Space Division Multiple Access for Wireless Sensor Networks

A uniform latin square of order k = m² is an k times k square matrix that consists of k symbols from 0 to k-1 such that no symbol appears more than once in any row or in any column. This property is also maintained in any m times m area of main subsquares in a k times k Latin square. The uniqueness of each symbol in the main subsquares presents very attractive characteristic in applying uniform latin squares to time slot allocation problem in sensor networks. In this paper, we propose a space division multiple access (SDMA) scheme for wireless sensor networks based on Uniform Latin squares. The SDMA divides the geographical area into space divisions, where there is one-to-one map between space divisions and time slots. Because of the uniqueness of the symbol value in any main subsquares, the mapping of time slots into space divisions guaranties a collision-free medium access to sensor nodes. We also study the effect of the use of multiple transmission power levels and corresponding packet lengths on the system throughput. To do so, a self-controlled multiple power level algorithm has been proposed to improve the throughput of a multiple power level system.