Abstract
With the increase of usage of wireless networks for purposes where the nodes are either stationary or minimally mobile, focus is also on increasing the network capacity of wireless networks. One such way is to use non-overlapping multiple channels provided by 802.11 by using multiple interfaces per node. Multiple nonoverlapped channels exist in the 2.4GHz and 5GHz spectrum. However, most IEEE 802.11-based multihop ad hoc networks today use only a single channel. As a result, these networks rarely can fully exploit the aggregate bandwidth available in the radio spectrum provisioned by the standards. Under this scenario, several challenges need to be addressed before all the available channels can be fully utilized. Major ones are design of underlying routing protocols and channel assignment algorithms to go with the existing offthe- shelf hardware. This report summarizes the existing work done in this direction. Also, it lists out three simulators which might be used for simulation studies of such architectures. Lastly, it discusses an extension of NS-2.29 compatible with latest version of gcc and supporting multiple-channel mutiple-interface assignment. Also it gives simulation study of implementation of Hyacinth[2] for more than 2 network interfaces per node.
1. Introduction
Wireless network technology, despite being extremely useful in mobile communication and computing application, suffers from low link-layer data rates. The 54 Mbps peak link-layer data rate of IEEE 802.11a/g wireless LAN interface stands no chance in front of huge bandwidths provided by wired technologies. Moreover, overheads of packet loss, packet errors, contention and packet headers, drastically reduce the actual goodput available to the wireless network applications. The data rate also falls quickly with increasing distance between signal source and destination. Interference from adjacent hops in a multi-hop network further decreases the available bandwidth. Usage of multiple channels thus removes both of the problems - it extends the available bandwidth and removes the problem of interference as now simultaneous communication is established between adjacent hops on a non-overlapping channel. The sudden increase in the rise of interest in this research area can be owed to wireless hardware costs which are steeply falling. Hence, it is now feasible to equip nodes with multiple 802.11 wireless interfaces. As we cannot equip the nodes with an interface for every non-overlapping channel due to power consumption and size constraints, we need to devise channel assignment algorithms which would switch the interfaces from one channel to other albeit at the cost of switching delay.


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