A Phase Feedback Based Extended Space-Time Block Code for Enhancement of Diversity

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.

Orthogonal space-time block coding is a transmit diversity method that has the potential to enhance forward capacity. For a communication system with a complex alphabet, full diversity and full code rate space-time codes are available only for two antennas, and for more than two antennas full diversity is achieved only when the code rate is lower than one. A quasi-orthogonal code could provide full code rate, but at the expense of loss in diversity, which results in degradation of performance. We propose a closed loop feedback scheme for quasi-orthogonal codes which provides full diversity while achieving the full code rate. We investigate, in particular, the performance of this scheme, when the feedback information is quantised and when the fading of the channel is frequency-selective.

Complex orthogonal designs of maximum possible rate of full, 3/4, and 3/4 have been presented for 2, 3, and 4 transmit antennas respectively. For 5 and 6 transmit antennas, two generalized complex orthogonal space-time block codes of rates 7/11 and 3/5 were proposed recently. In this paper, we propose three complex orthogonal space-time block codes whose rates are up to 2/3, 2/3, and 5/8 for 5, 6, and 7 transmit antennas, respectively. Simulation results are provided to demonstrate the significant performance gains made by the proposed space-time block codes

We present a new complex orthogonal space-time block code (STBC) for 8 transmit antennas, which is generated simply by padding a transmission vector for the 8th transmit antenna to the transmission matrix of the existing complex orthogonal STBC for 7 transmit antennas. The presented complex orthogonal STBC for 8 transmit antennas achieves the same maximal rate 5/8 as well as the same minimal decoding delay 56 as those of the previously constructed complex orthogonal STBC for 7 transmit antennas.

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.

A complex orthogonal design (COD) used in space-time block codes is a kind of combinatorial design. It has been well studied because it has a fast maximum-likelihood decoding algorithm and achieves full diversity. When designing CODs, there are seven characteristics that should be considered, which include code rate, decoding delay, transceiver signal linearization, peak-to-average power ratio, etc. In this paper, we study the relationships among these design criteria. We prove that the maximum rate of generalized CODs (GCODs) that meet the last five criteria is 1/2. Moreover, we present a new method to construct GCODs based on CODs. Using this method on balanced complex orthogonal designs (BCODs), we obtain a novel class of GCODs that performs almost perfectly with respect to all the seven properties.

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.

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).

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 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.

Recently, a full rate orthogonal space-time block code achieving full diversity while preserving low decoding complexity with very limited feedback was proposed. Based on a feedback of only p-1 bits, these codes exhibit a higher coding gain as well. In this work, we propose a low complexity, though close to optimal, feedback selection scheme. Furthermore, we analyze the performance of these codes with arbitrary number of transmit and receive antennas. We show that with this feedback based codes full diversity of n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RP</sub> is obtained. Finally, we provide closed form expressions for the ergodic and outage mutual information as well as error rates.

The outage probability of two-way relaying network with orthogonal space–time block coded (STBC) transmission is analysed. Two sources equipped with different numbers of antennas send orthogonal STBC coded signals with different parameters. The channel gain between two antenna elements is assumed to be Rayleigh faded. The amplify-and-forward (AaF) relay with a single antenna repeats the received signal after power scaling. Exact expressions for the outage probabilities are provided, where the authors integrate out the outage probability over one of the three different regions on the plane defined by the inverses of channel gains. According to the orthogonal STBC code rates and the source and relay powers, one integration region is selected among the three. The closed-form expression is verified via a set of comparisons with the simulation results. The authors also show that the maximum diversity is attained when the orthogonal STBC is applied at both sides of the two-way channel.

Space time block coding is a modulation scheme recently discovered for the transmit antenna diversity to combat the effects of wireless fading channels. Using the equivalent Single-Input Single-Output (SISO) model, this paper presents closed-form expressions for the exact Symbol Error Rate (SER) and Bit Error Rate (BER) of Orthogonal Space-Time Block Codes (OSTBCs) with M-ary Phase-Shift Keying (MPSK) and M-ary Quadrature Amplitude Modulation (MQAM) over flat uncorrelated Nakagami-m and Ricean fading channels.

In this letter, an orthogonal space-time (ST) block coding (STBC) technique for continuous phase modulation (CPM) is proposed and combined with a frequency domain equalizer (FDE) to obtain high performance gains over frequency-selective channels. The new method maintains the constant envelope and phase continuity of the CPM waveforms perfectly by using appropriate tail symbols during the addition of cyclic prefix and interblock transitions and, therefore, has no negative impact on the spectral efficiency. Because the STcoded CPM blocks remain orthogonal, FDE is applied as in the case of single antenna transmissions without any increase in the computational load. Simulations corroborate the performance improvement offered by STBC while also preserving the desired bandwidth efficiency of CPM.

Orthogonal space-time block codes (STBC) constitute a simple way of exploiting transmit diversity. If no channel knowledge is available at the transmitter the use of diversity can increase performance significantly. However, if some partial channel state information (CSI) is available, such as knowledge of the transmit correlation matrix, adapting transmission to this knowledge provides additional performance gains. In such case, adaptivity can be introduced by using a unitary eigenbeamformer with beams pointing along the directions of the eigenvectors of the transmit correlation matrix and applying a convenient power loading along the resulting beams. While for Rayleigh-fading channel eigenbeamforming has been shown to be optimum in terms of ergodic capacity, so far, no closed solution for the optimum power loading has been found. In the work at hand, orthogonal STBC are combined with eigenbeamforming in an orthogonal frequency-division multiplexing (OFDM) context and an optimum power loading is found, where optimality refers to an upperbound of pairwise error probability (PEP). The resulting signaling scheme can be viewed as an extension of STBC to OFDM with partial channel knowledge. The solution represents a very interesting trade-off between transmit diversity and antenna gain.