The Effects of Interference Threshold and SNR Hysteresis on Distributed Channel Assignment Algorithms for UFDMA

The effects of interference threshold and SNR acceptance threshold on channel capacity have been determined for several distributed channel assignment algorithms using Unsupervised FDMA (UFDMA), a multiple access scheme for the terrestrial radio environment. It is found that the effect of tightening the interference threshold reduces the call dropping probability at the expense of increasing the blocking probability for a given channel capacity. Introducing hysteresis in the SNR acceptance threshold is only beneficial in improving performance if a high level of call dropping can be tolerated, and in all circumstances reduces capacity for a fixed call blocking grade of service. These effects are then explained using a pictorial model which considers the frequency reuse behaviour using the concepts of Interference and SNR Exclusion Areas.