632 research outputs found
On the Delay of Geographical Caching Methods in Two-Tiered Heterogeneous Networks
We consider a hierarchical network that consists of mobile users, a
two-tiered cellular network (namely small cells and macro cells) and central
routers, each of which follows a Poisson point process (PPP). In this scenario,
small cells with limited-capacity backhaul are able to cache content under a
given set of randomized caching policies and storage constraints. Moreover, we
consider three different content popularity models, namely fixed content
popularity, distance-dependent and load-dependent, in order to model the
spatio-temporal behavior of users' content request patterns. We derive
expressions for the average delay of users assuming perfect knowledge of
content popularity distributions and randomized caching policies. Although the
trend of the average delay for all three content popularity models is
essentially identical, our results show that the overall performance of
cached-enabled heterogeneous networks can be substantially improved, especially
under the load-dependent content popularity model.Comment: to be presented at IEEE SPAWC'2016, Edinburgh, U
Fronthaul-Constrained Cloud Radio Access Networks: Insights and Challenges
As a promising paradigm for fifth generation (5G) wireless communication
systems, cloud radio access networks (C-RANs) have been shown to reduce both
capital and operating expenditures, as well as to provide high spectral
efficiency (SE) and energy efficiency (EE). The fronthaul in such networks,
defined as the transmission link between a baseband unit (BBU) and a remote
radio head (RRH), requires high capacity, but is often constrained. This
article comprehensively surveys recent advances in fronthaul-constrained
C-RANs, including system architectures and key techniques. In particular, key
techniques for alleviating the impact of constrained fronthaul on SE/EE and
quality of service for users, including compression and quantization,
large-scale coordinated processing and clustering, and resource allocation
optimization, are discussed. Open issues in terms of software-defined
networking, network function virtualization, and partial centralization are
also identified.Comment: 5 Figures, accepted by IEEE Wireless Communications. arXiv admin
note: text overlap with arXiv:1407.3855 by other author
Joint Beamforming and Power Control in Coordinated Multicell: Max-Min Duality, Effective Network and Large System Transition
This paper studies joint beamforming and power control in a coordinated
multicell downlink system that serves multiple users per cell to maximize the
minimum weighted signal-to-interference-plus-noise ratio. The optimal solution
and distributed algorithm with geometrically fast convergence rate are derived
by employing the nonlinear Perron-Frobenius theory and the multicell network
duality. The iterative algorithm, though operating in a distributed manner,
still requires instantaneous power update within the coordinated cluster
through the backhaul. The backhaul information exchange and message passing may
become prohibitive with increasing number of transmit antennas and increasing
number of users. In order to derive asymptotically optimal solution, random
matrix theory is leveraged to design a distributed algorithm that only requires
statistical information. The advantage of our approach is that there is no
instantaneous power update through backhaul. Moreover, by using nonlinear
Perron-Frobenius theory and random matrix theory, an effective primal network
and an effective dual network are proposed to characterize and interpret the
asymptotic solution.Comment: Some typos in the version publised in the IEEE Transactions on
Wireless Communications are correcte
Joint Hybrid Backhaul and Access Links Design in Cloud-Radio Access Networks
The cloud-radio access network (CRAN) is expected to be the core network
architecture for next generation mobile radio systems. In this paper, we
consider the downlink of a CRAN formed of one central processor (the cloud) and
several base-station (BS), where each BS is connected to the cloud via either a
wireless or capacity-limited wireline backhaul link. The paper addresses the
joint design of the hybrid backhaul links (i.e., designing the wireline and
wireless backhaul connections from the cloud to the BSs) and the access links
(i.e., determining the sparse beamforming solution from the BSs to the users).
The paper formulates the hybrid backhaul and access link design problem by
minimizing the total network power consumption. The paper solves the problem
using a two-stage heuristic algorithm. At one stage, the sparse beamforming
solution is found using a weighted mixed `1=`2 norm minimization approach; the
correlation matrix of the quantization noise of the wireline backhaul links is
computed using the classical rate-distortion theory. At the second stage, the
transmit powers of the wireless backhaul links are found by solving a power
minimization problem subject to quality-of-service constraints, based on the
principle of conservation of rate by utilizing the rates found in the first
stage. Simulation results suggest that the performance of the proposed
algorithm approaches the global optimum solution, especially at high
signal-to-interference-plus-noise ratio (SINR).Comment: 6 pages, 3 figures, IWCPM 201
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