17 research outputs found
Optimal Traffic Splitting Policy in LTE-based Heterogeneous Network
Dual Connectivity (DC) is a technique proposed to address the problem of
increased handovers in heterogeneous networks. In DC, a foreground User
Equipment (UE) with multiple transceivers has a possibility to connect to a
Macro eNodeB (MeNB) and a Small cell eNodeB (SeNB) simultaneously. In downlink
split bearer architecture of DC, a data radio bearer at MeNB gets divided into
two; one part is forwarded to the SeNB through a non-ideal backhaul link to the
UE, and the other part is forwarded by the MeNB. This may lead to an increase
in the total delay at the UE since different packets corresponding to a single
transmission may incur varying amounts of delays in the two different paths.
Since the resources in the MeNB are shared by background legacy users and
foreground users, DC may increase the blocking probability of background users.
Moreover, single connectivity to the small cell may increase the blocking
probability of foreground users. Therefore, we target to minimize the average
delay of the system subject to a constraint on the blocking probability of
background and foreground users. The optimal policy is computed and observed to
contain a threshold structure. The variation of average system delay is studied
for changes in different system parameters.Comment: Conferenc
Traffic Convexity Aware Cellular Networks: A Vehicular Heavy User Perspective
Rampant mobile traffic increase in modern cellular networks is mostly caused
by large-sized multimedia contents. Recent advancements in smart devices as
well as radio access technologies promote the consumption of bulky content,
even for people in moving vehicles, referred to as vehicular heavy users. In
this article the emergence of vehicular heavy user traffic is observed by field
experiments conducted in 2012 and 2015 in Seoul, Korea. The experiments reveal
that such traffic is becoming dominant, captured by the 8.62 times increase in
vehicular heavy user traffic while the total traffic increased 3.04 times. To
resolve this so-called vehicular heavy user problem (VHP), we propose a cell
association algorithm that exploits user demand diversity for different
velocities. This user traffic pattern is discovered first by our field trials,
which is convex-shaped over velocity, i.e. walking user traffic is less than
stationary or vehicular user traffic. As the VHP becomes severe, numerical
evaluation verifies the proposed user convexity aware association outperforms a
well-known load balancing association in practice, cell range expansion (CRE).
In addition to the cell association, several complementary techniques are
suggested in line with the technical trend toward 5G.Comment: 15 pages, 5 figures, 1 table, to appear in IEEE Wireless
Communications Magazin
Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks
Soaring capacity and coverage demands dictate that future cellular networks
need to soon migrate towards ultra-dense networks. However, network
densification comes with a host of challenges that include compromised energy
efficiency, complex interference management, cumbersome mobility management,
burdensome signaling overheads and higher backhaul costs. Interestingly, most
of the problems, that beleaguer network densification, stem from legacy
networks' one common feature i.e., tight coupling between the control and data
planes regardless of their degree of heterogeneity and cell density.
Consequently, in wake of 5G, control and data planes separation architecture
(SARC) has recently been conceived as a promising paradigm that has potential
to address most of aforementioned challenges. In this article, we review
various proposals that have been presented in literature so far to enable SARC.
More specifically, we analyze how and to what degree various SARC proposals
address the four main challenges in network densification namely: energy
efficiency, system level capacity maximization, interference management and
mobility management. We then focus on two salient features of future cellular
networks that have not yet been adapted in legacy networks at wide scale and
thus remain a hallmark of 5G, i.e., coordinated multipoint (CoMP), and
device-to-device (D2D) communications. After providing necessary background on
CoMP and D2D, we analyze how SARC can particularly act as a major enabler for
CoMP and D2D in context of 5G. This article thus serves as both a tutorial as
well as an up to date survey on SARC, CoMP and D2D. Most importantly, the
article provides an extensive outlook of challenges and opportunities that lie
at the crossroads of these three mutually entangled emerging technologies.Comment: 28 pages, 11 figures, IEEE Communications Surveys & Tutorials 201
Multipath streaming: fundamental limits and efficient algorithms
We investigate streaming over multiple links. A file is split into small
units called chunks that may be requested on the various links according to
some policy, and received after some random delay. After a start-up time called
pre-buffering time, received chunks are played at a fixed speed. There is
starvation if the chunk to be played has not yet arrived. We provide lower
bounds (fundamental limits) on the starvation probability of any policy. We
further propose simple, order-optimal policies that require no feedback. For
general delay distributions, we provide tractable upper bounds for the
starvation probability of the proposed policies, allowing to select the
pre-buffering time appropriately. We specialize our results to: (i) links that
employ CSMA or opportunistic scheduling at the packet level, (ii) links shared
with a primary user (iii) links that use fair rate sharing at the flow level.
We consider a generic model so that our results give insight into the design
and performance of media streaming over (a) wired networks with several paths
between the source and destination, (b) wireless networks featuring spectrum
aggregation and (c) multi-homed wireless networks.Comment: 24 page
An Efficient Uplink Multi-Connectivity Scheme for 5G mmWave Control Plane Applications
The millimeter wave (mmWave) frequencies offer the potential of orders of
magnitude increases in capacity for next-generation cellular systems. However,
links in mmWave networks are susceptible to blockage and may suffer from rapid
variations in quality. Connectivity to multiple cells - at mmWave and/or
traditional frequencies - is considered essential for robust communication. One
of the challenges in supporting multi-connectivity in mmWaves is the
requirement for the network to track the direction of each link in addition to
its power and timing. To address this challenge, we implement a novel uplink
measurement system that, with the joint help of a local coordinator operating
in the legacy band, guarantees continuous monitoring of the channel propagation
conditions and allows for the design of efficient control plane applications,
including handover, beam tracking and initial access. We show that an
uplink-based multi-connectivity approach enables less consuming, better
performing, faster and more stable cell selection and scheduling decisions with
respect to a traditional downlink-based standalone scheme. Moreover, we argue
that the presented framework guarantees (i) efficient tracking of the user in
the presence of the channel dynamics expected at mmWaves, and (ii) fast
reaction to situations in which the primary propagation path is blocked or not
available.Comment: Submitted for publication in IEEE Transactions on Wireless
Communications (TWC
Improved Handover Through Dual Connectivity in 5G mmWave Mobile Networks
The millimeter wave (mmWave) bands offer the possibility of orders of
magnitude greater throughput for fifth generation (5G) cellular systems.
However, since mmWave signals are highly susceptible to blockage, channel
quality on any one mmWave link can be extremely intermittent. This paper
implements a novel dual connectivity protocol that enables mobile user
equipment (UE) devices to maintain physical layer connections to 4G and 5G
cells simultaneously. A novel uplink control signaling system combined with a
local coordinator enables rapid path switching in the event of failures on any
one link. This paper provides the first comprehensive end-to-end evaluation of
handover mechanisms in mmWave cellular systems. The simulation framework
includes detailed measurement-based channel models to realistically capture
spatial dynamics of blocking events, as well as the full details of MAC, RLC
and transport protocols. Compared to conventional handover mechanisms, the
study reveals significant benefits of the proposed method under several
metrics.Comment: 16 pages, 13 figures, to appear on the 2017 IEEE JSAC Special Issue
on Millimeter Wave Communications for Future Mobile Network
A cell outage management framework for dense heterogeneous networks
In this paper, we present a novel cell outage management (COM) framework for heterogeneous networks with split control and data planes-a candidate architecture for meeting future capacity, quality-of-service, and energy efficiency demands. In such an architecture, the control and data functionalities are not necessarily handled by the same node. The control base stations (BSs) manage the transmission of control information and user equipment (UE) mobility, whereas the data BSs handle UE data. An implication of this split architecture is that an outage to a BS in one plane has to be compensated by other BSs in the same plane. Our COM framework addresses this challenge by incorporating two distinct cell outage detection (COD) algorithms to cope with the idiosyncrasies of both data and control planes. The COD algorithm for control cells leverages the relatively larger number of UEs in the control cell to gather large-scale minimization-of-drive-test report data and detects an outage by applying machine learning and anomaly detection techniques. To improve outage detection accuracy, we also investigate and compare the performance of two anomaly-detecting algorithms, i.e., k-nearest-neighbor- and local-outlier-factor-based anomaly detectors, within the control COD. On the other hand, for data cell COD, we propose a heuristic Grey-prediction-based approach, which can work with the small number of UE in the data cell, by exploiting the fact that the control BS manages UE-data BS connectivity and by receiving a periodic update of the received signal reference power statistic between the UEs and data BSs in its coverage. The detection accuracy of the heuristic data COD algorithm is further improved by exploiting the Fourier series of the residual error that is inherent to a Grey prediction model. Our COM framework integrates these two COD algorithms with a cell outage compensation (COC) algorithm that can be applied to both planes. Our COC solution utilizes an actor-critic-based reinforcement learning algorithm, which optimizes the capacity and coverage of the identified outage zone in a plane, by adjusting the antenna gain and transmission power of the surrounding BSs in that plane. The simulation results show that the proposed framework can detect both data and control cell outage and compensate for the detected outage in a reliable manner