Rate analysis and pilot reuse design for dense small cell networks

Sun, Qiang; Wang, Jue; Jin, Shi; Xu, Chen; Gao, Xiqi; Wong, Kai-Kit

doi:10.1109/icc.2015.7248758

Cited by 7 publications

(11 citation statements)

References 9 publications

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“…This leads to channel estimation impairments known as pilot contamination [1], which has been a fundamental bottleneck of massive MIMO systems. Several techniques have been proposed to mitigate the pilot contamination effect such as time-shifted pilot protocol [43], pilot reuse design [44], [45], eigenvaluedecomposition-based method [46] and pilot contamination precoding [47]. It was shown that the effect of pilot contamination can be mitigated completely based on several critical but optimistic assumptions.…”

Section: B Channel Estimation With Pilot Contaminationmentioning

confidence: 99%

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Downlink Spectral Efficiency of Distributed Massive MIMO Systems With Linear Beamforming Under Pilot Contamination

Wang

Zhu

et al. 2018

IEEE Trans. Veh. Technol.

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Abstract-In this paper, the downlink spectral efficiency of multi-cell multi-user distributed massive MIMO systems with linear beamforming is studied in the presence of pilot contamination. According to the levels of effective channel gain information at user side, we provide the lower bound and upper bound on user ergodic achievable downlink rate. Due to the different access distance from each user to different remote antenna units, the entries of user channel vectors are no longer identically distributed in distributed massive MIMO systems, which makes the spectral efficiency analysis challenging. Using the properties of Gamma distributions together with the approximate methods for non-isotropic vectors, we derive tractable but accurate closed-form expressions for the rate bounds with maximum ratio transmission (MRT) and zero-forcing (ZF) beamforming in distributed massive MIMO systems. Based on these expressions, user ultimate achievable rates are also given when the ratio of the total number of transmit antennas to the number of users goes to infinity. It is shown that MRT and ZF beamforming achieve the same ultimate rate no matter what levels of effective channel gain information at user side. Numerical results show that ZF achieves better performance gain and faster convergence speed than MRT. When the coherence interval is large, the downlink beamforming training scheme is more preferable for the distributed massive MIMO systems.

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Section: B Channel Estimation With Pilot Contaminationmentioning

confidence: 99%

“…Thus, pilot contamination mitigation techniques, e.g., pilot scheduling in [45], can significantly increase the user achievable rate.…”

Section: Upper Bound On Ergodic Achievable Ratementioning

confidence: 99%

Downlink Spectral Efficiency of Distributed Massive MIMO Systems With Linear Beamforming Under Pilot Contamination

Wang

Zhu

et al. 2018

IEEE Trans. Veh. Technol.

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“…In [11,12], the pilot reuse (PR) technique is utilized among the macro cells to reduce the pilot overhead, while UEs within a cell use orthogonal pilots. [20] studies pilot reuse in a dense small cell network. In a two-tier HetNet with multiple small cells, massive antenna arrays and large number of UEs, we propose to apply pilot reuse among the SCs in this paper, i.e., the same set of orthogonal pilots is reused among the small cells in one macro-cell.…”

Section: Introductionmentioning

confidence: 99%

Downlink Performance of Pilot-Reused HetNet With Large-Scale Antenna Arrays

Dai

Dong

Lin

2017

IEEE Trans. Commun.

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Considering a heterogeneous network (HetNet) where both macro base station (BS) and small cell (SC) nodes are equipped with massive antennas, this paper studies the performance for multiple-input multiple-output (MIMO) downlinks when the macro and small cells share the same spectrum and hence interfere with each other. Suppose that the largescale antenna arrays at both macro BS and SC nodes employ maximum-ratio transmission (MRT) or zero-forcing transmission (ZFT) precoding, and transmit data streams to the served users simultaneously. A new pilot reuse pattern among SCs is proposed for channel estimation. Taking into account imperfect channel state information (CSI), capacity lower bounds for MRT and ZFT are derived, respectively, in closed-form expressions involving only statistical CSI. Then asymptotic analyses for massive arrays are presented under specific power scaling laws. Subsequently, two user scheduling algorithms, greedy scheduling algorithm and asymptotical scheduling algorithm (ASA), are proposed based on derived capacity lower bounds and asymptotic analyses, respectively. ASA is demonstrated to be a near optimal in the asymptotic regime and has low complexity. Finally, the derived closed-form expressions are verified to be accurate predictors of the system performance by Monte-Carlo simulations. Numerical results demonstrate the effectiveness of asymptotic analysis and proposed user scheduling schemes. Index Terms-Heterogeneous network, MIMO, large-scale antenna arrays, pilot reuse, user scheduling. Y. Dai and X. Dong are with the

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“…Pilot reuse can cause pilot contamination, which limits the quality of the channel estimation and degrades system performance. In the literature, several approaches have been introduced to mitigate pilot contamination when pilots are reused among cells for different architectures of MIMO systems, including co-located massive MIMO [11]- [13], Network MIMO [14] and small cells scenarios [15], [16]. Among these researchers, the angle of arrival (AOA)-based methods have assumed pilot reuse within the same cell in co-located massive MIMO to reduce the pilot overhead [9], [10].…”

Section: Introductionmentioning

confidence: 99%