Abstract
Inter-cell interference has been identified as one of the major challenges of multiple-input–multiple-output (MIMO)-enabled cellular systems. This problem occurs when the same pilot sets are reused across adjacent cells to save bandwidth for data transmission. As a result, so-called pilot contamination occurs, which cannot be mitigated with an increased number of serving antennas. In this work, we proposed a partial pilot allocation scheme (PPA) to tackle the pilot contamination problem and consequently improve the uplink throughput of users in multi-cell massive MIMO systems. This was achieved by using the large-scale characteristics of the fading channel to keep users with a weak channel condition out of the effect of severe interference during the pilot allocation process. Simulation results showed that the proposed scheme outperformed both smart pilot allocation (SPA) and conventional schemes. In particular, PPA improved the uplink rate by 30% compared to the SPA—a recently proposed schema. Furthermore, our simulation results clearly showed that PPA improved the cumulative distribution function (CDF) of the signal-to-interference-plus-noise ratio (SINR) and uplink throughput.
Highlights
Massive multiple-input–multiple-output (MIMO) systems are one of the promising technologies that have conceived to meet the continuous increase in demand for high-speed data in future fifth generation (5G) wireless networks [1]
In multi-cell massive MIMO systems [9] which operate according to a synchronous TDD mode, the channel coherence block has a limited size; the number of orthogonal pilot sequences is insufficient for all users
In a multi-cell massive MIMO system which operates in the TDD mode, the τp time-frequency samples limit the number of pilot sequences Φ = [φ1, φ2, ..., φK ] T ∈ CK ×τp
Summary
Massive multiple-input–multiple-output (MIMO) systems are one of the promising technologies that have conceived to meet the continuous increase in demand for high-speed data in future fifth generation (5G) wireless networks [1]. In multi-cell massive MIMO systems [9] which operate according to a synchronous TDD mode, the channel coherence block has a limited size; the number of orthogonal pilot sequences is insufficient for all users. To solve this issue, the orthogonal pilot sequences have to be reused by each cell. The proposed scheme greatly reduces the effects of interfering users that cause a high level of interference within a typical cell of a multi-cell massive MIMO system It improves the throughput of users that are largely affected by intense pilot contamination because of their poor channel quality. Multiple-output (MIMO) system, as all users share the same pilot signal
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