—In this work, we propose a transmit diversity coding scheme with partial channel state information (CSI) at the transmitter to improve the performance of wireless systems. This scheme is equipped with 4 transmit and n receive antennas. For the case of flat fading channel, one, two or three feedback bits are used. Based on these feedback bits, 3 out of 4 transmit antennas are used for each transmission period. For frequency selective fading channel, one feedback frame is used to improve the performance. The proposed approach guarantees diversity order of 3n and very simple decoding complexity at the receiver. This is due to the fact that our approach is based on space time block coding (STBC). Our scheme significantly outperforms the conventional scheme with comparable bandwidth efficiency. Simulation results show that significant improvement in the performance of the proposed scheme is achieved compared to that of the conventional scheme. At bit error probability of 6.5*10, the performance of the proposed scheme is approximately 4 dB better than that of the conventional scheme. For the proposed scheme, as the number of feedback bits increases the performance increases.

■ Wireless communication using multiple-input multiple-output (MIMO) systems enables increased spectral efficiency for a given total transmit power. Increased capacity is achieved by introducing additional spatial channels that are exploited by using space-time coding. In this article, we survey the environmental factors that affect MIMO capacity. These factors include channel complexity, external interference, and channel estimation error. We discuss examples of space-time codes, including space-time low-density parity-check codes and spacetime turbo codes, and we investigate receiver approaches, including multichannel multiuser detection (MCMUD). The ‘multichannel’ term indicates that the receiver incorporates multiple antennas by using space-time-frequency adaptive processing. The article reports the experimental performance of these codes and receivers.

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paper discusses the fundamental concepts behind the real and complex orthogonal designs for space-time block coding used in wireless communication systems. Generalized real orthogonal design and complex orthogonal designs are discussed in this paper. Also a brief survey of existing orthogonal designs for space-time block coding is put forward in this paper.

of the Dissertation Universal Channel Codes and Trellis State-Diagram Reduction

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data rates within the limited radio frequency (RF) spectrum is always desirable that leads to radios with capabilities beyond a single-input single-output (SISO) topology. Recently introduced wireless systems have adopted multiple-input multiple-output (MIMO) topologies that use two or more transmitters and two or more receivers to send data simultaneously over the same RF bandwidth. The performance of MIMO system can be improved by using multiple antennas at transmitter and receiver so as to provide spatial diversity. In this paper, the performance analysis of MIMO system over AWGN fading channel with ZF receiver is presented. The effects of the antenna selection can also be analyzed from the simulated results. The BER (Bit Error Rate) performance characteristics of Zero-Forcing (ZF) receiver is investigated for M-PSK modulation technique over the AWGN channel.

With the evolution of the wireless system, the demand for high speed data services have been increasing day by day, which is impossible to be achieved by the conventional serial data transmission system, without trade-off between high speed data services and increasing the bandwidth of the system. Here, both the options are inconvenient, as one never demands the degradation of the service quality ( because if we increase data rate in serial data transmission ISI will gradually increase which make the extraction of actual information at receiver nearly impossible ) and secondly the need for extra spectrum in a limited spectrum scenario. In order to overcome this problem new parallel data transmission system was proposed, which is known as OFDM system. This study gives a summary of the basics of MIMOOFDM technology and focuses on the BER Analysis of MIMO-OFDM systems. The signal detection technology used in present work work for MIMO-OFDM system is Nakagami Distribution. In the study, the analysis of high level of modulations on MIMO-OFDM system is

Wireless designers constantly seek to improve the spectrum efficiency/capacity, coverage of wireless networks and link reliability. In this direction, Space-time wireless technology that uses multiple antennas along with appropriate signaling and receiver techniques that offers a powerful tool for improving the wireless performance is used in this thesis work. A special version of STBC called ‘Alamouti code’ is used. PSK modulation scheme is used for modulation of data. In this thesis work, the Space-Time Block Codes (STBC) is used in WLAN wireless network that uses multiple numbers of antennas at both transmitter and receiver. The STBC which includes the Alamouti Scheme for 2 transmit antenna and a different number of receiving antenna has been studied, simulated and analyzed. The simulation has been done in MATLAB. Throughput and several parameter performance has been analyzed using the MATLAB.A sample image is transmitted to compare the performance of various parameters like RMSE, PSNR, MAE etc. All the parameters are plotted against SNR (in dB) values ranging from -18 to 30. Various observations being made for the improvement in various parameters with increasing SNR and/or with changing diversity scheme. AWGN channel is used here for communication of sampled image data.

Wireless communication using multiple-input multiple-output (MIMO) systems enables increased spectral efficiency for a given total transmit power. Increased capacity is achieved by introducing additional spatial channels that are exploited using space-time coding. In this paper, the environmental factors that affect MIMO capacity are surveyed. These factors include channel complexity, external interference, and channel estimation error. The maximum spectral efficiency of MIMO systems in which both transmitter and receiver know the channel (using channel estimate feedback) is compared with MIMO systems in which only the receiver knows the channel. Channel complexity is studied using both simple stochastic physical scattering and asymptotic large random matrix models. Both uncooperative (worst-case) and cooperative (amenable to multiuser detection) interference are considered. An analysis for capacity loss associated with channel estimation error at the transmitter is introduced.

Wireless communication using multiple-input multiple-output (MIMO) systems enables increased spectral efficiency and improved reliability for a given total transmit power. We discuss channel phenomenology and space-time turbo coding. Space-time turbo codes combine the advantages of turbo codes with MIMO systems. The performance of receiver options is investigated, including multichannel multiuser detectors (MCMUD) that iteratively employ space-time-frequency adaptive processing, multiuser detection, and joint channel-data estimation. MIMO capacity is a strong function of channel phenomenology, motivating experimental performance evaluation. Results from outdoor experimental data using a 2 bits/s/Hz, 4/spl times/4 space-time turbo code are presented.

Wireless communication systems always demand higher data rates and better quality of service (QoS). Transmission reliability in a wireless channel with high path loss, time-varying multipath fading and power and bandwidth limitations, is a testing issue. Multiple-input multiple-output (MIMO) systems can reduce the effect of these channel interferences and achieve reliable signal transmission at high data rate. Space-time block code (STBC) is a coding scheme for the use of multiple transmits antennas providing a simple transmit diversity scheme. In certain MIMO fading environments, the offered channel capacity can be very low, where despite rich local scattering and uncorrelated transmit and receive signals, the system has a single degree of freedom. This effect has been termed as keyhole or pinhole effect. This contribution analyzes the average symbol error rate (SER) performance of MIMO systems employing orthogonal STBC with M-PSK constellations over fading channels in the presence of the keyhole. The Nakagami-m distribution has been considered for MIMO channel modeling. We derive the probability density function (PDF) of instantaneous signal-to-noise ratio (SNR) and an integral equation to calculate the average SER after space-time block decoding in such channels. Numerical results show that the keyhole significantly degrades the SER performance of the STBC in MIMO channels. The performance of such channels is a function of fading figure, m and diversity.

Wireless communication system is rapidly enhancing by various techniques by many researcher, to meet the requirement of accurate and fast data communication in fading environment. The MIMO technique plays an important role in this direction. The use of MIMO technique in the allow to use higher order modulation for maintaining the errors in limits. This paper described one of the MIMO techniques orthogonal space time block code for improving the BER of the QAM modulation based communication in Nakagami fading environment. The results show a drastic improvement in the BER.

Wireless communication is now a part of everyday life in the urban areas. Wireless LAN is mostly utilized communication system as an example. These wireless devices are data rate and range limited, for which the scientists are spending great efforts on finding ways to overcome these limitations. Multi input multi output (MIMO) antenna systems are the example through which these limitations have been reduced upto great extent which provides multilayer beamforming, diversity, and spatial multiplexing. Analysis of adaptive semiblind channel estimation scheme for MIMO antenna array systems with different code rate space time block coding (STBC) has been performed using the adaptive pilot assisted modulation scheme proposed earlier. Semi blind channel estimation method provides the best trade-off in terms of bandwidth overhead, computational complexity and latency. The result after using MIMO systems shows higher data rate and longer transmit range without any requirement of additional bandwidth or transmit power. This paper presents the detailed analysis of diversity coding techniques using MIMO antenna systems. Different STBC schemes have been explored and analyzed with the different code rate STBC using MATLAB environment and the simulated results have been compared in the semiblind environment which shows the improvement even in highly correlated antenna arrays, and is found close to the condition when channel state information is known to the channel.

We use Hurwitz-Radon matrices to construct a space-time code for parallel wireless mobile relays that are located anywhere between a source and a destination. Each relay receives a sequence of symbols (i.e., baseband signals corrupted by fading and noise) simultaneously from the source. These symbols are not decoded into information bits at the relays but are rearranged (i.e., space-time modulated) in their orders, amplitudes and phases according to the Hurwitz-Radon code. The relays do not exchange symbols with each other but forward the modified sequences of symbols in parallel to the destination. Our study shows that with R relays, an order of diversity around R/2 can be achieved, i.e., the averaged bit error rate is in the order of 1/SNR/sup R/2/ as opposed to 1/SNR for a single (regenerative) relay system. More than 10 dB power saving, from the baseline of the single relay system, can be achieved with eight (non-regenerative) relays.

We study the performance of differential orthogonal space-time block codes (OSTBC) over independent and semi-identically distributed block Rayleigh fading channels. In this semiidentical fading model, the channel gains from different transmit antennas to a common receive antenna are identically distributed, but the gains associated with different receive antennas are nonidentically distributed. Arbitrary fluctuation rates of the fading processes from one transmission block to another are considered. We first derive the optimal symbol-by-symbol differential detector, and show that the conventional differential detector is suboptimal. We then derive expressions of exact bit-error probabilities (BEPs) for both the optimal and suboptimal detectors. The results are applicable for any number of receive antennas, and any number of transmit antennas for which OSTBCs exist. For two transmit antennas, explicit and closed-form BEP expressions are obtained. For an arbitrary number of transmit antennas, a Chernoff bound on the BEP for the optimal detector is also derived. Our results show that the semi-identical channel statistics degrade the error performance of differential OSTBC, compared with the identical case. Also, the proposed optimal detector substantially outperforms the conventional detector when the channel fluctuates rapidly. But in near-static fading channels, the two detectors have similar performances

We study the performance of differential orthogonal space-time block codes (OSTBC) over independent and semi-identically distributed block Rayleigh fading channels. In this semiidentical fading model, the channel gains from different transmit antennas to a common receive antenna are identically distributed, but the gains associated with different receive antennas are nonidentically distributed. Arbitrary fluctuation rates of the fading processes from one transmission block to another are considered. We first derive the optimal symbol-by-symbol differential detector, and show that the conventional differential detector is suboptimal. We then derive expressions of exact bit-error probabilities (BEPs) for both the optimal and suboptimal detectors. The results are applicable for any number of receive antennas, and any number of transmit antennas for which OSTBCs exist. For two transmit antennas, explicit and closed-form BEP expressions are obtained. For an arbitrary number of transmit antennas, a Chernoff bound on the BEP for the optimal detector is also derived. Our results show that the semi-identical channel statistics degrade the error performance of differential OSTBC, compared with the identical case. Also, the proposed optimal detector substantially outperforms the conventional detector when the channel fluctuates rapidly. But in near-static fading channels, the two detectors have similar performances

We study the effective signal to interference-plus-noise ratio (SINR) of the MIMO detector (or decoder) for the MIMO system with decorrelation based receive transformation (MIMO-DRT), in which the decorrelation based transformation is employed on the received signal of the MIMO receiver. By performing eigendecomposition on the inverse of the covariance matrix for interference plus noise, we express the effective SINR of MIMO-DRT in terms of the eigenvalues of the covariance matrix for interference plus noise and derive the SINR gain (relative to the MIMO system without receive transformation) provided by MIMO-DRT. We prove that the SINR gain provided by MIMO-DRT is larger than or equal to one. Furthermore, we show by both the analytical results and the simulation results that the SINR gain provided by MIMO-DRT increases with the interference to noise ratio and converges to one as the number of cochannel users gets large.

We show that there exists an interesting relationship between the algebraic constraints of Amicable Orthogonal Design (AOD) matrices and the dispersion matrices of Quasi-Orthogonal Space-Time Block Code with minimum decoding complexity (MDC-QOSTBC). This insight leads to a novel concept of "Preferred AOD Pair", and we show that MDC-QOSTBC can be constructed from two AODs that form a Preferred AOD Pair. With the Preferred AOD Pair concept, we are able to derive the lower bound on code rate of square MDC-QOSTBC, and show them to be 1 and 3/4 for four and eight transmit antennas respectively. We also present a systematic method to construct Preferred AOD Pair and use them to obtain new MDC-QOSTBCs.