Parallel Combinatory Spread Spectrum System Based on Single Carrier Frequency Domain Equalization in Multipath Fading Channels

To solve the problem of performance limitation of direct sequence (DS) spread spectrum system in complex multipath environment, a parallel combinatory spread spectrum (PCSS) framework that combines single carrier frequency domain equalization (SCFDE) is proposed. Higher data rates and large processing gain can be achieved by PCSS transmission and the frequency-selective fading is overcome by frequency domain equalization, which is easy to implement at the receiver for the benefit of fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT). Moreover, in order to balance the transmission rate and reliability in different environments and tasks, an improved PCSS framework with adaptive processing gain is investigated by deploying variable spread spectrum factors under the condition that the number of FFT/IFFT processing points is fixed, by which the control logic is very simple and it is convenient for real implementation. Experimental results demonstrate that the proposed PCSS schemes based on SCFDE show good performance in overcoming multipath fading. In the meanwhile, higher bandwidth utilization can be obtained compared with traditional DS strategy.