Chunlong Bai

Hybrid-arq for layered space time MIMO systems with channel state information only at the receiver

The authors investigate hybrid automatic repeat request (H-ARQ) schemes for spatially multiplexed multiple-input multiple-output (MIMO) systems with channel state information available only at the receiver. In particular, the authors compare the multiple H-ARQ scheme and the single H-ARQ scheme with repetition. The authors first propose a system model for symbol detection for the multiple H-ARQ processes, and then discuss joint and separate detection algorithms for both multiple H-ARQ and single H-ARQ. Simulation results show that with linear detection the single H-ARQ outperforms multiple H-ARQ in the high signal-to-noise ratio region. With the vertical Bell Labs space-time (V-BLAST) architecture, multiple H-ARQ always outperforms single H-ARQ. Additionally, joint detection always outperforms separate detection.

Sub-block recovery scheme for iterative decoding of turbo codes

We present theoretical analysis to demonstrate that the previously proposed sub-block recovery scheme, which can be integrated into concatenated hybrid-ARQ error control coding schemes, is helpful in correcting a typical error pattern in turbo decoders. We investigate mechanisms that improve decoding quality with both SOVA and Log-MAP algorithms. Based on this analysis, we show that if the sub-block structure is used in a turbo coded system, the sub-block recovery scheme for iterative decoding results in improved packet error rate performance.

Sub-Block Recovery Scheme for Iterative Decoding of Turbo Codes with the Sub-Block Structure

Wireless communication systems usually employ a concatenated error control coding scheme consisting of an outer error detection code and an inner error correction code. Traditionally, these two codes are decoded separately. When the sub-block structure is used, each data block (input sequence) at the inner encoder consists of several sub-blocks and each of these sub-blocks is protected with the error detection code. The sub-block structure is used in the Wideband CDMA (WCDMA) system specified by the 3rd Generation Partnership Project (3GPP). In this paper, a sub-block recovery scheme is proposed for this concatenated error control coding scheme to utilize the error detection capability introduced by the outer code in the decoding of the inner code. We demonstrate that, if the inner code is a turbo code with a highly structured interleaver and iterative sub-optimal decoding is used, the sub-block recovery scheme is helpful in correcting a typical error pattern, which helps to improve the block error rate performance. We analyze the decoding performance when sub-block recovery is used together with the maximum likelihood (ML) algorithm as well as the log maximum-a-posteriori probability (Log-MAP) and the soft output Viterbi algorithm (SOVA) and demonstrate gains introduced by the sub-block recovery in the latter two cases using computer simulations.

WLC45-1: Turbo Coded Type-II H-ARQ Scheme with Incremental Redundancy Using Sub-Block Recovery

In this paper, a type-II H-ARQ scheme with incremental redundancy is proposed for a turbo coded system that uses the sub-block structure. Sub-block recovery is applied to the decoder and a method to dynamically select the bits for retransmission according to knowledge of the decoding status is proposed. The new scheme benefits from both the frequent termination technique and the built-in CRC of the constituent recursive systematic convolutional codes of the turbo encoder. Simulations show that for a turbo coded system that employs the sub-block structure, the new type-II H-ARQ scheme outperforms both type-I H-ARQ with the sub-block recovery and the traditional type-II H-ARQ scheme without sub-block recovery on both the AWGN channel and the flat Rayleigh fading channel.

Analysis of a sub-block recovery scheme for decoding a concatenated error control code

In this paper, theoretical analysis is presented for the sub-block recovery scheme that can be integrated into concatenated error control coding schemes used by communication systems employing hybrid-ARQ. Based on this analysis, we show that if the inner code is a turbo code and iterative sub-optimal decoding is used, the sub-block recovery scheme results in improved packet error rate performance. We also show that if the decoder uses the maximum likelihood decoding algorithm, the sub-block recovery scheme does not introduce performance improvement. We confirm our results by simulations of systems with SOVA and log-MAP algorithms.

Hybrid-ARQ for Layered Space Time MIMO Systems with Channel State Information Only at the Receiver

In this paper the authors investigate the hybrid automatic repeat request (H-ARQ) schemes for spatial multiplexing (SM) multiple-input multiple-output (MIMO) systems with channel state information available only at the receiver (CSIR). In particular, the authors compare the multiple H-ARQ scheme and the single H-ARQ scheme with repetition. The authors first propose a system model for symbol detection for the multiple H-ARQ processes, and then discuss joint detection algorithms and separate detection algorithms for both multiple H-ARQ and single H-ARQ. Simulation results show that with linear detection the single H-ARQ outperforms multiple H-ARQ in the high signal to noise ratio (SNR) region. With the vertical Bell Labs space time (V-BLAST) architecture, multiple H-ARQ always outperforms single H-ARQ and joint detection always outperforms separate detection.

Efficient list decoding for parallel concatenated convolutional codes

The focus of this research work is the sub-optimal list decoding algorithms for parallel concatenated convolutional codes (PCCCs) which improve the frame error rate (FER) performance. Error events and weight spectra for convolutional codes and PCCCs are analyzed with emphasis on their effects on list decoding. We explain the inefficiencies of list decoding algorithms for PCCCs that use a list generated from the component codes, and introduce a new algorithm based on the sub-block structure that generates a list directly for the PCCC. The additional complexity of the new algorithm is low and does not depend on the complexity of the component code. Simulations on the additive white Gaussian noise (AWGN) channel show that the new algorithm can lower the frame error floor by more than one order of magnitude.

SR-ARQ for MIMO OFDM Systems with Channel State Information Only at the Receiver

In this paper, we compare two selective-repeat automatic-repeat-request (SR-ARQ) protocols for spatial multiplexintiplexingg multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexed (OFDM) systems assuming perfect channel state information (CSI) only at the receiver. These two SR-ARQ protocols differ in the number of packets transmitted simultaneously. In one protocol, a single packet is transmitted on all subcarriers from all antennae at the same time. In the other protocol, multiple packets are simultaneously transmitted. For the latter protocol, we also consider schemes that differ in the way that the subcarriers transmitted from different antennae are grouped to support the transmission of multiple packets in parallel. We compare the throughput and the resequencing delay of these SR-ARQ protocols in a frequency selective fading channel. Simulation results suggest that in such a system, the single ARQ protocol is the best choice. If we have to transmit multiple packets in parallel, each packet should be transmitted over a subband of adjacent subcarriers emitted from all transmit antennae.

WLC32-1: ARQ for MIMO OFDM Systems with Non-Linear Preprocessing

In this paper, we develop a selective-repeat automatic-repeat-request (SR-ARQ) transmission scheme for multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems with non-linear preprocessing assuming perfect channel state information at both the transmitter and the receiver. In such a system in every time slot for ARQ transmission, there are a group of parallel channels of equal rate and differing error probability available between the transmitter and the receiver. Based on the knowledge of the signal to noise ratio (SNR) of these parallel channels, which is known to both the transmitter and the receiver, we first propose a dynamic parallel channel grouping rule to group parallel channels into effective channels, over which one packet is transmitted in one time slot, and we prove that this dynamic channel grouping rule will achieve maximum throughput. Furthermore, we adopt the dynamic channel assignment rule introduced by Shacham and Shin to assign packets to the effective channels in order to reduce resequencing delay. simulations in a frequency selective fading channel demonstrate the advantage of the proposed dynamic SR- ARQ transmission scheme over systems with a static parallel channel grouping rule and a static channel assignment rule in terms of throughput and resequencing delay.

Improved analysis of list decoding and its application to convolutional codes

In this paper, the concepts of effective weight enumerating function and generalized pairwise error event are introduced to predict the performance of linear block codes with list decoding. For the first time, a method to evaluate the actual effective codeword weights for a given code, rather than a lower bound on effective codeword weights, is proposed. Based on these actual effective codeword weights, the performance of a given code with list decoding can be predicted more accurately. We propose an analytical method to evaluate the performance of a given code with list decoding and consider terminated convolutional codes to show the validity of the analysis.