Space-time Coding Techniques Research Articles

WORKING ANALYSIS OF SPACE TIME TRELLIS CODE ON WIFI MIMO(2X2) SYSTEM OFDM

Wireless communication nowadays requires a system with reliable performance, efficient use of bandwidth, efficient power, and better coverage because it is in line with human needs for applications that require high and fast data rates. One of the concepts and methods to meet these needs is using an antenna technique with many transmitters and receivers or often called Multiple Input Multiple Output (MIMO), by adding a strategy at the time of delivery, namely the Space-Time Coding (STC) technique. In addition, the application of Orthogonal Frequency Division Multiplexing (OFDM) on MIMO-STC will more efficiently use bandwidth. The Space-Time Trellis Code (STTC) method is one of the diverse techniques in sending data with complex coding so that coding reinforcement is achieved and applied to the OFDM MIMO system. It is hoped that a system with reliable performance can be achieved. The simulation that is carried out presents the STTC and OFDM schemes on multi antennas (2 transmitters x 2 receivers) with a Combiner and Maximum Likelihood Sequence Estimator (MLSE) detection algorithm on the receiver. It is to get the quality of the sending signal in the performance analysis of Bit Error Rate (BER) with Signal to Noise Ratio (SNR). The simulation results are shown by modulation with M-array Phase Shift Keying (MPSK) and the number of symbols sent by giving different input parameter values. The results show that the number of carriers and the size of the Fast Fourier Transform (FFT) is large, and the modulation type with a small constellation produces a low BER and throughput at high SNR.

Space-Time Coding Technique for Coherent Frequency Diverse Array

Coherent frequency diverse array (FDA) radar is able to cover all directions with a stable gain by transmitting a single frequency-shifted waveform. However, it is revealed in this work that the range resolution scales linearly with the number of elements, which is limited by the fixed element number. By leveraging the relationship between the beam direction and the signal frequency, we link the sub-bands of the emitted signal to angular sectors. Based on the fact, a novel transmit diversity technique, referred to as two-dimensional (2-D) space-time coding (STC), is proposed to improve the range resolution. For a specific observation direction, the frequency band of each pulse is shifted by STC to synthesize a full bandwidth after the pulse accumulation. Furthermore, the piecewise LFM (linear frequency modulation) waveform design can be combined with the STC technique to synthesize the transmit beampattern flexibly without range resolution degradation for each pulse. Compared with the state-of-the-art technologies, the proposed STC technique has superiorities in range resolution improvement, ultra-low range sidelobe level, interference suppression, and beampattern design capability. In addition, multi-dimensional ambiguity functions are derived to assess the performance in range-angle-Doppler domain, including the range and angle resolutions, the sidelobe level (SLL) and the angular coverage. To satisfy practical demands, the general receive processing procedures are also designed. The proposed method and corresponding theoretical analysis are verified by extensive numerical results.

A Generalized Spatial Modulation System Using Massive MIMO Space Time Coding Antenna Grouping.

Massive multiple input multiple output (MIMO), also known as a very large-scale MIMO, is an emerging technology in wireless communications that increases capacity compared to MIMO systems. The massive MIMO communication technique is currently forming a major part of ongoing research. The main issue for massive MIMO improvements depends on the number of transmitting antennas to increase the data rate and minimize bit error rate (BER). To enhance the data rate and BER, new coding and modulation techniques are required. In this paper, a generalized spatial modulation (GSM) with antenna grouping space time coding technique (STC) is proposed. The proposed GSM-STC technique is based on space time coding of two successive GSM-modulated data symbols on two subgroups of antennas to improve data rate and to minimize BER. Moreover, the proposed GSM-STC system can offer spatial diversity gains and can also increase the reliability of the wireless channel by providing replicas of the received signal. The simulation results show that GSM-STC achieves better performance compared to conventional GSM techniques in terms of data rate and BER, leading to good potential for massive MIMO by using subgroups of antennas.

Space-Time Adaptive Processing Techniques (STAP) for Mitigation of Jammer Interference and Clutter Suppression in Airborne Radar Systems: A MATLAB Implementation-based Study

Radar Systems are used for the detection of objects by transmitting the electromagnetic waves in the free space. They operate in environments where there is a high possibility that the desired echo signal interferes with the signals from other sources. These signals include clutters and jammer signals. The jammer is a device that continuously emits the wideband radio signals in the radar environment, to saturate the receiver with noise or false information. Thus, the total received signal has three components- returns from target, clutter, and jammer combined i.e. it is a three dimensional signal. The use of conventional signal processing techniques is not desirable, as they cannot separate the desired echo signal from the other components, because the statistics of these components present in the received signal is not known. This problem needs to be accounted for, in airborne surveillance radars, as they have to identify and locate the targets in multiple interference environments. The Space-Time Adaptive Techniques (STAP) is a combination of spatial and temporal filtering that can nullify the jammer signal, and recognize the slow-moving targets. These techniques filter the signal in the angular and the Doppler domain for suppressing the unwanted signals. This paper presents a theoretical study of space-time adaptive coding techniques, and the MATLAB implementation of STAP algorithms; namely, SMI, DPCA, and ADPCA, to suppress clutter and jammer interference in the received pulse.

Performance Analysis of Grouped Multilevel Space-Time Trellis Coding Technique Using Cognitive Radio in Different Deployment Models

In this era, the number of users in a network is increasing tremendously at a faster rate; as a consequence, quality of service (QoS) is drastically deteriorating. To compensate such kinds of problems, we attempted to enhance the QoS of the network, which leads to an improvement in throughput, link quality, spectral efficiency, and many more. To meet the requirements mentioned above, many researchers intervene to advance and propose different techniques with an appropriate design methodology. In this work, we try to emphasize symbol error rate (SER) and frame error rate (FER) by implementing some of the existing space-time coding techniques like Space-Time Trellis Coding (STTC), multilevel space-time trellis coding (MLSTTC), and grouped multilevel space-time trellis coding (GMLSTTC). Though all these techniques are proved to be efficient enough, we explicitly included a powerful method of cooperative diversity-based spectrum sensing in cognitive radio scenario. From this analysis, we landed on to the conclusion that this technique is far better to deal with all these parameters, which can improve the QoS of the network. This paper has also analyzed the effect of the proposed model of GMLSTTC with cognitive radio on various deployment setups such as urban, suburban, and rural macrodeployment setup of the ITU-R M.2135 standard.

Blind Joint MIMO Channel Estimation and Decoding

We propose a method for multiple-input multiple-output (MIMO) decoding when channel-state information (CSI) is unknown to both the transmitter and receiver. The proposed method requires some structure in the transmitted signal for the decoding to be effective, in particular that the underlying sources are drawn from a hypercubic space. Our proposed technique fits a minimum volume parallelepiped to the received samples. This problem can be expressed as a non-convex optimization problem that can be solved with high probability by gradient descent. Our blind decoding algorithm can be used when communicating over unknown MIMO wireless channels using either binary phase-shift keying or MPAM modulation. We apply our technique to jointly estimate MIMO-channel gain matrices and decode the underlying transmissions with only knowledge of the transmitted constellation and without the use of pilot symbols. Our results provide theoretical guarantees that the proposed algorithm is correct when applied to MIMO systems with four or fewer transmit antennas. Empirical results show small sample size requirements, making this algorithm suitable for block-fading channels with coherence times typically seen in practice. Our approach has a loss of less than 3 dB compared to zero forcing with perfect CSI, imposing a similar performance penalty as space-time coding techniques without the loss of rate incurred by those techniques.

STTC design for vehicular communication systems employing fixed‐gain AF PLNC over cascaded fading channels

In this study, the authors combine physical layer network coding (PLNC) and space-time trellis coding (STTC) techniques to improve the error performance of vehicle-to-vehicle (V2V) communication systems where all fading channels are assumed to undergo double Rayleigh fading (DRF) which is worse than Rayleigh fading used in cellular communications. In the authors' analysis, they show that the DRF channels can be modelled by using the mixture gamma distribution. After that, pairwise error probability (PEP) analysis is performed for a fixed-gain amplify-and-forward PLNC V2V system employing STTC over the DRF channels, and an upper bound for the PEP is obtained. By examining the behaviour of the upper bound expression in the high SNR region, they derive a new design criterion for STTCs. Finally, using this criterion they propose novel STTCs with 4 and 8 states for V2V systems employing PLNC over the DRF channels.

Performance improvement of 4G OFDM systems using CTSTC techniques

The concatenation of channel coding and diversity schemes are essential in the 4G communication systems to improve the reliable data rate transmission. To address Bit Error Rate performance enhancement, the paper presents the coding gain and diversity gain benefits using the proposed CTSTC scheme by adding modified Turbo features and Space Time encoding features. Simulation results of are provided using MATLAB and compared the results with convolutional coded Space Time Coding technique.

MIMO Network and the Alamouti, STBC (Space Time Block Coding)

In the present world, the spectrum efficiency along with the capacity and coverage of wireless networks are being improved by wireless specialists. Wireless link performance could be enhanced and improved by using multiple antenna technology called Space time wireless technology. There exists some advancement in the present MIMO techniques which could further improve the overall wireless Local Area Network (LANs) and Wide Area Network (WANs). In Multipath fading performance gain is very important which could be achieved by using an efficient Space-Time Coding (STC) technique. This Space Time coding along with Alamouti Scheme is a very vibrant research topic. In the forthcoming generation of mobile communication there will be a need of high data rate, reliable communication link and vast multimedia capabilities, STBC is the one solution for these. This paper presents the Space-Time Block Codes (STBC) for wireless networks using Alamouti Scheme in which multiple antennas are being used at both transmitter and receiver. The simulations have been done in MATLAB.

Two Novel Space-Time Coding Techniques Designed for UWB MISO Systems Based on Wavelet Transform.

In this paper two novel space-time coding multi-input single-output (STC MISO) schemes, designed especially for Ultra-Wideband (UWB) systems, are introduced. The proposed schemes are referred to as wavelet space-time coding (WSTC) schemes. The WSTC schemes are based on two types of multiplexing, spatial and wavelet domain multiplexing. In WSTC schemes, four symbols are transmitted on the same UWB transmission pulse with the same bandwidth, symbol duration, and number of transmitting antennas of the conventional STC MISO scheme. The used mother wavelet (MW) is selected to be highly correlated with transmitted pulse shape and such that the multiplexed signal has almost the same spectral characteristics as those of the original UWB pulse. The two WSTC techniques increase the data rate to four times that of the conventional STC. The first WSTC scheme increases the data rate with a simple combination process. The second scheme achieves the increase in the data rate with a less complex receiver and better performance than the first scheme due to the spatial diversity introduced by the structure of its transmitter and receiver. The two schemes use Rake receivers to collect the energy in the dense multipath channel components. The simulation results show that the proposed WSTC schemes have better performance than the conventional scheme in addition to increasing the data rate to four times that of the conventional STC scheme.

Space Time Coding Techniques in MIMO: A Review

This paper explore the basic approaches used for of space-time coding technique. The emerging field of wireless evaluation such as Multiple Input Multiple Output (MIMO) and Antenna diversity plays an important role in space-time code design. Spatial diversity techniques by the means of multiple transmitting and receiving antennas and the performance of MIMO systems has been discussed for different space-time coding structures such as Alamouti, OSTBC3, OSTBC4 etc. Space-time coding techniques rely on the construction of matrices and the signal is to be transmitted at different period of time from multiple of antennas. These code structures utilises the diversity schemes to improve the bit error rate and thus to achieve higher data rates without bandwidth expansion. Keywords: BER, Multiple Input Multiple Output (MIMO), OSTBC3, OSTBC4, SNR, Spatial Diversity, STBC, STTC

On the Performance Enhancement When Combining STBC and Channel Estimation Techniques in Underground MIMO Channels

One way to enhance the channel data rate in enclosed environments is by incorporating multiple-input-multiple-output (MIMO) systems. Very often, this comes at the cost of data reliability. Motivated by the proven efficiency of space-time block coding (STBC) technique in conventional MIMO systems in improving the communication quality, we propose to incorporate it in wireless underground MIMO communication system and investigate data reliability at the reception in terms of bit error rate (BER). For this purpose, an intensive channel measurement campaign was performed in a mine-laboratory in northern Canada to obtain the perfect channel state. As a second step, the underground MIMO channel is estimated by sending a pilot sequence and using minimum mean square error (MMSE) principle on the received pilots. The resulting MIMO channel estimate is used to evaluate the data part in the STBC block and perform a decision using the maximum likelihood (ML) detector. Moreover, both the channel and transmitted data estimates are given analytically, and the degradation of the BER performance of the system due to MMSE estimation errors is studied using Monte Carlo simulations.

Adaptive Space–Time Coding Using ARQ

We study the energy-limited outage probability of the block space-time coding (STC)-based systems utilizing automatic repeat request (ARQ) feedback and adaptive power allocation. Taking the ARQ feedback costs into account, we derive closed-form solutions for the energy-limited optimal power allocation and investigate the diversity gain of different STC-ARQ schemes. In addition, sufficient conditions are derived for the usefulness of ARQ in terms of energy-limited outage probability. The results show that, for a large range of feedback costs, the energy efficiency is substantially improved by the combination of ARQ and STC techniques if optimal power allocation is utilized.

A low computational complexity V-BLAST/STBC detection mechanism in MIMO system

Abstract The idea of multiple antenna arrays has evolved into multiple-input multiple-output (MIMO) system, which provides transmit and receive diversities. It increases robustness of the effect of multipath fading in wireless channels, besides yielding higher capacity, spectral efficiency and better bit error rate (BER) performance. The spatial diversity gain is obtained by transmitting or receiving multiple copies of a signal through different antennas to combat fading and improves the system BER performance. However, the computational complexity of MIMO system is inevitably increased. Space-time coding (STC) technique such as Alamouti’s space-time block code (STBC) that combines coding, modulation and signal processing has been used to achieve spatial diversity. Vertical Bell Laboratories Layered Space-Time (V-BLAST) uses antenna arrays at both the transmitter and receiver to achieve spatial multiplexing gain. Independent data streams that share both frequency bands and time slots are transmitted from multiple antennas and jointly detected at the receiver. The theoretical capacity of V-BLAST increases linearly with the number of antennas in rich scattering environments. It's well-known that maximization of spatial diversity gain leads to degradation of spatial multiplexing gain or vice versa. In order to achieve spatial multiplexing and diversity gains simultaneously, the V-BLAST/STBC scheme has been introduced. This hybrid scheme increases MIMO system capacity and maintains reliable BER performance at the same time. However, both V-BLAST and STBC layers, in this hybid scheme, assume each other as an interferer. Thus, the symbols must be decoded with a suitable detection mechanism. In this paper, a new low complexity detection mechanism for V-BLAST/STBC scheme based on QR decomposition, denoted as low complexity QR (LC-QR) decomposition, is presented. The performance of the proposed LC-QR decomposition detection mechanism in V-BLAST/STBC transceiver scheme is compared with other detection mechanisms such as ZF, MMSE and QR decomposition. It is shown that the BER performance in V-BLAST/STBC scheme is better than V-BLAST scheme while its system capacity is higher than orthogonal STBC scheme when the LC-QR decomposition detection mechanism is exploited. Moreover, the computational complexity of proposed LC-QR decomposition mechanism is significantly lower than other abovementioned detection mechanisms.

English

The multicarrier code division multiple access (MCCDMA) is a strong candidate for the future wireless mobile communication systems put forth by service quality and system capacity. In order to exploit the maximum possible channel diversity and desirable correlation properties, the modification of MCCDMA system is addressed here to pave the way to remove the multiple access interference (MAI) effect and to increase the spectral efficiency (SE) due to the possible integration of space-time block coding (STBC) and multi input multi output (MIMO) techniques with two-dimensional orthogonal complete complementary (OCC) codes. The impact on modifications in the MCCDMA system is studied. Due to frequency selective fading and multipath effects, MCCDMA suffers from MAI due to loss of orthogonality among the users. In this paper, the constellation movement scheme is proposed to break the interference limitation in order to increase the SE and system capacity. In this scheme, the constellation of one of the users is moved adaptively relative to the other by an optimal angle based on quantized estimation to counteract MAI, caused by multipath effects without varying the transmit power in order to satisfy minimum distance threshold at the detectors. The simulation result shows that this modified MCCDMA system and proposed constellation movement scheme achieves significant performance improvement in terms of bit error rate (BER) and SE compared to conventional MCCDMA systems using unitary spreading codes. It also shows that the proposed scheme combats MAI against frequency selective fading and multipath effects and achieves a significant improvement in user capacity as the number of users increased. Key words: Multicarrier code division multiple access (MCCDMA), multiple access interference (MAI), orthogonal complete complementary (OCC) codes, channel states, adaptive constellations.

Performance Comparison of SER and SNR using different states of PSK in presence of various noises

To enhance the data rates of next generation wireless communication operating in frequency selective fading environments, the combination of orthogonal frequency division multiplexing (OFDM) and multiple input multiple output (MIMO) is proved to produce improved results. To analyze this combination, various changes in baseband signal processing are required which includes time and frequency synchronization, channel estimation and diversity gain. In this paper, a noise interference reduction technique for the improvement of high data rate in traditional space time coding technique (STTC) has been proposed. These codes generate the points of the constellation with the same probability. Therefore, the systematic search for good codes can be reduced to in this class. Finally, the performance of proposed techniques 2-state, 4-state and 16-state codes is evaluated by simulation and described by the Symbol Error Rate (SER) over fast Rayleigh fading channels with AWGN floor. Reduced noise based estimation schemes are widely favored as their implementation is relatively simple and most current wireless standards already provide for their use. Training sequences for multiple transmit antennas require properties of zero (or very low) cross correlation between sequences transmitted from different transmit antennas. Keywords: STTC; Symbol Error Rate; Signal to Noise Ratio; Orthogonal frequency division multiplexing.

Application of space-time coding technique in maritime communication

Development in maritime communication has swiftly increased over the past decade, however there is much more research needed to provide a perfect link. The geographically constrained nature of marine environment precludes reliable, high speed broadband wireless access at sea. To overcome this limitation, we introduce a novel approach on the application of space-time coding technique in WiMAX-based maritime communication. Since WiMAX has been lucrative in terrestrial communication system, we propose to extend the service coverage of WiMAX in marine environment. WiMAX offers a rich set of features with a number of multiple antenna techniques with their ability to exploit multipath signal propagation and achieve diversity. In this paper, we analyse the application of space-time coding technique in maritime ship-to-shore communication. In particular, we demonstrate the application of Alamouti scheme – space time block code to improve the BER of the system in various sea conditions.

Channel capacity and space-time block coding for coherent optical MIMO multi-mode fiber links

The capacity enhancement for random coherent optical multiple-input multiple-output (MIMO) channels in multi-mode fiber (MMF) links is investigated theoretically. Additionally, the performance of space-time block coding (STBC) techniques for achieving high reliability optical MIMO transmission is numerically examined. A comparative study is performed by considering several schemes that employ multiple transmitters/receivers. Simulation results of these schemes, in terms of bit error rate (BER) as a function of optical signal to noise ratio (OSNR), are provided.

Multi-amplitude Differential Space-time Block Coding Scheme for Square/Non-Square Code Matrix in MIMO Systems

Differential space-time coding (DSTC) technique has become a good choice when channel estimations are difficult to obtain in multiple antennas system. On the basis of analyzing the existing DSTC schemes, by introducing multi - level quadrature amplitude modulation (MQAM) and matrix transform method, we develop a multi - amplitude differential space-time block coding (STBC) scheme for square or non-square code matrix in MIMO systems , and give the derivation of calculation formula e of the coding advantage in detail. The developed scheme can effectively avoid the performance loss of conventional DSTC schemes based on PSK modulation (i.e. single amplitude DSTC) in high spectrum efficiency . It can be applied to non-square code matrix case , and thus overcomes the shortcoming that existing DSTC schemes are only suit able for square code matrix. Compared with single amplitude DSTC schemes, our scheme has higher spectrum efficiency by carrying information not only on phases but also on amplitudes. Moreover, our scheme has linear decoding complexity, higher coding advantage, and higher code rate for more than two antennas. The simulations results show that the proposed scheme can provide lower BER than the existing single amplitude differential STBC schemes for both square and non-square code matri ces .

SER analysis based on different modulation techniques in MIMO system

Physical limitations of the wireless medium create a technical challenge for reliable wireless communication. Moreover, the need for high-speed wireless Internet has led to the demand for technologies delivering higher capacities and link reliability than achieved by current systems. Multiple -input multiple-output (MIMO) based communication systems are capable accomplishing these objectives. Multiple input multiple output (MIMO) systems take advantage of spatial diversity obtained through the spatially separated antennas in a dense multipath scattering environment. Spatial diversity can increase the gain diversity consequently increase the reliability of the wireless link. Theoretical studies indicate that the capacity of MIMO systems grows linearly with the number of transmit antennas used. In this paper Space Time Coding techniques is covered which leads to much improvement in Symbol Error Rate within the same spectrum and bandwidth. Also a comparison is made between different modulation techniques.