Generalized partial feedback based orthogonal space-time block coding

Precoding techniques can be used in multiple input multiple output (MIMO) system to assign resources such as power and information optimally. This paper is concerned with limited feedback in precoded orthogonal space time block code (OSTBC) systems, which is a precoding technique for incomplete channel information response. The conventional approach to design the precoding codebook is based on the discrete Fourier transform (DFT) matrix, which has high computational complexity. In this paper, a new approach to design the precoding codebook for the limited feedback precoded OSTBC systems is proposed, which is based on the discrete fractional sine transform (DFRST) matrix. The proposed DFRST-based precoding codebook design approach has lower computational complexity comparing to that of the DFT-based design with very similar bit error rate (BER) performance.

SUMMARYThis paper introduces limited feedback technique into physical‐layer network coding (PLNC) scheme, which is the most spectrally efficient protocol in two‐way relay channels, consisted of one relay and two end nodes (sources). Decode‐and‐forward (DF) and partial‐decode‐and‐forward (PDF) strategies are considered for PLNC, and all nodes are assumed to have two antennas to allow transmission by Alamouti's orthogonal space–time block code to provide diversity. In DF, by limited feedback, one of the sources is informed about instantaneous channel state information (CSI) to increase the bit error rate (BER) performance at relay. The closed‐form upper and lower bounds on the bit error probability are derived for binary phase‐shift keying (BPSK) and quadrature PSK (QPSK) modulations and approved via computer simulations. In PDF strategy, each source has to know CSI between relay and the other source for decoding, which causes extra protocol complexity. Moreover, for the system in which all nodes have two antennas, classical PDF strategy does not satisfy orthogonality at the end nodes. Therefore, in this paper, a modified‐PDF (MPDF) strategy with limited feedback is proposed. In MPDF, for decoding at the end nodes, differential phase information between channel fading coefficients having maximum amplitudes is fed back to the sources by relay. This approach enables single‐symbol decoding, besides full diversity, and sources do not need to know CSI between relay and the other source. It is shown via computer simulations that MPDF strategy provides significantly better BER performance than the classical PDF for BPSK and QPSK modulations.Copyright © 2012 John Wiley & Sons, Ltd.

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.

In this paper we propose a generalization of extended orthogonal space-time block codes (EO-STBCs) for MIMO (multi-input/multi-output) channels using four transmit antennas for quasi-static flat fading channels. Since full rate and complex orthogonal space-time block codes (STBCs) do not exist for more than two transmit antennas, we propose a feedback based STBC scheme. In this scheme, phases of certain symbols are rotated according to the feedback from the receiver which is equivalent to rotating the phases of the corresponding channel coefficients. Simulation results show that this rotation phase feedback method achieves a satisfactory performance and outperforms the previous closed-loop space-time block codes, even when the feedback is quantized.

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.

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.

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).

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.

A paradigm for multiple-input multiple-output (MIMO) channel modeling demands diversity technique to compensate the effects of fading and shadowing. In this paper, error performance of MIMO system is analyzed with orthogonal space time block code (OSTBC) and maximal ratio combining (MRC) techniques over Weibull-gamma (WG) fading channel. WG distribution forms a composite channel model which is used to determine the effects of multipath as well as shadowing. In this scenario, exact analytical expressions for symbol error rate (SER) are computed for MIMO systems using OSTBC and MRC. Consequently, the effects of fading severity by varying shape parameters are also shown by simulation and analytical results.

Orthogonal space-time block codes (OSTBCs) have recently attracted considerable attention due to their properties of full diversity and low implementation complexity. However, most works in this area simply employ classic phase-shift keying (PSK) or quadrature amplitude modulation (QAM) constellations, which are not necessarily optimal for OSTBCs. In this paper, we consider the problem of designing signal constellations for communication systems using OSTBCs, where the channel state information (CSI) available at the receiver is an estimate of the time variant channel gains with a specific estimation error. We perform an asymptotic symbol error probability (SEP) analysis and derive a criteria to design constellations that match well with the level of the channel estimation error. New signal constellations are found by means of a gradient search over a continuous alphabet. Simulation results show that the obtained constellations outperform not only the conventional QAM constellation, but also other well-known constellations used for efficient data communications.

Future backscatter RFID systems are required to be more reliable and data intensive for emerging fields such as Internet of Things (IoT). Motivated by this, orthogonal space-time block code (OSTBC), which is very successful in mobile communications for its low complexity and high performance, has already been investigated for MIMO backscatter RFID. Also a recently proposed scheme called unitary query was shown to be able to considerably improve the reliability of MIMO backscatter RFID by exploiting query diversity. Therefore, incorporating the classical OSTBC (at the tag end) with the unitary query (at the query end) seems promising. However, in this paper, we first show that simple direct employment of OSTBC together with unitary query incurs a linear decoding problem and eventually leads to severe performance degradation. As a redesign of the unitary query idea and the classical OSTBC specifically for MIMO backscatter RFID, we present a BUTQ-mOSTBC design pair idea by proposing the block-level unitary query (BUTQ) at the query end and the corresponding modified OSTBC (mOSTBC) at the tag end. The proposed BUTQ-mOSTBC can resolve the linear decoding problem, keep the simplicity and high performance properties of the classical OSTBC, and achieve the query diversity for the MIMO backscatter RFID.

In recent literature, performance analyses of multiple-input multiple-output (MIMO) multiuser systems using orthogonal space-time block coding (OSTBC) over Nakagami-m fading via bit error rate (BER) estimation have been obtained. In addition, analyses of the average channel capacity of these systems were carried out. From these findings, it was reported that closed-form expressions of the average channel capacity are difficult to obtain because of the presence of a finite product of an incomplete Gamma function. This paper shows that a new closed-form upper bound expression on the average channel capacity for non-integer values of m can be derived which gives insights into performance of OSTBC MIMO systems. The new bound is shown to be tight and valid with sensible numerical results.

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 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