Changlong Xu

Cyclic Delay Diversity for Single Carrier-Cyclic Prefix Systems

This paper presents the application of cyclic delay diversity (CDD) to block-based single carrier cyclic prefix (SC-CP) systems. It is shown that diversity advantage is achieved even without additional coding due to the inherent cross-tone pre-coding present in SC-CP. We also present a CDD SC-CP transmission system for correlated channels. By using beamforming techniques, virtual uncorrelated channels are created for CDD transmissions. Simulations results show that the proposed schemes provide diversity gain. Furthermore, when beamforming is used together with CDD, array gain is also observed

Design of cyclic delay diversity for single carrier cyclic prefix (SCCP) transmissions with block-iterative GDFE (BI-GDFE) receiver

Single carrier cyclic prefix (SCCP) modulation has been adopted as one of the physical layer air-interfaces for IEEE802.I6 standards due to its less stringent requirement on peak-to-average power ratio (PAPR) than multicarrier modulation. As a single carrier transmission, however, the received SCCP blocks suffer from inter-symbol interference (ISI). The block iterative generalized decision feedback equalizer (BI-GDFE) is an effective interference cancellation scheme which generally shows performance improvement over linear equalizers. However, in order to achieve a significant gain, the channel must contain rich multipath components, and this may not necessarily be true in many systems. In this paper, we propose to apply cyclic delay diversity (CDD) to a SCCP system so that the possible performance improvement by using a BI-GDFE detector can be enhanced. The asymptotic performance of the proposed system is analyzed using random matrix results. We propose a scheme to determine the optimal delay parameter for CDD. Computer simulations have shown that by incorporating CDD into the transmitter and using a BI-GDFE receiver, the BER performance of the system can approach the MFB within several iterations for high SNR region.

A low complexity decoding algorithm for extended turbo product codes

In this letter, we propose a low complexity algorithm for extended turbo product codes by considering both the encoding and decoding aspects. For the encoding part, a new encoding scheme is presented for which the operations of looking up and fetching error patterns are no longer necessary, and thus the lookup table can be omitted. For the decoder, a new algorithm is proposed to extract the extrinsic information and reduce the redundancy. This new algorithm can reduce decoding complexity greatly and enhance the performance of the decoder. Simulation results are presented to show the effectiveness of the proposed scheme.

Shortened Turbo Product Codes: Encoding Design and Decoding Algorithm

Shortened turbo product codes (TPCs) have already been adopted in many standards. In this paper, we study shortened TPCs from two aspects, namely encoding design and decoding algorithm. To obtain different encoding block sizes, shortened-extended Hamming codes are used as the component codes of product codes in the IEEE 802.16 standard. To design a good structure for the shortened TPC, we compute the undetected error probability of its corresponding component codes. The component codes are shortened-extended Hamming codes, and their optimal generator polynomials are selected in terms of their undetected error probability. For the decoding algorithm, we present an efficient Chase decoding algorithm for shortened TPCs in flat fading channels. In the proposed scheme, the reliability factor used in Pyndiahs scheme is not needed; thus, the decoding complexity is greatly reduced by avoiding the normalization operation of the whole code word at each iteration. Simulation results are also presented to verify the performance of the proposed algorithm.

Dynamic QRDM Receivers for MIMO Beamforming Systems with Imperfect Channel State Information

For multiple-input multiple-output (MIMO) antenna systems, if perfect channel state information (CSI) is available at the transmitter and receiver sides, advanced beamforming (ABF) can be applied at both sides so that the transmitted data streams can be decoupled easily, and adaptive modulation can be utilized to maximize the throughput. When the available CSI is imperfect, however, the data streams cannot be decoupled completely with linear receive beamforming. In this paper, a dynamic QR decomposition based M-Algorithm (QRDM receiver) is proposed for recovering the data streams delivered by MIMO beamforming systems with adaptive modulation designed by imperfect CSI. We also propose a scheme to determine the decoding order for assisting the QRDM operation. The proposed schemes can also be applied to multiuser MIMO systems with random transmit beamforming where the random beams are hardly match the desired users CSI exactly. Computer simulations have shown that the proposed receiver is very robust to the CSI mismatch as compared to conventional linear receivers

Semi-Blind Channel Estimation For Linearly Precoded MIMO-CPSC

In this paper, linear preceding is introduced into MIMO-CPSC system to enhance channel estimation. Thanks to the preceding, the input symbols have well-defined statistical correlations. This property is then used for blind channel estimation. By modifying and eigen-decomposing the statistical auto-correlation matrix of the frequency domain received signals, the channels are estimated subject to a matrix (with size K x K, where K is the number of transmitters) ambiguity. Several linear precodings are presented. The precodings do not change the power of a precoded block. Also, there are fast algorithms to implement the precodings and decodings. Simulations show that the method is effective and robust.

MAP Decoding Algorithm for Extended Turbo Product Codes over Flat Fading Channel

In this paper, an efficient MAP iterative decoding algorithm is proposed for extended turbo product codes over flat fading channel. The overflow avoidance of extrinsic information and the stop criteria of iterative decoder are also discussed. Simulation results are presented to verify the performance and show the efficacy of the proposed decoding algorithm.

Channel Delay Management with Statistical Pre-Filtering for Single Carrier Cyclic Prefix Transmissions

We present a downlink single carrier cyclic prefix transmission method which employs directional beamforming and artificial delay for channels with dominant cluster paths. The proposed technology robustly manages the overall delay of the transmission channel for performance gain. For channels with delays larger than the cyclic prefix, the proposed method shortens the delay for IBI-free transmission. When the cyclic prefix duration exceeds that of the channel duration, the proposed technique can lengthen the effective channel delay to possibly improve the systems performance. Computer simulations are presented to verify the efficacy of the proposed transmission technology.

Turbo Product Codes for Mobile Multimedia Broadcasting With Partial-Time Jamming

Mobile multimedia broadcasting could suffer from multipath fading as well as partial-time jamming interference. In this paper, turbo product codes are proposed to suppress the effect of these interferences. We propose an efficient decoding algorithm using Chase decoder by taking into consideration the jamming state information. To make the variance of the jammed bits same as the other un-jammed bits, a scaling factor is used to adjust the amplitude of the received signal of the jammed bits. This processing benefits the followed Chase decoder. The upper and lower bounds of turbo product codes over such channels are derived and simulations have been performed to evaluate the derived bounds. Simulation results have shown that the proposed algorithm can mitigate the partial-time jamming greatly and the numerical bounds are tight for high signal-to-jamming ratio region

Chase decoding algorithm for shortened turbo product codes in flat fading channels

Chase decoding algorithm was originally proposed by Pyndiah for turbo product codes. In this paper, we present an efficient Chase decoding algorithm for shortened turbo product codes in flat fading channels. In the proposed scheme, the reliability factor used in Pyndiahs scheme is not needed, thus the decoding complexity is reduced greatly by avoiding the normalization operation of the whole codeword each iteration. Simulation results are also presented to verify the performance of the proposed algorithm.