677 research outputs found
Downlink and Uplink Cell Association with Traditional Macrocells and Millimeter Wave Small Cells
Millimeter wave (mmWave) links will offer high capacity but are poor at
penetrating into or diffracting around solid objects. Thus, we consider a
hybrid cellular network with traditional sub 6 GHz macrocells coexisting with
denser mmWave small cells, where a mobile user can connect to either
opportunistically. We develop a general analytical model to characterize and
derive the uplink and downlink cell association in view of the SINR and rate
coverage probabilities in such a mixed deployment. We offer extensive
validation of these analytical results (which rely on several simplifying
assumptions) with simulation results. Using the analytical results, different
decoupled uplink and downlink cell association strategies are investigated and
their superiority is shown compared to the traditional coupled approach.
Finally, small cell biasing in mmWave is studied, and we show that
unprecedented biasing values are desirable due to the wide bandwidth.Comment: 30 pages, 9 figures. Submitted to IEEE Transactions on Wireless
Communication
Downlink and Uplink Decoupling: a Disruptive Architectural Design for 5G Networks
Cell association in cellular networks has traditionally been based on the
downlink received signal power only, despite the fact that up and downlink
transmission powers and interference levels differed significantly. This
approach was adequate in homogeneous networks with macro base stations all
having similar transmission power levels. However, with the growth of
heterogeneous networks where there is a big disparity in the transmit power of
the different base station types, this approach is highly inefficient. In this
paper, we study the notion of Downlink and Uplink Decoupling (DUDe) where the
downlink cell association is based on the downlink received power while the
uplink is based on the pathloss. We present the motivation and assess the gains
of this 5G design approach with simulations that are based on Vodafone's LTE
field trial network in a dense urban area, employing a high resolution
ray-tracing pathloss prediction and realistic traffic maps based on live
network measurements.Comment: 6 pages, 7 figures, conference paper, submitted to IEEE GLOBECOM 201
Tractable Resource Management with Uplink Decoupled Millimeter-Wave Overlay in Ultra-Dense Cellular Networks
The forthcoming 5G cellular network is expected to overlay millimeter-wave
(mmW) transmissions with the incumbent micro-wave ({\mu}W) architecture. The
overall mm-{\mu}W resource management should therefore harmonize with each
other. This paper aims at maximizing the overall downlink (DL) rate with a
minimum uplink (UL) rate constraint, and concludes: mmW tends to focus more on
DL transmissions while {\mu}W has high priority for complementing UL, under
time-division duplex (TDD) mmW operations. Such UL dedication of {\mu}W results
from the limited use of mmW UL bandwidth due to excessive power consumption
and/or high peak-to-average power ratio (PAPR) at mobile users. To further
relieve this UL bottleneck, we propose mmW UL decoupling that allows each
legacy {\mu}W base station (BS) to receive mmW signals. Its impact on mm-{\mu}W
resource management is provided in a tractable way by virtue of a novel
closed-form mm-{\mu}W spectral efficiency (SE) derivation. In an ultra-dense
cellular network (UDN), our derivation verifies mmW (or {\mu}W) SE is a
logarithmic function of BS-to-user density ratio. This strikingly simple yet
practically valid analysis is enabled by exploiting stochastic geometry in
conjunction with real three dimensional (3D) building blockage statistics in
Seoul, Korea.Comment: to appear in IEEE Transactions on Wireless Communications (17 pages,
11 figures, 1 table
A Data-Aided Channel Estimation Scheme for Decoupled Systems in Heterogeneous Networks
Uplink/downlink (UL/DL) decoupling promises more flexible cell association
and higher throughput in heterogeneous networks (HetNets), however, it hampers
the acquisition of DL channel state information (CSI) in time-division-duplex
(TDD) systems due to different base stations (BSs) connected in UL/DL. In this
paper, we propose a novel data-aided (DA) channel estimation scheme to address
this problem by utilizing decoded UL data to exploit CSI from received UL data
signal in decoupled HetNets where a massive multiple-input multiple-output BS
and dense small cell BSs are deployed. We analytically estimate BER performance
of UL decoded data, which are used to derive an approximated normalized mean
square error (NMSE) expression of the DA minimum mean square error (MMSE)
estimator. Compared with the conventional least square (LS) and MMSE, it is
shown that NMSE performances of all estimators are determined by their
signal-to-noise ratio (SNR)-like terms and there is an increment consisting of
UL data power, UL data length and BER values in the SNR-like term of DA method,
which suggests DA method outperforms the conventional ones in any scenarios.
Higher UL data power, longer UL data length and better BER performance lead to
more accurate estimated channels with DA method. Numerical results verify that
the analytical BER and NMSE results are close to the simulated ones and a
remarkable gain in both NMSE and DL rate can be achieved by DA method in
multiple scenarios with different modulations
Interference-Aware Decoupled Cell Association in Device-to-Device based 5G Networks
Cell association in cellular networks is an important aspect that impacts
network capacity and eventually quality of experience. The scope of this work
is to investigate the different and generalized cell association (CAS)
strategies for Device-to-Device (D2D) communications in a cellular network
infrastructure. To realize this, we optimize D2D-based cell association by
using the notion of uplink and downlink decoupling that was proven to offer
significant performance gains. We propose an integer linear programming (ILP)
optimization framework to achieve efficient D2D cell association that minimizes
the interference caused by D2D devices onto cellular communications in the
uplink as well as improve the D2D resource utilization efficiency. Simulation
results based on Vodafone's LTE field trial network in a dense urban scenario
highlight the performance gains and render this proposal a candidate design
approach for future 5G networks.Comment: 5 pages, 5 figures. Accepted in IEEE VTC spring 201
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