Research On Cross - Layer Congestion Control Algorithm For Wireless Mesh Networks Based On Bandwidth Estimation

Wireless Mesh Networks (Wireless Mesh Network, referred WMN) is a multi-hop does not require a central server networks, self-organizing, self-healing, self-management, high storage, high-speed, low cost. In WMN, because node to node transmission disequilibrium between business, making a lot of link data streams are easy to focus on the Mesh data cache, there are nodes of the link load is too high, likely causing local congestion. In order to further improve the wireless communication service quality, improving communication performance WMN network has become a research hotspot of Information Industry. Since the characteristics of the network itself WMN, plus inherent hierarchical structure of the network, they have to avoid many of the existing data accumulation, the link is more difficult to apply algorithms smooth WMN. From improving the user experience, this paper mainly studied the problem WMN data accumulation proposed several solutions.Wireless network bandwidth resources are more limited, in order to solve the wireless link data easy to accumulate data link transmission must ensure smooth, secure the wireless link data stream there is no competition or lost, therefore, how to improve the bandwidth resources utilization is one of the most concern. The wireless network control data flow is mainly two protocols UDP and TCP, UDP does not exist on the data flow control protocol, TCP data flow control is hosted on congestion control protocol. In this paper, the Mesh network structure and the current cross-layer design ideas, from the solution good wireless link data stream transmission smooth starting, improving the utilization of limited bandwidth resources in wireless Mesh environment before using two different methods estimate the available network resources, combined with measurement bandwidth values, we propose a Mesh Network Bandwidth can be estimated based on cross-layer congestion control algorithms.The algorithm combined transport layer, MAC layer, the physical layer, at the appropriate time to detection of a local congestion, and to analyze the factors affecting link data service, using two different principles estimate the available network bandwidth. The first one is the source terminal over the outgoing traffic, the upper node route through the router depending on the sending end and receiving end to pressure into a temporary packet queue, then the temporary queue packets to the MAC layer, the temporary package according to the port number contained in the received MAC layer ACK returned information, combined traffic interference factors to calculate the effective bandwidth of the size, the type of the measured value to adjust the source data rate transfer resources. The second is to transfer data using TCP RTT (round trip time) to measure the length of the number of resources available bandwidth, when the RTT is large, the network is not good, relatively large network latency, packet loss frequency, the network bandwidth is available less. When the RTT value comparison hours, indicating relatively good network conditions, data transmission success rate is relatively large, by comparing the values obtained RTT adjacent two real-time bandwidth capacity. Design algorithms simulation model, measurements were performed under both methods improves TCP performance.