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Weighted Channel Assignment in Wireless Multi-hop Multi-channel Sensor Networks

IP.com Disclosure Number: IPCOM000170305D
Original Publication Date: 2008-Jun-03
Included in the Prior Art Database: 2008-Jun-03
Document File: 4 page(s) / 251K

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Abstract

Channel assignment in multi-channel and distributed wireless networks can be solved by edge coloring in the corresponding network graph. The edges represent links and the colors stand for channels. The solution is usually given by (sub-)optimal distributed mechanisms for edge coloring which typically results in one link per channel with no collisions. However, if the number of channels is lower than the network graph's maximum degree, more than one link per channel will be assigned by any edge-coloring algorithm. In this case, special techniques are required for balancing the overall network traffic among different channels. Also, QoS (Quality of Service) requirements have to be taken into account when assigning channels and edge collisions have to be minimized. At present, several solutions exist to the problem mentioned above. For instance, a weighted coloring algorithm can be utilized or the coloring can be coupled with routing in cross-layer protocols for maximizing performance over a multi-hop wireless network. Channel assignment can also be performed at the routing layer with a simple heuristic, minimizing conflicts among neighbors of each node.

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Weighted Channel Assignment in Wireless Multi-hop Multi-channel Sensor Networks

Idea: David Tacconi, PhD, IT-Trient; Francesco De Pellegrini, PhD, IT-Trient

Channel assignment in multi-channel and distributed wireless networks can be solved by edge coloring in the corresponding network graph. The edges represent links and the colors stand for channels. The solution is usually given by (sub-)optimal distributed mechanisms for edge coloring which typically results in one link per channel with no collisions. However, if the number of channels is lower than the network graph's maximum degree, more than one link per channel will be assigned by any edge-coloring algorithm. In this case, special techniques are required for balancing the overall network traffic among different channels. Also, QoS (Quality of Service) requirements have to be taken into account when assigning channels and edge collisions have to be minimized.

At present, several solutions exist to the problem mentioned above. For instance, a weighted coloring algorithm can be utilized or the coloring can be coupled with routing in cross-layer protocols for maximizing performance over a multi-hop wireless network. Channel assignment can also be performed at the routing layer with a simple heuristic, minimizing conflicts among neighbors of each node.

A novel solution to the problem mentioned above is presented in the following. A distributed method can be utilized for assigning channels to the edges of a wireless multi-hop multi-channel network, allowing network traffic balance among different channels. For the weighted channel assignment the average traffic load over time and QoS requirements have to be taken into account. Based on this, the link weights can be evaluated. The edge coloring is performed by every network node taking into account the evaluated link weights. The most weighted links are assigned to the "lightest" color (channel), i.e. those colors still being free or having low traffic load and/or low QoS requirements. Colliding edges can be handled by a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) or a corresponding random access protocol. These edges, however, share the channel, which entails that under high traffic conditions performance both in terms of latency and throughput is decreased. In case a link weight goes below or above a pre-assigned weight/threshold, the weighted channel assignment is re-run for the affected links.

A specific example for the presented solution is given in Figure 1. The nodes in a three-channel WSAN (Wireless Sensor and Actuator Network) communicate in a multi-hop manner. The network comprises ten nodes and has the link weights already assigned, taking into account the bidirectional traffic load and QoS requirements. The weighted channel assignment is performed at every network node, conventi...