The Maximum Processing Gain of the Spreading Signal in Multipath Fading Channels

Considering the joint algorithm of coherent detection and non-coherent detection, we focus on the maximum processing gain of spreading signal, which is 2-dimensional spread spectrum signal, relative to binary phase shift keying (BPSK) and transmitted in rich scattering multipath fading channels. In this paper, we first investigate the processing gain of spreading signal and analyze its expression. Then, by increasing signal bandwidth or symbol period infinitely, we obtain that the processing gain is bounded, and the maximum processing gain is determined by the channel parameters and the energy-per-bit to noise density ratio (E_b/N₀). By analysis and simulation, it is shown that the processing gain is not more than 30dB, when the spreading signal relative to BPSK, with E_b/N₀ 20dB, the maximum Doppler shift 100Hz, and the negative exponential factor 5E-6, is transmitted in rich scattering multipath fading channels.