We propose a 2Nr MIMO ARQ scheme that uses multi-strata space-time codes composed of two layers. The phase and transmit power of each layer are assigned adaptively at each transmission round to mitigate the inter-layer interference and improve the block error rate by retransmission. Simulation results show that the proposed scheme achieves better performance than the conventional schemes in terms of the throughput and the block error rate.

In this letter, we analyze the pairwise error probability (PEP) behaviour of distributed space-time code (DSTC) with amplify-and-forward relaying over Nakagami-m multipath channels. An upper bound of PEP for DSTC is derived. From our analysis, it is seen that of the paths from the source to relays and from relays to the destination, those with smaller diversity order result in an overall system performance bottleneck. Numerical examples are provided to corroborate our theoretical analysis.

We propose an implementation of the tapped delay line adaptive array (TDLAA) at the base station for improving the BER performance of asynchronous multi-user mobile communication over fast fading channels using multiple antennas. The data of each user at the mobile station, which applies two transmit antennas, are encoded by Space Time Block Code (STBC). The proposed scheme transmits the pilot signal and information data in alternate time slots. We derive performance criteria for designing such a scheme under the assumption that the fading is classified as fast fading. We show that the proposed scheme can suppress co-channel interference (CCI) and defeat Doppler spread effectively.

For unitary space-time code (USTC), the impact of spatial correlation on error performance is investigated. A tighter and simpler upper bound is derived for generalized likelihood ratio test decoder. We establish that the spatial correlation does not change the diversity gain, whereas it degrades the error performance of USTC. Motivated by the precoding of space-time block code, we designed a precoder for USTC to handle the case of the joint transmit-receive correlation. Numerical results show that the degradation in performance due to spatial correlation can be considerably compensated by the proposed algorithm.

LDCs system with finite-rate error-free feedback is proposed in this letter. The optimal transmission codeword is selected at the receiver and the codeword index is sent to the transmitter. A simple random search algorithm is introduced for codebook generation. Moreover, the max-min singular value criterion is adopted for codeword selection. Simulation results showed that, with only 3-4 feedback bits, the low-complexity Zero-Forcing receiver can approach the Maximum-Likelihood (ML) performance.

We introduce a differential space-time block code (DSTBC) integrated with trellis coded modulation with two transmit antennas. Our scheme enables transmission of DSTBC encoded symbols as trellis metric rather than concatenating an outer code. Unlike conventional DSTBC, different transmit symbol phase rotations are used for each transmit antenna in order to obtain more options for trellis branch. The set partitioning for proposed codes is derived as well. The decoder computes decision statistic using Viterbi Algorithm with different number of states undergoing Rayleigh fading channels. This approach can provide full diversity gain as well as coding gain simultaneously remaining full transmit rate, which cannot be obtained by conventional DSTBC.

This paper proposes a new family of space-time block codes whose transmission rate is 1 symbol per channel use. The proposed space-time codes can achieve full transmit diversity with larger coding gain for the constellation carved from the scaled complex integer ring κZ[i]. It is confirmed that the performances of the proposed space-time codes are superior to the existing space-time block codes by our simulation results.

In this paper, we propose a spatio-temporal equalizer for the space-time block coded transmission over the frequency selective fading channels with the presence of co-channel interference (CCI). The proposed equalizer, based on the tapped delay line adaptive array (TDLAA), performs signal equalization and CCI suppression simultaneously using the minimum mean square error (MMSE) method. It is to show that our scheme outperforms the previous two-stage combined adaptive antenna and delayed decision feedback sequence estimator (DDFSE) approach. We also show that performance can be further improved if the synchronization between the preceding and delayed paths is achieved.

In this paper, we propose a multiuser detection (MUD) scheme for space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) systems. We derive the optimum weight matrix used to decouple simultaneously signals from active multiple access users using the minimum mean square error (MMSE) multiuser detection method. The proposed scheme provides good performance over different models of the frequency selective fading channel. It is also to show that if the length of the cyclic prefix is larger than that of the channel, the performance of the detector depends on only the total energy extracted from multipath components but not the employed channel model, the number of multipath components or the delay of each multipath component.

Iterative multiuser detection and space-time coding are two promising techniques to increase the capacity and performance of coded multiuser systems in wireless channels. In this paper, a low-complexity iterative multiuser receiver is proposed using combined group multiuser detection and interference cancellation for space-time block coded MC-CDMA system. Turbo code is used for outer channel coding with log-MAP decoding. In each group, consisting of smaller number of users, multiuser likelihood ratios can be computed by employing MAP-based approach by taking into account of all possible transmitted symbols within each STBC time slot for these users. Moreover, once decoding information of all users are available after the first iteration, soft interference cancellation can be used instead of groupwise MAP-based detection for lower complexity, without sacrificing the performance significantly. Simulation results are presented in a Rayleigh multipath fading environment. The proposed receiver offers performance very close to that of single user system within a few iterations of joint detection and decoding.

This paper investigates a random-interleaver-based approach to space-time coding. The basic principle is to employ a good forward error correction (FEC) code and transmit randomly interleaved codewords over an antenna array. A low-cost estimation technique is considered. The complexity involved grows only linearly with the number of transmit antennas. Near-capacity performance can be achieved with moderate complexity.

In this letter, we investigate serially concatenated space-time codes (SC-STs) applying iterative decoding topologies in wideband code division multiple access (WCDMA) communication systems. In the decoding algorithm, an iterative (turbo) process is used, where a priori probability (APP) is exchanged between the symbol-by-symbol space-time (ST) decoder and the bit-by-bit convolutional decoder. The experimental results show that in a Rayleigh fading channel environment the serially concatenated interleaved space-time coding systems show significant error correction capability, and based on the applied system configurations, the nonrecursive ST code outperforms the recursive ST code.

This letter presents a new concatenated code and a new criterion for the new concatenated code in fast Rayleigh fading channel. The new concatenated code consists of the cascade of a new space-time trellis code (STTC) as an inner code and a new convolutional code as an outer code. The new criterion maximizes the minimum free distance for the new convolutional code and both the minimum trace and the average trace of distance matrix for the new STTC. The new concatenated code improves the frame error rate (FER) performance significantly with low complexity. The new STTC and convolutional code are designed so as to satisfy the new criterion for 4-state 4 phase shift keying (PSK). The results of the suggested concatenated code are obtained using two transmit antennas, and shown to be significantly superior to the new and existing STTCs. As the number of receive antennas increases, the performance of the new concatenated code significantly improves, for instance, reaches FER = 10-3 at signal-to-noise ratio (SNR) = 5.2 dB for four receive antennas. Note that the proposed concatenated code also improves significant FER performance by using only one receive antenna for high SNR.

In this paper, using the exact expression for the pairwise error probability derived in terms of the message symbol distance between two message vectors rather than the codeword symbol distance between two transmitted codeword matrices, the exact closed form expressions for the symbol error probability of any linear orthogonal space-time block codes in slow Rayleigh fading channel are derived for QPSK, 16-QAM, 64-QAM, and 2 56-QAM.

The effects of hybrid concatenated space-time (HC-ST) codes applying iterative a posteriori probability (APP) decoding are investigated. The bit error rate (BER) and frame error rate (FER) performance of the iterative decoded hybrid Tarokh, Seshadri, Calderbank space-time (TSC ST) coded system under flat Rayleigh fading is analyzed. At the FER 10-2 level the results show that the serially concatenated space-time (SC-ST) codes provide a coding gain of 3 dB compared to the TSC ST codes, where an additional coding gain of 1 dB beyond the SC-ST code performance can be obtained applying the HC-ST coding topology.

Space-Time Turbo code is an effective method for the enhancement of link capacity and maximizing the link-budget by balancing the coding gain obtained via Turbo codes and the diversity gain obtained through multiple antenna transmission. A study on an antenna selection scheme for Space-Time Turbo code for OFDM systems is presented in this paper. In the proposed method, the systematic bits and the punctured parity bits are sent from the selected antenna for each sub-carrier, while data transmission is suspended from the antenna experiencing poor channel conditions at the receiver. Simulation results show that the proposed method yields a 2.2 dB gain in the required TxEb/N0 relative to the conventional method, and makes the channel estimation accuracy more robust. Moreover, the proposed method reduces transmission power by about 4 dB compared to the conventional method.

Recently, there has been increasing interest in providing high quality and efficient broadband services over wireless and mobile links. Space-time code is designed to exploit multiple-input multiple-output antenna systems and by doing so an enormous increase in the capacity of wireless systems can be achieved. In this letter, a synchronization technique is proposed to improve the performance of multiple-input multiple-output system. The interpolation method is employed to estimate the coarse and fine frequency offset at the same time without additional complexity.

In this paper, a joint adaptive interference canceller (AIC) and maximum likelihood (ML) decoder scheme is proposed for a space-time coded DS-CDMA system with the difference between arrival times from transmit antennas. As the arrival time difference causes not only ISI and MAI, but also inter-antenna interference, performance degradation in the space-time coded DS-CDMA system is more severe than that of a regular DS-CDMA system with single transmit antenna. To mitigate the effect of the interference during space-time decoding, a joint algorithm for the proposed scheme merges adaptation process of the AIC into a ML decoding algorithm. Performance of the proposed scheme is evaluated for QPSK space-time trellis codes with two transmit antennas. It is shown that the proposed scheme achieves better performance than the conventional ML decoding scheme.

Space-time turbo codes have both advantages of space-time codes and turbo codes, and the space-time turbo code proposed by Su and Geraniotis is known to achieve full coding rate and full antenna diversity. This paper presents some improvements of their space-time turbo code in a two-antenna configuration. We first propose a new condition for full antenna diversity which imposes less constraints on the interleaver. Next, by applying a method used to improve turbo trellis-coded modulation to the space-time turbo code, we propose a new decoding algorithm which utilizes more precise estimates on extrinsic information. Simulation results show that the proposed condition assures full antenna diversity and the new decoding algorithm provides a better performance than that of Su and Geraniotis'.

It has been established that the criteria for space-time convolutional code (STCC) are based on the maximization of the minimum rank and the minimum determinant of distance matrix over quasistatic flat Rayleigh fading channel. This letter presents a new criterion, i.e., modified trace criterion which maximizes both the minimum trace and the average trace of distance matrix for a new STCC. A new STCC is systematically searched so as to maximize the minimum trace and the average trace, and shown to be superior to other known codes in quasistatic flat Rayleigh fading channel.