Space Time Block Coding

A reconfigurable space-time coding technique is investigated, for a high-speed downlink packet access multiple-antenna network, which combats the effects of antenna correlation. Reconfigurability is achieved at the link level by introducing a linear precoder in a space-time block coded system. The technique assumes knowledge of the long-term characteristics of the channel, namely the channel correlation matrix at the transmitter. The benefits of the proposed reconfigurable technique as compared to the conventional non-reconfigurable versions are evaluated via system-level simulations. In order to characterize the system-level performance accurately and, at the same time, use a feasible approach in terms of computational complexity, a suitable linkto-system interface has been developed. The average system throughput and the number of satisfied users are the performance metrics of interest. Simulation results demonstrate the performance enhancements achieved by the application of reconfigurable techniques as compared to their conventional counterparts.

A reconfigurable space-time coding technique is investigated, for a high-speed downlink packet access multiple-antenna network, which combats the effects of antenna correlation. Reconfigurability is achieved at the link level by introducing a linear precoder in a space-time block coded system. The technique assumes knowledge of the long-term characteristics of the channel, namely the channel correlation matrix at the transmitter. The benefits of the proposed reconfigurable technique as compared to the conventional non-reconfigurable versions are evaluated via system-level simulations. In order to characterize the system-level performance accurately and, at the same time, use a feasible approach in terms of computational complexity, a suitable linkto-system interface has been developed. The average system throughput and the number of satisfied users are the performance metrics of interest. Simulation results demonstrate the performance enhancements achieved by the application of reconfigurable techniques as compared to their conventional counterparts.

We propose a general framework based in the Gilbert model for cross-layer analysis of TCP and UDP over MIMO wireless systems. Our framework takes into consideration diverse system characteristics often difficult to express as a Gilbert model such as fading, space-time transmission schemes, modulation, channel coding and ARQ. We apply our framework to analyze the TCP performance of two representative MIMO systems, namely, the BLAST system and the orthogonal spacetime block coded (STBC) system. In particular, we investigate the optimal information rate that maximizes the TCP throughput, the effect of Doppler on the optimal TCP throughput and the optimal channel coding rate for various modulations. We provide simulations results from the ns-2 network simulator to demonstrate the accuracy of the proposed analytical framework in characterizing the TCP performance. We further apply the framework to two additional cross-layer applications: the analysis of the buffer occupancy on the base station, and the analysis of CBR video transmission over MIMO systems. We show that while the optimal rate for maximum TCP throughput is far from the channel capacity, the optimal rate for error and delay-tolerant video transmission requires much higher rates, and so the physical layer should be aware and adapt to the type of application in order to increase the system performance. We also show that mobility benefits systems with larger buffers, especially for TCP, as the ARQ scheme is able to recover the shorter burst errors. In general, our investigation shows that the type of application plays a crucial role in the optimization of a wireless system, and that our modelling framework is useful for the cross-layer analysis and design of those systems.

Space-time coding can achieve transmit diversity and power gain over spatially uncoded systems without sacrificing the bandwidth. There are various approaches in coding structures, including space-time block codes. A class of space-time block codes namely quasi-orthogonal space-time block code can achieve the full rate, but there are also interference terms resulting from neighboring signals during signal detection. This causes an increase in decoding complexity and a decrease in performance gain. In this paper, we demonstrate an efficient method to reduce decoding complexity and improved performance.

A novel subspace channel estimation is proposed for space-time block coded (STBC) multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Considering the zero-padding technique, the signal model of the STBC-OFDM system is first studied. The major drawback of the subspace method is the slow convergence which requires a large number of received symbols to compute the noise subspace. The repetition index scheme is developed here to increase the number of equivalent received symbols. Using the space-time coding property, the forward-backward method is presented to improve the convergence speed further. Moreover, the repetition index scheme transforms the white noise into non-white one. The noise prewhitening technique is proposed to reduce the non-white noise effect. Computer simulations show the effectiveness of the proposed forward-backward method and noise prewhitening technique.

Uzaysal modülasyon (SM), geleneksel işaret kümelerine ek olarak anten indisleriyle de bilgi iletmek temeline dayanan, yakın zamandaönerilmiş umut verici bir çok-girişli çok-çıkışlı (MIMO) iletim teknigidir. Bu bilgilendirici makalenin temel amacı, telsiz iletişim alanında çalışan araştırmacılara bu güncel ve yeni konuyu tanıtmak, SM konusunda yakın zamanda yapılan çalışmaları gözden geçirmek ve SM sistemlerinin hata başarımını iyileştirmek için literatürdeönerdigimiz iki yeni veözgün MIMO iletişim sistemini okurların dikkatine sunmaktır [12-16]. Uzayzaman blok kodlamalı uzaysal modülasyon (STBC-SM) olarak adlandırılan ilk sistemde SM, uzay-zaman blok kodlama (STBC) ile birleştirilmiştir. Dolayısıyla bu sistemde, bilgi simgeleri sadece uzay ve zaman bölgelerine degil aynı zaman anten bölgesine de dagıtılmıştır. STBC-SM için genel bir tasarım yöntemi verilmiş ve en büyük olabilirlikli (ML) kod çözücü incelenmiştir. Bilgisayar benzetimleri yardımıyla STBC-SM yapılarının klasik SM ve V-BLAST yapılarına göre oldukça iyi hata başarımı sagladıgı gösterilmiştir.İncelenen ikinci sistemde ise, ek kodlama kazançları elde etmek için, SM ile kafes kodlama birleştirilerek kafes kodlamalı uzaysal modülasyon (TC-SM) olarak adlandırılan bir MIMO iletişim sistemi sunulmuştur. Bir kafes kodlayıcı ile SM eşleyicinin birlikte tasarlandıgı bu sistemin çiftsel hata olasılıgı (PEP), ilişkisiz Rayleigh sönümlemeli kanallar için hesaplanarak kod tasarımölçütleri verilmiştir. Ardından buölçütler 4, 8 ve 16-durumlu TC-SM sistemlerinin elde edilmesinde kullanılmıştır. Bilgisayar benzetimleri sonucu incelenen TC-SM yapılarının klasik uzay-zaman kafes kodlara göre daha düşük kod çözme karmaşıklıgı ile daha iyi hata başarımları sagladıgı gösterilmiştir.

In wireless communication fading of channels is a serious cause of the received degraded signals. Orthogonal transmitter diversity such as time diversity and frequency diversity is quite simple to implement and, with optimum signal combining, can take full advantage of fading multipath channels. Receive diversity techniques like maximal ratio combining (MRC) have been popular means of introducing multiple antennas into communication systems. Space-Time Block Codes (STBC) that represent transmit diversity also exhibit similar complexity and performance as MRC. In this paper, we evaluated the performance of constellation rearrangement (CoRe), when used in conjunction with STBC coding is observed to improve the bit error rate of quadrature-amplitude modulation (QAM). CoRe is the process of finding a good bit to symbol mapping for each transmitting antenna, without changing the modulation level. A number of CoRe schemes have been proposed in the literature based on uniform QAM constella...

Multiple Input Multiple Outputs MIMO; Space-Time Coding (STC) improves the BER by adding diversity in the presence of a channel fading. The V-BLAST and D-BLAST techniques are designed to improve the data rate. The performance of these techniques is highly dependent on the MIMO channel environment. Space-time block coded spatial modulation (STBC-SM) combine’s spatial modulation (SM) and space-time block coding (STBC) to take advantage of the benefits of both. In the STBC-SM scheme, the transmitted information symbols are expanded not only to the space and time domains but also to the spatial (antenna) domain which corresponds to the on/off status of the transmit antennas available at the space domain, and therefore high spectral efficiency along with diversity advantage of STBC. The performance of the STBC-SM, V-BLAST and D-BLAST are compared at high and low SNR environment. It is observed that STBC-SM performs better than V-BLAST and D-BLAST but with more decoding complexity.

We introduce the concept of space-time supermodulation according to which additional low-rate and highly reliable information can be transmitted on top of traditionally modulated and space-time encoded information, without increasing the transmitted block length or degrading their errorrate performance. This is achieved by exploiting the temporal redundancy introduced by the space-time block codes and, specifically, by efficiently mapping transmission patterns to specific information content. We show that space-time supermodulation can be efficiently used in the context of machinetype communications to enable one-shot grant-free joint medium access and rateless data transmission while reducing or even eliminating the need for transmitting preamble sequences. As a result, compared with traditional approaches that use correlatable preamble sequences or encoded preambles to transmit the signature information of transmitted packets, space-time super-modulation can achieve significant throughput gains. For example, we show up to 35% throughput gains from the second best examined preamble-based scheme when transmitting blocks of 200 bits.

Kablosuz haberleşme sistemlerinin performansı kanal sönümlemelerinden etkilenmektedir. Yeni nesil kablosuz sistemlerin gelişimiyle beraber güvenilir bağlantı ihtiyaçları da artmaktadır. Kablosuz iletişimdeki en büyük zorluk, sönümlemelerden en az etkilenen kesintisiz iletişimin gerçekleştirilmesidir. Çeşitleme teknikleri ile çoklu anten teknolojileri bu noktada yardımcı olmaktadır. Bu çalışmada, alıcı ve vericide kullanılan Çoklu Giriş Çoklu Çıkış (MIMO) anten yapısı, hem iç hem de dış ortamdaki radyo yayılım ortamını modelleyen Weibull sönümleme kanalı ve İkili Faz Kaydırmalı Anahtarlama (BPSK) modülasyonu altında vericide çeşitleme tekniklerinden olan Alamouti Uzay Zaman Blok Kodlamanın (STBC) performansı analiz edilmiştir. Weibull sönümleme kanalında çoklu anten ve STBC kullanılmasının, Bit Hata Oranını (BER) azalttığı ve sistem performansını arttırdığı gözlemlenmiştir.

A reconfigurable space-time coding technique is investigated, for a high-speed downlink packet access multiple-antenna network, which combats the effects of antenna correlation. Reconfigurability is achieved at the link level by introducing a linear precoder in a space-time block coded system. The technique assumes knowledge of the long-term characteristics of the channel, namely the channel correlation matrix at the transmitter. The benefits of the proposed reconfigurable technique as compared to the conventional non-reconfigurable versions are evaluated via system-level simulations. In order to characterize the system-level performance accurately and, at the same time, use a feasible approach in terms of computational complexity, a suitable linkto-system interface has been developed. The average system throughput and the number of satisfied users are the performance metrics of interest. Simulation results demonstrate the performance enhancements achieved by the application of reconfigurable techniques as compared to their conventional counterparts.

Kablosuz haberleşme sistemlerinin performansı kanal sönümlemelerinden etkilenmektedir. Yeni nesil kablosuz sistemlerin gelişimiyle beraber güvenilir bağlantı ihtiyaçları da artmaktadır. Kablosuz iletişimdeki en büyük zorluk, sönümlemelerden en az etkilenen kesintisiz iletişimin gerçekleştirilmesidir. Çeşitleme teknikleri ile çoklu anten teknolojileri bu noktada yardımcı olmaktadır. Bu çalışmada, alıcı ve vericide kullanılan Çoklu Giriş Çoklu Çıkış (MIMO) anten yapısı, hem iç hem de dış ortamdaki radyo yayılım ortamını modelleyen Weibull sönümleme kanalı ve İkili Faz Kaydırmalı Anahtarlama (BPSK) modülasyonu altında vericide çeşitleme tekniklerinden olan Alamouti Uzay Zaman Blok Kodlamanın (STBC) performansı analiz edilmiştir. Weibull sönümleme kanalında çoklu anten ve STBC kullanılmasının, Bit Hata Oranını (BER) azalttığı ve sistem performansını arttırdığı gözlemlenmiştir.

A quasi-orthogonal space time block coding (QO-STBC) scheme that exploits Hadamard matrix properties is studied and evaluated. At first, an analytical solution is derived as an extension of some earlier proposed QO-STBC scheme based on Hadamard matrices, called diagonalized Hadamard space-time block coding (DHSBTC). It explores the ability of Hadamard matrices that can translate into amplitude gains for a multi-antenna system, such as the QO-STBC system, to eliminate some off-diagonal (interference) terms that limit the system performance towards full diversity. This property is used in diagonalizing the decoding matrix of the QO-STBC system without such interfering elements. Results obtained quite agree with the analytical solution and also reflect the full diversity advantage of the proposed QO-STBC system design scheme. Secondly, the study is extended over an interference-free QO-STBC multi-antenna scheme, which does not include the interfering terms in the decoding matrix. Then, following the Hadamard matrix property advantages, the gain obtained (for example, in 4x1 QO-STBC scheme) in this study showed 4-times louder amplitude (gain) than the interference-free QO-STBC and much louder than earlier DHSTBC for which the new approach is compared with.

Multiple Input Multiple Outputs MIMO; Space-Time Coding (STC) improves the BER by adding diversity in the presence of a channel fading. The V-BLAST and D-BLAST techniques are designed to improve the data rate. The performance of these techniques is highly dependent on the MIMO channel environment. Space-time block coded spatial modulation (STBC-SM) combine’s spatial modulation (SM) and space-time block coding (STBC) to take advantage of the benefits of both. In the STBC-SM scheme, the transmitted information symbols are expanded not only to the space and time domains but also to the spatial (antenna) domain which corresponds to the on/off status of the transmit antennas available at the space domain, and therefore high spectral efficiency along with diversity advantage of STBC. The performance of the STBC-SM, V-BLAST and D-BLAST are compared at high and low SNR environment. It is observed that STBC-SM performs better than V-BLAST and D-BLAST but with more decoding complexity.

Bu çalışmada, uzaysal modülasyon (SM) ile kafes kodlama birleştirilerek kafes kodlamalı uzaysal modülasyon (TC-SM) olarak adlandırılan bir çok-girişli çok-çıkışlı (MIMO) iletişim sistemiönerilmiştir. Bir kafes kodlayıcı ile SM eşleyicinin birlikte tasarlandıgı bu sistemin çiftsel hata olasılıgı (PEP), ilişkisiz Rayleigh sönümlemeli kanallar için hesaplanarak kod tasarımölçütleri verilmiştir. Ardından buölçütler 4, 8 ve 16-durumlu TC-SM sistemlerinin elde edilmesinde kullanılmıştır. Bilgisayar benzetimleri sonucuönerilen TC-SM yapılarının klasik uzay-zaman kafes kodlara göre daha düşük kod çözme karmaşıklıgı ile daha iyi hata başarımları sagladıgı gösterilmiştir.

In this paper, a quasi-orthogonal space time block coding (QO-STBC) scheme with maximum likelihood (ML) decoding via simple linear detection is compared to QOSTBC conventional ML decoder and QOSTBC with simplified zero forcing decoder. A conventional QOSTBC scheme can achieve the full rate, but at the cost of decoding complexity and diversity gain. These disadvantages of the conventional QO-STBC scheme are mainly a result of interference terms in the detection matrix. In this paper, the suggested QOSTBC scheme which eliminates interference terms is used to obtain linear detection. The proposed method achieves a great reduction in decoding complexity with respect to the conventional QO-STBC scheme, also a simplified zero forcing algorithms is compared to the suggested linear detection scheme.

Many existing works on space-time block codes (STBC) assume the channels are block-wise constant, but this assumption does not always hold. In the more general case of time-selective channels, the channel matrix is no longer orthogonal, so inter-symbol interference (ISI) is generated and the performance is greatly reduced. Several decoders have been proposed to eliminate the ISI, but it remains unclear how and to what extent the performance is affected by the ISI. In this paper, we introduce an approach to analyze the performance of STBC over time-selective channels, with arbitrary numbers of antennas for which orthogonal STBC's are defined. Exact error performances are obtained in closed form. Furthermore, the analysis reveals the relationship between the ISI and the structure of STBC matrices. Considering Gi systems, we then propose one proposition and two design criteria, following which it is easy to design or search for better STBC's that have less ISI compared with the original code matrix. Index Terms-Bit-error probability (BEP), design criteria, optimum code, orthogonal STBC, time-selective channel. I. INTRODUCTION O RTHOGONAL space-time block codes (STBC) [1] are commonly used in MIMO systems, due to the simple maximum likelihood (ML) decoding structure. However, this decoding structure is based on the assumption that the channels are block-wise constant, which is not always true in practice. If the channels vary from symbol to symbol, the orthogonality will be corrupted and inter-symbol interference (ISI) is introduced, so the linear ML decoder [1] is no longer optimum. Considering time-selective channels, [2]-[12] proposed different decoders for orthogonal STBC. Reference [2] first proposed a suboptimum detection scheme with the conventional linear decoder. It retains the linear decoding structure, but has an irreducible error floor in the high signal-to-noise ratio (SNR) region. Later, zero-forcing (ZF) decoders for two transmit antennas were presented in [3], [4], where the ISI was completely removed. The ZF decoder was extended to threeand four-transmit-antenna cases in [5]-[7]. Besides the linear decoders above, there are also non-linear decoders, including

Kablosuz haberleşme sistemlerinin performansı kanal sönümlemelerinden etkilenmektedir. Yeni nesil kablosuz sistemlerin gelişimiyle beraber güvenilir bağlantı ihtiyaçları da artmaktadır. Kablosuz iletişimdeki en büyük zorluk, sönümlemelerden en az etkilenen kesintisiz iletişimin gerçekleştirilmesidir. Çeşitleme teknikleri ile çoklu anten teknolojileri bu noktada yardımcı olmaktadır. Bu çalışmada, alıcı ve vericide kullanılan Çoklu Giriş Çoklu Çıkış (MIMO) anten yapısı, hem iç hem de dış ortamdaki radyo yayılım ortamını modelleyen Weibull sönümleme kanalı ve İkili Faz Kaydırmalı Anahtarlama (BPSK) modülasyonu altında vericide çeşitleme tekniklerinden olan Alamouti Uzay Zaman Blok Kodlamanın (STBC) performansı analiz edilmiştir. Weibull sönümleme kanalında çoklu anten ve STBC kullanılmasının, Bit Hata Oranını (BER) azalttığı ve sistem performansını arttırdığı gözlemlenmiştir.

https://www.ijert.org/particular-and-unique-solutions-of-spin-dependent-dglap-evolution-equations-in-leading-order-and-structure-functions-at-small-x
https://www.ijert.org/research/particular-and-unique-solutions-of-spin-dependent-dglap-evolution-equations-in-leading-order-and-structure-functions-at-small-x-IJERTV2IS100878.pdf

In this paper the spin-dependent singlet and non-singlet structure functions have been
obtained by solving Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equations in leading
order in the small x limit. Here we have used Taylor series expansion and then the particular
and unique solution to solve the evolution equations. We have also calculated t evolutions of
deuteron, proton, neutron structure functions and x-evolution of deuteron structure functions
and the results are compared with the SLAC E-143 Collaboration data.`

Kablosuz haberleşme sistemlerinin performansı kanal sönümlemelerinden etkilenmektedir. Yeni nesil kablosuz sistemlerin gelişimiyle beraber güvenilir bağlantı ihtiyaçları da artmaktadır. Kablosuz iletişimdeki en büyük zorluk, sönümlemelerden en az etkilenen kesintisiz iletişimin gerçekleştirilmesidir. Çeşitleme teknikleri ile çoklu anten teknolojileri bu noktada yardımcı olmaktadır. Bu çalışmada, alıcı ve vericide kullanılan Çoklu Giriş Çoklu Çıkış (MIMO) anten yapısı, hem iç hem de dış ortamdaki radyo yayılım ortamını modelleyen Weibull sönümleme kanalı ve İkili Faz Kaydırmalı Anahtarlama (BPSK)  modülasyonu altında vericide çeşitleme tekniklerinden olan Alamouti Uzay Zaman Blok Kodlamanın (STBC) performansı analiz edilmiştir. Weibull sönümleme kanalında çoklu anten ve STBC kullanılmasının, Bit Hata Oranını (BER) azalttığı ve sistem performansını arttırdığı gözlemlenmiştir.

Many wireless networks are rapidly become part of our daily life. However, range and data rate in wireless devices are limited. One method is to use Multiple-Input Multiple-Output (MIMO) communication system to overcome these limitations. The multiple antennas allow MIMO systems to perform diversity coding (space-time coding), and spatial multiplexing. Beamforming consists of transmitting the same signal with different gain and phase (called weights) over all transmits antennas such that the receiver signal is maximized. Diversity consists of transmitting a single space-time coded stream through all antennas. Spatial multiplexing increases network capacity by splitting a high rate signal into multiple lower rate streams and transmitting them through the different antennas. The results of using these MIMO techniques is higher data rate or longer transmit range without requiring additional bandwidth or transmit power. This paper presents a detailed study of diversity coding for MIMO systems. Different spacetime block coding (STBC) schemes including Alamouti's STBC for 2 transmit antennas as well as orthogonal STBC for 3 and 4 transmit antennas are explored. Finally, these OSTBC techniques are implemented in MATLAB and Simulink. Performance analysis is carried out and system results are observed by transmitting mp3 audio clip using QPSK, 16-QAM, and 64-QAM modulation schemes in Rayleigh fading distributions.

High speed data communications are in fact succeeded by MIMO based Alamouti technique. In order to meet the rapid developments in digital devices the mentioned technique could not meet the requirements, so there is a need to develop a new technique Conjugate Symmetric – Sequency ordered Complex Hadamard Transform (CS – SCHT) to meet the enhanced speeds of the digital devices is presented in this paper. This fast and efficient algorithm to compute the CS-SCHT is developed using sparse matrix factorization method, its computational load is examined and compared to that of Hadamard Transform (HT) and Sequency – ordered Complex Hadamard Transform (SCHT). The outcomes attained are compared with HT and SCHT based Alamouti OSTBC. A substantial enhancement of bit error rate (BER) is perceived from simulation results.