Distributed Antenna System for Mitigating Shadowing Effect in 60 GHz WLAN

Abstract

The 60 GHz unlicensed frequency band has been adopted to support high data rate WLAN applications. The problem of this frequency band is that the wireless signal is vulnerable to the shadowing of objects. Especially in indoor scenarios, humans may frequently block the signal paths that cause disconnections of devices. This problem can be mitigated by using multiple antennas that can create rich signal paths between the devices. The idea presented in this paper is to employ a distributed antenna system (DAS) architecture enabled by radio-over-fiber technology to alleviate the shadowing problem. In the DAS architecture, multiple remote antenna units (RAUs), each of them equipped with an antenna array, are connected with the same WLAN access points via optical fibers. But there are questions that need to be answered, including the beamforming strategy with multiple RAUs, and the placement and the required number of the RAUs. These questions are related to factors like room size, population density, etc. We discuss these questions in this paper and present our findings through theoretical models and extensive simulations, which can be referred to for practical implementations. We find that the proposed 60 GHz DAS can significantly improve the link connectivity. Even when only two RAUs are used, the signal coverage can be improved to an acceptable percentage in heavy shadowing scenarios.

Diversity gain of millimeter-wave massive MIMO systems with distributed antenna arrays

“…. , f rK r (24) where f ti stands for the N t × 1 steering vector of phases for the ith RAU at the transmitter, and f rj stands for the N r × 1 steering vector of phases for the jth RAU at the transmitter. Theorem 2 Consider the case that the antenna array configuration at each RAU is ULA and L ij = L for any i and j.…”

“…In order to enlarge the diversity gain and/or multiplexing gain in mmWave massive MIMO communication systems, this paper considers a more general antenna array architecture, called distributed antenna subarray architecture, which includes co-located array architecture as special cases. It is pointed out that deploying distributed antennas has shown a promising technique to increase spectral efficiency and expand the coverage of wireless communication networks [21][22][23][24][25]. As such, it is of great interest to consider distributed antenna deployment in the context of mmWave massive MIMO systems.…”

Diversity Analysis of Millimeter-Wave OFDM Massive MIMO Systems

“…We sort the corresponding s and s based on this sort. Then, one can decompose the channel matrix defined in (5) as In a similar way to [14], [17], one can see that when the number of antennas at both the transmitter and the receiver goes to infinity, the optimal fully-digital precoders can be calculated by the hybrid precoding design in which…”