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A statistical frame based TDMA protocol for human body communication.

Nie Z, Li Z, Huang R, Liu Y, Li J, Wang L - Biomed Eng Online (2015)

Bottom Line: A beacon frame with the contained synchronous and poll information is designed to reduce the possibility of collisions of request frames.Dynamic time slot allocation mechanism is presented to manage the burst traffic and reduce the active period in each beacon period.The theory analysis is proceed and the result is evaluated in the hardware platform.

View Article: PubMed Central - PubMed

Affiliation: Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518005, China. zd.nie@siat.ac.cn.

ABSTRACT

Background: Human body communication (HBC) using the human body as the transmission medium, which has been regarded as one of the most promising short-range communications in wireless body area networks (WBAN). Compared to the traditional wireless networks, two challenges are existed in HBC based WBAN. (1) Its sensor nodes should be energy saving since it is inconvenient to replace or recharge the battery on these sensor nodes; (2) the coordinator should be able to react dynamically and rapidly to the burst traffic triggered by sensing events. Those burst traffic conditions include vital physical signal (electrocardiogram, electroencephalogram etc.) monitoring, human motion detection (fall detection, activity monitoring, gesture recognition, motion sensing etc.) and so on. To cope with aforementioned challenges, a statistical frame based TDMA (S-TDMA) protocol with multi-constrained (energy, delay, transmission efficiency and emergency management) service is proposed in this paper.

Methods: The scenarios where burst traffic is often triggered rapidly with low power consumption and low delay is handled in our proposed S-TDMA. A beacon frame with the contained synchronous and poll information is designed to reduce the possibility of collisions of request frames. A statistical frame which broadcasts the unified scheduling information is adopted to avoid packet collisions, idle listening and overhearing. Dynamic time slot allocation mechanism is presented to manage the burst traffic and reduce the active period in each beacon period. An emergency mechanism is proposed for vital signals to be transmitted. The theory analysis is proceed and the result is evaluated in the hardware platform.

Results: To verify its feasibility, S-TDMA was fully implemented on our independently-developed HBC platform where four sensor nodes and a coordinator are fastened on a human body. Experiment results show that S-TDMA costs 89.397 mJ every 20 s when the payload size is 122 bytes, 9.51% lower than Lightweight MAC (LMAC); the average data latency of S-TDMA is 6.3 ms, 7.02% lower than Preamble-based TDMA (PB-TDMA); the transmission efficiency of S-TDMA is 93.67%, 4.83% higher than IEEE 802.15.6 carrier sense multiple access/collision avoidance (CSMA/CA) protocol.

Conclusions: With respect to the challenges of HBC based WBANs, a novel S-TDMA protocol was proposed in this paper. Compared to the traditional protocols, the results demonstrate that S-TDMA successfully meets the delay and transmission efficiency requirements of HBC while keeping a low energy consumption. We also believe that our S-TDMA protocol will promote development of HBC in wearable applications.

No MeSH data available.


Related in: MedlinePlus

Flow chart of the emergency mechanism (T represents transmit, R represents receive). This figure demonstrates how S-TDMA handles burst traffic.
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Fig3: Flow chart of the emergency mechanism (T represents transmit, R represents receive). This figure demonstrates how S-TDMA handles burst traffic.

Mentions: In addition, there is an emergency mechanism for vital signals to be transmitted. The emergency mechanism is shown in Figure 3. If a sensor node has an emergency frame to send, the coordinator will cut off the current processing and deal with the emergency node point to point immediately without waiting for the next beacon period. The coordinator can detect an emergency frame through the first byte of the frame. If the emergency data come before the sensor node send the request frame, the sensor node will send an emergency request frame to the coordinator. When allocating time slots in the statistical frame, the node with emergency will be given the first time slot. If there are more than one sensor nodes which have emergency data at this time period, the emergency nodes will be allocated the first few time slots. If the emergency data come when another sensor node is sending frames to the coordinator, the sensor node with emergency data will send the emergency request frame three times (the number of times can be set according to the working circumstances and channel characteristics). Inevitably, there will be two consecutive collisions (one time less that the set number of times) which can cause energy consumption, but it is well worth when delay is taken into consideration. When the coordinator detects two transmission failures, it will stop the current process and sent a polling packet to the sensor nodes. The polling packet will make sure whether there is an emergency node (or more than one emergency sensor nodes). Then, if there is an emergency node, the coordinator will arrange a slot to it during which the sensor node sent an emergency request again. When the coordinator receives the emergency request frame, it will react to the request immediately. When there are more than one emergency sensor nodes, the coordinator will arrange time slots according to the number of sensor nodes during which they send request to the coordinator. Then, the coordinator will react to the request. After the emergency, the coordinator will recover the processing according to the time period when the emergency comes. If the emergency occurs during the beacon frame, statistical frame or acknowledge frame period, the coordinator will resend a beacon frame, statistical frame or acknowledge frame to the sensor nodes; if the emergency occurs during the request frames, data frames or Re-TR period, the coordinator will ask the sensor nodes to retransmit the frames to it; if the emergency occurs during the sleeping period, it will wake up the coordinator to deal with it. In order to minimize the cost of the overhead, the frame format of request frame and statistical frame should be designed as simple as possible, so that all sensor nodes in WBAN can enter into sleep mode as soon as possible. The whole keynote and the design thinking are to reduce the service period of the radio transceiver and make the whole energy consumption to the least.Figure 3


A statistical frame based TDMA protocol for human body communication.

Nie Z, Li Z, Huang R, Liu Y, Li J, Wang L - Biomed Eng Online (2015)

Flow chart of the emergency mechanism (T represents transmit, R represents receive). This figure demonstrates how S-TDMA handles burst traffic.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4495947&req=5

Fig3: Flow chart of the emergency mechanism (T represents transmit, R represents receive). This figure demonstrates how S-TDMA handles burst traffic.
Mentions: In addition, there is an emergency mechanism for vital signals to be transmitted. The emergency mechanism is shown in Figure 3. If a sensor node has an emergency frame to send, the coordinator will cut off the current processing and deal with the emergency node point to point immediately without waiting for the next beacon period. The coordinator can detect an emergency frame through the first byte of the frame. If the emergency data come before the sensor node send the request frame, the sensor node will send an emergency request frame to the coordinator. When allocating time slots in the statistical frame, the node with emergency will be given the first time slot. If there are more than one sensor nodes which have emergency data at this time period, the emergency nodes will be allocated the first few time slots. If the emergency data come when another sensor node is sending frames to the coordinator, the sensor node with emergency data will send the emergency request frame three times (the number of times can be set according to the working circumstances and channel characteristics). Inevitably, there will be two consecutive collisions (one time less that the set number of times) which can cause energy consumption, but it is well worth when delay is taken into consideration. When the coordinator detects two transmission failures, it will stop the current process and sent a polling packet to the sensor nodes. The polling packet will make sure whether there is an emergency node (or more than one emergency sensor nodes). Then, if there is an emergency node, the coordinator will arrange a slot to it during which the sensor node sent an emergency request again. When the coordinator receives the emergency request frame, it will react to the request immediately. When there are more than one emergency sensor nodes, the coordinator will arrange time slots according to the number of sensor nodes during which they send request to the coordinator. Then, the coordinator will react to the request. After the emergency, the coordinator will recover the processing according to the time period when the emergency comes. If the emergency occurs during the beacon frame, statistical frame or acknowledge frame period, the coordinator will resend a beacon frame, statistical frame or acknowledge frame to the sensor nodes; if the emergency occurs during the request frames, data frames or Re-TR period, the coordinator will ask the sensor nodes to retransmit the frames to it; if the emergency occurs during the sleeping period, it will wake up the coordinator to deal with it. In order to minimize the cost of the overhead, the frame format of request frame and statistical frame should be designed as simple as possible, so that all sensor nodes in WBAN can enter into sleep mode as soon as possible. The whole keynote and the design thinking are to reduce the service period of the radio transceiver and make the whole energy consumption to the least.Figure 3

Bottom Line: A beacon frame with the contained synchronous and poll information is designed to reduce the possibility of collisions of request frames.Dynamic time slot allocation mechanism is presented to manage the burst traffic and reduce the active period in each beacon period.The theory analysis is proceed and the result is evaluated in the hardware platform.

View Article: PubMed Central - PubMed

Affiliation: Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518005, China. zd.nie@siat.ac.cn.

ABSTRACT

Background: Human body communication (HBC) using the human body as the transmission medium, which has been regarded as one of the most promising short-range communications in wireless body area networks (WBAN). Compared to the traditional wireless networks, two challenges are existed in HBC based WBAN. (1) Its sensor nodes should be energy saving since it is inconvenient to replace or recharge the battery on these sensor nodes; (2) the coordinator should be able to react dynamically and rapidly to the burst traffic triggered by sensing events. Those burst traffic conditions include vital physical signal (electrocardiogram, electroencephalogram etc.) monitoring, human motion detection (fall detection, activity monitoring, gesture recognition, motion sensing etc.) and so on. To cope with aforementioned challenges, a statistical frame based TDMA (S-TDMA) protocol with multi-constrained (energy, delay, transmission efficiency and emergency management) service is proposed in this paper.

Methods: The scenarios where burst traffic is often triggered rapidly with low power consumption and low delay is handled in our proposed S-TDMA. A beacon frame with the contained synchronous and poll information is designed to reduce the possibility of collisions of request frames. A statistical frame which broadcasts the unified scheduling information is adopted to avoid packet collisions, idle listening and overhearing. Dynamic time slot allocation mechanism is presented to manage the burst traffic and reduce the active period in each beacon period. An emergency mechanism is proposed for vital signals to be transmitted. The theory analysis is proceed and the result is evaluated in the hardware platform.

Results: To verify its feasibility, S-TDMA was fully implemented on our independently-developed HBC platform where four sensor nodes and a coordinator are fastened on a human body. Experiment results show that S-TDMA costs 89.397 mJ every 20 s when the payload size is 122 bytes, 9.51% lower than Lightweight MAC (LMAC); the average data latency of S-TDMA is 6.3 ms, 7.02% lower than Preamble-based TDMA (PB-TDMA); the transmission efficiency of S-TDMA is 93.67%, 4.83% higher than IEEE 802.15.6 carrier sense multiple access/collision avoidance (CSMA/CA) protocol.

Conclusions: With respect to the challenges of HBC based WBANs, a novel S-TDMA protocol was proposed in this paper. Compared to the traditional protocols, the results demonstrate that S-TDMA successfully meets the delay and transmission efficiency requirements of HBC while keeping a low energy consumption. We also believe that our S-TDMA protocol will promote development of HBC in wearable applications.

No MeSH data available.


Related in: MedlinePlus