CAR: Coding-Aware Opportunistic Routing for Unicast Traffic in Wireless Mesh Networks

Abstract

An intermediate node in an inter-flow network coding scheme needs to know exactly which are the previous hop and next hop of a packet before coding. It is difficult to incorporate inter-flow network coding into opportunistic routing (OR) because the next hop of a packet in OR can't be determined in advance. Codingaware opportunistic routing (CAR) is proposed in this paper to address this problem on fixed wireless mesh networks (WMNs). Meanwhile, it aims to maximize the number of native packets coded in each single transmission. It dynamically selects a route for a given flow according to the real-time coding opportunities. There are no control packets in CAR, which greatly reduces the overhead costs. CAR gives the coded packet that consists of a larger number of native packets with a smaller forwarding delay. The forwarder with the largest number of native packets coded together is ultimately selected to send data. Simulations demonstrate that CAR achieves significantly better throughput gains and derives a reasonable end-to-end delay in both cross topology and mesh topology under both transmission control protocol (TCP) and user datagram protocol (UDP) traffic, as explained below. CAR achieves more than 35 % throughput improvement under TCP traffic and more than 15 % throughput improvement under UDP traffic, compared to other state-of-art protocols in cross topology, respectively. CAR also provides a several-fold increase in throughput in a large scale network (mesh topology). In a word, CAR significantly improves network performance of a WMN.

A Modified IEEE 802.11 MAC for Optimizing Broadcasting in Wireless Audio Networks

“…If P is the percent of the maximum acceptable packet loss rate, the maximum acceptable probability of collision will be p T = P/100. Using (5) we can obtain an expression for the critical number of active STAs as follows:…”

“…Research in this ield focuses mainly on the cross-layer optimization of single broadcasting streams [3,4]. Authors in [5] propose a resource allocation solution that improves Quality of Service (QoS) for multimedia wireless transmission and it can be a practical solution for real-time wireless networks. However, this requires a wireless network with relatively high bandwidth.…”

“…Journal of Network and Systems Management From (5) it is shown that broadcasting in a saturated IEEE 802.11 ad-hoc network is afected only by the number of STAs in the network and the size of CW. Plotting (5) in Fig. 3, we can see that the probability of collision in a multi-broadcasting environment reaches dramatically high values when the number of broadcasting STAs increases [21].…”

Joint Inter-Flow Network Coding and Opportunistic Routing in Multi-Hop Wireless Mesh Networks: A Comprehensive Survey

“…To illustrate the idea, let us look at the example provided in Fig. 7, reproduced with some changes from [75]. At the beginning, there exist two flows in the network between N 1 and N 2 , and the third flow from N 3 to N 5 is added later at time t 1 .…”

“…In some described works, the closeness to the destination (i.e., to find the forwarder set) is calculated in terms of the hop count or the geographic distance [75], [76], which does not necessarily represent the quality of the path. In addition, in many studies, the path traveled by the node can be excessively longer than the shortest path [7], [54], [75], [76], [79], which can increase the end-to-end delay, and degrade the performance. Even most of those studies that take into account the length of the route and select the forwarder set from nodes around the shortest path cannot combine packets of more than two flows [77] or require the source to know the shortest path and embed it in the packet header [4], [66], [80].…”