Space-time block coding for four transmit antennas with closed loop feedback over frequency selective fading channels

Orthogonal space-time block coding is a transmit diversity method that has the potential to enhance forward capacity. For a communication system with a complex alphabet, full diversity and full code rate space-time codes are available only for two antennas, and for more than two antennas full diversity is achieved only when the code rate is lower than one. A quasi-orthogonal code could provide full code rate, but at the expense of loss in diversity, which results in degradation of performance. We propose a closed loop feedback scheme for quasi-orthogonal codes which provides full diversity while achieving the full code rate. We investigate, in particular, the performance of this scheme, when the feedback information is quantised and when the fading of the channel is frequency-selective

A new approach to joint full-rate STBC and long-code WCDMA for four transmit antenna MIMO systems

In this work, we propose a novel combination of an extended orthogonal space-time block code (EO- STBC) or a quasi-orthogonal space-time block code (QO-STBC) and a long-code wideband code division multiple access (WCDMA) scheme to exploit spatial diversity in future wireless communication systems. For a mobile communication system, a key parameter is the system capacity. Multiple antennas at the transmitter and receiver in a system have been recognized as a major technology breakthrough to increase the capacity of a wireless communication network. To mitigate this limited capacity problem, two full transmit rate STBCs are integrated into the long-code WCDMA system with four transmit antenna. The bit error rate (BER) performance for the proposed technique is compared with other conventional methods for quasi-static wireless channels. Simulation results show that the proposed full rate STBC scheme when combined with the receive antenna selection technique method yields improved BER performance schemes

Study and Simulation of Quasi and Rotated Quasi Space Time Block Codes in MIMO systems using Dent Channel model

Multiple Input Multiple Output (MIMO) has become one of the most exciting fields in modern engineering. It is mainly used to increase data rate and capacity of wireless communication system. In this paper, we exploit the space and time diversity to decode the quasi and rotated quasi space time block codes (QOSTBC) based on dent channel model. For Doppler shifting and Rayleigh distribution we make use of dent channel model. This provides fast decoding and gives better performance of communication system.BER analysis is presented in terms of diversity and code rate. KEYWORDS: MIMO, Quasi Orthogonal Space-Time Block codes (QOSTBC), rotated QOSTBC, Maximum Likelihood (ML) decoding

Single-Symbol-Decodable Differential Space-Time Modulation Based on QO-STBC

We present a novel differential space-time modulation (DSTM) scheme that is single-symbol decodable and can provide full transmit diversity. It is the first known singlesymbol- decodable DSTM scheme not based on Orthogonal STBC (O-STBC), and it is constructed based on the recently proposed Minimum-Decoding-Complexity Quasi-Orthogonal Space-Time Block Code (MDC-QOSTBC). We derive the code design criteria and present systematic methodology to find the solution sets. The proposed DSTM scheme can provide higher code rate than DSTM schemes based on O-STBC. Its decoding complexity is also considerably lower than DSTM schemes based on Sp(2) and double-symbol-decodable QOSTBC, with negligible or slight trade-off in decoding error probability performance.Comment: Accepted for IEEE Trans Wireless Comm

Code diversity in multiple antenna wireless communication

The standard approach to the design of individual space-time codes is based on optimizing diversity and coding gains. This geometric approach leads to remarkable examples, such as perfect space-time block codes, for which the complexity of Maximum Likelihood (ML) decoding is considerable. Code diversity is an alternative and complementary approach where a small number of feedback bits are used to select from a family of space-time codes. Different codes lead to different induced channels at the receiver, where Channel State Information (CSI) is used to instruct the transmitter how to choose the code. This method of feedback provides gains associated with beamforming while minimizing the number of feedback bits. It complements the standard approach to code design by taking advantage of different (possibly equivalent) realizations of a particular code design. Feedback can be combined with sub-optimal low complexity decoding of the component codes to match ML decoding performance of any individual code in the family. It can also be combined with ML decoding of the component codes to improve performance beyond ML decoding performance of any individual code. One method of implementing code diversity is the use of feedback to adapt the phase of a transmitted signal as shown for 4 by 4 Quasi-Orthogonal Space-Time Block Code (QOSTBC) and multi-user detection using the Alamouti code. Code diversity implemented by selecting from equivalent variants is used to improve ML decoding performance of the Golden code. This paper introduces a family of full rate circulant codes which can be linearly decoded by fourier decomposition of circulant matrices within the code diversity framework. A 3 by 3 circulant code is shown to outperform the Alamouti code at the same transmission rate.Comment: 9 page

Enhancement of Twice Quasi Orthogonal Space Time Block Coded (QOSTBC) Performance System in MIMO MC-CDMA

Advanced wireless technology to support high reliability and low complexity needed along with acccelerated development of technology information and communication. Nowadays researchers and industry have started preparing the world by developing Massive MIMO technology that can support the evolution of 4G to 5G. There are some studies that discussed several techniques to overcome problems in communication systems with high reliability. One of the techniques required in massive MIMO implementation is proper space time coding.In the era of 4G, space time block code developed rapidly with two kinds of orthogonal schemes that are categorized into two groups: orthogonal and orthogonal quasi. Orthogonal space time block code that can only be used in simple modulation , with quasi orthogonal space time block code modulation complex can be applied and orthogonality value generated by QOSTBC will be higher than OSTBC so as to increase the reliability of the data. In previous research has been proposed QOSTBC using MC-CDMA as multicarrier, result of this system still has orthogonal which is less stable causing decrease of system performance This research will be proposed a MIMO system scheme which is an improvement of QOSTBC that used a transmission diversity technique. Full diversity in this technique will occur if multiple symbols are transmitted into two transmitting parts that are transmitted at different time slots. This improvement from QOSTBC is Twice QOSTBC uses a provision in two codeword matrices to be sent are arranged diagonally so as to have higher levels of orthogonality. The detection also involves nonlinear processing, which further complicates the system. To solve these problems, we propose a zero forcing EVCM which eliminates the system complexity. In this case Twice QOSTBC highly structured (4x1) can be replaced as an equivalent EVCM channel H. From the simulation results when used 4 pieces antenna at the transmitter the proposed results outperform other QOSTBC techniques with a difference around 3 dB for 10?6 BER. We can concluded that in general the proposed sytem maintained a better performance compared to other Space Time Coding scheme because the data is transmitted through two symbols at once which is repeated with the second codeword and the effect of diaganol matrices at the transmitter can fully the orthogonality of scheme. The decoder ZF EVCM has a very similar structure as the code matrix S of the underlying Twice QSTBC which can eliminates the system complexity