Browsing by Keyword "Turbo codes"
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Item Joint Turbo coding and source-controlled modulation of cycle-stationary sources in the bandwidth-limited regime(2010) Ochoa, Idoia; Crespo, Pedro M.; Del Ser, Javier; Hernaez, Mikel; IAIn this paper we propose a novel one-layer coding/shaping transmission system for the bandwidth-limited regime based on singlelevel codes and sigma-mapping [1]. Specifically, we focus on cyclestationary information sources with independent symbols. High spectral efficiencies can be achieved by combine at the transmitter a Turbo code with a sigma-mapper. Furthermore, the encoded symbols are modulated by using an asymmetric energy allocation technique before entering the aforementioned sigma-mapper. The corresponding decoder iterates between the Turbo decoder and the sigma-demapper, which exchange progressively refined extrinsic probabilities of the encoded symbols. For the Additive White Gaussian Noise (AWGN) channel, simulation results obtained for very simple Turbo codes show that the proposed system attains low bit error rates at signal-to-noise ratios relatively close to the corresponding Shannon limit. These promising results pave the way for future investigations towards reducing the aforementioned energy gap, e.g. by utilizing more powerful Turbo codes.Item Turbo joint source-channel coding of non-uniform memoryless sources in the bandwidth-limited regime(2010-04) Ochoa, Idoia; Crespo, Pedro; Ser, Javier Del; Hernaez, Mikel; IAThis letter proposes a novel one-layer coding/ shaping scheme with single-level codes and sigma-mapping for the bandwidth-limited regime. Specifically, we consider nonuniform memoryless sources sent over AWGN channels. At the transmitter, binary data are encoded by a Turbo code composed of two identical RSC (Recursive Systematic Convolutional) encoders. The encoded bits are randomly interleaved and modulated before entering the sigma-mapper. The modulation employed in this system follows the unequal energy allocation scheme first introduced in [1]. The receiver consists of an iterative demapping/decoding algorithm, which incorporates the a priori probabilities of the source symbols. To the authors knowledge, work in this area has only been done for the power-limited regime. In particular, the authors in [2] proposed a scheme based on a Turbo code with RSC encoders and unequal energy allocation. Therefore, it is reasonable to compare the performance with respect to the Shannon limit of our proposed bandwidthlimited regime scheme with this former power-limited regime scheme. Simulation results show that our performance is as good or slightly better than that of the system in [2].