Successive interference cancellation amiable space-time codes with good multiplexing-diversity tradeoff

Antenna spacings, the angle spread and the Rice factor significantly affect the correlation of fading coefficients in a multi-antenna system. We study the effect of these parameters on the performance of different types of detection schemes in a BLAST architecture. We show that the detection method based on lattice decoding is more resistant to the correlated fading than other types of detection which are based on successive interference cancellation. We notice that highly correlated fades significantly degrade the performance of detection techniques based on successive interference cancellation whereas they slightly affect the lattice decoding algorithm. We also study the effects of correlated fades on some space-time block codes. We show that space-time block codes from orthogonal design are more resistant to correlation than other high rate linear space-time block codes.

Coordinated Multipoint Transmission and Reception (CoMP) and Enhanced Inter-cell Interference Coordination (eICIC) are two important features in 3GPP LTE-Advanced. Through CoMP and interference coordination, system performance, especially cell edge throughput is significantly improved. In 3GPP LTE-Advanced, CoMP discussion has been focusing on dynamic coordination schemes which require fast links between coordinating points. On the contrary, eICIC is considered as a semi-static co ordination scheme which is enabled through X2 backhaul interface. This paper provides an overview of CoMP and eICIC schemes discussed in the standardization process of LTE-Advanced. Performance results are provided to evaluate a novel scheme which combines dynamic CoMP and semi-static eICIC coordination under super-cell heterogeneous network deployment.

On the basis of analyzing of some existing differential space-time coding (DSTC) schemes, we develop a differential space-time block coding scheme based on multiple levels quadrature amplitude modulation (MQAM) in this paper. By introducing MQAM, the developed scheme can avoid the performance loss of conventional DSTC schemes based on MPSK modulation due to the decrease of minimum distance between constellation symbols in high spectrum efficiency. Compared with the existing DSTC schemes, the developed scheme has lower computational complexity and simple decoder. Moreover, it can achieve higher code rate in the case of more than two transmitter antennas. Theoretic analysis shows that the scheme has higher coding gain than existing differential unitary space-time coding scheme and differential orthogonal space-time coding scheme, and corresponding simulation results also show that our scheme has lower bit error rate (BER) when compared with the above two schemes.

Differential space-time coding (DSTC) has received much interest as it obviates the requirement of the channel state information at the receiver while maintaining the desired properties of space-time coding techniques. In this paper, by introducing star quadrature amplitude modulation (star QAM) method, two kinds of multiple amplitudes DSTC schemes are proposed. One is based on differential unitary space-time coding (DUSTC) scheme, and the other is based on differential orthogonal space-time coding (DOSTC) scheme. Corresponding bit-error-rate (BER) performance and coding-gain analysis are given, respectively. The proposed schemes can avoid the performance loss of conventional DSTC schemes based on phase-shift keying (PSK) modulation in high spectrum efficiency via multiple amplitudes modulation. Compared with conventional PSK-based DSTC schemes, the developed schemes have higher spectrum efficiency via carrying information not only on phases but also on amplitudes, and have higher coding gain. Moreover, the first scheme can implement low-complexity differential modulation and different code rates and be applied to any number of transmit antennas; while the second scheme has simple decoder and high code rate in the case of 3 and 4 antennas. The simulation results show that our schemes have lower BER when compared with conventional DUSTC and DOSTC schemes.

In 3GPP LTE-Advanced Release 11, coordinated multi-point transmission and reception (CoMP) which applies interference coordination between base stations (or eNBs) was introduced to improve cell-edge performance of the network and specified under the assumption that ideal backhaul is deployed. However, in practice, network operators may have non-ideal backhaul, especially between macro eNB and small eNB, which may result in limited CoMP gain. Hence, in this paper, a centralized coordination scheme based on two-step processing which can reduce backhaul delay impact on CoMP is introduced. In the first step of the centralized coordination scheme, the central coordinator decides and forwards resource allocation of the cells in coordination area. In the second step, each eNB conducts user scheduling on the resources allocated to each of its cells and applies link adaptation to meet the link performance requirement for the interference condition according to the resource allocation result. Simulation results show that the coordination based on two-step processing outperforms other coordinated scheduling schemes and maintains CoMP gain even in non-ideal backhaul.

In this paper, Beam Pattern Scanning (BPS), a transmit diversity technique, is compared with two well known transmit diversity techniques, space-time block coding (STBC) and space-time trellis coding (STTC). In BPS (also called beam pattern oscillation), controlled time varying weight vectors are applied to the antenna array elements mounted at the base station (BS). This creates a small movement in the antenna array pattern directed toward the desired user. In rich scattering environments, this small beam pattern movement creates an artificial fast fading channel. The receiver is designed to exploit time diversity benefits of the fast fading channel. Via the application of simple combining techniques, BPS improves the probability-of-error performance and network capacity with minimal cost and complexity. In this work, to highlight the potential of the BPS, we compare BPS and Space-Time Coding (i.e., STBC and STTC) schemes. The comparisons are in terms of their complexity, system physical dimension, network capacity, probability-of-error performance, and spectrum efficiency. It is shown that BPS leads to higher network capacity and performance with a smaller antenna dimension and complexity with minimal loss in spectrum efficiency. This identifies BPS as a promising scheme for future wireless communications with smart antennas.

A new space-time coding (STC) scheme for multiple-input multiple-output synthetic aperture radar systems is proposed in this paper. In the new scheme, two successive signal periods are put into one transmit duration to minimize the time-variant channel effect. The even and odd components of the transmitted waveforms are modulated into distinct Doppler frequencies in the azimuth direction and can be separated by bandpass filter in the range-Doppler domain. The presented STC scheme can suppress the interchannel ambiguous energy caused by the time-variant channel responses, which typically occur in conventional STC schemes, and increase the signal-to-noise ratio of the echoes by a decoding matrix. To further suppress the interference, a waveform called time and frequency comb-like chirp (TFCC) is proposed. With the application of the complementary comb-like structure in the time and frequency domains, two TFCC waveforms are short-term shift-orthogonal and constant envelope. Moreover, these corresponding TFCC waveforms can share the same antenna and time gate without sacrificing any TFCC waveforms' peak level. The theoretical analysis and simulation results illustrate the feasibility of the proposed scheme.

Most existing space-time coding (STC) schemes have been developed for flat fading channels. To obtain antenna diversity gain, they rely on channel state information (CSl) required at the receiver through channel estimation techniques. This paper proposes a new decision feedback decoding scheme for Alamouti-based space-time block coding (STBC) transmission over time-selective fading channels. In wireless channels, time-selective fading effects arise mainly due to Doppler shift and carrier frequency offset. Modelling the time-selective fading channels as the first-order Gauss-Markov processes, we use recursive algorithms such as Kalman filtering, LMS and RLS algorithms for channel tracking. The proposed scheme consists of the symbol decoding stage and channel tracking algorithms. Computer simulations confirm that the proposed scheme shows the better performance and robustness to time-selectivity.

The average bit error rate (ABER) performance of an orbital angular momentum (OAM) multiplexing-based free-space optical (FSO) system with multiple-input multiple-output (MIMO) architecture has been investigated over atmospheric turbulence considering channel estimation and space-time coding. The impact of different types of space-time coding, modulation orders, turbulence strengths, receive antenna numbers on the transmission performance of this OAM-FSO system is also taken into account. On the basis of the proposed system model, the analytical expressions of the received signals carried by the k-th OAM mode of the n-th receive antenna for the vertical bell labs layered space-time (V-Blast) and space-time block codes (STBC) are derived, respectively. With the help of channel estimator carrying out with least square (LS) algorithm, the zero-forcing criterion with ordered successive interference cancellation criterion (ZF-OSIC) equalizer of V-Blast scheme and Alamouti decoder of STBC scheme are adopted to mitigate the performance degradation induced by the atmospheric turbulence. The results show that the ABERs obtained by channel estimation have excellent agreement with those of turbulence phase screen simulations. The ABERs of this OAM multiplexing-based MIMO system deteriorate with the increase of turbulence strengths. And both V-Blast and STBC schemes can significantly improve the system performance by mitigating the distortions of atmospheric turbulence as well as additive white Gaussian noise (AWGN). In addition, the ABER performances of both space-time coding schemes can be further enhanced by increasing the number of receive antennas for the diversity gain and STBC outperforms V-Blast in this system for data recovery. This work is beneficial to the OAM FSO system design.

A downlink beamforming combined space-time coding and power control scheme for DS-CDMA systems in frequency selective fading channel is presented in this paper, in which the space-time coding is implemented by using two array antennas and the beamforming weights and transmitted power vector are obtained by an iterative algorithm such that the whole radiated power is minimized while the signal-to-interference and noise (SINR) requirements is maintained. Then a simplified algorithm for decreasing the complexity due to the existence of multipaths is suggested using equivalent one-path channel vector (EOCV) to replace multipath vectors. Simulations compare the performance between conventional space-time coding scheme and our method.

Multiple-input-multiple-output (MlMO) techniques promise huge capacity increase in fading channels. Group-wise space-time coding is a tradeoff between complexity and performance. In this paper, structure of particular component space-time code trellises is exploited using partial information from Viterbi decoder of the simultaneously decoded interfering component code. We have shown that calculating the a posteriori probabilities of different states of the encoder at each time, and predicting the conditional mean and covariance of interference for the next time index, the system performance is improved by soft interference cancellation. The word-error-rate (WER) performance improvement for a system with 4 transmit 4 receive antennas is 1.7 dB and 1.5 dB for 2-space-time codes with 8 and 16 states, respectively. In addition, the parallel structure does not have decoding delay as in successive interference cancellation and is highly modular for VLSI implementation.

Existing space-time codes have focused on multiple- antenna systems with linear modulation schemes such as phase- shift keying and quadrature amplitude modulation. Continuous phase modulation (CPM) is an attractive scheme for digital transmission because of its constant envelope which is needed for power efficient transmitters. Recent research has shown that space-time coded CPM can achieve transmit diversity to improve performance while maintaining the compact spectrum of CPM signals. However, these efforts mainly combine space- time coding (STC) with CPM to achieve spatial diversity at the cost of a high decoding complexity. In this paper, we design space-time block codes (STBC) for binary CPM with modulation index h = 1/2 and derive low-complexity receivers for these systems. The proposed scheme has a much lower decoding complexity than STC CPM with the Viterbi decoder and still achieves near-optimum error performances.

The block layered space-time codes, with the intent of simultaneously achieving high coding gain and high code rate, have been suggested. These codes are based on the design mechanisms of existing layered space-time codes and space-time block codes. The previously known concept of a layer has been modified to a block layer wherein a block layer has more than one antenna transmitting at the same instant and hence the name for this scheme. The role of the layers is to provide multiplexing. Each block layer incorporates Alamouti's transmit diversity scheme which decreases the decoding complexity and the component Alamouti codes are built on rotated constellations. The block layers are made transparent to each other by Diophantine approximation. The use of space-time codes improves the coding gain for the suggested code design scheme. This scheme has been implemented for four transmit antennas and four receive antennas but can easily be extended to any number of antennas depending on the code rate desired. The proposed codes achieve a normalized rate of 2-symbol/s. Simulation results show that the block layered space-time codes outperform threaded algebraic space-time (TAST) codes in certain scenarios

According to information theory, non-orthogonal transmission can achieve the multiple-user channel capacity with an onion-peeling like successive interference cancellation (SIC) based detection followed by a capacity approaching channel code. However, in multiple antenna system, due to the unideal characteristic of the SIC detector, the residual interference propagated to the next detection stage will significantly degrade the detection performance of spatial data layers. To overcome this problem, we proposed a modified power-domain non-orthogonal multiple access (P-NOMA) scheme joint designed with space-time coding for multiple input multiple output (MIMO) NOMA system. First, with proper power allocation for each user, inter-user signals can be separated from each other for NOMA detection. Second, a well-designed quasi-orthogonal space-time block code (QO-STBC) was employed to facilitate the SIC-based MIMO detection of spatial data layers within each user. Last, we proposed an optimization algorithm to assign channel coding rates to balance the bit error rate (BER) performance of those spatial data layers for each user. Link-level performance simulation results demonstrate that the proposed time-space-power domain joint transmission scheme performs better than the traditional P-NOMA scheme. Furthermore, the proposed algorithm is of low complexity and easy to implement.

Abstract-- As a promising radio access technology for future 5G network, novel multiple access (NMA) is aimed to improve spectrum efficiency and access capability via design of successive interference cancellation (SIC) amenable pattern in single domain (e.g. power domain, code domain, and space domain) or joint multiple domains. In this paper, a pattern in joint space and power domain is designed for NMA system. The proposed pattern jointly adopts a quasi-orthogonal space-time block code (Q-OSTBC) in space domain and power allocation (PA) scheme for users in power domain, which is in conjunction with SIC based linear receiver. The pattern utilizes Q-OSTBC with unequal diversity order to mitigate the error propagation in the SIC based detector for each user, and PA for multiple users with different channel gain to improve the spectrum efficiency. Simulation results show that the designed pattern can effectively mitigate error propagation in SIC based system. We also investigate the performance of SIC based receiver with or without channel decoding during the reconstruction of interference, simulation results indicate that the reconstruction with decoding outperform the one without decoding, especially under the condition of low signal-to-noise ratio (SNR). Due to the diversity gain, the NMA system using the designed pattern can obtain higher average sum rate compared to its counterpart, i.e. the combination of Vertical Bell Layered Space-Time code (VBLAST) and PA.