Near Optimum Power Control and Precoding under Fairness Constraints in Network MIMO Systems

Gábor Fodor,Pablo Soldati,Mikael Johansson

doi:10.1155/2010/251719

Abstract

We consider the problem of setting the uplink signal-to-noise-and-interference (SINR) target and allocating transmit powers for mobile stations in multicell spatial multiplexing wireless systems. Our aim is twofold: to evaluate the potential of such mechanisms in network multiple input multiple output (MIMO) systems, and to develop scalable numerical schemes that allow real-time near-optimal resource allocation across multiple sites. We formulate two versions of the SINR target and power allocation problem: one for maximizing the sum rate subject to power constraints, and one for minimizing the total power needed to meet a sum-rate target. To evaluate the potential of our approach, we perform a semianalytical study inMathematicausing the augmented Lagrangian penalty function method. We find that the gain of the joint optimum SINR setting and power allocation may be significant depending on the degree of fairness that we impose. We develop a numerical technique, based on successive convexification, for real-time optimization of SINR targets and transmit powers. We benchmark our procedure against the globally optimal solution and demonstrate consistently strong performance in realistic network MIMO scenarios. Finally, we study the impact of near optimal precoding in a multicell MIMO environment and find that precoding helps to reduce the sum transmit power while meeting a capacity target.

Highlights

Several works proposed and demonstrated various forms of tight network coordination as a means to provide high spectral efficiency in multicell multiple input multiple output (MIMO) cellular networks [1, 2]
Since network MIMO systems in general and multicell spatial multiplexing systems in particular inherently support the exchange of control information among multiple base stations, they can readily benefit of joint radio resource management functions, such as multicell scheduling, power control and precoding [8,9,10]
The sum rate decreases as the SINR distribution becomes more fair

Summary

Introduction

Several works proposed and demonstrated various forms of tight network coordination as a means to provide high spectral efficiency in multicell multiple input multiple output (MIMO) cellular networks [1, 2]. Such coordination among the cells deployed over a certain geographical area has initially aimed at coordinating transmitter and receiver algorithms [3,4,5]. For the uplink, it has been shown that coordinated power control can minimize the overall transmit power so as to maintain a predetermined signal-to-noise-and-interference (SINR) target [13]

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Conclusion