Cross-Layer Optimization and Network Coding in CSMA/CA-Based Wireless Multihop Networks

Abstract

In this paper, we consider the CSMA/CA multihop networks where the two end-nodes transmit their packets to each other and each intermediate node adopts network coding for delivering bidirectional flows. In addition, the neighbor nodes are randomly uniformly deployed with the Poisson Point Process. By varying the combination of the physical carrier-sensing range of the transmitter node and the target signal-to-interference ratio (SIR) set by the receiver node, we can control the interference level in the network and the degree of spatial reuse of a frequency band. The larger the carrier-sensing range is, the smaller the interference level, while the smaller the opportunity of getting a channel by a node. Similarly, the higher the target SIR value is, the more probable the retransmission (by the exponential random backoff) is, while the better the link quality on successful transmission is getting. Under this tradeoff context, we find the optimal combinations of these two factors that make the end-to-end throughput of the flow maximal for three different retransmission schemes.Index Terms-Carrier-sensing multiple access/collision avoidance (CSMA/CA), carrier-sensing range, cross-layer optimization, network coding (NC), Poisson point process (PPP), target signal-to-interference ratio (SIR), wireless multihop networks.

Space-time efficient wireless network coding

“…In [12] [13], the authors investigated the trade-off between spatial reuse and network coding gain. Although they provided theoretical performance limits of coding aware power control, the centralized nature makes them hard to be used in practice In [14] [15], distributed coding aware rate control mechanisms were proposed.…”

Throughput and delay analysis of network coded ALOHA in wireless networks

“…Intuitively, (17) represents that the maximum coding gain is two because two packets are coded. However, the actual coding gain is lower than two due to the packet conservation law constraint.…”

“…Intermediate nodes in the network combine code packets, and intermediate or destination receivers decode these coded packets using known packets. From the medium usage point of view, network coding gives better performance by using the medium less when compared to the traditional communication method, in which each packet uses the medium exclusively [16,17].…”

“…These assumptions are relaxed in our article. Network coding gain has been analyzed [17] within the CSMA/CA MAC layer, and we determined the set of the target signal-to-interference ratio (SIR) value and the carrier-sensing range that jointly maximize the throughput. Our results in this article are summarized as follows: (1) The maximum throughput of coded ALOHA is greater than that of the conventional ALOHA (coding gain is about 1.3).…”

Asymptotic Gain of Network-Coded Retransmission in Wireless Networks

“…It is known that the network coding enhances the network capacity by reducing the number of transmissions [9], [10]. In our system, however, the number of transmissions rather increases because network coding is utilized for error recovery.…”