4-ary network coding for two nodes in cooperative wireless networks: exact outage probability and coverage expansion

Jin-Taek Seong,Heung-No Lee

doi:10.1186/1687-1499-2012-366

Abstract

The fact that sensor nodes are powered by limited-capacity batteries makes power efficiency; one of the most critical issues in wireless sensor networks (WSNs). Advanced communication techniques combined with network coding and cooperative schemes have attracted considerable attention as ways to improve power efficiency in wireless transmission as well as to achieve high throughput and spectral efficiency in WSNs. In this study, we consider cooperative wireless networks with two nodes and one base station, and investigate the effect of using non-binary network coding on the enhancement in power efficiency. First, we derive the exact and general outage probability in our network coding scheme. We show that full diversity order can be obtained using a non-binary network code with GF(4) in the considered network. We use this result to study the extent to which the coverage area of a wireless source node can be expanded by network coding without increasing transmit power. Our results indicate that the benefit in terms of coverage expansion is substantial. The results included in this study show the influence of optimal power allocation on power efficiency. The optimum ratio of power allocation varies according to the wireless channel environments and the field size of network codes.

Highlights

In wireless sensor networks (WSNs), sensor nodes operate on the limited energy source of onboard batteries, making power efficiency a key issue because replacement or recharging of batteries is difficult
Evaluation of coverage area expansion The contour of outage probabilities evaluated at 10–4 for the source nodes 1 (N1) is plotted in Figure 4, where the blue and red lines indicate the results of using the binary network coding (BNC) and non-binary network coding (NBNC)-4 schemes, respectively
The power efficiency is investigated as the size of finite fields for the linear network coding is increased from 2 to 4, and as the allocation of transmit power, i.e., the power used at the source node versus the power at the relay node, is varied

Summary

Introduction

In wireless sensor networks (WSNs), sensor nodes operate on the limited energy source of onboard batteries, making power efficiency a key issue because replacement or recharging of batteries is difficult. The very highenergy expenditure of WSNs makes long-range message transmission undesirable. There are several ways to improve power efficiency, such as optimal transmit power allocation [1-5]. Channel fading is one of the underlying causes of performance degradation in wireless networks. One naïve approach to combating fading is to increase the transmit power. A more advanced method is to use diversity techniques, which can be employed without increasing the transmit power. Many diversity techniques have been developed and employed in time, frequency, and space domains.

Objectives

Results

Discussion

Conclusion