RRH based massive MIMO with “on the Fly” pilot contamination control
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TLDR
A novel coded pilot approach is introduced, which allows each RRH unit to detect pilot collisions, and can yield densification benefits in the form of increased multiplexing gains per UL pilot dimension with respect to conventional reuse schemes and some recent approaches assigning pseudorandom pilot vectors to the active users.Abstract:
Dense large-scale antenna deployments are one of the most promising technologies for delivering very large throughputs per unit area in the downlink (DL) of cellular networks. We consider such a dense deployment involving a distributed system formed by multi-antenna remote radio head (RRH) units connected to the same fronthaul serving a geographical area. Knowledge of the DL channel between each active user and its nearby RRH antennas is most efficiently obtained at the RRHs via reciprocity based training, that is, by estimating a user's channel using uplink (UL) pilots transmitted by the user, and exploiting the UL/DL channel reciprocity. We consider aggressive pilot reuse across an RRH system, whereby a single pilot dimension is simultaneously assigned to multiple active users. We introduce a novel coded pilot approach, which allows each RRH unit to detect pilot collisions, i.e., when more than a single user in its proximity uses the same pilot dimensions. Thanks to the proposed coded pilot approach, pilot contamination can be substantially avoided. As shown, such a strategy can yield densification benefits in the form of increased multiplexing gains per UL pilot dimension with respect to conventional reuse schemes and some recent approaches assigning pseudorandom pilot vectors to the active users.read more
Citations
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Sparse Signal Processing for Grant-Free Massive Connectivity: A Future Paradigm for Random Access Protocols in the Internet of Things
TL;DR: It is argued that massive multiple-input, multiple-output (MIMO) is especially well suited for massive IoT connectivity because the device detection error can be driven to zero asymptotically in the limit as the number of antennas at the base station (BS) goes to infinity by using the multiplemeasurement vector (MMV) compressed sensing techniques.
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Random Access Protocols for Massive MIMO
TL;DR: This article addresses the need for random access by the devices to pilot sequences used for channel estimation, and shows that Massive MIMO is a main enabler to achieve fast access with high data rates, and delay-tolerant access with different data rate levels.
Proceedings ArticleDOI
Random vs Structured Pilot Assignment in Cell-Free Massive MIMO Wireless Networks
TL;DR: This paper addresses the performance improvement that structured pilot assignment policies can bring about, relative to a random pilot assignment, in cell-free massive MIMO wireless networks.
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Modified Conjugate Beamforming for Cell-Free Massive MIMO
TL;DR: This modification of conjugate beamforming for the forward link of cell-free massive MIMO networks eliminates the self-interference and yields a performance that, without forward pilots, closely approaches what would be achieved with such pilots in place.
Journal ArticleDOI
Massive MIMO Pilot Decontamination and Channel Interpolation via Wideband Sparse Channel Estimation
TL;DR: In this paper, the authors proposed a low-complexity algorithm that uses the received UL wideband pilot snapshots in an observation window comprising several coherence blocks (CBs) to obtain an estimate of the angle-delay power spread function (PSF) of the received signal.
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