Spread ALOHA throughput improvement using mismatched filtering

Abstract

For the purpose of signal spreading in spread ALOHA systems, sequences with low autocorrelation sidelobe level have been used with the matched filter being used at the receiver side for the despreading. Even the presence of low autocorrelation sidelobes, reduces the throughput of the spread ALOHA system in comparison to the conventional ALOHA system. A different filtering method, named mismatched filtering, is introduced here where an almost negligible amount of signal to noise ratio (SNR) is sacrificed in order to minimise, if not completely remove, the autocorrelation sidelobes. As a result, the throughput of the spread ALOHA system is almost identical to the throughput of the conventional ALOHA system. Simulations have been performed to compare the throughput of the spread ALOHA system using mismatched and matched filtering with the conventional ALOHA system without signal spreading.