A Fast Convergecast Method for Tree-Based Wireless Sensor Networks

How fast can information be collected in a wireless sensor network organized as tree? To address this issue we explore and evaluate a few techniques using realistic simulation models under the many-to-one communication paradigm known as convergecast. We first consider time scheduling on a single frequency channel, where we aim at minimizing the schedule length i.e. the number of time slots required to complete a convergecast. Then we combine scheduling with transmission power control to mitigate the effect of interference. It also helps to reduce the schedule length under a single frequency. Here we investigated two cases: (i) when nodes transmit at maximum power, and (ii) when nodes adjust their transmission power according to the specific algorithm. We also observe that power control is more effective in reducing the schedule length for denser deployments than in sparser ones where the results tend to be similar. Scheduling transmissions using multiple frequencies is more efficient than the power control scheme. We give lower bounds on the schedule length when interference is completely eliminated, and propose algorithms that achieve these bounds. We also evaluate the performance of various channel assignment methods and find empirically that for moderate size networks of about 100 nodes, the use of multi-frequency scheduling can suffice to eliminate most of the interference. Lastly, we evaluate the impact of different interference and channel models on the schedule length.