Distributed optimal congestion control and channel assignment in wireless mesh networks

Wireless mesh networks have numerous advantages in terms of connectivity as well as reliability. Traditionally the nodes in wireless mesh networks are equipped with single radio, but the limitations are lower throughput and limited use of the available wireless channel. In order to overcome this, the recent advances in wireless mesh networks are based on multi-channel multi-radio approach. Channel assignment is a technique that selects the best channel for a node or to the entire network just to increase the network capacity. To maximize the throughput and the capacity of the network, multiple channels with multiple radios were introduced in these networks. In the proposed system, algorithms are developed to improve throughput, minimise delay, reduce average energy consumption and increase the residual energy for multi radio multi-channel wireless mesh networks. In literature, the existing channel assignment algorithms fail to consider both interflow and intra flow interferences. The limitations are inaccurate bandwidth estimation, throughput degradation under heavy traffic and unwanted energy consumption during low traffic and increase in delay. In order to improve the performance of the network distributed optimal congestion control and channel assignment algorithm (DOCCA) is proposed. In this algorithm, if congestion is identified, the information is given to previous node. According to the congestion level, the node adjusts itself to minimise congestion

WE TCP-AP: Wireless Enhanced TCP-AP

Congestion control in wireless networks is strongly dependent on the dynamics and instability of wireless links. It is known that TCP experiences serious performance degradation problems in wireless networks. New approaches based on TCP try to overcome these problems but, although their performance is increased, they incur in congestion control errors, since they do not evaluate accurately the capacity and available link bandwidth in wireless networks. This is also the case of TCP-AP (Adaptive Pacing) that, although presenting clear advantages in wireless networks when compared to other TCP-based approaches, its performance is still lower than rate-based approaches. In this paper we propose a new congestion control protocol based in TCP-AP, the Wireless Enhanced TCP-AP (WE TCPAP).This protocol relies on the MAC layer information gathere by a new method to accurately estimate the available bandwidth and the path capacity over a wireless network path. The new congestion control mechanism is evaluated in different scenarios in wireless mesh and ad-hoc networks, and compared against several approaches for wireless congestion control. It is shown that the new WE TCP-AP outperforms the base TCP-AP, with a more stable behavior and better channel utilization, and its performance gets close to the one of ratebased protocols. This is a very important result, as we show that TCP-based approaches are still able to have good performance in wireless mesh and ad-hoc networks

Insights into the Design of Congestion Control Protocols for Multi-Hop Wireless Mesh Networks

The widespread deployment of multi-hop wireless mesh networks will depend on the performance seen by the user. Unfortunately, the most predominant transport protocol, TCP, performs poorly over such networks, even leading to starvation in some topologies. In this work, we characterize the root causes of starvation in 802.11 scheduled multi-hop wireless networks via simulations. We analyze the performance of three categories of transport protocols. (1) end-to-end protocols that require implicit feedback (TCP SACK), (2) Explicit feedback based protocols (XCP and VCP) and (3) Open-loop protocol (UDP). We ask and answer the following questions in relation to these protocols: (a) Why does starvation occur in different topologies? Is it intrinsic to TCP or, in general, to feedback-based protocols? or does it also occur in the case of open-loop transfers such as CBR over UDP? (a) What is the role of application behavior on transport layer performance in multi-hop wireless mesh networks? (b) Is sharing congestion in the wireless neighborhood essential for avoiding starvation? (c) For explicit feedback based transport protocols, such as XCP and VCP, what performance can be expected when their capacity estimate is inaccurate? Based on the insights derived from the above analysis, we design a rate-based protocol called VRate that uses the two ECN bits for conveying load feedback information. VRate achieves near optimal rates when configured with the correct capacity estimate

A novel technique to enhance throughput and fairness over wireless mesh networks

This extended abstract was submitted to and published in the ReSCon '12 Book of Abstracts. The fifth SED Research Student Conference (ReSCon2012) was hosted over three days, 18-20 June 2012, in the Hamilton Centre at Brunel University