Hybrid SD/MRC one-shot linear decorrelating detector for asynchronous CDMA systems

The one-shot linear decorrelating detector (LDD) was proposed to reduce the computational complexity and delay required in the conventional LDD, but it still requires high complexity. Another one-shot LDD with low complexity was proposed. To improve its performance, this detector uses maximal ratio combining (MRC) at the two outputs of the left piece of the present bit and the right piece of the next bit in a one-shot window. In spite of the aid from MRC, the performance of the one-shot LDD with post-MRC is worse than the one-shot LDD. To overcome this problem, we propose a one-shot LDD with pre-SDC/post-MRC that employs selection diversity combining (SDC) with multiple antenna elements in front of the one-shot LDD with post-MRC. In asynchronous random CDMA systems over fading channels, the largest SNR of SDC, near-far resistance (NFR) of the one-shot LDD, and the output SNR of MRC are random variables. We derive the probability density functions (PDFs) for these random variables and calculate the bit error rate (BER) of the proposed detector using the obtained PDFs. In comparison of mathematical analysis and computer simulation results, we observe good agreement.