Mitigating Pilot Contamination in Multi-Cell Hybrid Millimeter Wave Systems

Abstract

In this paper, we investigate the system performance of a multi-cell multi-user (MU) hybrid millimeter wave (mmWave) multiple-input multiple-output (MIMO) network adopting the channel estimation algorithm proposed in [1] for channel estimation. Due to the reuse of orthogonal pilot symbols among different cells, the channel estimation is expected to be affected by pilot contamination, which is considered as a fundamental performance bottleneck of conventional multicell MU massive MIMO networks. To analyze the impact of pilot contamination on the system performance, we derive the closed-form approximation expression of the normalized mean squared error (MSE) of the channel estimation performance. Our analytical and simulation results show that the channel estimation error incurred by the impact of pilot contamination and noise vanishes asymptotically with an increasing number of antennas equipped at each radio frequency (RF) chain deployed at the desired BS. Thus, pilot contamination is no longer the fundamental problem for multi-cell hybrid mmWave systems.

Multi-Cell Hybrid Millimeter Wave Systems: Pilot Contamination and Interference Mitigation

“…Specifically, mmWave massive MIMO cellular systems provide a huge trunk of the unlicensed bandwidth of the order of gigahertz to achieve ultra-high data rate communication. In practice, to strike a balance between Part of this manuscript has been accepted and presented at the IEEE ICC 2018 [1]. L. Zhao the data rate, hardware cost 1 , system complexity, and power consumption, hybrid mmWave MIMO systems are proposed for practical implementation [8], [18], [22], [24].…”

“…With a shrinking cell radius, distances from neighbouring BSs to the desired user decrease, which may lead to severe inter-cell interference to the desired user. Recently, it is also mentioned in work [29] that the received interference significantly increases when 1 The hardware cost is mainly contributed by RF, intermediate frequency (IF) and analog to digital converter/digital to analog converter (ADC/DAC) associated with each RF chain. 2 Typical mmWave inter-site-distances (ISDs) would be 100-200 meters with experienced rates ranged from a few hundreds of Mbps to a few Gbps.…”

“…Specifically, mmWave massive MIMO cellular systems provide a huge trunk of the unlicensed bandwidth of the order of gigahertz to achieve ultra-high data rate communication. In practice, to strike a balance between Part of this manuscript has been accepted and presented at the IEEE ICC 2018 [1]. L. Zhao, Z. Wei, D. W. K. Ng, and J. Yuan are with the School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney, NSW 2052, Australia (Email: lou.zhao@unsw.edu.au; zhiqiang.wei@unsw.edu.au; w.k.ng@unsw.edu.au; j.yuan@unsw.edu.au).…”

“…the data rate, hardware cost 1 , system complexity, and power consumption, hybrid mmWave MIMO systems are proposed for practical implementation [8], [18], [22], [24]. Due to the hybrid MIMO structure, the required number of radio frequency (RF) chains equipped at a base station (BS) and users are much smaller than the number of antennas equipped at the BS and users.…”

“…at the top of this page, where cos (φ l,k ), cos (∆φ l,k ), cos (θ l,k ), and cos (θ i ) are uniformly distributed over [−1,1]. Besides, they are independent with each other.…”