Energy Efficiency and Delay Performance Analysis of Cooperative MIMO with Cooperative AF Relay in Wireless Sensor Network

Abstract

An efficient design of a Wireless Sensor Network (WSN) has recently drawn increasing attention from research community. In a WSN sensors are often powered by non-rechargeable and non-replaceable batteries. Hence, it is essential to apply energy-efficient techniques to improve the lifetime of this network. Cooperative communication is such a proven method that uses spatial diversity to achieve significant gain and eventually increases network lifetime prominently. This thesis work has explored the benefits of two existing cooperative communication protocols- Cooperative Relaying and Cooperative Multiple-Input-Multiple-Output (C-MIMO). Cooperative Relaying is an effective method for WSN which reduces total energy consumption by exploiting the spatial diversity made available through cooperating nodes that relay signals for each other. Cooperative MIMO is another major breakthrough in the field of WSN. C-MIMO is a special type of MIMO technique where multi-antenna structure of MIMO is formed via cooperation in a network of single antenna nodes. Selective approach of C-MIMO is considered in this work. At first a network with cooperative Amplify-and-Forward (AF) relay terminal is designed and its total energy consumption equation is developed. It is shown that this network performs better in energy consumption than the traditional relay networks and the optimum relay location is also determined. Then the dual hop network is advanced into a multi-hop scenario. It is seen that with increasing hop numbers while traditional relay network consumes less energy, cooperative relay with single antenna based source and destination incurs more energy. To solve this problem a combination of these two approaches is proposed, i.e. selective cooperative MIMO network with cooperative AF relay. An experimental framework is developed for the total energy consumption of our proposed network. Both dual-hop and multi-hop network are considered while satisfying an average bit error rate (BER) requirement at the destination over Rayleigh fading channels. Energy and delay characteristics of proposed network model are observed via simulations. Simulation results show that our proposed model outperforms selective C-MIMO by 17%, traditional C-MIMO by 24% and SISO model by 48% in total energy consumption per bit after certain distance (~400m). The impacts of transmission distance between source and destination, relay number and relay position on total energy consumption per bit are evaluated and discussed. Delay difference (DD) is also calculated between SISO and proposed model and positive DD is observed after 68m which indicates proposed model’s delay efficiency over SISO model. Finally it is observed that for larger scale WSNs (>600m) selective C-MIMO with equispaced multi-hop (hop=4) cooperative AF relay performs more efficiently than three-hop (~9.4%) or dual-hop (~35%) C-MIMO networks.