Abstract
The pilot contamination caused by sharing the non-orthogonal pilots among users is considered to be a bottleneck of the massive multi-input multi-output (MIMO) systems. This paper proposes a pilot scheduling scheme based on the degradation to address this problem. Through computing the degradation of the users, the proposed scheduling assigns the optimal pilot sequence to the user who suffers from the greatest degradation in a greedy way. Moreover, the proposed scheme is further optimized with an extra set of orthogonal pilot sequences, which is called pilot scheduling scheme based on user grouping. Simulation results show that the target cell’s achievable sum rate of the proposed scheme is much higher than the random pilot scheduling (RPS) and the smart pilot assignment (SPA) schemes; also, our scheme can reduce the impact of shadowing fading on the target cell’s achievable sum rate effectively.
Highlights
Massive multi-input multi-output (MIMO) [1,2,3] is one of the key technologies in 5G, which can greatly boost the channel capacity, spectral efficiency, and connection density by utilizing a large number of antennas at the base station (BS)
7 Conclusions In this paper, a pilot scheduling scheme based on the degradation is proposed to maximize the target cell’s achievable sum rate in massive MIMO systems
By exploiting the large-scale characteristics of fading channels, the proposed scheme assigns the optimal pilot sequence to the user who suffers from greatest degradation greedily
Summary
Massive multi-input multi-output (MIMO) [1,2,3] is one of the key technologies in 5G, which can greatly boost the channel capacity, spectral efficiency, and connection density by utilizing a large number of antennas at the base station (BS). To obtain the maximum of the target cell’s achievable sum rate, exhaustive search is a simple way to find the optimal solution [24] This method is of great complexity and limited by the system coherence time; the random pilot scheduling (RPS) schemes are usually chosen instead [4]. Both RPS and SPA do not take into account the users’ uplink requirement, leading to a rate loss in the target cell’s achievable sum rate that users cannot meet the requirement of QoS adequately To solve this problem, a pilot scheduling scheme based on the performance degradation is proposed in this paper. A pilot scheduling scheme based on user grouping according to different levels of pilot contamination is introduced when an extra set of orthogonal pilot sequences is available.
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