Interference has strong effect on the available bandwidth of wireless local area network (WLAN) based mesh networks. The channel assignment problem for multi-radio multi-channel multihop WLAN mesh networks is complex NP-hard, and channel assignment, routing and power control are tightly coupled. To mitigate the co-channel interference and improve capacity in multi-channel and multi-interface WLAN mesh networks, a power-efficient spatial reusable channel assignment scheme is proposed, which considers both channel diversity and spatial reusability to reduce co-channel interference by joint adjusting channel, transmission power and routing. In order to assign channel appropriately, an efficient power control scheme and a simple heuristic algorithm is introduced to achieve this objective, which adjust the channel and power level of each radio according to the current channel conditions so as to increase the opportunity of channel spatial reusability. The proposed channel assignment scheme also takes load, capacity and interference of links into consideration. Simulation results show the effectiveness of our approach and demonstrate that the proposed scheme can get better performance than other approaches in terms of throughput, blocking ratio, energy consumption and end-to-end delay.

Power-Efficient Spatial Reusable Channel Assignment Scheme in WLAN Mesh Networks

Wireless Mesh Networks (WMNs) introduce a new paradigm ‎wireless broadband Internet access by providing high data ‎service, scalability, and self-healing abilities at reduced ‎‎high throughput for multi-cast applications (e.g. ‎streaming broadcast) in WMNs is challenging due to the ‎and the change of channel quality. To overcome ‎issue, cross-layer has been proposed to improve the ‎ormance of WMNs. ‎coding is a powerful coding technique that has been ‎to be the very effective in achieving the maximum multi-cast ‎In addition to achieving the multi-cast ‎network coding offers other benefits such as load ‎and saves bandwidth consumption. This ‎presents a review the fundamental concept types of medium access control ‎‎ layer, routing protocols, cross-layer and network ‎for wireless mesh networks. Finally, a list of directions for further research is considered. 

/pdf/overview-of-wireless-mesh-networks-5aquwjnd2m.pdf

Overview of Wireless Mesh Networks

In wireless Ad hoc networks, using multi-channel technique on MAC layer to increase the network capacity is a promising technology. By extending the RTS/CTS mechanism of IEEE802.11 standard, we propose a busy tone-based multi-channel MAC protocol, which can significantly improve the network throughput by using busy tone to distribute the multiple channels and overcome the multi-channel hidden terminal problem. On the basis of the protocol, this paper further takes the advantage of channel width adaptation technique, with which one channel can be effectively divided into several sub-channels so that the collision probability can be decreased and the network throughput can be further improved. NS2 simulation results show that, firstly, the proposed MAC protocol can significantly improve the throughput via using multiple channels and the improvement on throughput is in direct ratio to the number of channels; Secondly, without increasing the total bandwidth, dividing a channel into several sub-channels via the technique of channel width adaptation can also improve the network performance.

Ad Hoc Networks Multi-Channel MAC Protocol Design and Channel Width Adaptation Technology

With the innovation of Cognitive Radio Wireless Mesh Network’s, Opportunistic Spectrum Allocation can possibly moderate spectrum lack, by letting Secondary User’s a chance to sense and use unused bits of opportunistic licensed spectrum without any unfavourable effect on the Primary User’s. In Cognitive Radio Wireless Mesh Network’s, the Medium-Access-Control protocols characterizes the utilization of spectrum proficiently by allocating the channels among the users. Majority of proposed Medium-Access-Control protocols are utilizing Common-Control-Channel for dealing with the assets of Secondary-Users. The major downsides of these Medium-Access-Control protocols are broadcasting of Control-channel when substantial number of Secondary-User exists. In contrast with these Medium-Access-Control protocols, we develop an algorithm Time-Slotted-Allocation-Medium-Access-Control (TSA-MAC) protocol which is based on Clustered Time-Division-Medium-Access approach, which permits Secondary-User’s to allocate opportunistic spectrum with the help of co-operative decisions by exchange control information. In this approach, we are dividing the channels as different slots on which Secondary-User’s can transfer control and data packets. The TSA-MAC protocol will enhance the throughput for the Secondary-User’s over the communication channel. And also this method will facilitate to decide and allocate free channels for Secondary-User’s without interfering with Primary User’s.

Cluster-Based Opportunistic Spectrum Allocation in CRWMN’s Using Co-operative Mechanism

IEEE 802.11 wireless local area networks (WLANs) have been considered as potential solutions for constructing infrastructures of wireless mesh networks (WMNs). For connections going through multiple wireless hops, the interference and transmission range issue at physical layer, terminal problems at link layer, and unsatisfactory performance at transport layer may render 802.11 Medium Access Control (MAC) protocol inappropriate for wireless mesh networks. In fact, the hidden and exposed terminal problems magnify if interference range is multiple times wider than transmission range. The multi-radio multi-channel WLAN is a possible solution for multi-hop mesh networks. In this paper, a multi-channel MAC protocol is extended to combat the interference range and the hidden terminal problems for multi-hop wireless mesh networks. Besides, thorough simulation results indicate that the design offers excellent throughput performance in WLAN environments.

W.-C. Hung

Papers

MAC Design for Interference Issues in Multi-Channel Wireless Mesh Networks