Ultra-wideband detect and avoid procedure for WiMAX victims

Detect and avoid (DAA) procedures aim at improving ultra-wideband (UWB) coexistence with existing narrowband/wideband licenced/unlicenced victim terminals operating in the same band at the same time and area. The authors propose a DAA procedure that can be used to reduce the percentage of time the UWB interferes with victims operating in a time division duplexing (TDD) mode. The authors consider a system scenario where a TDD terminal has a primary role and UWB devices create a secondary network on a local area basis. A DAA procedure is implemented only in the UWB devices that adapt their transmissions in order to avoid or reduce interference on primary device(s) in the same area. The performance of the proposed DAA procedure is presented and discussed and its dependence on some key UWB transmission parameters, bit rate and the emitted power is evidenced. It is shown that the DAA timeout parameters can be tuned so as to arbitrarily reduce the average percentage of time the UWB interferes with the considered victim systems even well below the limits imposed by regulatory bodies. It is shown that interference reduction is obtained at the expense of reduced performance of the UWB transmission. The proper selection of DAA timeouts for a desired percentage of UWB interference and UWB link efficiency is discussed.