Utilizing Channel State Information for Enhancement of Wireless Communication Systems

Channel State Information;Antenna Weight Verification;Joint Source-Channel Coding;Mode 1 of 3GPP;Closed-Loop Transmit Diversity;Beamforming;Fading Channel Modeling;Fading Channel Prediction;Sum-Sinusoidal Fading Model;Kalman Estimation;Mobile Channel Tracking;Feedback Delay;Feedback Error;Blind Antenna Weight Verification;Electrical and Computer Engineering

Heidari, Abdorreza

University of Waterloo

关键词: Channel State Information;    Antenna Weight Verification;    Joint Source-Channel Coding;    Mode 1 of 3GPP;    Closed-Loop Transmit Diversity;    Beamforming;    Fading Channel Modeling;    Fading Channel Prediction;    Sum-Sinusoidal Fading Model;    Kalman Estimation;    Mobile Channel Tracking;    Feedback Delay;    Feedback Error;    Blind Antenna Weight Verification;    Electrical and Computer Engineering;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/3413/1/Thesis_Reza_22.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

One of the fundamental limitations of mobile radiocommunications is their time-varying fading channel. Thisthesis addresses the efficient use of channel state informationto improve the communication systems, with a particularemphasis on practical issues such as compatibility with theexisting wireless systems and low complexity implementation.The closed-loop transmit diversity technique is used to improvethe performance of the downlink channel in MIMO communicationsystems. For example, the WCDMA standard endorsed by 3GPPadopts a mode of downlink closed-loop scheme based on partialchannel state information known as mode 1 of3GPP. Channel state information is fed backfrom the mobile unit to the base station through a low-rateuncoded feedback bit stream. In these closed-loop systems,feedback error and feedback delay, as well as the sub-optimumreconstruction of the quantized feedback data, are the usualsources of deficiency.In this thesis, we address the efficient reconstruction of thebeamforming weights in the presence of the feedbackimperfections, by exploiting the residual redundancies in thefeedback stream. We propose a number of algorithms forreconstruction of beamforming weights at the base-station, withthe constraint of a constant transmit power. The issue of thedecoding at the receiver is also addressed. In one of theproposed algorithms, channel fading prediction is utilized tocombat the feedback delay. We introduce the concept of BlindAntenna Verification which can substitute the conventionalAntenna Weight Verification process without the need for anytraining data. The closed-loop mode 1 of 3GPP is used as abenchmark, and the performance is examined within a WCDMAsimulation framework. It is demonstrated that the proposedalgorithms have substantial gain over the conventional methodat all mobile speeds, and are suitable for the implementationin practice. The proposed approach is applicable to otherclosed-loop schemes as well.The problem of (long-range) prediction of the fading channel isalso considered, which is a key element for manyfading-compensation techniques. A linear approach, usually usedto model the time evolution of the fading process, does notperform well for long-range prediction applications. We proposean adaptive algorithm using a state-space approach for thefading process based on the sum-sinusoidal model. Also toenhance the widely-used linear approach, we propose a trackingmethod for a multi-step linear predictor. Comparing the twomethods in our simulations shows that the proposed algorithmsignificantly outperforms the linear method, for bothstationary and non-stationary fading processes, especially forlong-range predictions. The robust structure, as well as thereasonable computational complexity, makes the proposedalgorithm appealing for practical applications.