Feasibility study of coexistence between spread spectrum and analog broadcasting systems

The study considers the viability and limitations of a spread spectrum radio concept. This concept proposed a spectrum overlay of a spread spectrum system on the existing narrowband FM broadcasting system. The overlaid spread spectrum (SS) system is assumed to utilize direct sequence (DS) spreading, using maximal length pseudorandom sequences with long spreading codes. We studied the performance analysis of the SS system due to the overlaying analog FM system, consisting of multiple narrowband FM stations. The received narrowband interference (NBI) on the SS receiver performance was calculated and compared with a set of threshold criteria that derived in previous studies by the authors, in terms of carrier-to-interference ratio (CIR). The probability of error for the SS signal was determined for various types of spreading scenarios, for various signal-to-interference ratios and for different processing gains. The obtained parameters will ascertain the restrictions and the feasibility of the concept.