| Abstract |
A major issue concerning wireless transmission nowadays is the existence of interference. Interference constitutes a key factor for reduced capacity and performance of wireless systems, such as the Wireless Local Networks or the Wireless Metropolitan Networks. The procedure for assigning channels in a wireless network should account for the interference between the same or adjacent channels amongst the links of the network itself, as well as interference caused by external networks. In this thesis we first propose a new approach for modeling interference, based on the “multi-point link conflict graph”. The proposed conflict graph requires a priori knowledge of the wireless network topology, in terms of links between wireless interfaces. Each vertex in the conflict graph corresponds to a point-to-point, a point-to-multipoint, or a multipoint-to-multipoint link of the actual network. An edge between vertices in the conflict graph exists, when the links that correspond to the vertices can interfere. The second contribution of this thesis is to propose and evaluate a channel assignment algorithm based on the aforementioned multi-point link conflict graph. Two important parts of the algorithm are the order in which links are assigned a channel and the metric used to choose the best channel for a link. Implementation and evaluation of the channel assignment algorithm was performed in an experimental, wireless metropolitan multi-radio mesh network consisting of directed antennas and point-to-point connections. The proposed multi-point link conflict graph model was compared to another approach for capturing interference, based on creating traffic on links that have been assigned channels. Our experiments indicate that both methods tend to have the same performance, in terms of average packet delay and latency. Additionally, the experiments suggested that channel selection metrics and the channel assignment order do not significantly affect the algorithm’s performance, in the case of a wireless metropolitan network with a small number of links.
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