In this paper, multilevel coding is tailored for cooperative communication, where the source deploys a layered encoding structure. Due to the BER difference for different coding levels, there is some possibility that ...
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ISBN:
(纸本)9781424425198
In this paper, multilevel coding is tailored for cooperative communication, where the source deploys a layered encoding structure. Due to the BER difference for different coding levels, there is some possibility that the relay, despite of successful decoding in upper coding levels, might not be able to correctly decode in lower levels. We propose a hybrid relaying scheme to cope with this problem, where the relay deploys decode-and-forward in upper levels and compress-and-forward in lower levels. Simulation results demonstrate that this hybrid technique approaches a fine balance among the complexity, BER performance and transmission efficiency.
In this paper, we propose a multi-level physical-layer network coding (MPLNC) scheme that optimizes the relay performance for both symmetric and asymmetric traffic in a Gaussian two-way relay channel. The proposed MPL...
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In this paper, we propose a multi-level physical-layer network coding (MPLNC) scheme that optimizes the relay performance for both symmetric and asymmetric traffic in a Gaussian two-way relay channel. The proposed MPLNC scheme enables each source to employ multiple linear binary codes for encoding, one per modulation level, and the relay node to decode superimposed network codewords at each modulation level. We first derive the achievable rate for the transmission of arbitrary constellations and then prove that MPLNC with multistage decoding (MPLNCMSD) can achieve the achievable rate if binary code rates are properly chosen for both sources. Furthermore, the design criteria for the proposed MPLNC scheme is investigated, which includes the rate design rule and the labeling strategy. Moreover, we derive the error exponent and an upper bound of the overall error probability for MPLNC. Our analysis and simulation results show that MPLNCMSD has a significant performance advantage in comparison to the existing bit-interleaved coded modulation (BICM)-based PLNC scheme.
Grouped multilevel space-time trellis codes (GMLSTTCs) utilize multilevel coding (MLC), antenna grouping and space time trellis codes (STTCs) for simultaneously providing coding gain, diversity improvement and increas...
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Grouped multilevel space-time trellis codes (GMLSTTCs) utilize multilevel coding (MLC), antenna grouping and space time trellis codes (STTCs) for simultaneously providing coding gain, diversity improvement and increased spectral efficiency. The performance of GMLSTTCs is limited due to predefining of the antenna groups. It has been shown that when perfect or partial channel state information is available at the transmitter, the performance and capacity of space-time coded system can be further improved. In this paper, we present a new code designed by combining MLC, STTCs, antenna grouping and channel state information at transmitter, henceforth referred to as adaptively grouped multilevel space time trellis codes (AGMLSTTCs). AGMLSTTCs use a single full-diversity STTC at initial some levels and multiple STTCs at some later levels. The single full diversity STTC at each initial level spans all transmit antennas and the STTC at each later level spans a group of transmit antennas. The channel state information at the transmitter is used to adaptively group the transmit antennas for the later levels. Instantaneous channel power gain is calculated between each transmit antenna and all the receive antennas. A subset of transmit antennas having maximum channel power gain is selected to form a group. The simulation results show that AGMLSTTCs enable to transmit more than one data symbol per time slot with improved error performance over GMLSTTCs with predefined transmit antenna grouping.
It has been shown that multilevel space-time trellis codes (MLSTTCs) designed by combining multilevel coding (MLC) with space-time trellis codes (STTCs) can provide improvement in diversity gain and coding gain of the...
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It has been shown that multilevel space-time trellis codes (MLSTTCs) designed by combining multilevel coding (MLC) with space-time trellis codes (STTCs) can provide improvement in diversity gain and coding gain of the STTCs. MLSTTCs assume perfect channel state information (CSI) at receiver and no knowledge of CSI at transmitter. Weighted multilevel space-time trellis codes (WMLSTTCs), designed by combining MLSTTCs and perfect CSI at transmitter are capable of providing improvement in coding gain of MLSTTCs. In this paper, we present improvement in performance of MLSTTCs by using channel feedback information from the receiver for adaptive selection of generator sequences. The selected generator sequences are used for encoding the component STTCs. The receiver compares current channel profile at receiver with a set of predetermined channel profiles, and sends an index of a predefined channel profile closest to the current channel profile to the transmitter. The transmitter selects a code set that matches best with the current channel profile at receiver using the index. The selected code set having different sets of generator sequences is used by STTC encoders to generate dynamic space-time trellis codes (DSTTCs). The DSTTCs act as component codes in multilevel coding for generating new codes henceforth referred to as multilevel dynamic space-time trellis codes (MLDSTTCs). Analysis and simulation results show that MLDSTTCs provide improvement in performance over MLSTTCs.
The performance of adaptively grouped multilevel space-time trellis codes (AGMLSTTCs) is limited due to predefined component space-time trellis codes (STTCs) used in multilevel coding and lack of beamforming. In this ...
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The performance of adaptively grouped multilevel space-time trellis codes (AGMLSTTCs) is limited due to predefined component space-time trellis codes (STTCs) used in multilevel coding and lack of beamforming. In this paper, we present improvement in performance of AGMLSTTCs by combining beamforming and dynamic selection of component STTCs with AGMLSTTCs to design new codes henceforth referred to as weighted adaptively grouped multilevel dynamic space-time trellis codes. The channel state information at transmitter (CSI) is used to select a code set having different sets of generator sequences. The selected code set is used for generating dynamic STTCs (DSTTCs). The DSTTCs are used as component codes in multilevel coding. We use a single full-diversity DSTTC at some initial levels and multiple DSTTCs at some later levels. The single full diversity DSTTC at each initial level spans all transmit antennas and the DSTTC at each later level spans a group of transmit antennas. The CSI is further used to provide a beam forming scheme by properly weighting transmitted signals. Weights are selected that based on CSI at transmitter. The simulation results show that AGMLSTTCs combined with beamforming and DSTTCs provide significant improved error performance over grouped multilevel space-time trellis codes and AGMLSTTCs.
Reed-Solomon (RS) codes are commonly utilized in magnetic recording systems to correct error bursts. Soft-output Viterbi algorithm (SOYA) is a commonly used detector to provide soft information to error-correcting dec...
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ISBN:
(纸本)9781479923588
Reed-Solomon (RS) codes are commonly utilized in magnetic recording systems to correct error bursts. Soft-output Viterbi algorithm (SOYA) is a commonly used detector to provide soft information to error-correcting decoders. We propose a novel architecture of multilevel interleaved RS coding scheme that not only provides better performance but also has less complexity than an equivalent RS code. This architecture implements an error event detector using the soft information generated by the SOYA detector.
Orthogonal Frequency Division Multiplexing (OFDM), aided by proper channel coding schemes, can realize very dependable transmission in fading channels. For the purpose of improving the performance of the OFDM based DR...
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ISBN:
(纸本)9781479973392
Orthogonal Frequency Division Multiplexing (OFDM), aided by proper channel coding schemes, can realize very dependable transmission in fading channels. For the purpose of improving the performance of the OFDM based DRM digital AM broadcasting in MF and HF channels, this paper designs MLC-LDPC-OFDM transmission scheme that is suitable for MF and HF channels. The equivalent channel capacities of MLC-LDPC-OFDM with two different decoding strategies, namely IMSD and PDL, are analyzed, basing on which this paper redesigns the code rates of MLC. In addition, the calculation of likelihood ratio in LDPC decoding is modified according to channel models. The simulation results show that the proposed schemes have better performance than the existing ones in MF and HF channels.
We propose a computationally efficient scheme to decode two-dimensional (2D) intersymbol interference (ISI) channel with M-ary input. The basic idea is to equalize the channel stage by stage. To begin with the stage w...
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ISBN:
(纸本)9781424427338
We propose a computationally efficient scheme to decode two-dimensional (2D) intersymbol interference (ISI) channel with M-ary input. The basic idea is to equalize the channel stage by stage. To begin with the stage with the highest signal power level, the BCJR algorithm is used to equalize each level by averaging the interference of the undecoded levels. Both the hard and soft decisions are passed to the next stages. The scheme hugely reduces the complexity of full-branch BCJR on the entire received page of data and makes the equalization applicable. Based on the statistic output of each stage the overall information rates are evaluated. Furthermore, the coding simulation results are presented. All of these results show the proposed scheme is a good candidate for decoding such M-ary 2D ISI channels.
We consider a two-way relay channel in which two transmitters want to exchange information through a central relay. The relay observes a superposition of the transmitted signals from which a function of the transmitte...
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We consider a two-way relay channel in which two transmitters want to exchange information through a central relay. The relay observes a superposition of the transmitted signals from which a function of the transmitted messages is computed for broadcast. We consider the design of codebooks which permit the recovery of a function at the relay and derive information-theoretic bounds on the rates for reliable decoding at the relay. In the spirit of compute-and-forward, we present a multilevel coding scheme that permits reliable computation (or, decoding) of a class of functions at the relay. The function to be decoded is chosen at the relay depending on the channel realization. We define such a class of reliably computable functions for the proposed coding scheme and derive rates that are universally achievable over a set of channel gains when this class of functions is used at the relay. We develop our framework with general modulation formats in mind, but numerical results are presented for the case where each node transmits using 4-ary and 8-ary modulation schemes. Numerical results demonstrate that the flexibility afforded by our proposed scheme permits substantially higher rates than those achievable by always using a fixed function or considering only linear functions over higher order fields. Our numerical results indicate that it is favorable to allow the relay to attempt both compute-and-forward and decode-and-forward decoding. Indeed, either method considered separately is suboptimal for computation over general channels. However, we obtain a converse result when the transmitters are restricted to using identical binary linear codebooks generated uniformly at random. We show that it is impossible for this code ensemble to achieve any rate higher than the maximum of the rates achieved using compute-and-forward and decode-and-forward decoding. Finally, we turn our attention to the design of low density parity check (LDPC) ensembles which can practically achieve
A new space-time coding scheme is drawn based upon the concepts of multilevel coding, space-time block coding (STBC), and spatial modulation (SM). In light of a STBC-SM scheme, an interblock-correlated multilevel code...
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A new space-time coding scheme is drawn based upon the concepts of multilevel coding, space-time block coding (STBC), and spatial modulation (SM). In light of a STBC-SM scheme, an interblock-correlated multilevel code is combined in conjunction with set partitioning of the expanded transmission matrix set according to the coding gain distance criterion. The error performance of an example code is compared with the traditional STBC-SM scheme in computer simulation. Under the situation of the same spectral efficiency and space diversity order, the proposed scheme is superior as regards its bit error performance.
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