Journal of Communications and Information Networks, Vol.3, No.2, Jun. 2018
DOI: 10.1007/s41650-018-0010-9 Research paper
Priority-Based Resource Scheduling in
Hybrid-Access LTE Femtocell
S. Fouziya Sulthana, R. Nakkeeran
Abstract—Femtocell technology is an emerging solution
that is promising for improving indoor coverage problems
and enhancing cell capacity. In a femtocell network, the
overall system performance depends on the access method
utilized, which specifies whether a specific user equipment
can connect to the femtocell network. Three access meth-
ods are defined for long-term evolution (LTE) femtocell
networks: open access, closed access and hybrid access.
For fair and effective use of resources, hybrid access is
preferred. Because some of the resources are shared
among nonregistered users, it is essential to regulate their
scheduling schemes. This study investigates resource
scheduling for femtocell networks in hybrid access mode,
which gives preferential access to the high-priority traffic
of nonsubscribers. High-priority traffic metric (T
HP
)
is calculated for high-priority users, and low-priority
traffic metric (T
LP
) is calculated for low-priority users.
Then, individual sorted lists are formed for (T
HP
) and
(T
LP
). Nonsubscribers from the (T
HP
) list are allocated
initially, after which UEs from the (T
LP
) list are chosen
for allocation based on resource availability, thereby
increasing the overall average throughput of high-priority
users in a network.
Keywords—LTE, macrocell, femtocell, resource alloca-
tion, scheduling
I. INTRODUCTION
F
emtocells are considered as a favorable solution for the
emerging high-bandwidth requirements of multimedia
applications
[1,2]
. Together with advanced technologies such
as long-term evolution (LTE), it is expected that there will be
an increase in the overall network capacity. Femtocells are
small, low-power base stations that can be overlaid on existing
cellular networks
[3]
. To this end, the 3rd Generation Partner-
Manuscript received Apr. 26, 2017; accepted Sept. 19, 2017. The asso-
ciate editor coordinating the review of this paper and approving it for publi-
cation was G. D. Yu.
S. F. Sulthana, R. Nakkeeran. Department of Electronic Engineering,
School of Engineering and Technology, Pondicherry University, Puducherry
605014, India (e-mail: fouziya@pec.edu; nakkeranpu@gmail.com).
ship Project (3GPP) has initiated the deployment of hetero-
geneous networks in LTE-Advanced specifications. Hetero-
geneous networks consist of macrocells and low-power nodes
such as microcells, picocells, and femtocells
[4]
. Femtocells
are mainly developed to provide broadband connectivity in
indoor environments. The traffic generated from indoor en-
vironments suffers from poor signal quality and higher pene-
tration losses, which leads to a requirement for more resources
to guarantee the required quality of service (QoS). Femtocells
have therefore been introduced to overcome the indoor cover-
age problem and enhance the cell capacity by offloading the
traffic from macrocell Evolved Node Bs (eNodeBs). From an
operator’s point of view, this traffic offloading will lead to the
need for fewer macrocell sites, which results in huge Capital
Expenditure (CAPEX) savings and uninterrupted user experi-
ence in both indoor and outdoor environments
[5]
.
Femtocells operate in the licensed frequency bands, and
can be easily installed by consumers upon enabling small-
coverage radio-based stations, also called Home eNodeBs
(HeNodeBs). However, the extensive installation of femto-
cells can cause severe interference-related issues
[6]
. Because
macrocells and femtocells use shared spectrum, strong cross-
tier interference can exist between both the tiers. The severity
of the cross-tier interference depends significantly on the ac-
cess mechanism used in the femtocell network
[7]
. In access
control mechanisms, users can be classified as subscribers
who are registered users or nonsubscribers who are random
mobile users, depending on the connectivity privileges.
Three access methods have been proposed for femtocells
in the 3GPP specifications: closed access, open access, and
hybrid access, as shown in Fig. 1.
In closed-access mode, only subscribers are granted ac-
cess to the corresponding femtocells. Although this ac-
cess method increases the QoS of registered user equip-
ment (UE), it will result in severe interference-related is-
sues. Many studies have been performed to achieve inter-
ference mitigation, including power control
[8-11]
, spectrum-
sharing techniques
[12-14]
, and cognitive approaches
[15,16]
. In
Ref. [17], the resource-allocation problem in a two-tier or-
thogonal frequency-division multiple access (OFDMA) based
network is studied, where the femtocells employ closed-
access mode and have cognitive radio capability to sense the