Conventional Space-time Block Codes Research Articles

Bandwidth Efficiency Improvement for Differential Alamouti Space-Time Block Codes Using M-QAM

We propose a technique that enhances the bandwidth efficiency of the two transmit antenna differential space-time block code (DSTBC) by use of space-time block code (STBC) expansion and trellis coding. STBC expansion is realized by expanding the conventional Alamouti STBC using unitary matrix transformation. This is followed by trellis code-aided mapping of additional bits to space-time codes of the expanded set. Trellis code-aided mapping of additional bits enhances the bandwidth efficiency of the proposed DSTBC scheme. The proposed scheme sends more information bits in each transmitted space-time code than the conventional differential detection-aided DSTBC (CDD-DSTBC) scheme, and yet retains the same error performance. For each additional bit sent with the transmitted space-time codeword, the proposed scheme using 16QAM achieves a 12.5% increase in bandwidth efficiency, while the scheme using 64QAM realises an 8.3% increase. Simulation results demonstrate that the error performance of the proposed scheme tightly matches that of CDD-DSTBC with improvement in bandwidth efficiency. The bandwidth efficiency is enhanced at the expense of a moderate increase of the computational complexity at the receiver.

Bayesian Compressive Sensing Assisted Space–Time Block Coded Quadrature Spatial Modulation

A novel multiple-input and multiple-output transmission scheme termed as space–time block coded quadrature spatial modulation (STBC-QSM) is proposed. It amalgamates the concept of quadrature spatial modulation (QSM) and space–time block coding (STBC) to exploit the diversity benefits of STBC relying on sparse radio frequency chains. In the proposed STBC-QSM scheme, the conventional constellation points of the STBC structure are replaced by the QSM symbols; hence, the information bits are conveyed both by the antenna indices as well as by conventional STBC blocks. Furthermore, an efficient Bayesian compressive sensing (BCS) algorithm is developed for our proposed STBC-QSM system. Both our analytical and simulation results demonstrated that the proposed scheme is capable of providing considerable performance gains over the existing schemes. Moreover, the proposed BCS detector is capable of approaching the maximum likelihood detector's performance despite only imposing a complexity near similar to that of the minimum mean square error detector in the high signal-to-noise ratio regions.

Power efficient 2 × 1 space–time block code system with antenna shuffling

A transmit antenna shuffling method is proposed for a power efficient 2 × 1 space–time block code (STBC) system. Unlike a conventional STBC system that has identical power amplifiers (PAs), an asymmetric STBC (A-STBC) transmitter considered in this Letter has two asymmetric PAs, i.e. low-power and high-PAs. Considering the asymmetric PAs, the authors propose an antenna shuffling method with 1-bit feedback to improve the power efficiency (PE) of the STBC system. Numerical results verify that the proposed A-STBC system with 1-bit feedback antenna shuffling achieves a better PE-and-rate tradeoff and the potential ability of the small amount of feedback information for the power efficient systems.

A Multi-relay Cooperative Communication Using Space Time Spatial Phase Coding Based on OFDM

Among schemes to obtain diversity gain, space-time block code (STBC) and spatial phase coding (SPC) have been widely studied for the cooperative wireless relaying system. However, conventional STBC has a problem that cannot deal with change in the number of relays due to low throughput. In this paper, we propose a SPC that multi-relay transmission is possible and a space-time spatial phase coding (STSPC) using the proposed SPC scheme and STBC. The STSPC scheme provides improved bit error rate performance and full rate.

Performance analysis of combining scheduling and space–time block coding under channel estimation error

This study analyses performance-based implications of combining user scheduling and space–time block coding (STBC) (i.e. joint diversity) under channel estimation error. The exact closed-form expression of joint diversity for the achievable rate is derived. Moreover, the approximate closed-form expression of joint diversity for the outage achievable rate is derived through Gaussian approximation. The exact closed-form expression of joint diversity for the outage probability is finally derived, including the quantification of the order of diversity and the signal-to-noise ratio (SNR) gain. Using analytical results, it is demonstrated that both the achievable rate and the outage achievable rate of joint diversity improves as the number of user terminals increases through multiuser diversity. The approximate results of the analysis and simulation of the outage achievable rate for joint diversity are well matched as the number of users increases. The outage probability enhances with the number of user terminals through diversity order improvement, whereas the SNR gain is identical to that in conventional non-scheduling STBC.

Outage Performance Analysis of Incremental Relay Selection for STBC AF Cooperative Networks

In this paper, selection and incremental schemes are investigated for multi-input multi-output (MIMO) cooperative systems in which multiple amplify-and-forward relays and space---time block coding (STBC) are applied. In order to make an efficient use of the degrees of freedom of channel and provide full diversity order in the multi-relay STBC network, the selection and incremental protocols are employed by exploiting limited feedback from destination. Maximum ratio combination technique is applied at the destination. Outage probabilities of the both cooperative schemes are analytically derived at high signal to noise ratio regime. It is shown the incremental selection STBC scheme leads to a higher performance compared to the STBC selection relaying scheme and conventional STBC MIMO channels; so that the outage capacity provided by the incremental selection scheme is twice of the selection scheme at the low outage probabilities.

Distributed Cyclotomic QOSTBC with Low End-to-End Delay for Full-Duplex Multi-relay Systems

In this paper, we propose a novel distributed space-time block coding (STBC) scheme for multi-relay system. We consider the full-duplex cooperation which is more spectrally efficient than the half-duplex cooperation. In full-duplex mode, the new scheme requires relay nodes to stack only every two successive symbols for swapping. Thus, the end-to-end delay may be lower than that induced by orthogonal STBC and conventional quasi-orthogonal STBC (QOSTBC) schemes. We show the new distributed STBC is capable of achieving cooperative diversity by using multi-dimensional rotated signal constellation. Besides, due to the simpler maximum-likelihood metric compared to that of conventional QOSTBC, the code achieves a lower decoding complexity without any performance degradation. To furthermore reduce complexity, the fast sphere decoder is adopted for the proposed code. The proposed transmission scheme is evaluated and compared in terms of performance by simulation.

Single‐symbol decodable space‐time block code for multi‐input–multi‐output systems with four transmit antennas

This study presents an orthogonal design of space-time block code (STBC) that is single symbol decodable and enables full diversity and full rate transmission in a quasi-static channel environment. In the proposed scheme, full diversity is achieved by use of constellation rotation and co-ordination interpolation as is the case for the co-ordinate interleaved orthogonal design, whereas the transmission matrix of the proposed code consists of orthogonal columns with all non-zero elements, alleviating the concern about high peak-to-average power ratio. In particular, the proposed code offers lower complexity of channel estimation, and exhibits lower symbol error rate than the conventional quasi-orthogonal STBC when an maximum-likelihood decision-directed channel estimator is assumed. The advantages of the proposed code over the conventional codes are demonstrated through computer simulations. In addition, the selection of the angle of rotation for the proposed design is also presented, regarding the impact of channel estimation error.

Quasi-Orthogonal Space-Time Block Code with Givens Rotation for SC-FDE Transmission in Frequency Selective Fading Channels

Conventional space-time block codes are normally designed and studied for Rayleigh flat fading channels. As Single Carrier Frequency-Domain Equalization (SC-FDE) can help to combat the Inter-Symbol Interference (ISI) caused by multipath radio channels, this paper investigates quasi- orthogonal space-time block code (QOSTBC) with Givens rotation in order to enhance the reliability of the SC-FDE transmission in the frequency selective fading channels. To use QOSTBC with Givens rotation for the SC-FDE system, the encoding is performed on the data block basis, and we derive the corresponding decoding method performing in the frequency domain at the receiver. With Givens rotation, the correlation of channel equivalent matrix is eliminated, and the decoding can be performed with linear combiner at the receiver. Such a proposed scheme can achieve full rate transmission and provide high diversity gain. Simulation results show that the BER performance of the proposed scheme is better than QOSTBC for four transmit antennas, and is better than OSTBC (orthogonal space-time block code) in the low SNR regime. 1

차세대 통신 시스템을 위한 향상된 하이브리드 MIMO 기법

In this paper, a terrestrial transmission system is proposed for the next generation digital television (DTV) system by applying a hybrid multi-input multi-output (MIMO) technology based on linear dispersion codes (LDCs). The digital video broadcasting-2nd generation terrestrial (DVB-T2) system adopted a space time block code (STBC) for improving receive performance. However, the data rate of STBC is not increased in proportion to the transmitter. The hybrid STBC scheme utilizes several STBC transmission blocks for increasing data rate. It is possible to increase the data rate and performance in the receiver by utilizing LDC. The performances of the proposed and conventional hybrid STBC schemes are evaluated through computer simulations.

A Simple Multiphase Coding Technique for Transmit Diversity in Continuous Fading Channels

We propose a simple constellation-precoding technique for coherent phase-shift keying (PSK) modulation. The constellation of coded symbols is designed for a multiple-input-multiple-output (MIMO) system in frequency-nonselective Nakagami-m fading channels. Such a signaling mechanism, which is composed of the precoding technique and orthogonal pulse shaping, is shown to provide error performance and bandwidth efficiency comparable with those of the conventional space-time block codes (STBCs). We present a low-complexity coherent receiver, error bounds, and a code-search criterion for the considered system, which can alternatively operate with or without full channel-state information (CSI). Numerical and simulation results are provided to verify the significant performance improvement obtained by the proposed diversity scheme over Nakagami-m fading. The proposed approach is shown to be more robust against the decrease of adjacent fading sample correlation than the conventional STBCs while continuous fading is considered. For certain wireless environment limitations such as full CSI absence and fast fading, the scheme provides an alternative solution to mitigate the fading effects at the cost of low implementation complexities.

Decoding alamouti STBC from received signal power

We present two decoding schemes for Alamouti space-time block codes (STBC) that do not require full knowledge of the received signal. Our schemes are able to decode signals directly from the received signal power, without knowledge of the signal amplitude and phase. This in turn allows for reduced susceptibility to fast fading and lower receiver complexity. Such decoding approach is not possible for the case of conventional Alamouti STBC scheme. It is shown that the proposed First Quadrant Transmission (FQT) is able to deliver the best performance on par with the conventional Alamouti STBC scheme even when the conventional scheme has full knowledge of the received signal. Our recommendations are based on the novel complex to real Alamouti STBC mapper and the sign ambiguity elimination method, both presented in this letter.

Cooperative Diversity with Multiple-Antenna Nodes in Fading Relay Channels

In this paper, we investigate the performance of a single-relay cooperative scenario where the source, relay and destination terminals are equipped with multiple transmit/receive antennas. We assume that conventional space-time block codes are employed in the underlying source-to-destination (SrarrD), source-to-relay (S rarr R) and relay-to-destination (R rarr D) links, and consider both decode-and-forward (DaF) and amplify - and-forward (AaF) relaying techniques. For the latter one, we consider two variants based on the availability of channel state information (CSI); namely, blind AaF and CSI-assisted AaF. Through the derivation of pairwise error probability, we quantify analytically the impact of multiple antenna deployment for each relaying technique under various scenarios which involve relay location and power control assumptions imposed on cooperating nodes. Our transmission model assumes that the source and destination terminals are equipped with MS transmit and N receive antennas, respectively, and the relay terminal is equipped with MR receive and MT transmit antennas. For a scenario where R rarr D and S rarr D links are balanced and S rarr R link experiences sufficiently large SNR, our performance analysis demonstrates that the maximum achievable diversity order is MT min(MS, N)+MSN for blind AaF scheme and N(MT+MS) for both CSI-assisted AaF and DaF schemes. For another scenario where R rarr D link has a sufficiently large SNR and S rarr R and S rarr D links are balanced, CSI-assisted AaF, blind AaF and DaF schemes achieve diversity orders of MS(N + MR), MS(N + MT), and MSN, respectively. Other scenarios involving the availability of non-fading R rarr D link and poor inter-user channel quality are further investigated. An extensive Monte Carlo simulation study is also presented to corroborate the analytical results and to provide detailed performance comparisons among the three relaying techniques under consideration.

Full-Rate STBCs from Coordinate Interleaved Orthogonal Designs in Time-Selective Fading Channels

Space-time block codes (STBCs) from coordinate interleaved orthogonal designs (CIODs) have attracted a great deal of attention due to their full-diversity and linear maximum likelihood (ML) decodability. In this letter, we propose a simple detection technique, particularly for full-rate STBCs from CIODs to overcome the performance degradation caused by time-selective fading channels. Furthermore, we evaluate the effects of time-selective fading channels and imperfect channel estimation on STBCs from CIODs by using a newly-introduced index, the results of which demonstrate that full-rate STBCs from CIODs are more robust against time-selective fading channels than conventional full-rate STBCs.

Equalization Techniques for Distributed Space-Time Block Codes With Amplify-and-Forward Relaying

In this paper, we investigate equalization methods for cooperative diversity schemes over frequency-selective fading channels. Specifically, we consider three equalization schemes proposed originally for conventional space-time block codes (STBC) and extend them to distributed STBC in a cooperative transmission scenario with amplify-and-forward relaying. The distributed STBC equalization schemes are named after their original counterparts as distributed time-reversal (D-TR) STBC, distributed single-carrier (D-SC) STBC, and distributed orthogonal frequency division multiplexed (D-OFDM) STBC. The underlying orthogonality of distributed STBC results in decoupled data streams at the receiver side allowing low-complexity implementations. Without loss of generality, we consider a single-relay scenario where the source-to-relay SrarrR, relay-to-destination RrarrD, and source-to-destination SrarrD links experience possibly different channel delay spreads. Under the assumption of perfect power control for the relay terminal and high signal-to-noise ratio (SNR) for the underlying links, our performance analysis demonstrates that D-TR-STBC, D-SC-STBC, and coded D-OFDM-STBC schemes are able to achieve a maximum diversity order of min(L1,L3)+L2+2 where L1, L2, and L3 are the channel memory lengths for SrarrR, SrarrD, and RrarrD links, respectively. This illustrates that the minimum of the multipath diversity orders experienced in SrarrR and RrarrD links becomes the performance bottleneck for the relaying path. For the case of a nonfading relaying path where line-of-sight propagation is possible in either one of these underlying links, we demonstrate that diversity orders of L1+L2+2 and L3+L2+2 are achievable assuming nonfading SrarrR and RrarrD links, respectively. An extensive Monte Carlo simulation study is presented to corroborate the analytical results and to provide detailed performance comparisons among the three candidate equalization schemes

Subband Adaptive Array for Space-Time Block Coding

Diversity transmission using space-time block coding (STBC) shows a degraded performance in frequency selective fading (FSF) channel. In this paper, assuming the CSI is unknown at both transmitter and receiver while a pilot signal is available during the training period, we propose a MIMO transmission scheme using STBC by adopting subband adaptive array (SBAA) processing. The receive signal is converted into the frequency-domain and adaptive processing is done at each subband. A novel construction of SBAA is introduced to process received signal based on STBC. Simulation results demonstrate that the proposed scheme has a better performance compare to conventional STBC, and has a better performance and less computational load compare to STBC-TDLAA.

Quasi-Orthogonal STBC System Using Unequal Power Allocation Scheme

Quasi-orthogonal Space Time Block Code (STBC) was designed to provide full transmission rate when using more than two antennas. However, it cannot have a full diversity gain because of the interference resulted from its quasi orthogonality property. In order to achieve full diversity from quasi-orthogonal STBC, the interference can be removed by a Simple Correlation Canceling (SCC) algorithm which improves a system performance significantly. However, the SCC algorithm has a disadvantage that produces noise enhancement, thereby resulting in performance degradation. Accordingly, without increasing an extra system complexity, an unequal power allocation scheme in a transmitter is proposed to achieve a better system performance than the conventional STBC system using the SCC algorithm. Also, the unequal power allocation scheme enables a receiver to use a simple decoding procedure that does not produce noise enhancement.

Decision feedback detection with error compensation for hybrid space-time block codes

Spatial division multiplexing (SDM) techniques increase the total throughput by transmitting independent information streams through multiple transmit antennas whereas space time coding (STC) techniques utilize diversity gain. Hybrid space-time block code (STBC) schemes proposed combine the above two techniques to maximize the link performance. We propose a decision feedback detection method to improve the performance of the hybrid STBC scheme for orthogonal frequency division multiplexing (OFDM). In this scheme, we take the error propagation effect into account to enhance the detection performance. Simulation results show that the proposed method outperforms the conventional hybrid STBC detection algorithm by more than 3dB at 1% frame error rate for frequency selective fading channels.

Differential Space Time Block Codes Using Nonconstant Modulus Constellations for Four Transmit Antennas

We extend the differential space time block code (STBC) using nonconstant modulus constellations of two transmit antennas to four transmit antennas case. The proposed method obtains larger minimum Euclidean distances than those of conventional differential STBC with PSK constellations. We derive the symbol error rate (SER) performance of the proposed method and demonstrate the SER performance using computer simulations for both static and fast fading channels. For transmission rates greater than 2 bits/channel use and 3 bits/channel use, the proposed method outperforms the conventional differential STBC.

Differential space time block codes using nonconstant modulus constellations

We propose differential space time block codes (STBC) using nonconstant modulus constellations, e.g., quadrature amplitude modulation (QAM), which cannot be utilized in the conventional differential STBC. Since QAM constellations have a larger minimum distance compared with the phase shift keying (PSK), the proposed method has the advantage of signal-to-noise ratio (SNR) gain compared with conventional differential STBC. The QAM signals are encoded in a manner similar to that of the conventional differential STBC. To decode nonconstant modulus signals, the received signals are normalized by the channel power estimated forgoing training symbols and then decoded with a conventional QAM decoder. Assuming the knowledge of the channel power at the receiver, the symbol error rate (SER) bound of the proposed method under independent Rayleigh fading assumption is derived, which shows better SER performance than the conventional differential STBC. When the transmission rate is more than 3 bits/channel use in time-varying channels, the simulation results demonstrate that the proposed method with the channel power estimation outperforms the conventional differential STBC. Specifically, the posed method using the channel power estimation obtains a 7.3 dB SNR gain at a transmission rate of 6 bits/channel use in slow fading channels. Although the performance gap between the proposed method and the conventional one decreases as the Doppler frequency increases, the proposed method still exhibits lower SER than the conventional one, provided the estimation interval L is chosen carefully.