Noncoherent Multiple-symbol Detection Research Articles

BER Analysis of Decision-Feedback Multiple-Symbol Detection in Noncoherent MIMO Ultrawideband Systems

In this paper, we investigate noncoherent multiple-input-multiple-output (MIMO) ultrawideband (UWB) systems where the signal is encoded by differential space-time block code (DSTBC). DSTBC enables noncoherent MIMO UWB systems to achieve diversity gain. However, the traditional noncoherent symbol-by-symbol differential detection (DD) for DSTBC-UWB suffers from performance degradation compared with coherent detection. We introduce a noncoherent multiple-symbol detection (MSD) scheme to enhance the performance of DSTBC-UWB systems. Although the MSD scheme can boost the performance more as the observation window size becomes larger, the complexity of the exhaustive search for MSD also exponentially increases in terms of the window size. To decrease the computational complexity, the concept of decision feedback (DF) is introduced to the MSD for DSTBC-UWB in this paper. The resultant DF-MSD yields reasonable complexity and solid performance improvement. We provide the bit-error-rate analysis for the proposed DF-MSD. Both theoretical analysis and simulation results validate the proposed scheme.

Decision-feedback multiple symbol detection for differential space-time block coded UWB systems

The symbol-by-symbol differential detection scheme, originally employed to detect differential space-time block coded (DSTBC) ultra-wideband (UWB) signal in previous work, suffers from a performance degradation compared with coherent detection. In this paper, a noncoherent multiple symbol detection (MSD) scheme is proposed to enhance the performance of DSTBC-UWB system. After the signal model of DSTBC-UWB is analyzed, the optimal maximum likelihood (ML) MSD is derived and then a suboptimal ML-MSD is obtained by channel approximating. However, exhaustive search based MSD is impractical in DSTBC-UWB systems since its complexity increases exponentially with observation window size. To decrease the computational complexity, the decision-feedback (DF) scheme is introduced to MSD. The resultant DF-MSD yields reasonable complexity and solid performance improvement.

Sphere Decoding Based Multiple Symbol Detection for Differential Space-Time Block Coded Ultra-Wideband Systems

In this letter, a sphere decoding (SD) based noncoherent multiple symbol detection (MSD) scheme is proposed for differential space-time block coded (DSTBC) ultra-wideband (UWB) impulse radio systems. Exhaustive search based maximum likelihood (ML) MSD is impractical in DSTBC-UWB systems since its complexity exponentially increases with observation window size. To decrease the computational complexity, the original MSD metric is transformed into another equivalent form which can be implemented by SD for DSTBC-UWB systems.

Noncoherent Multiple-Symbol Detection in Coded Ultra-wideband Communications

Recently, ultra wideband (UWB) impulse radio systems based on noncoherent detection, such as transmitted reference and differential modulation systems, have drawn a lot of attention for their potential applications in low-rate and low-cost communications. In this paper, a unified approach is presented to develop and analyze a noncoherent multiple-symbol detection (MSD) algorithm for various UWB signaling formats in multi- path environments. Pair-wise error probabilities of coherent and noncoherent MSD algorithms are derived and compared. The intrinsic connection between the coherent and noncoherent MSD algorithms is revealed, tradeoff curves between their performance and complexity are obtained, and optimal transmission signal design rules for noncoherent detection are provided. The bit error rates are shown through simulations to verify the analysis and to evaluate the performance of the developed algorithms in realistic environments.

Multiple-symbol detection for orthogonal modulation in CDMA system

We investigate in this paper the performance of orthogonal modulations with noncoherent multiple-symbol detection (MSD). It is shown that for uncoded systems, the asymptotic error performance of the MSD is almost as good as that of the ideal coherent detector. The application of MSD to the CDMA IS-95 reverse link, which represents a coded system, is also considered. The simulation results show that the MSD receiver is about 0.5 dB better than the conventional symbol-by-symbol detector in both the additive white Gaussian noise and Rayleigh fading channels. Finally, reduced-complexity MSD receivers with little performance degradation are also presented in this paper.