Asymptotic Rate Analysis of Large-Scale Distributed Antenna System (DAS): From Cellular DAS to Virtual-Cell based DAS 
报告人：香港城市大学-代琳 教授
时间：2017年4月21日 下午 14:00am 
地点：无线谷1号楼 1319会议室

Title: Asymptotic Rate Analysis of Large-Scale Distributed Antenna System (DAS): From Cellular DAS to Virtual-Cell based DAS 
Speaker: Lin Dai (代琳) 
Abstract: 
The distributed antenna system (DAS) has attracted considerable attention from both industry and academia, and gained increasing momentum especially with the popularity of the Cloud Radio Access Network (C-RAN). In contrast to the conventional cellular systems where antennas are co-located at the tower-mounted base station (BS) in each cell, in a DAS, many low-power remote antenna ports are geographically distributed over a large area and connected to a central processor by fiber. The appealing features of distributed antennas have made it a promising candidate for next-generation (5G) mobile communication systems. 
For 5G mobile communication systems, a large amount of BS antennas are expected to be deployed to meet the ever increasing demand of high data rate. Extensive studies have been focused on the capacity analysis of cellular systems with large antenna arrays at BSs (popularly known as “massive MIMO”). If the BS antennas are distributed, on the other hand, how the capacity scales with the number of BS antennas is less understood. In this talk, I will introduce my recent work on the rate scaling laws of downlink large-scale cellular DASs. I will start from the single-cell case, and demonstrate that bounds are useful for analyzing the rate scaling behavior. A comparative study to the rate with co-located BS antennas reveals that although a higher scaling order can always be achieved with distributed BS antennas, the rate gains become more pronounced when an orthogonal precoding scheme is adopted. For the multi-cell case, I will further show that despite a higher average user rate, the cell-edge problem is indeed exacerbated if distributed BS antennas are used. To achieve more uniform rate performance among users, virtual cells should be adopted, which are formed in a user-centric manner. I will conclude the talk by discussing how to optimally choose the virtual cell size to maximize the average user rate of a virtual-cell based DAS.