Collaborative Channel Equalization: Analysis and Performance Evaluation of Distributed Aggregation Algorithms in WSNs

In wireless sensor networks (WSN), collaboration is a way to improve the quality of data communication between sensor nodes with restricted resources in terms of memory, processing and energy storage. For receive collaboration, various array processing schemes such as receive beamforming and collaborative channel equalization (CCE) can be used for aggregating data received by each node in the network. The key challenge is the limitation on the number of nodes which can collaborate because of the increased computational load and memory demand when the multiple signals are aggregated. This problem arises when sensor nodes in a CDMA based WSN collaborate, although the low power property of CDMA technique makes it suitable for WSN applications. Here receive collaboration is investigated in CDMA networks using CCE as the collaboration algorithm. We present two novel distributed signal aggregation algorithms: partial and hierarchical aggregation, which distribute computational load and memory demands on collaborative nodes. The positive impacts of receive collaboration on the signal quality and reliability are confirmed experimentally in a WSN scenario using software radios. Then the requirements of collaborative reception using CCE combined with the novel aggregation methods in terms of computational and memory load, as well as energy consumption are evaluated. The results indicate that the distributed signal aggregation algorithms, especially hierarchical aggregation, have computational and memory requirements less than that of centralized CCE, providing greater flexibility and scalability which enables collaboration in WSNs on a larger scale than previously possible.