DSSS vs. FHSS narrowband interference performance issues

D spread spectrum (DSSS) and frequency-hopping spread spectrum (FHSS) technologies have different physical mechanisms for rejecting narrowband interference. Because of these physical differences, they perform differently in the presence of the same levels of narrowband interference. This is an important case for successful operation in the ISM bands. After presenting the physical mechanisms by which these spread spectrum methods reject narrowband interferers, measured examples are shown to illustrate DSSS and FHSS interference rejection. Performances of DSSS and FHSS in the presence of a large out-ofband interferer are also measured and compared. Comparisons between the two spread spectrum methods are drawn highlighting the conditions under which they perform identically, and also when one method performs better than the other. The proper choice of direct sequence or frequency hopping as a spread-spectrum technique depends on the actual environment in which the system will be deployed.