Abstract
Coordinated multi-point (CoMP) schemes have been widely studied in the recent years to tackle the inter-cell interference. In practice, latency and throughput constraints on the backhaul allow the organization of only small clusters of base stations (BSs) where joint processing (JP) can be implemented. In this work we focus on downlink CoMP-JP with multiple antenna user equipments (UEs) and propose a novel dynamic clustering algorithm. The additional degrees of freedom at the UE can be used to suppress the residual interference by using an interference rejection combiner (IRC) and allow a multistream transmission. In our proposal we first define a set of candidate clusters depending on long-term channel conditions. Then, in each time block, we develop a resource allocation scheme by jointly optimizing transmitter and receiver where: a) within each candidate cluster a weighted sum rate is estimated and then b) a set of clusters is scheduled in order to maximize the system weighted sum rate. Numerical results show that much higher rates are achieved when UEs are equipped with multiple antennas. Moreover, as this performance improvement is mainly due to the IRC, the gain achieved by the proposed approach with respect to the non-cooperative scheme decreases by increasing the number of UE antennas.
Highlights
Coordination among base stations (BSs) has been widely studied in the recent years to tackle inter-cell interference which strongly limits the rates achieved in cellular systems, in particular by the user equipments (UEs) at the cell-edge [1]
We assume that UE scheduling, beamforming design, transmission rank selection, and power allocation are performed, as described in Sections 2.2 and 3.1, for the static schemes: in particular, UEs are served by using multi-user eigenmode transmission (MET) [25] with equal power allocation among the eigenmodes and a greedy UE selection is performed within each BS cluster
A two-step procedure is applied following a fast fading time scale: (a) first, a weighted sum rate is estimated within each candidate BS cluster by performing UE selection, precoding, power and transmission rank selection, and (b) the central unit (CU) schedules the set of non-overlapping BS clusters that maximizes the estimated system weighted sum rate
Summary
Coordination among base stations (BSs) has been widely studied in the recent years to tackle inter-cell interference which strongly limits the rates achieved in cellular systems, in particular by the user equipments (UEs) at the cell-edge [1]. The main contribution of this work, described, is a practical algorithm for dynamic BS clustering and corresponding UE scheduling developed in the considered setup with multiple antenna BSs, with equal power allocation and MET, that transmit toward multiple antenna UEs. we recall that at UEs, the multiple receive antennas are used to perform IRC with SIC ([26], Ch. 10); while the rank lk(t) allocated to UE k is given by the number of columns of the precoder, the remaining degrees of freedom at UE are used to partially suppress the residual ICI. Note that IRC both minimizes the mean square error and maximizes the SINR at the detection point [23]
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