We consider transmissions over the frequency-nonselective time-selective fading channel and derive the soft-decision-aided maximum a posteriori probability (SDA-MAP) channel estimator that utilizes the entire received...
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We consider transmissions over the frequency-nonselective time-selective fading channel and derive the soft-decision-aided maximum a posteriori probability (SDA-MAP) channel estimator that utilizes the entire received signal sequence, including both pilot signals and data signals, and the a priori statistical information of the transmitted data symbols. This paper theoretically demonstrates how the soft data decisions should be incorporated into the channel estimation process. An iterative implementation of the SDA-MAP estimator is proposed, which uses the feedback of earlier soft decisions and the feedforward of later soft decisions to estimate the current channel gain. This approximate SDA-MAP implementation is similar in structure to the expectation-maximization algorithm. Simulation results show that the receiver using this iterative SDA-MAP estimator outperforms the conventional pilot-symbol-assisted modulation receiver in which the channel estimates are obtained from only the pilot signals. An application to iterative decoding using the lte turbo code is also provided.
turbocodes facilitate near-capacity transmission throughputs by achieving a reliable iterative forward error correction. However, owing to the serial data dependence imposed by the logarithmic Bahl-Cocke-Jelinek-Ravi...
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turbocodes facilitate near-capacity transmission throughputs by achieving a reliable iterative forward error correction. However, owing to the serial data dependence imposed by the logarithmic Bahl-Cocke-Jelinek-Raviv algorithm, the limited processing throughputs of the conventional turbo decoder implementations impose a severe bottleneck upon the overall throughputs of real-time communication schemes. Motivated by this, we recently proposed a floating-point fully parallel turbo decoder (FRED) algorithm, which eliminates the serial data dependence, allowing parallel processing and hence significantly reducing the number of clock cycles required. In this paper, we conceive a technique for reducing the critical datapath of the FRED, and we propose a novel fixed-point version as well as its very large scale integration (VLSI) implementation. We also propose a novel technique, which allows the FRED to also decode shorter frames employing compatible interleaver patterns. We strike beneficial tradeoffs amongst the latency, core area, and energy consumption by investigating the minimum bit widths and techniques for message log-likelihood ratio scaling and state metric normalization. Accordingly, the design flow and design tradeoffs considered in this paper are also applicable to other fixed-point implementations of error correction decoders. We demonstrate that upon using Taiwan Semiconductor Manufacturing Company (TSMC) 65-nm low-power technology for decoding the longest long-term evolution frames (6144 b) received over an additive white Gaussian noise channel having E-b/N-0 = 1 dB, the proposed fixed-point FP ID VLSI achieves a processing throughput of 21.9 Gb/s and a processing latency of 0.28 mu s. These results are 17.1 times superior to those of the state-of-the-art benchmarker. Furthermore, the proposed fixed-point FRED VLSI achieves an energy consumption of 2.69 mu J/frame and a normalized core area of 5 mm(2)/Gb/s, which are 34% and 23% lower than those of the be
A modification of the BCJR algorithm is derived for convolutionally-coded transmissions over the time-selective, frequency-flat, Rayleigh fading channel with pilot-symbol-assisted channel estimation. The derivation de...
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ISBN:
(纸本)9781538645024
A modification of the BCJR algorithm is derived for convolutionally-coded transmissions over the time-selective, frequency-flat, Rayleigh fading channel with pilot-symbol-assisted channel estimation. The derivation demonstrates why the minimum mean-square error (MMSE) channel estimator is required and how the acquired channel estimate and the estimation error variance should be used in the maximum a posteriori probability decoding. Using the lte turbo code as an example, we show that the newly derived algorithm outperforms the conventional BCJR algorithm in both standard turbo decoding and iterative channel estimation and decoding. The work demonstrates the importance of incorporating channel estimation accuracy in turbo decoding.
The combination of multicarrier signals with nonorthogonal frequency spacing (spectrally efficient frequency division multiplexing, SEFDM) and forward error correction (FEC) schemes is analyzed for lte convolutional a...
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ISBN:
(纸本)9783319463018;9783319463001
The combination of multicarrier signals with nonorthogonal frequency spacing (spectrally efficient frequency division multiplexing, SEFDM) and forward error correction (FEC) schemes is analyzed for lte convolutional and turbocodes. BER performance of coded and uncoded OFDM and SEFDM is considered while keeping the spectral efficiency constant. Also puncturing patterns are selected for providing different code rates of the lteturbo-code encoder with very small step size. It is shown that compared with uncoded OFDM the best value of SEFDM compression factor providing better BER performance can be found. But for coded OFDM coded SEFDM always performs worse due to waterfall behaviour of BER curves, thus restricting the application borders of SEFDM.
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