Journal ArticleDOI
Making smart use of excess antennas: Massive MIMO, small cells, and TDD
TLDR
It is suggested that time division duplexing (TDD) could be a key enabler for a new heterogeneous network architecture with the potential to provide ubiquitous coverage and unprecedented spectral area efficiencies.Abstract:
In this paper, we present a vision beyond the conventional Long Term Evolution Fourth Generation (LTE-4G) evolution path and suggest that time division duplexing (TDD) could be a key enabler for a new heterogeneous network architecture with the potential to provide ubiquitous coverage and unprecedented spectral area efficiencies. This architecture is based on a cochannel deployment of macro base stations (BSs) with very large antenna arrays and a secondary tier of small cells (SCs) with a few antennas each. Both tiers employ a TDD protocol in a synchronized fashion. The resulting channel reciprocity enables not only the estimation of large-dimensional channels at the BSs, but also an implicit coordination between both tiers without the need to exchange user data or channel state information (CSI) over the backhaul. In particular, during the uplink (UL), the BSs and SCs can locally estimate the dominant interference sub-space. This knowledge can be leveraged for downlink (DL) precoding to reduce intra- and inter-tier interference. In other words, the BSs and SCs “sacrifice” some of their degrees of freedom for interference rejection. Our simulation results demonstrate that the proposed architecture and precoding scheme can achieve a very attractive rate region compared to several baseline scenarios. For example, with 100 antennas at each BS and four antennas at each SC, we observe an aggregate area throughput of 7.63 Gb/s/km2 (DL) and 8.93 Gb/s/km2 (UL) on a 20 MHz band shared by about 100 mobile devices.read more
Citations
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Journal ArticleDOI
Resource Allocation for Energy Efficiency in 5G Wireless Networks
TL;DR: The critical EE in 5G wireless networks is tackled, whose most significant challenge is due to its belonging to the fractional programming in the optimization field, i.e., nonconvex programming, which leaves many difficult tasks for improving network EE performance.
Journal ArticleDOI
Joint Resource Allocation, Placement and User Association of Multiple UAV-Mounted Base Stations With In-Band Wireless Backhaul
TL;DR: A placement algorithm that jointly optimizes the resource allocation and user association for multiple UBSs with in-band wireless backhaul is proposed using convex optimization theory and an equivalent spectrum efficiency is defined to simplify the optimization problem.
Journal ArticleDOI
Location-Aware Pilot Assignment for Massive MIMO Systems in Heterogeneous Networks
TL;DR: Simulation results demonstrate that the proposed pilot reuse scheme for massive MIMO-HetNet can support more users and increase both the uplink and the downlink sum-rate capacity, in comparison to the conventional scheme, particularly when the antenna number at the MBSs is sufficiently large.
Journal ArticleDOI
A dynamic clustering algorithm for downlink CoMP systems with multiple antenna UEs
TL;DR: A novel dynamic BS clustering algorithm with corresponding UE scheduling for downlink CoMP-JP with multiple antenna user equipments (UEs) where the additional degrees of freedom are used to suppress the residual interference by using an interference rejection combiner and allow a multi-stream transmission.
Journal ArticleDOI
A Unified Model for the Design and Analysis of Spatially-Correlated Load-Aware HetNets
TL;DR: A unified framework for the performance analysis of arbitrary-loaded downlink heterogeneous networks (HetNets) in which interfering sources are inherently spatially-correlated, which allows for relaxation of several major limitations in the existing state-of-the-art models.
References
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On Limits of Wireless Communications in a Fading Environment when UsingMultiple Antennas
G. J. Foschini,M. J. Gans +1 more
TL;DR: In this article, the authors examined the performance of using multi-element array (MEA) technology to improve the bit-rate of digital wireless communications and showed that with high probability extraordinary capacity is available.
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Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas
TL;DR: A cellular base station serves a multiplicity of single-antenna terminals over the same time-frequency interval and a complete multi-cellular analysis yields a number of mathematically exact conclusions and points to a desirable direction towards which cellular wireless could evolve.
Journal ArticleDOI
Scaling Up MIMO: Opportunities and Challenges with Very Large Arrays
Fredrik Rusek,Daniel Persson,Buon Kiong Lau,Erik G. Larsson,Thomas L. Marzetta,Fredrik Tufvesson +5 more
TL;DR: The gains in multiuser systems are even more impressive, because such systems offer the possibility to transmit simultaneously to several users and the flexibility to select what users to schedule for reception at any given point in time.