Adaptive Selection Combining Receiver over Time Varying Frequency Selective Fading Channel in Class-A Noise

An adaptive selection combining (SC) scheme is proposed for time varying mobile communication channel in Class-A impulsive noise. The receiver adaptively selects a diversity branch out of the available branches and discards the others. This is performed by computing the maximum likelihood (ML) metric of each diversity branch and selects the branch with the maximum metric. The proposed adaptive SC scheme dynamically adjusts the threshold value according to the time variations of the channel. Equalization and data detection are performed after combining using maximum likelihood sequence estimation implemented by Viterbi algorithm (MLSE-VA). The minimum survivor technique is employed to reduce the complexity of the receiver. 1. Introduction In wireless communication networks, fading phenomenon imposes serious limitations upon the system performance. Diversity techniques as means of achieving high capacity communication systems and combating fading effects have been the subject of interest for many years. The traditional diversity combining techniques include maximal ratio combining (MRC), equal gain combining (EGC), and selection combining (SC). MRC coherently combines all diversity branches after weighing each branch with the respective gain of the branch. EGC coherently combines all diversity branches after weighing each branch with equal gain. In SC only one diversity branch is used for data reception. The usual way of selecting this branch is to choose the branch with the largest instantaneous SNR. Most literature in diversity is mainly limited to the conventional assumption of AWGN. AWGN realistically represents the thermal noise at the receiver but ignores the impulsive nature of atmospheric noise, electromagnetic interference, or man-made noise. Automatic ignition noise and power transmission lines are examples of impulsive noise sources encountered mainly in metropolitan areas [1]. One of the noise models that combines the Gaussian noise with a non-Gaussian impulsive noise is Class-A impulsive noise proposed by Middleton. Despite the practical and theoretical importance of the problem, only few results on diversity combining for Class-A noise are available in the literature [1–6]. In [1], the performance of a multirelay network with amplify-and-forward relaying over a flat Rayleigh fading channel in impulsive noise is considered. In [2], the performance of maximum ratio combining (MRC), equal gain combining (EGC), selection combining (SC), and postdetection combining under Class-A impulsive noise is analyzed. In [3], the bit error rate of diversity