Abstract
We consider the downlink of a multicell system comprised of base stations (BSs) and user terminals equipped with multiple antennas respectively on the condition that arbitrary BS cooperation and distance dependent propagation path loss are assumed. In this paper, we consider homogeneous networks for the rectangular coordinates and show the cell edge performance of cellular networks based on distance from their cell center, i.e., BS. We focus on the downlink capacity of edge users in the cellular networks and show that BS cooperation can improve the spectral efficiency. The BSs cooperate for their transmission to the cell edge users in order to improve their signal-to-interference-plus-noise ratio (SINR) for inter-cell interference (ICI) cancelation in downlink multicell systems. When fractional frequency reuse (FFR) is applied to the cell edge, it is conjectured that BS cooperation, or a coordinated multipoint (CoMP), will further improve the system performance. Simulation results show that the proposed scheme outperforms the reference schemes in terms of the cell edge SINR with a minimal impact on the path loss exponent in the networks.
Highlights
In conventional cellular networks, a major degrading factor affecting the system performance is inter-cell interference (ICI)
Though the capacity region of Multi-input multi-output (MIMO) broadcast channel (BC) is an unsolved problem for lack of a general theory on non-degraded broadcast channels, an achievable region for MIMO broadcast channel was obtained by applying the dirty paper coding (DPC) [5] at the transmitter [6,7,8] which established the duality of achievable region and the capacity region of the MIMO
This makes the solution of sum capacity of MIMO BC possible, since the solution of sum capacity of MIMO BC is in general a non-convex optimization, while MIMO multiple access channel can be solved by convex optimization
Summary
A major degrading factor affecting the system performance is inter-cell interference (ICI). The exact expression for the capacity for cooperative scheme with resource constraint to perform better than normal transmission, i.e., Ccoop > Cnc, is shown below: 4.1 Inter-cell interference: an example 2-cell case The received signal strength goes down as the path loss increases with distance from the serving BS. When a frequency reuse scheme, for example, with a reuse of three, is applied, the interference from these multiple users receiving on the downlink in BS1 is eliminated This results in a larger improvement in SINR and correspondingly larger improvements in downlink capacity or throughput. Since the starting SINR with reuse of one is low, the capacity scales approximately linearly with SINR and results in larger gains in downlink capacity for cell edge users.
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