Coordinated Multi-Point Transmission With Imperfect CSI and Other-Cell Interference

Abstract

International audienceCoordinated Multi-Point (CoMP) transmission for LTE-Advanced systems promises enhanced throughput and coverage performance, especially for cell edge users. However, the performance of CoMP systems heavily depends on the feedback quality and channel imperfections. In this paper, we investigate the impact of quantized and delayed channel state information (CSI) on the average achievable rate of joint transmission (JT) and coordinated beamforming (CBF) systems. We derive closed-form expressions and accurate approximations on the expected sum rate of CoMP systems with imperfect CSI assuming small-scale Rayleigh fading, pathloss attenuation, and other-cell interference (OCI). Furthermore, for analytical tractability, we employ a moment matching technique that approximates the distributions of the received desired and interference signals. Based on our analytical framework, we show that CBF and JT to multiple users are more sensitive to CSI imperfections than single-user JT and we identify switching points and optimal operating regimes for each scheme. Furthermore, we propose an adaptive multimode transmission technique that switches between CoMP schemes to maximize the sum rate. Finally, the proposed approximate framework enables us to identify key system parameters, such as feedback resolution, delay, pathloss, and transmit SNR for which CoMP becomes a judicious choice of transmission strategy as compared to non-cooperative transmission

Capacity Analysis of Joint Transmission CoMP With Adaptive Modulation

“…ASE for JT CoMP with discrete-rate adaptation with different quantized modulation schemes (BERtar = 10 −3 , γ j = 4.5 dB, and γ k = 5.5 dB). into (7) and using integration by parts to simplify the terms to be integrated. Whenγ j =γ k =γ η ave,3 =…”

“…In [6], the performance of CoMP when orthogonal beamforming is utilized was focused on. Finally, in [7], the impact that quantized (and delayed) channel state information (CSI) has on the average data rate that JT and coordinated beamforming CoMP can achieve was investigated.…”

On the Robustness of Coordinated Beamforming to Uncoordinated Interference and CSI Uncertainty

“…The latter modeling of the OCI's vector elements was used in the analysis of [5], where it was considered that OCI is made up of a large number of interference terms, and thus can be effectively approximated as Gaussian. For general values of m ≥ 0.5 in (5), the adopted model resembles that of [7], [14], [15], where the amplitude distribution of each element of g b , computed using both the hexagonal grid and stochastic geometry models, was approximated by a Gamma RV through the moment matching approach. Starting from (1) and considering the OCI model of (5), it can be easily concluded that the received power of the desired signal at MT b with channel estimation and that of its received aggregate OCI are related as in the left-hand side of (4), yielding…”

Decentralized Joint Precoding for WSRMax with Pilot Aided Beamformer Estimation

“…These designs try to limit the JP cluster sizes and, thus, implicitly reduce the backhaul overhead. The impact of partial or imperfect CSI feedback to CB and JP has been studied, e.g., in [10]. Pilot contamination in TDD based transceiver training for coordinated beamforming has been considered in [11].…”