Complex signal transmission using real orthogonal space-time block codes with feedback

The conventional orthogonal space-time block code (OSTBC) with limited feedback has fixed p-1 feedback bits for the specific ntp transmit antennas. A new partial feedback based OSTBC which provides flexible feedback bits is proposed in this paper. The proposed scheme inherits the properties of having a simple decoder and the full diversity of OSTBC, moreover, preserves full data rate. Simulation results show that for ntp transmit antennas, the proposed scheme has the similar performance with the conventional one by using p-1 feedback bits, whereas has the better performance with more feedback bits.

Full rate Balanced Space-Time Block Coding (BSTBC) was previously proposed which achieves full diversity for arbitrary number of transmit antennas when one or more feedback bits are transmitted via feedback channel. Extended Balanced Space-Time Block Coding (EBSTBC) provides an improved coding gain with respect to the BSTBC. However, no analytical results concerning EBSTBC have been provided. In this paper, we propose a new technique that the coding gain is calculated over average SNR. Using this technique, the effect of feedback bits on the bit error rate performance of the EBSTBC is investigated. The proposed coding gain calculation technique can be applied to any kind of fully diverse Orthogonal Space-Time Block Codes (OSTBCs).

It is well known that the performance of the wireless communication systems can be enhanced by using multiple transmit and receive antennas, which is generally referred to as the MIMO technique, and has been incorporated into the IEEE 802.11n standard, i.e. one of the Wi-Fi systems. The MIMO technique has also been adopted by the 3GPP Long Term Evolution (LTE) and the 3GPP2 Ultra Mobile Broadband (UMB) standards. The space-time coding is a promising way to realize the gain in the wireless communications system using MIMO. The space time block code, and the orthogonal space time block code in particular have been proposed in research and implemented in practical wireless communication systems due to their low computational complexity in maximum likelihood decoding implementation. However, the code rates of the orthogonal space time block codes are usually lower than $3/4$ when the number of transmit antennas is greater than two, which limit their throughput. To increase the code rate and the throughput of the orthogonal space time block code for more than two transmit antennas, a family of new space-time block codes (STBC) for 3 and 4 transmit antennas in a MIMO wireless communication system have been proposed in this Ph.D. research. These new codes are orthogonal and achieve full diversity, full rate using Triple QPSK'' modulation, which is proposed in this research. We investigated the performance of these STBCs when the channel state information (CSI) is perfectly known at the receiver. The CSI is not known to the transmitter in all of the studies in this dissertation. An analytical bound of the probability of bit error is developed and the Monte Carlo simulation is used when investigating these new STBC codes. In practical wireless communication system, the CSI is generally not available at the receiver and it is usually estimated by the receiver through the pilot signals or training signals known to the receiver. No matter what channel estimation method is used, the estimate of CSI will not match the CSI exactly and is noisy. The performance of these new STBCs using theTriple QPSK'' modulation when the estimate of the CSI is employed to detect the symbol is investigated in this dissertation. An upper bound of the bit error probability is developed when the noisy CSI is used to detect the symbols. The performance of the new STBCs using the Triple QPSK'' modulation is also evaluated using Monte Carlo simulation. When the CSI is not available to either the receiver or the transmitter, the differential encoding and decoding algorithm is applied to these new STBCs, which use theTriple QPSK'' modulation. The results showed that these orthogonal STBCs achieve full diversity full rate using ""Triple-QPSK"" modulation with differential detection. This provides a means of achieving space diversity and multiplexing gain without the CSI. A new differential encoding and decoding algorithm is proposed and analyzed for STBCs with 3 transmit antennas, whose transmission matrix is not square matrix, as part of this Ph.D. research. The STBCs using this algorithm achieve full diversity the MIMO system can possibly provide.

The blind maximum-likelihood (ML) detection of orthogonal space-time block codes (OSTBCs) is a computationally challenging optimization problem. Fortunately, for BPSK and QPSK OSTBCs, it has been shown that the blind ML detection problem can be efficiently and accurately approximated by a semideflnite relaxation (SDR) approach [1]. This paper considers the situation where the 16-QAM signals are employed. Due to the nonconstant modulus nature of 16-QAM signals, the associated blind ML OSTBC detection problem has its objective function exhibiting a Rayleigh quotient structure, which makes the SDR approach not directly applicable. In the paper, a linear fractional SDR (LF-SDR) approach is proposed for efficient approximation of the optimum blind ML solution. In this approach, the blind ML 16-QAM OSTBC detection problem is first approximated by a quasi-convex relaxation problem. Generally quasi-convex problems may be computationally more complex to handle than convex problems, but we show that the optimum solution of our quasi-convex problem can be efficiently obtained by solving a convex problem, namely a semideflnite program. Simulation results demonstrate that the proposed LF-SDR based blind ML detector outperforms the norm relaxed blind ML detector and the blind subspace channel estimator [2], especially in the one- receive-antenna scenario.

In many practical parameter estimation problems, the statistical properties of the sources can be exploited to improve the quality of the estimates. In this paper we consider the correlation and Kullback matching criteria (CM and KM respectively), which are applied to the problem of blind channel estimation under orthogonal space-time block coded (OSTBC) transmissions. Specifically, it is shown that the special OSTBC structure provides straightforward closed form solutions, which reduce to the extraction of the principal eigenvector of the observation correlation matrix modified by the code matrices and a set of weighting factors. Additionally, we prove that the KM technique is equivalent to the CM approach for low SNRs, and to the relaxed blind maximum likelihood (ML) decoder for high SNRs. Finally, the performance of the proposed techniques is illustrated by means of several simulation examples.

Orthogonal space-time block codes (OSTBCs) have several desirable properties for delay limited communication over a coherent narrowband (/sub at/) fading multiple antenna channel. In particular, they provide full diversity, and maximum likelihood detection can be achieved via linear processing and symbol-by-symbol detection. As a result, the maximal symbol rate and minimal latencies of OSTBCs have been well studied. In this paper, we construct orthogonal block codes for frequency-selective multiple antenna channels, and study their symbol rate and latency properties. Our code construction is based on direct application of the orthogonality constraints. This enables us to show that the maximum symbol rate of an orthogonal block code for a channel with memory length L is 1/L times the maximum rate of an OSTBC for the same antenna configuration. Orthogonal codes that achieve this maximal rate can be simply constructed via the Kronecker product of a rate maximal OSTBC with an identity matrix of size L. This Kronecker design scheme can also be applied to construct orthogonal block codes for frequency-selective channels with other desirable properties, such as minimal latency.

We propose two phase constraining (PC) schemes using quantized feedback for multiple-input single-output (MISO) systems. The PC schemes are generalizations of the quadrature phase constraining (QPC) scheme. One PC scheme cophases channel gains with respect to the first transmit antenna channel gain, and the other PC scheme cophases channel gains by positioning all the channel gains into a fixed sector. We analyze the combined channel gain for both PC schemes, and find that the PC scheme that cophases with respect to the first transmit antenna channel gain provides 1.2 dB power gain over an orthogonal space-time block code (OSTBC) when the number of transmit antennas is four and the number of feedback bits is three.

We propose the Hadamard matrix as a codebook for multiple-input multiple-output (MIMO) beamforming systems, and show that a quantized equal gain transmission (QEGT) scheme using the Hadamard codebook has the same symbol error probability performance as a receiver selection diversity combining scheme operating in independent generalized Rayleigh fading channels. We show that a MIMO beamforming system using quantized feedback over Rician fading channels can be analyzed by considering a corresponding receiver selection combining scheme operating in single-input multiple-output (SIMO) systems over correlated generalized Rician fading channels. Also, we propose a greedy cophasing scheme for MIMO beamforming systems using quantized feedback. The greedy cophasing scheme provides 3.2 dB power gain over an orthogonal space-time block code when the number of transmit antennas is four, the number of receive antennas is one, and the number of feedback bits is three.

Alamouti code is the only known Orthogonal Space Time Block Code (OSTBC) with rate-1. All other known orthogonal codes have rate less than unity. The orthogonal property of OSTBCs reduces the decoding complexity to a large extent. High data rate Space Time Block Codes for arbitrary number of transmit antennas were recently proposed based on Division Algebras. But these STBCs are not orthogonal. Therefore their decoding complexity is very high. In this paper we propose high data rate Alamouti codes from field extensions for two transmit antennas. Our codes have better coding gain than the both high rate codes from division algebra and the rate-1 Alamouti code.

The effect of spatial correlation on the performance of orthogonal space-time block codes (OSTBCs) over multiple-input-multiple-output (MIMO) Rician fading channels is studied. Asymptotic error-rate formulas for OSTBC with high average signal-to-noise ratios (ASNRs) over arbitrarily correlated Rician MIMO channels are derived in terms of the diversity and coding gains. Our results show that, in correlated fading, the phase vector phi of the channel line-of-sight (LOS) components affects the effective Rice K-factor at the OSTBC receiver output and, hence, may result in a coding gain that is significantly higher than that for independent Rician MIMO channels. Furthermore, when the channel covariance matrix is rank deficient and under some additional mild conditions, the error and outage probabilities of OSTBC achieve those in a nonfading additive-white-Gaussian-noise channel. For both cases of full-rank and rank-deficient channel covariance matrices, analytical expressions of optimal and worst case phase vectors phi, and exact upper and lower bounds of OSTBC performance are derived. These results provide new insights into the achievable performance of OSTBC over correlated Rician MIMO channels and, if incorporated into future multiple antenna systems design, will bring about significant performance enhancement

We present a novel approach to blind symbol detection in multiple-input multiple-output (MIMO) systems that use orthogonal space-time block codes. Our approach is based on a relaxed maximum likelihood (ML) joint channel and symbol estimation. The proposed technique has a simple closed-form solution and is free of most of the shortcomings of the previously presented blind receivers. In particular, there is no signal-to-noise ratio (SNR) penalty, as in differential encoding techniques, provided that the coherence time of the channel is large enough. Moreover, our approach does not use any pilot symbols as some other (semi-)blind techniques do.

In this paper, the problem of blind channel estimation under orthogonal space-time block coded (OSTBC) transmissions is solved by minimizing some distance measure between the theoretical and estimated correlation matrices of the observations. Specifically, the minimization of the Euclidean distance and the Kullback-Leibler divergence leads, respectively, to the Euclidean correlation matching (ECM) and Kullback correlation matching (KCM) criteria. The proposed techniques exploit the knowledge of the source correlation matrix to unambiguously recover the multiple-input multiple-output (MIMO) channel. Furthermore, due to the orthogonality properties of OSTBCs, both the ECM and KCM criteria result in closed form solutions. In particular, the channel estimate is given by the principal eigenvector of a matrix, which is obtained from the estimated correlation matrix of the observations modified by the code matrices and a set of weights. In the ECM case, the weights are fixed and equal to the eigenvalues of the source correlation matrix, whereas the KCM weights depend on both the signal-to-noise ratio (SNR) and the source eigenvalues. Additionally, we show that the proposed approaches are equivalent in the low SNR regime, whereas in the high SNR regime the KCM criterion is asymptotically equivalent to the relaxed blind maximum-likelihood (ML) decoder. Finally, the performance of the proposed criteria is illustrated by means of some numerical examples.

In this paper we present a new simple cooperative relaying scheme. The proposed scheme is compared with simple cooperative schemes with virtual orthogonal space time block coding (OSTBC) and quasi orthogonal space time block coding (QOSTBC). Every of these three schemes includes one base station with two antennas, two relay stations each with a single antenna and one mobile station with a single antenna. The aim of the proposed scheme is to preserve, as much as it is possible bit error rate (BER) performance of the cooperative scheme with virtual OSTBC, but with increased code rate. It is shown that the presented scheme obviously outperforms simple cooperative scheme with virtual QOSTBC, while in comparison with simple cooperative scheme with virtual OSTBC has very similar BER performance and increased code rate.

Ultra Wideband (UWB) communication system and MIMO transmission technique recently have attracted much attention. Space time block coding combines with UWB M-ary PSK and M-QAM modulation schemes for the use of multiple transmit antennas providing a simple transmit diversity scheme with the same diversity order as maximal ratio receiver combing. Using the equivalent single input single out (SISO) model, we present a closed form expression for the exact symbol error rate (SER) of orthogonal space time block codes (STBCs) over UWB flat Nakagami-m models.

The main aim of the physical layer is to boost the data rates over wireless channel with better quality of services (QOS), thereby, increasing the efficiency and reliability of new generation wireless communication systems especially 5G/6G system. Performance of various space time block codes like quasi orthogonal space time block codes and rotational quasi orthogonal space time block codes is investigated using various decoding algorithms like Sphere Decoder, K 1, K 2, K 3, K 4 Sphere decoders. The Sphere Decoder has been modified in terms of K detection algorithms based on spectral efficiency. Different modulations are used to validate the analytic analysis. Simulations are performed in MATLAB software and the results obtained shows the significant incremented spectral efficiency.