Double Space-time Transmit Diversity Research Articles

Double Space–Time Line Codes

In this paper, an M × 4 double space-time line code (D-STLC) is designed for a system with M-transmit and four-receive antennas whose channel state information is available at the transmitter. By delivering two independent STLC data streams simultaneously, both spatial diversity and multiplexing gains are obtained, like a 4 × M double space-time transmit diversity (DSTTD) system that transmits two space-time block coded data streams. It is analytically shown that the decoding signal-to-interference-plus-noise ratios of D-STLC and DSTTD are identical to each other, and furthermore, it is numerically verified that the proposed D-STLC significantly outperforms a conventional M × 4 STLC scheme and other existing spatial-diversity and spatial-multiplexing schemes, such as precoded space-time block code and precoded spatial multiplexing, in terms of achievable rate and bit-error-rate performance as the signal-to-noise ratio and/or transmission data rate increase.

Cognitive radio network based DSTTD-CDMA system

In this contribution, the performance of double space time transmit diversity (DSTTD) based multiple-input and multiple-output system with spatial diversity is investigated for cognitive radio network (CRN) based code-division-multiple-access (CDMA) system. CRN is realized in order to invoke available idle spectrum for reliable communication between base station and mobile station. DSTTD is constructed using two space- time processing unit. DSTTD is proven to provide high throughput .The user-specific spreading code is generated using sub-band frequency of CRN. Time-Frequency domain signature sequence is exploited to distinguish secondary users. The performance of CRN based DSTTD-CDMA scheme is analyzed using coded system. At each MS, iterative type of decoder is implemented to estimate secondary users’ information. The performance is analyzed for coded CRN based DSTTD-CDMA system for channel model with Stanford University Interim along with long-term evolution specifications. It is observed through simulation results that coded CR DSTTD-CDMA system establish proficient communication for secondary users while offering higher throughput and higher spectral efficiency and better performance in the context of bit-error-rate with fewer value of signal-to-noise ratio. Further, it is discerned that decoding algorithm obviate adjacent-channel interference along with secondary multi-user interference and CRN based CDMA system in conjunction DSTTD offers solution for high data rate application.

On the Combination of Double Space Time Transmit Diversity With Spatial Modulation

In this paper, we propose a spatially modulated space-time block coding scheme, called DT-SM, by combining the conventional double space time transmit diversity (DSTTD) with spatial modulation. First, we design a set of four basic spatial constellation (SC) codewords and an extended set of 16 SC codewords for four transmit antennas by using computer search based on the rank and determinant criterion. We then present a generalized algorithm to design SC codewords for an arbitrary number of transmit antennas greater than four. Compared with DSTTD, the proposed scheme attains the same transmit diversity order, while offering higher spectral efficiency. Besides, we derive a union bound for the bit error rate (BER) of the proposed DT-SM scheme in a quasi-static Rayleigh fading channel with spatial correlation. In order to achieve the performance of maximum-likelihood (ML) estimation at reduced detection complexity, we develop a sphere decoder based on the conventional Schnorr-Euchner sphere decoder. BER performance and detection complexity of the DT-SM scheme are evaluated by computer simulations. It is shown that the proposed DT-SM outperforms many existing MIMO and SM-based MIMO schemes at reasonable detection complexity, even in correlated MIMO channels.

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.

Double space‐time transmit diversity with spatial modulation

A hybrid scheme of the double space-time transmit diversity (DSTTD) and spatial modulation (SM) is proposed. The spectral efficiency of proposed scheme is twice that of DSTTD. Additional bits are transmitted by transmit antenna combinations of SM without widening the bandwidth. An optimised rotated constellation is also proposed according to the antenna combination to reduce inter-channel interference.

Mitigating ambient noise and multi-path propagation in underwater communication using the DSTTD-OFDM system

We consider turbo coded multi-carrier double space–time transmit diversity (DSTTD) system that employs orthogonal frequency division multiplexing (OFDM) for the transmission of acoustic signals in underwater communication, where acoustic interference and ambient noise are the major channel deficiencies. DSTTD employs two space–time block codes at the transmitter. At each receiver, we implement space–time Block-Nulling detection technique to increase throughput. We consider the iterative decoding algorithm at the receiver to alleviate the effects of ambient noise and acoustic interference. Further, we implement multi-carrier modulation technique to mitigate the effects of multipath propagation. We investigate the effects of eleven tap delay pertaining to shallow water channel model for the DSTTD-OFDM system. Our simulation results reveal that our considered system with Block-Nulling technique provides better bit error rates for lower signal-to-noise ratio when compared to a minimum mean square error detector-based system. Further, it achieves higher throughput with fewer computations at the receivers.

Achieving Arbitrary Multiplexing Rates for MIMO-OFDM Systems by Hybrid Cyclic Delay Diversity

This paper proposes a new hybrid cyclic delay diversity (HCDD) scheme for multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Unlike the existing double space time transmit diversity (DSTTD) and stacked cyclic delay diversity (SCDD) schemes that are suitable for integer multiplexing rates, the proposed HCDD scheme can achieve arbitrary non-integer multiplexing rates. Our results demonstrate that the HCDD scheme can provide flexibility in selecting the required number of transmitting antennas and in adjusting diversity and multiplexing gains to match various users requirements. The advantages of the proposed HCDD, including the flexible rate assignment and less complex receivers, are presented in applications of scalable video broadcasting (SVB).

Performance of joint transmit scheme assisted multiple-input multiple-output multi-carrier IDMA system

In this paper, we present the performance of a multiple-input multiple-output multi-carrier interleave division multiple access (MC-IDMA) system assisted by combined vertical Bell Laboratories layered space–time architecture and space–time block code processing over correlated frequency-selective channels for downlink communication. In MC-IDMA system, multi-carrier is realized by orthogonal frequency division multiplexing, which can eliminate the effects of time dispersion. At the mobile station, we employ zero forcing maximum-a-posteriori and minimum mean square error MAP (MMSE/MAP) multi-user detectors (MUD) to mitigate the effects of multi stream interference and iterative chip detection to combat the effects of multiple access interference. The performance of the considered system is compared with double space–time transmit diversity (DSTTD) aided MC-IDMA system. The simulation results show that the considered scheme outperforms DSTTD MC-IDMA and MC-CDMA system with MMSE/MAP MUD in terms of achievable bit error rate.

Performance of multi-user transmitter preprocessing assisted MIMO system over correlated frequency-selective channels

In this contribution we present the performance of a multi-user transmitter preprocessing (MUTP) assisted multiple-input multiple-output (MIMO) space division multiple access (SDMA) system, aided by double space time transmit diversity (DSTTD) and space time block code (STBC) processing for downlink (DL) and uplink (UL) transmissions respectively. The MUTP is invoked by singular value decomposition (SVD) which exploits the channel state information (CSI) of all the users at the base station (BS) and only an individual user’s CSI at the mobile station (MS). Specifically, in this contribution, we investigate the performance of multi-user MIMO cellular systems in frequency-selective channels from a transmitter signal processing perspective, where multiple access interference (MAI) is the dominant channel impairment. In particular, the effects of three types of delay spread distributions on MUTP assisted MIMO SDMA systems pertaining to the Long Term Evolution (LTE) channel model are analyzed. The simulation results demonstrate that MUTP can perfectly eliminate MAI in addition to obviating the need for complex multi-user detectors (MUDs) both at the BS and MS. Further, SVD-based MUTP results in better achievable symbol error rate (SER) compared to popularly known precoding schemes such as block diagonalization (BD), dirty paper coding (DPC), Tomlinson–Harashima precoding (THP) and geometric mean decomposition (GMD). Furthermore, when turbo coding is invoked, coded SVD aided MUTP results in better achievable SER than an uncoded system.

A Simple Layered Space-Time Block Nulling Technique for DSTTD Systems

A double space-time transmit diversity (DSTTD) system employs four transmit antennas to multiplex two Alamouti space-time block code (STBC) units. In this letter, a specially-designed canceling mechanism is presented, which can efficiently separate the two STBC units for such systems. We show that the orthogonal structure, and so the merit of Alamouti STBC, can be kept. Compared with some previous interference cancelation methods, the proposed one requires much fewer floating-point operations (flops) while achieving similar error-rate performance.

On Angle Feedback and Antenna Shuffling in Double Space-Time Transmit Diversity Systems

In this letter, we compare angle feedback and transmit antenna shuffling schemes for double space-time transmit diversity (DSTTD) systems with four transmit antennas and at least two receive antennas. We show that a DSTTD system with one bit of angle feedback does not provide better performance than the same system with one bit of transmit antenna shuffling. We also present a simplified general result about the selection of antenna shuffling matrix from six permutation matrices to facilitate our arguments. In simulation, we observe that antenna shuffling outperforms angle feedback in i.i.d. Rayleigh fading channels.

Antenna Selection with Superposition for 4 x 2 DSTTD Systems

From 1820 4 times 4 binary matrices, 253 binary preprocessing matrices are designed for double space-time transmit diversity (DSTTD) systems with two 2 times 2 space-time block code (STBC) encoders. Among them, six matrices yielding the highest average minimum-post-processing SNR are proposed from numerical experimentation under uncorrelated channel conditions. The proposed preprocessing performs a superposition of the first and second (second and first) STBC symbols and a selection of two transmit antennas. Simulation results show that the proposed method provides 1.7 dB (1.8 dB) SNR improvement in uncorrelated (correlated) channel environment at 10-3 bit error rate over the conventional antenna shuffling method.

A new ML based interference cancellation technique for layered space-time codes

This paper presents a new and simple decoding algorithm for layered space time block codes such as the two independent Alamouti's codes which are also called the double space-time transmit diversity (DSTTD) system. By using group interference suppression and successive interference cancellation, we can treat DSTTD as two independent space-time block codes (STBC). We can then decode both of these STBC's through a simple maximum likelihood (ML) detector with null space-based interference cancellation. We also compare the proposed interference cancellation (IC) scheme with the conventional MMSE IC scheme. The performance of the proposed IC scheme is comparable to that of the MMSE IC scheme while the complexity reduction factor of the proposed scheme can be up to 5 compared to the MMSE IC scheme.

Double Space Time Transmit Diversity OFDM System with Antenna Shuffling in Spatial Correlated Frequency Selective MIMO Channels

In this paper, we study low complexity transceiver for double space time transmit diversity (DSTTD) and orthogonal frequency division multiplexing (OFDM) system with antenna shuffling. Firstly, we propose a novel antenna shuffling method based on the criterion of minimizing the condition number of channel correlation matrix. The condition number is an indicator about the quality of the channel. By selecting the minimum of condition number which has better channel quality, consequently, a linear detector with respect to this new channel may achieve better performance results. A low complexity variant of the condition number calculation is also proposed, and it is shown that this criterion can be reduced to the minimum mean square error (MMSE) based criterion. Furthermore, the weighted soft decision Viterbi decoding is applied to mitigate noise enhancement inherent to zero forcing (ZF) and MMSE linear receivers and improve error rate performance. Next, we propose an algorithm to reduce the amount of feedback by exploiting the fact that the channel frequency responses across OFDM subcarriers are correlated. In the proposed algorithm, subcarriers are clustered in blocks, which are allocated the same shuffling pattern with the largest number of the shuffling patterns in the cluster. This way, the signaling overhead can be reduced in comparison with each subcarrier based feedback. Extensive simulations show that the proposed techniques for DSTTD-OFDM system outperform other existing techniques under both uncorrelated and highly spatial correlated frequency selective MIMO fading channels.

Joint transceiver design for DSTTD with low-complexity precoder and MMSE-OSIC

In this paper, we propose a jointly designed diagonal precoder and minimum mean-square error receiver with ordered successive interference cancellation (MMSE-OSIC) for the double space-time transmit diversity (DSTTD) system with low feedback and low-complexity. The proposed transceiver utilizes the structure of the equivalent channel of DSTTD, showing lower computational complexity and better error rate performance than the conventional antenna shuffling schemes with the channel state information at the transmitter.

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.

Error Performance of Double Space Time Transmit Diversity System

The theoretical error performance of double space time transmit diversity (DSTTD) system with optimum combining receiver is analyzed in this paper. By employing both spatial multiplexing and transmit diversity in one system, DSTTD provides practical tradeoff between system spectral efficiency and diversity gain. We derive exact analytical expressions to describe the symbol error rate for DSTTD systems. The effects of both diversity gain and antenna interference introduced by spatial multiplexing are quantified in the results. In addition, the performance of DSTTD system with successive interference cancellation is also investigated. Simulation results are in excellent agreement with the theoretical results obtained in this paper.

A Computationally Efficient Criterion for Antenna Shuffling in DSTTD Systems

The application of double space-time transmit diversity (DSTTD) scheme to multicarrier systems, such as orthogonal frequency division multiplexing (OFDM) systems, requires calculating the determinations of the antenna permutation matrices for all subcarriers, resulting in a heavy computation load. In this paper, we show that the signal-to-noise ratio (SNR)-based antenna shuffling criterion for DSTTD systems can be reduced to a simple criterion that evaluates determinants of 2 times 2 submatrices of the 4 times 4 equivalent channel matrix. The new criterion can lighten the computational load by about 95%. Furthermore, it is shown that the minimum mean square error (MMSE)-based criterion for antenna permutation can also be reduced to the same criterion.

A simplified adaptive modulation scheme for D-STTD systems with linear receivers

In this letter, we consider D-STTD (Double Space Time Transmit Diversity) with an adaptive modulation (AM) scheme. The simple criteria for AM are proposed according to linear receivers and the corresponding AM schemes are derived to minimize bit error rate under the constraint of the total data rate and total transmit power. The D-STTD system using the proposed AM scheme requires low computational complexity and small feedback information. The performance of D-STTD system using the proposed scheme is improved by 7 dB or more in signal to noise ratio corresponding to 10/sup -4/ bit error rate.