Channel characterization and modeling for large-scale antenna systems

In light of the emerging fifth generation (5G) mobile communications, large-scale antenna systems (LSAS, also known as large-scale MIMO, massive MIMO, etc.) present a highly promising solution to meet the demanding requirements of even higher network capacity, throughput, spectrum- and energy-efficiency than 4G systems. Channel measurements show that unlike conventional MIMO, quite a few new channel characteristics need to be taken into consideration when modelling the LSAS. Employing appropriate channel models is critically important not only for the performance evaluation of different candidate 5G technologies, but also for the development of new algorithms and products exploiting the LSAS. This paper presents the current progress on channel characterization of LSAS and discusses the major open issues. The key differentiating channel characteristics of LSAS (e.g., non-stationarity, near-field effects, etc.) are summarized, which poses new challenges to channel modeling as well as systems design and network simulation for LSAS. In order to develop comprehensive channel models for LSAS, further investigation through thorough field measurement and validation is necessary to reveal the channel characteristics of LSAS operating in various deployment scenarios with different antenna configurations.