Space-Time Block Coding for Wireless Communications

Abstract Wireless designers constantly seek to improve the spectrum efficiency/capacity, coverage of wireless networks, and link reliability. Space-time wireless technology that uses multiple antennas along with appropriate signalling and receiver techniques offers a powerful tool for improving wireless performance. Some aspects of this technology have already been incorporated into various wireless network and cellular mobile standards. More advanced MIMO techniques are planned for future mobile networks, wireless local area network (LANs) and wide area network (WANs). Multiple antennas when used with appropriate space-time coding (STC) techniques can achieve huge performance gains in multipath fading wireless links. The fundamentals of space-time coding were established in the context of space-time Trellis coding by Tarokh, Seshadri and Calderbank. Alamouti then proposed a simple transmit diversity coding scheme and based on this scheme, general space-time block codes were further introduced by Tarokh, Jafarkhani and Calderbank. Since then space-time coding has soon evolved into a most vibrant research area in wireless communications. Recently, space-time block coding has been adopted in the third generation mobile communication standard which aims to deliver true multimedia capability. Space-time block codes have a most attractive feature of the linear decoding/detection algorithms and thus become the most popular among different STC techniques. The decoding of space-time block codes, however, requires knowledge of channels at the receiver and in most publications, channel parameters are assumed known, which is not practical due to the changing channel conditions in real communication systems. This thesis is mainly concerned with space-time block codes and their performances. The focus is on signal detection and channel estimation for wireless communication systems using space-time block codes. We first present the required background materials, discuss different implementations of space-time block codes using different numbers of transmit and receive antennas, and evaluate the performances of space-time block codes using binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), and quadrature amplitude modulation (QAM). Then, we investigate Tarokh’s joint detection scheme with no channel state information thoroughly, and also propose a new general joint channel estimation and data detection scheme that works with QPSK and 16-QAM and different numbers of antennas. Next, we further study Yang’s channel estimation scheme, and expand this channel estimation scheme to work with 16-QAM modulation. After dealing with complex signal constellations, we subsequently develop the equations and algorithms of both channel estimation schemes to further test their performances when real signals are used (BPSK modulation). Then, we simulate and compare the performances of the two new channel estimation schemes when employing different number of transmit and receive antennas and when employing different modulation methods. Finally, conclusions are drawn and further research areas are discussed

Space-time turbo coding for CDMA mobile communications

Against the background of the rapid evolution of mobile communication systems in the areas of service provision and capacity enhancement described above, the main focus of the research is on coded space-time processing techniques. The use of space-time processing is an attractive solution because it can mitigate the effects of multipath fading as well as suppress co-channel interference, therefore, significantly improving system performance. The topics are presented in the context of designing mobile communication systems where the two core areas of spatial processing and error coding are to be integrated in an optimum way. Of particular importance in this thesis, will be those CDMA based solutions for the mobile sector and the new performance analysis issues that need to be addressed as a result of the introduction of heterogeneous services and service environments into a single, mobile cellular access network. Furthermore, novel applications of turbo transmit and receive antenna diversity and beamforming techniques to mobile cellular access networks aimed at increasing the efficiency of such networks are considered. The thesis has the following goals: • To establish a general spatial/temporal channel model for use in the evaluation of coded space-time processing concepts applied to CDMA networks. • To analyze the performance of uncoded cellular CDMA systems incorporating space-time techniques using analytical methods in a number of realistic application scenarios. • To design, implement and evaluate coding strategies for incorporation into the space-time CDMA systems. This objective can be broken down into the following items: --- Space-time coding systems when considering multiple transmit antennas for the downlink. --- Coded space-time systems when considering multiple receive antennas for the uplink. • To establish the performance of coded space-time CDMA cellular networks under realistic scenarios. This thesis introduces many (some novel) space-time turbo coded techniques to increase the downlink capacity of a cellular CDMA network using multiple transmit antennas. For improving the uplink capacity, coded space-time diversity and beamforming techniques, employing multiple receive antennas, are considered. In order to quantify the performance improvements that may be achieved, a framework for the evaluation of these systems are constructed. Using this framework the BEP of all the space-time coding systems are derived analytically, and evaluated under identical propagation scenarios. The results presented show that the use of space-time turbo coded processing is an attractive solution since it can improve system performance significantly under conditions of multipath fading for both the uplink and downlink. It is shown that the two core areas of spatial processing and channel coding can be integrated in an optimum way to increase the capacity of existing cellular CDMA networks.Thesis (DPhil (Electronic Engineering))--University of Pretoria, 2007.Electrical, Electronic and Computer Engineeringunrestricte

Wireless industrial monitoring and control networks: the journey so far and the road ahead

While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks

Delay Performance of MISO Wireless Communications

Ultra-reliable, low latency communications (URLLC) are currently attracting significant attention due to the emergence of mission-critical applications and device-centric communication. URLLC will entail a fundamental paradigm shift from throughput-oriented system design towards holistic designs for guaranteed and reliable end-to-end latency. A deep understanding of the delay performance of wireless networks is essential for efficient URLLC systems. In this paper, we investigate the network layer performance of multiple-input, single-output (MISO) systems under statistical delay constraints. We provide closed-form expressions for MISO diversity-oriented service process and derive probabilistic delay bounds using tools from stochastic network calculus. In particular, we analyze transmit beamforming with perfect and imperfect channel knowledge and compare it with orthogonal space-time codes and antenna selection. The effect of transmit power, number of antennas, and finite blocklength channel coding on the delay distribution is also investigated. Our higher layer performance results reveal key insights of MISO channels and provide useful guidelines for the design of ultra-reliable communication systems that can guarantee the stringent URLLC latency requirements.Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl