Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/29906
Title: Some fundamental issues in receiver design and performance analysis for wireless communication
Authors: WU MINGWEI
Keywords: MLSD-NCSI, fading, Gaussian Q, quadratic receiver, outage, ARQ
Issue Date: 21-Jan-2011
Source: WU MINGWEI (2011-01-21). Some fundamental issues in receiver design and performance analysis for wireless communication. ScholarBank@NUS Repository.
Abstract: This thesis studies two fundamental issues in wireless communication, i.e. robust receiver design and performance analysis. In wireless communication with high mobility, the channel statistics or the channel model may change over time. Applying the joint data sequence detection and (blind) channel estimation approach, we derive the robust maximum-likelihood sequence detector that does not require channel state information (CSI) or knowledge of the fading statistics. We show that its performance approaches that of coherent detection with perfect CSI when the detection block length L becomes large. To detect a very long sequence while keeping computational complexity low, we propose three pilot-based algorithms: the trellis search algorithm, pilot-symbol-assisted block detection and decision-aided block detection. We compare them with block-by-block detection algorithms and show the former's advantages in complexity and performance. The commonly used performance measures at the physical layer are average error probabilities, obtained by averaging instantaneous error probabilities over fading distributions. For average performance of coherent receivers, we propose to use the convexity property of the exponential function and apply the Jensen's inequality to obtain a family of exponential lower bounds on the Gaussian Q-function. The tightness of the bounds can be improved by increasing the number of exponential terms. The coefficients of the exponentials are constants, allowing easy averaging over fading distribution using the moment generating function MGF method. This method is applicable to finite integrals of the exponential function. It is further applied to the two-dimensional Gaussian Q-function, symbol error probability (SEP) of M-ary phase shift keying, SEP of M-ary differential phase shift keying and signals with polygonal decision regions over additive white Gaussian channel, and their averages over general fading. The tightness of the bounds is demonstrated. For average performance of differential and noncoherent receivers, by expressing the noncentral Chi-square distribution as a Poisson-weighted mixture of central Chi-square distributions, we obtain an exact expression of the error performance of quadratic receivers. This expression is in the form of a series summation involving only rational functions and exponential functions. The bit error probability performances of optimum and suboptimum binary differential phase shift keying (DPSK) and quadrature DPSK receivers over fast Rician fading with Doppler shift are obtained. Numerical computation using our general expression is faster than existing expressions in the literature. Moving on to the perspective of the data link layer, we propose to use the probability of instantaneous bit error outage as a performance measure of the physical layer. It is defined as the probability that the instantaneous bit error probability exceeds a certain threshold. We analyze the impact of channel estimation error on the outage performance over Rayleigh fading channels, and obtain the optimum allocation of pilot and data energy in a frame that minimizes the outage probability. We further extend the outage concept to packet transmission with automatic repeat request (ARQ) schemes over wireless channels, and propose the probability of instantaneous accepted packet error outage (IAPEO). It is observed that, in order to satisfy a system design requirement of maximum tolerable IAPEO, the system must operate above a minimum signal-to-noise ratio (SNR) value. An ARQ scheme incorporating channel gain monitoring (ARQ-CGM) is proposed, whose IAPEO requirement can be satisfied at any SNR value with the right channel gain threshold. The IAPEO performances of ARQ-CGM with different retransmission protocols are related to the conventional data link layer performance measures, i.e. average accepted packet error probability, throughput and goodput.
URI: http://scholarbank.nus.edu.sg/handle/10635/29906
Appears in Collections:Ph.D Theses (Open)

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