We develop a general downlink model for multi-antenna heterogeneous cellular
networks (HetNets), where base stations (BSs) across tiers may differ in terms
of transmit power, target signal-to-interference-ratio (SIR), deployment
density, number of transmit antennas and the type of multi-antenna
transmission. In particular, we consider and compare space division multiple
access (SDMA), single user beamforming (SU-BF), and baseline single-input
single-output (SISO) transmission. For this general model, the main
contributions are: (i) ordering results for both coverage probability and per
user rate in closed form for any BS distribution for the three considered
techniques, using novel tools from stochastic orders, (ii) upper bounds on the
coverage probability assuming a Poisson BS distribution, and (iii) a comparison
of the area spectral efficiency (ASE). The analysis concretely demonstrates,
for example, that for a given total number of transmit antennas in the network,
it is preferable to spread them across many single-antenna BSs vs. fewer
multi-antenna BSs. Another observation is that SU-BF provides higher coverage
and per user data rate than SDMA, but SDMA is in some cases better in terms of
ASE.

研究多天线异构蜂窝网络中的下行链路模型，考虑了不同基站之间在发射功率、目标信干噪比、部署密度、发射天线数量和多天线传输类型等方面的差异，并比较了空分多址、单用户波束成形和单输入单输出传输三种技术的覆盖率概率、用户速率等指标，提出了关于区域频谱效率的统计比较工具。研究发现，为了提高网络的总体性能，将天线分布在多个单天线基站上比分布在少量多天线基站上更为优越；单用户波束成形技术能提供更高的覆盖率和用户速率，但空分多址在某些方面的区域频谱效率更高。