Online SNR estimation for parallel combinatorial SS systems in Nakagami fading channels

In this paper, a simple and accurate online SNR estimator is proposed for parallel combinatorial SS (PC/SS) systems in Nakagami fading channels. The PC/SS systems are a kind of partial-code-parallel multicode DS/SS systems. Our proposed SNR estimator estimates the SNR at the correlator output by using a statistical ratio of the sum of correlator outputs for pre-assigned PN codes. We investigate the SNR estimation accuracy in Nakagami fading channels through computer simulations. Numerical results show that the the proposed SNR estimator brings superior estimation performance to that in conventional estimator that was proposed by Summers and Wilson (1998). In addition, we apply it to the convolutional coded PC/SS systems with iterative demodulation and decoding to evaluate the estimation performance from the viewpoint of error rate. By using our estimator, the bit error rate performance is close to the performance with perfect knowledge of the SNR information in Nakagami fading channels and correlated Rayleigh fading channels.