Home // International Journal On Advances in Telecommunications, volume 10, numbers 3 and 4, 2017 // View article

Joint Beamforming, Terminal Scheduling, and Adaptive Modulation with Imperfect CSIT in Rice Fading Correlated Channels with non-persistent Co-channel Interference

Authors:
Ramiro Samano Robles

Keywords: Beamforming; Scheduling; Resource allocation; Imperfect CSIT; Maximum Ratio Combining (MRC)

Abstract:
This paper presents a resource allocation algorithm for multi-user wireless networks with non-persistent co-channel interference. The analysis considers a network with one base station (BS) that employs an $N$ multiple antenna transmitter (beamformer) to schedule (in a time-division format) a set of $J$ one-antenna terminals in the presence of $K$ non-persistent interferers. The transmitter is assumed to employ Maximum-Ratio Combining (MRC) beamforming with spatially-correlated branches and channel envelopes modelled as Rice-distributed processes. The BS has access to an imperfect (outdated) copy of the instantaneous Channel State Information (CSI) of each terminal. Based on this CSI at the transmitter side (CSIT), the BS proceeds to select (at each time interval or time-slot) the terminal with the highest measured channel strength. This imperfect CSIT is also used to calculate the coefficients of the beamformer that will be used to transmit information towards the scheduled terminal, as well as for selecting the most appropriate modulation format (via threshold-based decision). The main merits of this work are the following: 1) joint analysis of MRC-based beamforming, terminal scheduling based on maximum channel strength, and modulation assignment, and 2) impact analysis of spatial correlation, line-of-sight (LOS), co-channel interference, and imperfect CSIT. Results suggest that maximum channel strength scheduling helps in rejecting co-channel interference and the degrading effects of imperfect CSIT (due to multi-user diversity gains). Spatial correlation could some times lead to better performance than the uncorrelated case, particularly in the low SNR (Signal-to-Noise Ratio) regime. Conversely, uncorrelated branches always outperform the correlated case in the high SNR regime. Spatial correlation tends to accumulate over the antenna array thus leading to a more noticeable performance degradation and more allocation errors due to the outdated CSIT assumption. The LOS channel component is found to contribute to a better reception in general, but it also reduces the ability to counteract the degrading effects of imperfect CSIT due to the lack of diversity combining gains.

Pages: 186 to 195

Copyright: Copyright (c) to authors, 2017. Used with permission.

Publication date: December 31, 2017

Published in: journal

ISSN: 1942-2601