Impact of network coding on TCP performance in wireless mesh networks

Abstract

Since it was originally proposed by Ahlswede et al. (2000), network coding (NC) has been the focus of many research efforts and proposals. In particular, NC has been put forward as a means to increase the capacity of wireless mesh networks, by exploiting the broadcast nature of wireless links. However, in spite of the fairly large number of papers on the subject of network coding, the impact of NC on TCP performance in wireless mesh networks is still not fully understood. By means of a thorough simulation study, this paper aims thus at providing insights about the interaction between TCP's congestion control mechanisms and the underlying NC done by wireless relays. In particular, we focus on the influence of the main parameters related to the coding buffer used by such relays to encode packets. Our results suggest the feasibility of devising engineering rules for setting such parameters. Another main conclusion, in line with previous preliminary findings by the authors (Hassayoun et al., 2010) is that TCP performance can indeed be improved by the use of NC, but only as long as the wireless channel quality is above a certain level.

Adaptive Wireless Network Coding for Infrastructure Wireless Mesh Networks

“…A TCP connection uses acknowledgments that travel from the destination node to the source node and DATA packets that travel from source to destination. Therefore, WNC can take advantage of this property to increase the use of the network capacity [15,17]. 3.…”

“…A constant maximum waiting time for all the packets is used to avoid the increment of the coding delay. This approach is presented and analyzed in [14,15]. In these contributions, a fixed buffer timeout is associated to each packet to limit its sojourn time in the coding buffers.…”

“…For example, in [14], Huang et al demonstrate that WNC decreases the loss rate and improves the network capacity. In [15], the results show that WNC may increase the TCP throughput up to 33%. According to [16], the encoding of DATA and ACK packets from a single TCP flow may increase the TCP throughput up to 17%.…”

Providing Reliable Services over Wireless Networks Using a Low Overhead Random Linear Coding Scheme

“…COPE exploits the broadcast nature of the wireless medium, since the neighbouring nodes are able to overhear packets not directly addressed to them. COPE was shown to reduce the number of transmissions, yielding a significant performance gain, but some other works [7], proved that its gain is much lower when the conditions of the wireless links get worse.…”

Reliable communications over lossy wireless channels by means of the combination of UDP and Random Linear Coding

“…However, the complexity of these coding techniques is rather high and the improvements they bring about are not as outstanding as originally expected, in particular when the conditions of the wireless link are poor [8]. For these reasons, another different coding approach, which encodes packets that belong to the same flow, and therefore can be referred to as intra-flow coding scheme, is gaining more and more relevance.…”