Energy-efficient transmission in wireless body area networks

Biosensors [1] are usually located in, on or around the human body - forming a Wireless Body Area Network (WBAN) - to collect information for a particular purpose. As biosensors are small-sized, low-weighted and energy-restricted, energy efficiency becomes a key issue in the R&D of WBAN. To facilitate subsequent development, the IEEE 802.15.6 task group created a standard for WBAN [2] which operates with one-hop star and two-hop restricted tree topologies. In its two-hop extension protocol, relaying nodes - working as a micro hub - need to process node joining and schedule the transmission of two-hop nodes. This tends to reduce the lifetime of relaying nodes. To improve the situation, this paper introduces a new two-hop extension protocol which allows relaying nodes to help relay only the uploaded packets from relayed nodes and lets the hub directly transmit packets to the downlink relayed nodes, thus reducing the energy consumption and complexity of relaying nodes. An analytical evaluation on energy consumption, transmission overhead and throughput shows that our protocol is able to prolong the lifetime of relaying nodes and meanwhile preserve advantages of the original two-hop transmission, such as lengthening the lifetime of relayed nodes or cutting down bit error rates.