Space-time Transmit Diversity Research Articles

Novel polar-coded space-time transmit diversity scheme over Rician fading MIMO channels

In this paper, a polar-coded space-time transmit diversity (STTD) scheme is proposed in order to improve the performance of multiple-input multiple-output (MIMO) system. In Rician fading MIMO channels, the corresponding polar-coded STTD system can be equivalent to a single transmission channel for each polar code bit. Density evolutions for the polar-coded STTD systems are proposed based on the analyses of the single transmission channel. The proposed density evolutions provide preferable guidance to construct polar codes for the polar-coded STTD systems. Simulation results show that the BER performance of polar-coded STTD system is significantly improved as the number of antennas increases and the influence of the variable Rician K-factor of MIMO channels gradually vanishes. The proposed 2 × 2 polar-coded STTD system can provide better frame error rate (FER) performance than low-density parity-check (LDPC)-based system under low and mid code rates, and the average advantage is 0.3 dB approximately when the code rate is 0.25 and 0.2 dB when the code rate is 0.5.

Mitigating Co-channel interference using transmitter pre-processing for double space-time transmit diversity aided IDMA system

A double space-time transmit-diversity (DSTTD) architecture achieves higher throughput by employing four transmit antennas and four receive antennas. In this article, we compute Error-Rate (ER) performance of DSTTD-Interleave-division multiple-access (IDMA) system using Multi-user transmitter pre-processing (MUTP) for standard channel models. We realize MUTP using SVD technique to mitigate Co-channel interference (CCI) effects apart from Multi-user Interference (MUI), which are considered to be major channel impairments. The MUTP exploits the signal space of the entire active user's channel state information (CSI). We estimate CSI and quantize using vector quantization at each mobile unit and formulate TP by recovering at base station. Our simulation result reveals that considered system with MUTP technique achieves better ER with less SNR while offering high data rate for downlink transmission. Further, we observe that the ER performance of our considered system depends on code book size of vector quantized parameters.

System analysis of DSTTD-CDMA system with polarization diversity for frequency-selective channel

In this treatise, we consider the image transmission by means of turbo coded Double Space-Time Transmit-Diversity (DSTTD) Code Division Multiple Access (CDMA) structured module using Polarization diversity (PD) through wireless networks. We consider Advanced Encryption Standard (AES) algorithm for data hiding and discrete wavelet transform (DWT) technique for image compression. We consider dual-Polarized antenna both at transmitter and mobile station (MS) to establish PD. At each MS, we implement non-linear detector which comprises of Block-nulling technique, which can separate two STBC block units and offers higher throughput. In specific, we examine the effects of nine tap delay pertaining to LTE-Extended vehicular channel models for DWT and encrypted image transmission of coded DSTTD-CDMA system. From our simulation, we observe that our system with PD provides secured image transmission with better picture quality for less SNR which offers high throughput with compact size of MS in the perspective of downlink DL communication.

Effect of scattering environment on estimation quality in V2I and V2V communications

In this paper, we use a set of modulated discrete prolate spheroidal sequences (MDPSS) to represent a band-limited channel in the scenario with scattering from one or more clusters which can be used in both vehicle-to-infrastructure (V2I) or vehicle-to-vehicle (V2V) communication cases. Then we evaluate the performance of 2×1 space-time transmit diversity (STTD) system with Alamouti coding and imperfect channel estimation at the receiver. We consider examples of different scattering environments which represent vehicular communication in urban areas, derive expressions for autocorrelation function of channel gains and verify it by simulation. Scattering effect on estimation quality of the system is examined in terms of minimum mean square error (MMSE) and bit error rate (BER).

Using hierarchical data mining to characterize performance of wireless system configurations

This paper presents a statistical framework for assessing wireless systems performance using hierarchical data mining techniques. We consider WCDMA (wideband code division multiple access) systems with two-branch STTD (space time transmit diversity) and 1/2 rate convolutional coding (forward error correction codes). Monte Carlo simulation estimates the bit error probability (BEP) of the system across a wide range of signal-to-noise ratios (SNRs). A performance database of simulation runs is collected over a targeted space of system configurations. This database is then mined to obtain regions of the configuration space that exhibit acceptable average performance. The shape of the mined regions illustrates the joint influence of configuration parameters on system performance. The role of data mining in this application is to provide explainable and statistically valid design conclusions. The research issue is to define statistically meaningful aggregation of data in a manner that permits efficient and effective data mining algorithms. We achieve a good compromise between these goals and help establish the applicability of data mining for characterizing wireless systems performance.

Approximate SER for M-PSK using MRC and STTD Techniques over Fading Channels

In this study, approximate symbol error rate (SER) expressions for M-ary phase shift keying (M-PSK) modulation scheme over independent and identically distributed (i.i.d) slow-flat Rician and Rayleigh fading channels are derived. Simulation results show the superior impact of using the maximum ratio combining (MRC) space diversity technique on the overall performance. In particular, the communication reliability (i.e., capacity and coverage) will increase by increasing the diversity order (i.e., the number of the combiner’s branches), where less power is needed to achieve the same probability of error. Then, a comparison between the approximate and exact probability of symbol error is performed and the results are shown to be comparable (1–2 dB). Next, approximate SER expression is derived over i.i.d slow-flat Nakagami-m fading channels. In particular, space time transmit diversity (STTD) technique is used to enhance the reliability of the proposed model using two transmit antennas and one receive antenna. The simulation results show the effect of the Nakagami-m parameter, m, on the SER where the performance will improve by increasing the value of m where fading is less severe in this case. Furthermore, the performance of the SER is lower for higher values of SNR and is worse for high order PSK modulation schemes.

도심환경에서 각도-시간 송신다이버시티의 성능분석

In multipath fading channel, diversity is essential to mitigate the impairments. In this paper, we have proposed the angle diversity scheme called ATTD(Angle Time Transmit Diversity) instead of Alamouti"s STTD(Space Time Transmit Diversity) and have analyzed the performance of the proposed scheme when signal powers caused by the transmission to different angles are different.<BR> Based on it, we have measured the wireless vector-channel in the urban area, which has lots of high-story buildings, using the data collected from the 8 by 4 smart array antenna system that we made. According to the measured data, the received signals from different angles have different signal powers. Our performance analysis results show that the proposed scheme has better performance than the space diversity scheme when the received path signal power is at least -7dB compare to the strongest path signal power.

Performance Analysis of Alamouti Transmit Diversity with QAM in Imperfect Channel Estimation

In this paper, the performance of multi-level quadrature amplitude modulation (M-QAM) systems is studied analytically when Alamouti space-time transmit diversity (STTD) coding is used for transmission over Rayleigh fading channels. The effect of self-interference (interference from another simultaneously transmitted symbol in the STTD scheme for the same user) due to imperfect channel estimation is investigated. Based on the characteristic function method, a closed-form expression of the bit error rate (BER) is derived. Numerical results for 16/64-QAM show that, with the Alamouti STTD technique, the BER performance of the QAM system can be improved significantly. The effect of receive antenna diversity is also investigated. It is shown that high-order QAM constellations can be employed even in low signal to noise ratio (SNR) with the transmit diversity technique in conjunction with receive antenna diversity.

Performance Comparison between CDTD and STTD for DS-CDMA/MMSE-FDE with Frequency-Domain ICI Cancellation

SUMMARY Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can provide a better bit error rate (BER) performance than rake combining. However, the residual inter-chip interference (ICI) is produced after MMSE-FDE and this degrades the BER performance. Recently, we showed that frequency-domain ICI cancellation can bring the BER performance close to the theoretical lower bound. To further improve the BER performance, transmit antenna diversity technique is effective. Cyclic delay transmit diversity (CDTD) can increase the number of equivalent paths and hence achieve a large frequency diversity gain. Space-time transmit diversity (STTD) can obtain antenna diversity gain due to the space-time coding and achieve a better BER performance than CDTD. Objective of this paper is to show that the BER performance degradation of CDTD is mainly due to the residual ICI and that the introduction of ICI cancellation gives almost the same BER performance as STTD. This study provides a very important result that CDTD has a great advantage of providing a higher throughput than STTD. This is confirmed by computer simulation. The computer simulation results show that CDTD can achieve higher throughput than STTD when ICI cancellation is introduced.

Performance Analysis of the D-STTD Communication System with AMC Scheme

In this paper, we propose a Double-Space Time Transmit Diversity (D-STTD) communication system with Adaptive Modulation and Coding (AMC) scheme and analyze its performance using simulation experiments. The simulation results show that the probability of selecting a high Modulation and Coding Scheme (MCS) level increased as the Signal to Noise Ratio (SNR) improved. Furthermore, the D-STTD communication system with AMC scheme provided a more uniform throughput distribution throughout the entire SNR range compared to its counterpart which did not apply AMC scheme. Also, the maximum throughput of the D-STTD communication system with AMC scheme was twice that of a conventional AMC communication system or a Space Time Transmit Diversity (STTD) communication system with AMC scheme.

Equivalent Capacity-Based Joint Multilevel Coding and Space–Time Transmit Diversity Design

A novel space-time block-coding-assisted and sphere-packed multilevel-coded (STBC-SP-MLC) modulation arrangement is proposed, which combines an MLC-based scheme with a twin-antenna-aided STBC for the sake of providing a transmit diversity gain. The SP modulation invokes a 4D D 4 constellation space. A new bit-to-SP symbol mapper is designed for the sake of improving the system's performance. This involves mapping the MLC bits to the SP symbols of Layer-1 and Layer-2 in D 4 space. The binary switching algorithm is used to determine the optimum cost function used for designing different mapping strategies. The so-called equivalent capacity-based design invoking the 4-D signal space is used to determine the optimum coding rate of the STBC-SP-MLC scheme's component codes. Finally, we investigate a hybrid bit-to-SP symbol-mapping strategy for the STBC-SP-MLC scheme, which is capable of providing unequal error protection.

Distributed Relay Diversity Systems for OFDM-Based Networks

In this paper, distributed relay diversity systems are analyzed, modeled and evaluated in an Orthogonal Frequency Division Multiplexing (OFDM) based networks. The investigated distributed relay diversity schemes extend the ideas of a single hop transmit antenna schemes such as Cyclic Delay Diversity (CDD), Space Time Transmit Diversity (STTD), transmit Coherent Combining (CC) and Selection Diversity (SD) to distributed diversity systems. In contrast to the classical single hop system, the antennas in the distributed systems belongs to distributed relays instead of being co-located at the transmitter. The distributed relay diversity methods considered in this paper: Relay CDD (RCDD), Relay Alamouti (i.e.STTD), Relay CC (RCC) and Relay SD (RSD) are compared to the traditional 1-hop system. Analytical expressions for the received Signal to Interference Noise Ratio (SINR) are derived and used in a dynamic multi-cell multi-user simulator. Results show considerable SINR gains for both Round Robin and Max-SINR schedulers. The SINR gains translate into substantial cell throughput gains, up to 200%, compared to 1-hop systems. Despite its low complexity, the RCDD scheme has similar performance to that of other more sophisticated 2-hop schemes such as Relay Alamouti and Relay Coherent Combining. Marginally better results are observed for the Relay Selection Diversity scheme.

Space–Time MMSE Advanced Detector for Multisatellite Systems Under Nonideal Conditions

The transmitter diversity is accepted as one of the main techniques for improving performance, capacity, or simply for facing fading or power impairments in wireless communication systems such as downlink universal mobile telecommunications system (UMTS), satellite UMTS, and short-range communications (IEEE802.11 family, UWB, etc.). Unfortunately, the space- time transmit diversity (STTD) needs the channel knowledge at the receiver, and thus, errors in the estimation process at the receiver can drastically reduce the diversity gain. This paper deals with the development of two new schemes of space-time MMSE receivers implemented for the forward link of a wideband code division multiple access (WCDMA) multisatellite system and their performance evaluation under nonideal conditions. The aim of this paper is to show that the schemes proposed are able to better mitigate multiple access interference, that they show robustness against an imperfect knowledge of the channel state, and that they do not need a synchronization of the symbols transmitted by the satellites in order to let STTD technique work properly. A comparison with other two space-time MMSE detectors which have already been dealt with in the literature is also included. The detectors are compared by means of the simulation of a realistic multisatellite WCDMA environment. Bit error rates are calculated by means of Monte Carlo simulations, assuming a time-varying satellite channel model. The results show that the receivers proposed in this paper outperform the detectors presented in the literature in the vehicular channel, i.e., when the receiver has a high mobility, although a 30deg of channel phase coefficient estimation error is present.

Space-Time Cyclic Delay Transmit Diversity for a Multi-Code DS-CDMA Signal with Frequency-Domain Equalization

Frequency-domain equalization (FDE) can take advantage of the frequency-selectivity of the channel to improve the transmission performance in a frequency selective fading channel. To further improve the transmission performance, the transmit diversity technique can be used. Cyclic delay transmit diversity (CDTD) can strengthen the frequency-selectivity while space-time transmit diversity (STTD) can achieve the antenna diversity gain. In this paper, we propose a 4-antenna space-time cyclic delay transmit diversity (STCDTD), which is a combination of 2-antenna STTD and 2-antenna CDTD schemes, for orthogonal multi-code direct sequence code division multiple access (DS-CDMA) using FDE. We evaluate the BER performance and the throughput performance by computer simulation and compare them with the original CDTD and STTD schemes.

Frequency-Domain Space-Time Block Coded-Joint Transmit/Receive Diversity for Direct-Sequence Spread Spectrum Signal Transmission

SUMMARY Recently, we proposed space-time block coded-joint transmit/receive antenna diversity (STBC-JTRD) for narrow band transmission in a frequency-nonselective fading channel; it allows an arbitrary number of transmit antennas while limiting the number of receive antennas to 4. In this paper, we extend STBC-JTRD to the case of frequency-selective fading channels and propose frequency-domain STBC-JTRD for broadband direct sequence-spread spectrum (DSSS) signal transmission. A conditional bit error rate (BER) analysis is presented. The average BER performance in a frequency-selective Rayleigh fading is evaluated by MonteCarlo numerical computation method using the derived conditional BER and is confirmed by computer simulation of the signal transmission. Performance comparison between frequency-domain STBC-JTRD transmission and joint space-time transmit diversity (STTD) and frequency-domain equalization (FDE) reception is also presented.

Joint Frequency-Domain STTD and Antenna Diversity Reception Based on MMSE Criterion for OFDM/TDM

In this letter, we introduce frequency-domain space-time transmit diversity (STTD) encoding/decoding to orthogonal frequency division multiplexing combined with time division multiplexing (OFDM/TDM) on a frame-by-frame basis (i.e., over several concatenated OFDM signals in the frequency-domain) to achieve both spatial and frequency diversity gains and improve the bit error rate (BER) performance. The theoretical BER performance is evaluated by numerical computation using the derived conditional BER and confirmed by computer simulation.

Space-Time Block Coded Joint Transmit/Receive Diversity in a Frequency-Nonselective Rayleigh Fading Channel

Antenna diversity is an effective technique for improving the transmission performance in a multi-path fading channel. Recently, transmit diversity has been attracting much attention since it can alleviate the complexity problem of the mobile terminals. Joint transmit diversity/receive diversity achieves a much improved transmission performance. In this paper, we propose a new space-time block coding algorithm for joint transmit/receive diversity, which requires the channel state information (CSI) only at the transmitter side. Unlike the conventional space-time transmit diversity (STTD), the space-time block coded joint transmit/receive diversity (STBC-JTRD) can use arbitrary number of transmit ; antennas, while the number of receive antennas is limited to 4. STBC-JTRD achieves a larger diversity gain than joint STTD/receive antenna diversity. The bit error rate (BER) analysis in a frequency-nonselective Rayleigh fading channel is presented. The BER performance is evaluated and is confirmed by the computer simulation.

Performance of Turbo Coding With Improved Interference Estimation on the CDMA Space Time Transmit Diversity Forward Link

This paper proposes an approach to improve turbo code performance on the space time transmit diversity (STTD) code-division multiple-access (CDMA) forward link through better estimation of the channel state information (CSI) required by the mobile turbo decoder. An improved CSI estimation scheme that accounts for the unique nature of CDMA STTD intracell interference is presented. It is compared to a standard CSI estimation scheme that assumes all STTD interference and noise can be represented as additive white Gaussian noise at the mobile receiver input. An STTD CDMA forward link simulation shows that link performance is significantly improved when the mobile turbo decoder uses the more accurate CSI provided by improved estimation. However, the degree of improvement depends on the turbo decoding algorithm, mobile velocity, and whether the base station is using STTD or single-antenna transmission

Dual antenna cooperative diversity techniques

This paper presents the application of two spatial transmission techniques which can be used in a cooperative diversity wireless network, where each mobile terminal has two antenna elements. Initially the current body of work in single antenna cooperative diversity is expanded to include the effect of cooperative diversity upon the capacity of a link. This is to serve as a baseline model for comparison with the dual antenna methods. This paper then introduces two techniques which can be used for cooperative diversity where mobile terminals are each equipped with two antenna elements. Using the same metrics as the single antenna case, a comparison is made between the results from simulations of each technique. It is shown that dual antenna elements offer considerable advantage over the single antenna element case, and that two antenna element space-time transmit diversity (STTD) based cooperative diversity is preferred at low SNRs.

Orthogonal Space-Time Spreading Transmit Diversity

In this paper, a new 2-antenna transmit diversity, called orthogonal space-time spreading transmit diversity (OSTSTD) combined with delay transmission, is proposed. At the transmitter, N data symbols to be transmitted are spread using N different orthogonal space-time spreading codes (each represented by N x N matrix) and are transmitted from two transmit antennas after adding different time delays. At the receiver, 2step space-time despreading is carried out to recover the N transmitted data symbols. The first step recovers the N orthogonal spatial channels by taking the correlation between the received space-time spread signal and the time-domain spreading codes. The second step recovers the N transmitted data symbols using minimum mean square error (MMSE) despreading. The average bit error rate (BER) performance in a Rayleigh fading channel is evaluated by computer simulation. It is confirmed that the OSTSTD provides better BER performance than the Alamouti's space-time transmit diversity (STTD) at the cost of transmission time delay.