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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

The workflow of the program. This figure demonstrates the working procedure of S-TDMA. To simplify the process, we take the situation when there is one sensor node and one coordinator as an example.
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Fig2: The workflow of the program. This figure demonstrates the working procedure of S-TDMA. To simplify the process, we take the situation when there is one sensor node and one coordinator as an example.

Mentions: After receiving the request frames, the coordinator will add up all the requested time slots needed by the sensor nodes to form a statistical frame. Therefore, the statistical frame contains the total time slot request and different requests of all sensor nodes. Then, the coordinator sends the statistical frame with scheduling information to all sensor nodes, after which it prepares to receive data frames. All sensor nodes have the whole WBAN scheduling information and work accordingly. If no sensing event occurs after receiving the statistical frame, sensor nodes will set their radios into sleep mode until the next scheduled beacon frame comes. Otherwise, each sensor node will just wait until the granted time slot comes to send its data frame. Then, the coordinator will add up all the data frames from the sensor nodes, extract their information and compare it to that in the request frame, respectively. In this way, the coordinator determines which sensor nodes have experienced packet loss and arrange time slots for them in the acknowledge frame. The acknowledge frame will be sent to all the sensors nodes except those in the sleep mode. Each node will determine whether it has lost packet or not. If so, it will retransmit the lost data during the time slot allocated to it in the acknowledge frame (Re-TR period shown in Figure 1); if not, it will enter into sleep mode immediately. The duration of the data frame is adjusted by the coordinator based on the current traffic characteristics. To save energy, a period of inactivity is reserved for sensor nodes, allowing them to enter into sleep mode. Each data frame has a packet number assigned, so that the received packets are counted to maintain data integrity. Theoretically, S-TDMA protocol is compact and flexible. The workflow of the program is shown in Figure 2.Figure 2


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)

The workflow of the program. This figure demonstrates the working procedure of S-TDMA. To simplify the process, we take the situation when there is one sensor node and one coordinator as an example.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig2: The workflow of the program. This figure demonstrates the working procedure of S-TDMA. To simplify the process, we take the situation when there is one sensor node and one coordinator as an example.
Mentions: After receiving the request frames, the coordinator will add up all the requested time slots needed by the sensor nodes to form a statistical frame. Therefore, the statistical frame contains the total time slot request and different requests of all sensor nodes. Then, the coordinator sends the statistical frame with scheduling information to all sensor nodes, after which it prepares to receive data frames. All sensor nodes have the whole WBAN scheduling information and work accordingly. If no sensing event occurs after receiving the statistical frame, sensor nodes will set their radios into sleep mode until the next scheduled beacon frame comes. Otherwise, each sensor node will just wait until the granted time slot comes to send its data frame. Then, the coordinator will add up all the data frames from the sensor nodes, extract their information and compare it to that in the request frame, respectively. In this way, the coordinator determines which sensor nodes have experienced packet loss and arrange time slots for them in the acknowledge frame. The acknowledge frame will be sent to all the sensors nodes except those in the sleep mode. Each node will determine whether it has lost packet or not. If so, it will retransmit the lost data during the time slot allocated to it in the acknowledge frame (Re-TR period shown in Figure 1); if not, it will enter into sleep mode immediately. The duration of the data frame is adjusted by the coordinator based on the current traffic characteristics. To save energy, a period of inactivity is reserved for sensor nodes, allowing them to enter into sleep mode. Each data frame has a packet number assigned, so that the received packets are counted to maintain data integrity. Theoretically, S-TDMA protocol is compact and flexible. The workflow of the program is shown in Figure 2.Figure 2

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