XCP-Winf and RCP-Winf: Congestion Control Techniques for Wireless Mesh Networks

In wireless networks a packet can be lost due to numerous reasons, such as congestion, medium related errors, routing and mobility. In these scenarios, the real congestion status of the network is crucial to develop accurate and efficient congestion control protocols. Some of the most known and recent protocols developed to provide faster and lighter congestion control are the eXplicit Control Protocol (XCP) and the Rate Control Protocol (RCP). These protocols have been proposed essentially to work in wired networks and environments; however, there are already new versions of XCP for wireless networks. Moreover, although these protocols estimate the available bandwidth of the links, this estimation is not accurate for wireless networks. This paper proposes new flow control protocols for wireless mesh networks, based in XCP and RCP, which we have designated as XCPWinf and RCP-Winf. These congestion control mechanisms are supported on a new method to estimate the available bandwidth and the path capacity over a wireless network path, denoted as rt-Winf, through a cross-layer approach. The estimation is performed in real-time and without the need to intrusively inject packets in the network. This is accomplished by resorting to the CSMA-CA scheme with RTS/CTS packets to determine each node's channel allocation. The results obtained, through the simulation of these protocols in different scenarios, show that rt-Winf is able to significantly increase the efficiency of congestion control mechanisms.