Three-Stage Turbo MBER Multiuser Beamforming Receiver Using Irregular Convolutional Codes (original) (raw)
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Traditional Turbo EQualization (TEQ) schemes suffer from residual bit errors due to the non-recursive nature of the channel imposing Inter-Symbol-Interference (ISI). The performance of the traditional TEQ scheme may, however, be improved if an intermediate recursive channel codec is invoked, which results in a three-stage serially concatenated system. This intermediate code is necessary, especially when the inner module cannot be rendered recursive, for example, when a Minimum Mean Square Error (MMSE) equalizer is invoked. Our EXtrinsic Information Transfer (EXIT) chart analysis explicitly explains the performance gain, and based on this explanation IRregular Convolutional Codes (IRCCs) are constructed to be used as the outer code for the sake of achieving near capacity performance. Furthermore, the proposed analysis and design procedure may be applied in the context of diverse iterative receivers employing multiple soft-in/soft-out (SISO) modules.
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Iterative Minimum Mean Square Error (MMSE) equalization and channel decoding is appealing, since it exhibits a lower complexity than maximum a posteriori (MAP) turbo equalization. However, the MMSE equalizer's attainable performance is upper-bounded by that recorded for transmission over the coded AWGN channel, a phenomenon usually referred to as "error shoulder". In order to circumvent this performance limitation, we propose a three-stage concatenated transceiver constituted by inner and outer coding as well as MMSE equalization, which achieves significant iteration gains, despite using low-complexity serially concatenated memory-1 convolutional codes. It is demonstrated that this three-stage scheme outperforms the traditional two-stage MMSE turbo equalization scheme above a certain E b /N 0 threshold. Furthermore, the convergence behavior of the proposed scheme is analyzed with the aid of 3D EXtrinsic Information Transfer (EXIT) charts and their 2D projections, leading to a number of practical iterative receiver design guidelines.
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This paper studies the mutual information transfer characteristics of a novel iterative soft interference cancellation (SIC) aided beamforming receiver designed for quadrature phase shift keying (QPSK) modulated systems communicating over additive white Gaussian noise (AWGN) channels. Based on the extrinsic information transfer (EXIT) chart technique, we investigate the convergence behaviour of an iterative minimum bit error rate (MBER) multiuser detection scheme as a function of the system parameters and channel conditions. We also compare the achievable performance and convergence behaviour of different multiuser detectors (MUD) and channel decoders. Our simulation results show that the EXIT chart analysis is sufficiently accurate for reliably predicting the performance of the MBER MUD, despite its potentially non-Gaussian output distribution because we invoke the histogram-based approximation of the true distribution. As expected, the proposed SIC-MBER MUD outperforms the SIC aided minimum mean square error (SIC-MMSE) MUD.
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This paper studies mutual information transfer properties of iterative multiuser detector with linear precoding schemes for single carrier communications in multipoint-to-point multiple input multiple output (MIMO) channels. Based on multidimensional extrinsic information transfer (EXIT) analysis, we analyze the impact of linear precoding on the convergence properties of the detectors jointly designed with the precoders based on minimum sum mean squared error (MMSE) and maximum sum mutual information rate criteria. Results demonstrate that the use of the linear precoding schemes enhance the separability of the EXIT curves of the simultaneous streams over without precoding; This invokes the idea that different code rate be allocated to the each transmitted streams at the transmitters.
Adaptive Iterative Decoding for Expediting the Convergence of Unary Error Correction Codes
IEEE Transactions on Vehicular Technology, 2015
Multimedia encoders typically generate symbols having a wide range of legitimate values. In practical mobile wireless scenarios, the transmission of these symbols is required to be bandwidth efficient and error resilient, motivating both source coding and channel coding. However, Separate Source and Channel Coding (SSCC) schemes are typically unable to exploit the residual redundancy in the source symbols, which cannot be totally reduced by finite-delay, finite-complexity schemes, hence resulting in a capacity loss. Until recently, none of the existing Joint Source and Channel Codes (JSCCs) were suitable for this application, since their decoding complexity increases rapidly with the size of the symbol alphabet. Motivated by this, we proposed a novel JSCC referred to as the Unary Error Correction (UEC) code, which is capable of exploiting all residual redundancy and eliminating any capacity loss, while imposing only a moderate decoding complexity. In this paper, we show that the operation of the UEC decoder can be dynamically adapted, in order to strike an attractive trade-off between its decoding complexity and its error correction capability. Furthermore, we conceive the corresponding Three Dimensional (3D) EXtrinsic Information Transfer (EXIT) charts for controlling this dynamic adaptation, as well as the decoder activation order, when the UEC code is serially concatenated with a turbo code. In this way, we expedite the iterative decoding convergence, facilitating a gain of up to 1.2 dB compared to both SSCC and to its non-adaptive UEC benchmarkers, while maintaining the same transmission bandwidth, duration, energy and decoding complexity.
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This paper presents a low complexity iteratively detected space-time transmission architecture based on Generalized Multi-Layer Space-Time (GMLST) codes and IRregular Convolutional Codes (IRCCs). The GMLST combines the benefits of the Vertical Bell-labs LAyered Space-Time (V-BLAST) scheme and Space-Time Coding (STC). The GMLST is serially concatenated with a Unity-Rate Code (URC) and an IRCC which are used to facilitate near-capacity operation with the aid of an EXtrinsic Information Transfer (EXIT) chart based design. Reduced-complexity iterative multistage Successive Interference Cancellation (SIC) is employed in the GMLST decoder, instead of the significantly more complex Maximum Likelihood (ML) detection. For the sake of approaching the maximum attainable rate, iterative decoding is invoked to achieve decoding convergence by exchanging extrinsic information across the three serial component decoders. Finally, it is shown that the SIC-based iteratively detected IRCC-URC-GMLST system is capable of providing a feasible trade-off between the affordable computational complexity and the achievable system throughput.
2007 IEEE 66th Vehicular Technology Conference, 2007
Serially concatenated and iteratively decoded Irregular Variable Length Coding (IrVLC) combined with precoded Fast Frequency Hopping (FFH) M-ary Frequency Shift Keying (MFSK) is considered. The proposed joint source and channel coding scheme is capable of low Signal-to-Noise Ratio (SNR) operation in Rayleigh fading channels contaminated by Partial Band Noise Jamming (PBNJ). The IrVLC scheme is comprised of a number of component Variable Length Coding (VLC) codebooks employing different coding rates for encoding particular fractions of the input source symbol stream. These fractions may be chosen with the aid of EXtrinsic Information Transfer (EXIT) charts in order to shape the inverted EXIT curve of the IrVLC codec so that it can be matched with the EXIT curve of the inner decoder. We demonstrate that using the proposed scheme near-zero bit error ratio may be achieved at low SNR values and the IrVLC based scheme yields a further gain of up to 0.3dB over the identical-rate single-class VLC based benchmarker scheme.
On Multi-User EXIT Chart Analysis Aided Turbo-Detected MBER Beamformer Designs
IEEE Transactions on Wireless Communications, 2000
This paper studies the mutual information transfer characteristics of a novel iterative soft interference cancellation (SIC) aided beamforming receiver communicating over both additive white Gaussian noise (AWGN) and multipath slow fading channels. Based on the extrinsic information transfer (EXIT) chart technique, we investigate the convergence behavior of an iterative minimum bit error rate (MBER) multiuser detection (MUD) scheme as a function of both the system parameters and channel conditions in comparison to the SIC aided minimum mean square error (SIC-MMSE) MUD. Our simulation results show that the EXIT chart analysis is sufficiently accurate for the MBER MUD. Quantitatively, a two-antenna system was capable of supporting up to K=6 users at E b /N0=3dB, even when their angular separation was relatively low, potentially below 20 • .