SummaryIn this work, we introduce a new chip-level linear modified-SIC multi-user structure that is asymptotically equivalent to successive over-relaxation (SOR) iteration, which is known to outperform the conventional GaussSeidel iteration by an order of magnitude in terms of convergence speed. The main advantage of this scheme is that it uses directly the spreading codes and not the cross-correlation coefficients and thus reduces significantly the overall computational complexity. This is critical for the design of low-complexity multiuser detectors for longcode CDMA systems such as IS95 and UMTS. We use a matrix algebraic approach to show the equivalence of the proposed scheme to linear matrix filtering. This allows obtaining an analytical expression for both the bit-error rate (BER) and the asymptotic multiuser efficiency (AME). Moreover, we study the convergence behavior of the proposed scheme and prove that it converges if the relaxation factor is within the interval ]0, 2[. Simulation results are in excellent agreement with theory.
In this work a reduced complexity chip-level linear SIC multiuser structure that is asymptotically equivalent to successive over-relaxation (SOR) iteration, which is known to outperform the conventional Gauss-Seidel iteration by an order of magnitude in terms of convergence speed, is proposed. The main advantage of the proposed scheme is its low computational complexity compared to other chip-level and symbol-level SIC schemes equivalent to successive over-relaxation (SOR) iteration. We study the convergence behaviour of the proposed scheme and prove that it converges if the relaxation factor is in the interval ]0, 2[. Simulation results are in excellent agreement with theory.
We introduce a chip-level linear group-wise successive interference cancellation (GSIC) multiuser structure that is asymptotically equivalent to block successive over-relaxation (BSOR) iteration, which is known to outperform the conventional block Gauss-Seidel iteration by an order of magnitude in terms of convergence speed. The main advantage of the proposed scheme is that it uses directly the spreading codes instead of the cross-correlation matrix and thus does not require the calculation of the crosscorrelation matrix (requires 2NK 2 floating point operations (flops), where N is the processing gain and K is the number of users) which reduces significantly the overall computational complexity. Thus it is suitable for long-code CDMA systems such as IS-95 and UMTS where the cross-correlation matrix is changing every symbol. We study the convergence behavior of the proposed scheme using two approaches and prove that it converges to the decorrelator detector if the over-relaxation factor is in the interval ]0, 2[. Simulation results are in excellent agreement with theory.
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