In this paper we are concerned with the problem of data forwarding from a wireless body area network (WBAN) to a gateway when body shadowing affects the ability of WBAN nodes to communicate with the gateway. To solve this problem we present a new WBAN architecture that uses two communication technologies. One network is formed between on-body nodes, and is realized with capacitive body-coupled communication (BCC), while an IEEE 802.15.4 radio frequency (RF) network is used for forwarding data to the gateway. WBAN nodes that have blocked RF links due to body shadowing forward their data through the BCC link to a node that acts as a relay and has an active RF connection. For this architecture we design a network layer protocol that manages the two communication technologies and is responsible for relay selection and data forwarding. Next, we develop analytical performance models of the medium access control (MAC) protocols of the two independent communication links in order to be used for driving the decisions of the previous algorithms. Finally, the analytical models are used for further optimizing energy and delay efficiency. We test our system under different configurations first by performing simulations and next by using real RF traces.
In this paper we present and contrast two approaches, Cooperative Network Coding (CNC) and Cooperative Diversity Coding (CDC) to achieving reliable wireless body area networks. CNC combines cooperative communications and network coding, while CDC combines cooperative communication and diversity coding. These approaches also provide enhanced throughput and transparent self-healing which are desirable features that Wireless Body Area Networks should offer. Additionally, these feed-forward techniques are especially suitable for real-time applications, where retransmissions are not an appropriate alternative. Although, these techniques provide similar benefits, simulation results show that CDC provides higher throughput than CNC because of the fact that the network topology is known and few hops between the source and destination. Moreover, CDC has lower complexity, since the source and destination nodes know the coding coefficients. In this paper, a cluster-based cooperative communication scheme is introduced in which each cluster acts as a virtual node with multiple antennas. The presented model considers the effects of random deployment of nodes and hence their random distribution across the network. Taking these effects into account, a pairwise-error probability analysis for a generic space-time code structure is provided. The analysis reveals that the diversity and coding gain of the system depends on both the code structure as well as the nodes' distribution, and hence new code design criteria are developed. Simulation results are presented to confirm the theoretical analysis. Clustering and relaying techniques are important approaches towards mitigating the problem of finite network lifetime in wireless sensor networks. To this end, given a clustered wireless sensor network (WSN) (with defined cluster heads and their associated clusters) and a given relay node placement, we present a distributed service allocation algorithm for the relay node for maximizing network lifetime. We evaluate the performance of our method through theoretical analysis as well as simulations, and demonstrate the superior performance of our proposed method compared to a greedy periodic approach.