Quality-aware network coding for wireless networks

Abstract

Not long after the birth of network coding in 2000 did the research community realize the tremendous increase in network capacity that could be provided by network coding. Motivated by this prospect, a considerable amount of work has been devoted to developing network coded retransmission schemes in wireless networks. However, most of the existing work ignores the fact that, in wireless communication, a packet received with errors still contains useful information. In this thesis, we propose Quality-Aware Network Coding (QANC) to utilize the information available in erroneous packets to accelerate retransmissions in different network settings, where the means of performing network coding is guided by the Signal-to-Noise Ratios (SNRs) of the received packets. We first develop an easy-to- implement sum-SNR criterion based on Binary Phase-Shift Keying (BPSK) modulation. The linearly network coded retransmission scheme is shown to achieve better throughput and exhibits less decoding delay in Demodulate-and-Forward (DmF) relay channels. Next, we extend the same idea to more general PSK modulation schemes where the number of constellation points is restricted to powers of 2. We apply the extended network coded retransmission scheme to single-hop broadcast channels and compare it with Random Linear Network Coding (RLNC) scheme and Instantly-Decodable Network Coding (IDNC) schemes. The proposed scheme is found to outperform IDNC in terms of throughput and decoding delay. It is also shown that the proposed scheme outperforms RLNC in reasonably large network. Moreover, the proposed scheme is robust against feedback loss and requires little bandwidth for feedback. Finally, we propose an improved binary joint network-channel coding scheme, where again the means of performing network coding is determined by the SNRs of the received packets. After comparing the proposed joint coding scheme with existing counterparts, we find that the Bit-Error Rate (BER), throughput, and delay of the proposed scheme are improved. All observations throughout the study suggest that it may be worthwhile to consider quality information, e.g., SNR values, when designing network coded retransmission schemes in wireless communication systems.

Date of Award	3 Oct 2014
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Chi Wan SUNG (Supervisor)