Downlink Scheduling in Network MIMO Using Two-Stage Channel State Feedback

Abstract

In this paper, we propose a user scheduling scheme which is based merely on the ergodic rate. We derive the ergodic rate of each user for our network MIMO system from the average Signal-to-Noise Ratio (SNR) and the covariance of prediction error. Further more, we design a joint precoding for the selected users. The precoding matrices are contrived according to the predicted Channel State Information at Transmitter (CSIT) in the future time slot to reduce the deviation caused by delay. Such a network MIMO system is under consideration, where the users are cooperatively served by multiple Base Stations (BSs). User scheduling and joint precoding are executed by a central unit connected to all BSs. Both the above functions require the CSIT which is acquired by an uplink feedback overhead. Simulation results demonstrate a conspicuous improvement in user spectral efficiency with reduced feedback.

Cognitive Radio Networks

“…On the other hand, the accuracy of CSIT requires intensive feedback that takes up too much resource for the information data when there is a large number of users. To this end, in chapter 4 [27], a design of subcarrier allocation and precoding using reduced feedback scheme is motivated to solve the above contradiction. Small scale fading has little influence on subcarrier allocation.…”

“…OFDM is considered as a excellent modulation scheme for CR networks [43] for the reason that it facilitates spectrum sensing and provides great flexibility. OFDM is considered in a proposed subcarrier allocation scheme in chapter 4 [27]. WOFDM adopts orthogonal wavelet bases to replace sine functions and excludes Cyclic Prefix (CP) in OFDM.…”

“…Une bonne précision du CSIT exige un retour (feedback) important et donc coûteux en présence de beaucoup d'utilisateurs. Nous consacrons le chapitre 4 (voir aussi [27])à la réduction de ces coûts en proposant une allocation de sous porteuse moins gourmande en information de retour sur le CSIT et qui traite en même temps l'effet du fading (ouévanouissements). En effet, Small Scale Fading (SSF) a peu d'influence sur la répartition de la sous-porteuse alors qu'il est important pour le pré-codage.…”