted time slots to each biosensor to assure collision-free transmission. By using the heartbeat rhythm which is inherited in human body HMAC takes the advantage. H-MAC attains time synchronization in TDMA without circulating periodic timing information, which lessens the energy cost. In H-MAC, synchronization information can be extracted from its biosensors, which are linked with or straightforwardly driven by the heartbeat pulsation [19].
Sa ee To avoid collision due to clocks drift AGBA maintain synchronization of devices. Guard band time is inserted between two consecutive time slots using AGBA[7]. The guard band time is based on clock drift of devices and is adjustable. Guard band is supervised by Drift Adjustment Factor (DAF) to avoid waste of bandwidth using extra guard bands. GTS is used to avoid collision [18]. Med MAC takes low data traffic into significance which is not suited in WBANs where date rates for wearable and implanted sensors may be high. errr H-MAC is heartbeat driven TDMA based MAC protocol. Traffic collision is one of the most important features of BSN’s. The main task of the sensors is to collect all kind of psychological parameters. For ex: - When a person walks very fast or his temperature rises, the heartbeat rate blood pressure rate also roses with the rate of breathing. A single physiological fluctuation may wake up numerous radio sensors and incur a series of medium access request. H-MAC is a TDMA-based MAC protocol which is energy efficient and is designed for star- topology BSNs, in which an external network coordinator exists which is powerful. The coordinator could be a smart cell phone, a wrist worn pulse monitoring watch, or a PDA. Since the outer device can be re-energized easily, it could be served as gateway to other networks and may possess more computing resources. H-MAC assigns devoted time slots to each biosensor to assure collision-free transmission. By using the heartbeat rhythm which is inherited in human body HMAC takes the advantage. H-MAC attains time synchronization in TDMA without circulating periodic timing information, which lessens the energy cost. In H-MAC, synchronization information can be extracted from its biosensors, which are linked with or straightforwardly driven by the heartbeat pulsation [19].
Table 2: Summary of Existing MAC Protocols — ——— Oe Wise MAC is a medium access control protocol designed for wireless sensor networks. This uses the preamble sampling technique to minimize the power consumed when listening to an idle medium and is based on non-persistent CSMA. The uniqueness in this protocol consists in developing the knowledge of the one’s direct neighbors sampling schedule to use a wake-up preamble of minimized size. No set-up signaling and network-wide synchronization is required; it is adaptive to the traffic load. In low traffic conditions provides ultralow power consumption. Sampling of the medium is done by the sensor nodes with constant period. Relative sampling schedule offsets of nodes are independent. When the medium is busy, sensor node waits for the medium to become idle by continuously sensing the signal. A wake-up preamble equal to the size of the sampling period is added in
Table 2: Summary of Existing MAC Protocols — ——— Oe Wise MAC is a medium access control protocol designed for wireless sensor networks. This uses the preamble sampling technique to minimize the power consumed when listening to an idle medium and is based on non-persistent CSMA. The uniqueness in this protocol consists in developing the knowledge of the one’s direct neighbors sampling schedule to use a wake-up preamble of minimized size. No set-up signaling and network-wide synchronization is required; it is adaptive to the traffic load. In low traffic conditions provides ultralow power consumption. Sampling of the medium is done by the sensor nodes with constant period. Relative sampling schedule offsets of nodes are independent. When the medium is busy, sensor node waits for the medium to become idle by continuously sensing the signal. A wake-up preamble equal to the size of the sampling period is added in
A Review Of Mac Protocols For Wireless Body Area Networks Contention Access Period (CAP) and Contention Free Period (CFP) are two parts of uplink frame. CAF uses CSMA/CA technique, where for sending packets to the coordinator for Guaranteed Time Slots (GTS) node: have to compete with other nodes. However, during CAP nodes can also communicate for small data packets. I1 CFP coordinator assigns GTS to sensor nodes to avoid collision. For uplink frame in CAP, due to Clear Channel Assessment (CCA) and collision issues CSMA/CA ends up with high energy consumption [20].
A Review Of Mac Protocols For Wireless Body Area Networks Contention Access Period (CAP) and Contention Free Period (CFP) are two parts of uplink frame. CAF uses CSMA/CA technique, where for sending packets to the coordinator for Guaranteed Time Slots (GTS) node: have to compete with other nodes. However, during CAP nodes can also communicate for small data packets. I1 CFP coordinator assigns GTS to sensor nodes to avoid collision. For uplink frame in CAP, due to Clear Channel Assessment (CCA) and collision issues CSMA/CA ends up with high energy consumption [20].
Various existing MAC protocols for WBANS have been analyzed with the main focus on energy consumption. Various advantages and disadvantages of these protocols have been discussed. Due to different hardware constraints and application requirements, no one protocol is being accepted as a standard. To achieve requirements of WBANSs like energy efficiency, scalability, fairness reduced implementation complexity, support for divers applications interoperability reduced synchronization overhead and quality of service anew protocol need to be developed. front of every data frame at the transmitter side to make certain that the Receiver will be awake when the dat portion of the packet arrives. When the channel is idle WISE MAC consumes less energy. WISE MAC has lon wakeup preambles which limit throughput and consumes large power [21].
Various existing MAC protocols for WBANS have been analyzed with the main focus on energy consumption. Various advantages and disadvantages of these protocols have been discussed. Due to different hardware constraints and application requirements, no one protocol is being accepted as a standard. To achieve requirements of WBANSs like energy efficiency, scalability, fairness reduced implementation complexity, support for divers applications interoperability reduced synchronization overhead and quality of service anew protocol need to be developed. front of every data frame at the transmitter side to make certain that the Receiver will be awake when the dat portion of the packet arrives. When the channel is idle WISE MAC consumes less energy. WISE MAC has lon wakeup preambles which limit throughput and consumes large power [21].

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