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Low Complexity Stopping Criteria for UMTS Turbo-Decoders
- in Proc. VTC 2003-Spring Vehicular Technology Conference The 57th IEEE Semiannual, Jeju, Korea
, 2003
"... Abstract — Turbo-Codes are part of the third generation wireless communications system (UMTS). A Turbo-Decoder consists of two soft-in soft-out component decoders, which exchange information (soft-values) in an iterative process. The number of iterations for decoding strongly depends on the channel ..."
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Cited by 6 (2 self)
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Abstract — Turbo-Codes are part of the third generation wireless communications system (UMTS). A Turbo-Decoder consists of two soft-in soft-out component decoders, which exchange information (soft-values) in an iterative process. The number of iterations for decoding strongly depends on the channel characteristic which can change from block to block due to fading. In this paper, we present two new stopping criteria which can be implemented on dedicated hardware or DSP with negligible overhead. The new criteria operate on the sum of the absolute soft output values, calculated after each component decoder and is referred to as sum reliability. We compare the communications performance and average number of iterations of our proposed criteria to other criteria in literature using a fixed-point 8-state Turbo-Decoder implementation in an UMTS FDD-Downlink chain. An analysis of the arithmetic complexity and memory demand yields minimal overhead with excellent performance compared to other stopping criteria. I.
Approximate MIMO iterative processing with adjustable complexity requirements
- IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY
, 2012
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Design Rules for Adaptive Turbo Equalization in Fast-Fading
- in Proc. Intern. Conf. Communication Systems & Networks
, 2002
"... This paper uses the mutual information (MI) transfer metric to characterize the behavior of an adaptive turbo equalization scheme. We consider recursive systematic convolutional coding at the input to a multipath fastfading channel. The equalizer is a recent adaptive, nearoptimal APP algorithm that ..."
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Cited by 2 (0 self)
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This paper uses the mutual information (MI) transfer metric to characterize the behavior of an adaptive turbo equalization scheme. We consider recursive systematic convolutional coding at the input to a multipath fastfading channel. The equalizer is a recent adaptive, nearoptimal APP algorithm that incorporates MMSE channel estimation. We develop design rules for this turbo equalizer using EXIT charts. We optimize the use of pilot bits and determine the best ratio of code bits to pilot bits, for fixed data and symbol rates.
Fidelity charts and stopping/termination criteria for iterative multiuser detection,” to appear at
- 4th International Symposium on Turbo Codes and Related Topics
, 2006
"... An iterative multiuser detection (IMUD) receiver is considered for a code-division multiple-access (CDMA) system with turbo codes. Fidelity is considered as a metric for convergence analysis and an approximation of fidelity as a function of variance of the log-likelihood ratios is introduced. Fideli ..."
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An iterative multiuser detection (IMUD) receiver is considered for a code-division multiple-access (CDMA) system with turbo codes. Fidelity is considered as a metric for convergence analysis and an approximation of fidelity as a function of variance of the log-likelihood ratios is introduced. Fidelity charts are compared with extrinsic information transfer (EXIT) charts as tools for convergence analysis and a close approximation of the relationship between fidelity and mutual information is proposed. We then use this function to approximate a closed form expression for the EXIT function of an interference canceller. Further, we propose a new stopping criterion for the turbo decoder and the IMUD receiver which achieves complexity saving of up to 50 % over conventional designs. 1
Comparison of Convolutional Coupled Codes and Partially Systematic Turbo Codes for Medium Code Lengths
"... Two classes of concatenated codes of rate 1/2 and medium code lengths (600, 2000) are considered: convolutional coupled codes and partially systematic turbo codes. As opposed to the classical turbo code (Berrou, Glavieux), which is a systematic code, coupled codes contain no systematic bits and part ..."
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Two classes of concatenated codes of rate 1/2 and medium code lengths (600, 2000) are considered: convolutional coupled codes and partially systematic turbo codes. As opposed to the classical turbo code (Berrou, Glavieux), which is a systematic code, coupled codes contain no systematic bits and partially systematic turbo codes only some systematic bits. These codes can still be iteratively decoded and they show even better distance properties. This leads to better error rate performances in a wide range of signal-to-noise ratios, especially in the "flattening region". The two code classes and their performances are presented and compared.
