A Multi-channel Multi-rate Distributed Access Protocol Design And Model Analysis In WLAN Mesh Networks

WLAN mesh networks,when used as a new broadband wireless network, can combine theadvantages of WLAN networks and ad hoc networks.It provides a new choice for the broadbandwireless access service. Thenetworking potential inWLAN mesh networks is gradually becomingmore well-known. Several standardization organizations have began to study and explored thestandards of the networking protocol in WLAN mesh networks. IEEE802.11protocol,which hasalready been widely recognized by the industry, is a standard protocol in wireless networks.Inrecent years, the802.11protocol system has gradually been adding support for multiple rates inphysical layer.For example, IEEE802.11b protocol supports four rates,1Mbps,2Mbps,5.5Mbpsand11Mbps, IEEE802.11a protocol supports eight rates from6Mbps to54Mbps. Althoughtheprotocol above supports multiple rates in physical layer, A dynamic speed selection mechanismis not given in MAC layer. In the multi-rate network, a low-speed rate linktakes longer tocomplete the data transfer, which greatly limits the advantages of high-speed links and consumesmuch more network resources. The problem above decreases the performance of the network. Tosolve the problem, many researchers began to use multi-channel technology in the multi-ratenetwork. A node uses the multi-channel through a dynamic channel switching in a single-interfacemulti-channel network. But the transceiver nodes maybe in the different channels when they wantto book a channel. As a result,channel reservation will fail.Around relevant issues, the main innovations of this paper include:(1) In this paper, we have a detailed analysis of the performance anomaly when multiplelinks using different transmission rates share a common wireless channel, and the missing receiverproblem in single-radio multi-channel networks. Furthermore, based on IEEE802.11DCF, wepropose a distributed multi-channel rate adaptive media access control (MAC) protocol forWLAN mesh networks. The neighboring nodes can cooperatively inform the transmitter of thechannel used by the receiver in the proposed protocol. Besides, the receiver can choose thefeasible transmission rate and channel and send back them to the transmitter. With the abovemechanisms, the links having same transmission rate are assigned on the same channel.Simulation results show that the proposed protocol can eliminate the interference between thelinks using different transmission rates, and effectively solve the missing receiver problem, thussignificantly improve the overall performance of the network.(2) To research the channel switching issues in WLAN mesh network, this paper proposes asimple channel assignment protocol named SM-MAC, andthen it analyzes the protocol by three-dimensional Markov chain modeling. The model accurately describes the retransmissions ina single-channel and the channel switching process in the multiple channels. Meanwhile,itindicates the impact of both on network performance. The model supports the basic access modeand the RTS/CTS access mode. The simulation proves the model is accurate.