Improved Switched Combining with cooperative diversity for wireless body area networks: Empirical analysis and theory

Abstract

An improved form for Switched Combining (SwC) with on-body cooperative communications is presented, particularly suited to the 'everyday' wireless body area network (BAN) wireless channel. Two and three-branch cooperative coherent SwC is analyzed theoretically and empirically and compared with cooperative coherent selection combining (SC), and a previous switched combining implementation. New expressions for outage probability and approximate switching rate are derived for the proposed SwC. Three locations for relays/hubs are considered, along with seven sensor locations, all using extensive on-body "open-access" channel measurements. The outage performance of SwC is not considerably degraded with respect to SC with large improvement over single-link communications, and significant improvement over the previous SwC. The benefit of the proposed SwC is shown as the two and three-branch switching rate for this SwC, is typically between 10% and 15% of that of SC. Further, compared to the previous switched combining method, there is only a small increase in switching rate at the same time as improved outage performance. The low switching rate here may allow for easier implementation in practical IEEE 802.15.6 BAN.

Energy‐efficient, reliable wireless body area networks: cooperative diversity switched combining with transmit power control

“…Cooperative SwC: Here we investigate L = 3-branch cooperative diversity switched combining as described in [3], where there are two possible dual-hop branches (i.e. each sensor to relay to destination) and one single-hop branch (i.e.…”

“…Two mechanisms that can be used to achieve this are cooperative receive diversity, which is allowed in IEEE 802.15.6 [1], and transmit power control (PC). Here, we propose a simple transmit PC, using a 'sample-and-hold' channel prediction method following from [2], to be incorporated with simple cooperative switch-and-examine combining (SwC) following from [3]. Using extensive empirical 'open-access' data [4] we show that a combination of these two mechanisms significantly improves communications reliability, in terms of reduced outages, and increases energy efficiency, while maintaining low radio complexity and operational efficiency, further evidenced by second-order statistics such as the switching rate.…”

An Adaptive Relay Transmission Scheme for Reliable Data Forwarding in Wireless Body Area Networks

“…Therefore, the best relay node from the set of relay nodes must be selected to forward the packet from the source. In [22], channel gain characterized the path loss effect on body channels which is considered to be a major factor affecting the link reliability. In general, the best channel gain link in the second hop can provide the best quality of data transmission.…”