异构网中大规模MIMO场景下波束赋形设计

近年来,人们对于无线通信系统的数据传输速率的需求越来越大.大规模多输入多输出技术(MIMO)与小小区技术是能够满足人们高速增长的无线通信需求的关键技术.研究在一个异构网中的波束赋形问题,其中宏小区基站的配置为Massive MIMO,同时宏小区中包含小小区.在这样的场景下,宏基站配置大量天线,小小区基站配置少数天线,用户配置单天线.研究在这样的场景下,通过波束赋形设计,最大化所有用户的传输速率.该问题的目标函数是一个非凸的问题.通过运用半正定松弛(SDR)方法以及基于泰勒展开的一阶近似方法,将原问题转化为一个凸的近似问题,然后运用迭代方法求解.仿真结果证明,方案可以有效地提高包含Massive MIMO的异构网场景下的系统吞吐率以及能量效率.

Beamforming in heterogeneous networks with Massive MIMO

The wireless communication system is now facing an astounding data traffic increase in a decade.Massive multiple-input multiple-output(MIMO) and small cell(SC) networks are two promising technologies to meet the increasing data traffic demand.This paper studies the beamforming design problem in a two-tier network consisting of a massive MIMO macro tier overlaid with a second tier of SCs.In this scenario,the Base Station (BS) uses a large excess of base station antennas(up to a few hundred antennas) while the SC is equipped with only a small number of antennas.Possible improvements of energy efficiency is investigated.The object is to maximize the transmission rate of the network under the sum power constraint.This object leads to a nonconvex complicated structure,and makes the considered beamforming design problem difficult to handle.To solve this problem,a beamforming design scheme is proposed to transform the original problem into a convex approximation problem,by employing semidefinite relaxation(SDR) and first-order approximation technique based on Taylor expansion.Numerical results show that the strategy can improve system throughput.