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808 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 28, NO. 6, AUGUST 2010
Distributed Antenna-Based EPON-WiMAX
Integration and Its Cost-Efficient Cell Planning
Min-Gon Kim, Gangxiang Shen, and JungYul Choi, Members, IEEE, Bokrae Jung, Student Member, IEEE,
Hong-Shik Park, Member, IEEE, and Minho Kang, Senior Member, IEEE
Abstract—Achieving the benefits of high-capacity of optical
networks and the mobility feature of wireless networks leads to
integrate EPON and WiMAX for a promising broadband access
solution. To efficiently put both benefits together, we propose
an integration architecture of EPON-WiMAX based upon a
Distributed Antenna (DA) environment, where collaborative Base
Stations (BSs) concurrently transmit same wireless downlink
signals (specifically for multicast and broadcast services (MBSs))
to Mobile Stations (MSs) in overlapped cell coverage areas. It
helps enlarge the region of the available network coverage area
by increasing Signal to Interference and Noise Ratio (SINR)
in overlapped cell coverage areas through cooperation between
Optical Line Terminal (OLT) and Optical Network Unit (ONU)-
BS. We also present an cost-efficient cell planning to optimally
control the size of overlapped cell coverage areas for the proposed
DA-based integration architecture with a case study under
a required region of the available network coverage area in
consideration of the number of ONU-BSs and the distance
between ONU-BSs. Performance evaluation results show that
the proposed DA-based integration architecture enhances cost
efficiency compared to the Traditional Antenna (TA) (non-DA)-
based integration architecture with a similar level of spectral
efficiency of MSs.
Index Terms—EPON, WiMAX, integrated network, dis-
tributed antenna, cell planning, cost analysis.
I. INTRODUCTION
THE MODERN broadband access systems for high band-
width and operational efficiency has been considered im-
portantly due to the growing popularity of quad-play services
(e.g., video, voice, data, and mobility to a Mobile Station
(MS)). As key technologies for worldwide Fiber To The Home
(FTTH), Fiber-Wireless (FiWi) access technique variants are
being taken into consideration by utilizing the merits of both
high-capacity of optical communications and mobility feature
of wireless communications. Among optical and wireless com-
munications advances, the Ethernet Passive Optical Networks
Manuscript received 18 August 2009; revised 23 January 2010. Part of this
work was first conducted at University of Melbourne when he was there as
a visiting research engineer.
M.-G. Kim is with the public &original technology research center, Daegu
Gyeongbuk Institute of Science &Technology (DGIST), Daegu, Republic of
Korea (e-mail: kmg0803@gmail.com).
G. Shen was with University of Melbourne when he did this work,
and now he is with Ciena Corporation, Baltimore, America (e-mail:
egxshen@gmail.com).
J. Choi is with Network R&D Laboratory, KT Corporation, Daejeon,
Republic of Korea (e-mail: passjay@kt.com).
B. Jung is with the Department of Information and Communications
Engineering, Korea Advanced Institute of Science and Technology (KAIST),
Daejeon, Republic of Korea (e-mail: gaole3@kaist.ac.kr).
H.-S. Park and Minho Kang are with the Department of Electrical Engineer-
ing, Korea Advanced Institute of Science and Technology (KAIST), Daejeon,
Republic of Korea (e-mail: parkhs@ee.kaist.ac.kr, minhokang@kaist.ac.kr).
Digital Object Identifier 10.1109/JSAC.2010.100806.
(EPON) [1]-Worldwide Interoperability for Microwave Access
(WiMAX) (IEEE 802.16) [2] integration has been regarded as
a promising solution for achieving the aforementioned features
by implementing an integrated box, so called Optical Network
Unit (ONU)- Base Station (BS) including an EPON ONU and
an WiMAX BS. Fundamentally, they are well-matched with
each other on account of their service objectives, multiple
access mechanisms, and capacity hierarchy (e.g., each ONU
possessing about 65Mbps bandwidth (in case of the optical
split ratio = 1:16) is matched with the total capacity offered
by a single BS in WiMAX systems (=70Mbps over a 20MHz
channel)) [3].
Fundamentally, EPON systems [1], a part of the EPON-
WiMAX integration, can offer high bandwidth but an weak-
ness on the cost aspect due to relatively expensive deployment
cost. Particularly, the total length of the deployed optical fibers
has to be taken into account more important than other system
components, because the total deployment cost of EPON
systems is mostly affected by the cost of trenching and laying
optical fibers [4]. On the other hand, WiMAX systems [2],
the other part of the EPON-WiMAX integration, can lower
deployment cost and support mobility under limited wireless
transmission performance due to spectrum, shadowing, fading,
and InterCell Interferences (ICIs). Specifically, ICI is interfer-
ence from other wireless signals of other neighbor BSs, which
could lower the Signal to Interference and Noise Ratio (SINR),
and hence it can have a bad effect on wireless downlink
transmission performance in both aspects of the achievable
data rate of an MS and the available size of cell coverage
area.
In order to mitigate ICI in the EPON-WiMAX integration
architecture, we adopt a Distributed Antenna (DA) environ-
ment, where collaborative BSs concurrently transmit same
wireless downlink signals (specifically for Multicast Broadcast
Services (MBSs)) to MSs and thus increased SINR in over-
lapped cell coverage areas can be achieved. Consequently, it
can enhance the wireless downlink transmission performance
(e.g., the available network coverage area, the achievable data
rate of MSs, and ICI [5], [13]). In particular, under a lim-
ited region of the integrated network, the more collaborative
ONU-BSs produce the better wireless downlink transmission
performance, but it inevitably demands a longer total length of
the deployed optical fibers and thus a higher total deployment
cost of the network has to be followed [4], [5]. Owing
to this tradeoff relationship between the wireless downlink
transmission performance and total deployment cost of the
integrated network, a delicate cell planning is required for cost
efficient network design and dimensioning [5], [6]. Thus, we
0733-8716/10/$25.00 c
2010 IEEE
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KIM et al.: DISTRIBUTED ANTENNA-BASED EPON-WIMAX INTEGRATION AND ITS COST-EFFICIENT CELL PLANNING 809
develop a cost-efficient cell planning in consideration of (i)
the number of ONU-BSs and (ii) the distance between ONU-
BSs to optimally control the size of overlapped cell coverage
areas for the proposed DA-based integration architecture. It is
used to conduct a case study regarding spectral efficiency of
MSs and total deployment cost of the integrated network under
varying the required region of the network coverage area.
Performance evaluation results substantiate that the proposed
DA-based integration architecture enhances cost efficiency
compared to the TA-based integration architecture with a
similar level of spectral efficiency of MSs.
To achieve this end, this paper is structured as follows.
Related works regarding the integration of FiWi access tech-
niques and DA environments are described in Section 2.
Section 3 introduces the integration architecture based upon
the DA environment on the aspect of network coverage area
compared to the TA environment. The problem definition, and
transmission and cost models for evaluating the performance
of the proposed DA-based integration architecture compared to
the TA-based integration architecture are presented in Section
4. Based upon these models, performance evaluation including
comparison between the DA and TA environments and a case
study is shown in Section 5. Finally, Section 6 concludes this
paper.
II. RELATED WORKS
Much research effort has been carried out on the integra-
tion of FiWi access techniques in viewpoint of the physical
layer [7], the integrated MAC layer pertaining to bandwidth
allocation and scheduling [8]–[10], wireless communications
network perspectives [11]–[13], and architecture and scenarios
perspectives [3], [14]. First, in the physical layer, a new
modulation scheme, so called Radio-over-Fiber (RoF) was
introduced by using a single modulator to provide both wired
and wireless services concurrently [7]. It made it possible
to physically reduce the gap between optical and wireless
sides. However, the RoF scheme is not fully standardized
yet and not widely deployed to date. Second, in the MAC
layer, an optimal utility-based bandwidth allocation scheme
for video-on-demand (VoD) services [8] and a QoS-aware
dynamic bandwidth allocation (DBA) scheme under the con-
cept of a Combined ONU-BS (COB) [9] were proposed over
an integrated optical and WiMAX networks. In addition, a
QoS-aware scheduling scheme in a Hybrid ONU-BS (HOB)
architecture was investigated [10]. Bandwidth allocation and
scheduling in the MAC layer is well advanced for support-
ing the defined QoS types in optical and wireless networks
simultaneously. Third, in wireless communications network
perspectives, different types of FiWi networks focusing on
the placement of mesh points were proposed in Wireless
Mesh Networks (WMN) [11], [12]. Besides, advanced coding
techniques (e.g., Space Time Coding (STC) [23]) for improv-
ing perceived SINRs of MSs for better wireless downlink
transmission performance were adopted for IPTV services
[13]. Finally, the architecture issues arisen in the integration
of EPON and WiMAX were insightfully discussed in [3], and
several scenarios for the integration of FiWi access techniques
in an Independent ONU-BS (IOB) architecture was proposed
[14]. As presented in the aforementioned studies, it is obvious
that there have been some considerations for reducing the gap
between optical and wireless sides but not a consideration for
deployment cost management, one of the most important fac-
tors for practical success to deploy broadband access networks.
Only recently were there studies that tried to minimize the total
deployment cost of PON networks [4], [22]. Thus, minimizing
the total deployment cost of the integrated network need to be
considered importantly.
For performance enhancement of the EPON-WiMAX in-
tegration, it is available to apply some research studies on
enhancing DA techniques in a wireless environment [13]
including two types of transmission: Cooperative Single Cell
Transmission (CSCT) [15], [16] that ONU-BSs transmit data
only to User Equipments (UEs) within their cell coverage by
controlling the transmission according to the transmissions
of other ONU-BSs, and Cooperative Multi-Cell Transmission
(CMCT) [17], [18] that data is routed to and transmitted by
other ONU-BSs. DA techniques can expand the available size
of the network coverage area by letting collaborative BSs
with DAs concurrently transmit wireless downlink signals to
MSs for mitigation of ICI in overlapped cell coverage areas
[5], [13]. However, under a limited region of the integrated
network, the more collaborative ONU-BSs produce the better
wireless downlink transmission performance, but it inevitably
demands a longer total length of the deployed optical fibers
and thus a higher total deployment cost of the network has
to be followed [4], [5]. Hence, it is essential to consider
total deployment cost because of the tradeoff relationship
between those in the integrated networks. As a consequence,
an cost-efficient cell planning, which reduces both the number
of ONU-BSs and the distance between ONU-BSs in the
integrated network for the reduction of the total deployed
length of optical fibers, is imperative to create synergistic
effects on enhancement of cost efficiency [5]. Therefore, in
the following sections, the DA-based integration architecture
and how to plan cells with a newly proposed cost efficiency
evaluator will be presented.
III. DISTRIBUTED ANTENNA-BASED INTEGRATION
ARCHITECTURE
A. Components and Operations
The major components of an integrated EPON-WiMAX
network include an OLT, an optical splitter, optical fibers,
and ONU-BSs. The OLT located in the Central Office (CO)
is connected with multiple ONU-BSs via an optical splitter.
It has powerful computational capability to perform traffic
management to and from ONU-BSs, including a classifier to
divide packets into their corresponding queues and a scheduler
to schedule packets in the queues. The optical fibers from the
OLT are connected to the splitter and fans out to multiple
optical drop fibers connected to ONU-BSs for supporting the
connected ONU-BSs (typically, the optical split ratio ranges
from 1:4, 1:8, 1:16, 1:32, 1:64, to up to 1:128; namely, a 1:N
optical splitter means that up to N ONU-BSs can be connected
to the splitter), as illustrated in Fig. 1. Due to the power budget
in the EPON, the limited number of splitting ratio may be
allowed, which directly influence on the maximum number of
ONU-BSs in the EPON.
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810 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 28, NO. 6, AUGUST 2010
Optical
Line
Terminal
(OLT)
ONU-BS0
ONU-BS2
ONU-BS1
ONU-BS3ONU-BS4
ONU-BS5ONU-BS6
20km
1:N
Splitter
Cell coverage area
Optical line
Fig. 1. Distributed Antenna (DA)-based integration architecture for broadcast access services.
The ONU-BS acting as a hybrid device, the key component
of the EPON-WiMAX integration, includes the functions of an
ONU in EPON systems and a BS in WiMAX systems so that it
reduces the gap between EPON systems and WiMAX systems.
In the literature survey, there are three types of ONU-BSs:
(i) Independent ONU-BS (IOB) [3], which directly connects
an ONU to a BS and thus lets the scheduling performed
independently with lower device cost (i.e., the IOB can not
guarantee the required Service Level Agreement (SLA) for
users and bandwidth efficiency); (ii) Combined ONU-BS
(COB) [9], which logically connects an ONU to a BS with
a WiMAX-EPON (WE) bridge, a physical joint controller
(JC), and thus lets the scheduling performed centrally (i.e.,
the COB can guarantee the required SLA for users and
bandwidth efficiency); and (iii) Hybrid ONU-BS (HOB) [3],
which physically connects an ONU to a BS with a logical
JC, and thus lets the scheduling performed centrally (i.e., its
effects are same with the COB and lower device cost can
be achieved than the COB). For tht DA-based integration
architecture, all types of the ONU-BSs can be adopted,
because the features of those are only related to cost, QoS
mapping between EPON and WiMAX for guaranteeing SLA,
and bandwidth utilization perspectives, but not the wireless
downlink transmission performance.
In order to implement a DA environment on the integration
architecture, a set of cooperations between an OLT and ONU-
BSs has to be defined. Basically, BS-user (BU) association
(between each MS (user) and a set of ONU-BSs) and rate
assignment (selected by the OLT about transmission rate
defining the modulation scheme taken by ONU-BSs) need
to be implemented. Moreover, when an ONU-BS recognizes
that an MS is leaving (or subject to a bad channel for some
period of time) depending on the minimum perceived power
at the MS that an ONU-BS is responsible for, it issues a
tear-down request to the OLT. Then, for the power break
down mechanism, the OLT will reconfigure the modulation
scheme and power breakdown for the remaining associated
ONU-BSs of the MS. To achieve the periodic reconfiguration,
the OLT periodically collects a report from each ONU-BS,
which contains a list of all the active MSs identified by the
ONU-BS with their relatively long-term SINR levels. The
OLT then performs BU reassociation and rate reassignment,
as well as power breakdown. Each ONU-BS dynamically
adjusts power for the MSs to compensate for the short-term
channel condition fluctuation on account of mobility and any
possible turbulence. This is referred to as dynamic power
allocation, and has to be designed jointly with the scheduling
policy. Therefore, based on these operations, the integration
architecture can support DA techniques.
B. Benefit of a Distributed Antenna (DA) environment on
network coverage area
The main benefit of a DA environment is to enable to
expand network coverage area, depicted in Fig. 2. Differing
from a TA environment, where a single associated ONU-BS
transmits a wireless downlink signal to an MS, a DA envi-
ronment is based upon a Space Time Coding (STC) technique
[23]. It is a method employed to improve the reliability of
wireless downlink transmission in wireless communications
systems using multiple DAs of collaborative ONU-BSs [13].
It transmits multiple and redundant copies of a data stream
to the MS between transmission and reception in a good
enough state to allow reliable decoding. Therefore, MSs in
overlapped cell coverage areas of several collaborative ONU-
BSs can take much more aggressive modulation and coding
ratio (i.e., much better SINRs of MSs can be achieved) due
to the concurrently transmitted wireless downlink signals of
collaborative ONU-BSs. Then, the achievable data rates of
MSs can be significantly increased, although DA techniques
will definitely consume resources from all of the collaborative
ONU-BSs. In addition, the available network coverage area
can be expended under a DA environment compared to a TA
environment, because some parts out of the network coverage
area could be transferred to a part of the network coverage
area. This mostly comes from the fact that the SINRs of MSs
at the edges of the overlapped cell coverage areas increase, as
depicted in Fig. 2. Consequently, for cost efficient deployment
of the integrated network under a required region of network
coverage area, these positive effects of a DA environment on
the wireless downlink transmission performance, specifically
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KIM et al.: DISTRIBUTED ANTENNA-BASED EPON-WIMAX INTEGRATION AND ITS COST-EFFICIENT CELL PLANNING 811
ONU-BS 1ONU-BS 2
MS0 at Spot 0
MS2 at Spot 2
Expanded network coverage areas
Space Time Code (STC) 0, 1, and 2 are orthogonal
STC2
STC1
ONU-BS 0
MS1 at Spot 1
STC0
Fig. 2. Downstream data transmission operation and effects of a DA
environment on network coverage area.
the expansion of the available network coverage area, can be
applicable to the DA-based integration architecture.
The detailed examples of the wireless downlink transmis-
sion operation regarding the achievable data rate of an MS
under DA and TA environments are as follows. Basically,
the wireless downlink transmission operation under a DA
environment in non-overlapped cell coverage areas is the
same as that under a Traditional Antenna (TA) environment;
namely, the key difference between DA and TA environments
comes from the transmission in overlapped cell coverage areas.
According to the location of an MS, the transmission operation
can be categorized into three: 1) Spot 0, where MS0is in a
non-overlapped cell coverage area; 2) Spot 1, where MS1is
in an area overlapped by the cell coverage areas of two ONU-
BSs; and 3) Spot 2, where MS2is in an area overlapped by
the cell coverage areas of three ONU-BSs as depicted in Fig.
2.
1) MS0at Spot 0 in a non-overlapped cell coverage area
supported by a single ONU-BS: Since there is no difference
between the wireless donwlink transmission operations under
DA and TA environments at Spot 0 due to the fact that
there is only one associated ONU-BS (i.e., ONU-BS0is
associated), the achievable data rate of MS0at Spot 0 under
both environments (DRDA
0and DRTA
0) is given by:
DRDA
0=DRTA
0=B·log2(1 + P0
N0
).(1)
where Bis the bandwidth of the channel in Hertz (Hz).
2) MS1at Spot 1 in an area overlapped by the cell coverage
areas of two ONU-BSs: Since ICI due to power leakage from
one cell to another in an overlapped cell coverage area under
a TA environment can have a negative impact on the SINRs
of MSs, such as the MS1at Spot 1. Thus, the achievable data
rate of MS1at Spot 1 (DRTA
1) under a TA environment is
given by:
DRTA
1=B·(log2(1+ P0
P1+N0
)+log2(1+ P1
P0+N0
)).(2)
On the opposite, under a DA environment, the DAs of col-
laborative ONU-BSs joins the wireless downlink transmission
to MS1, and thus the achievable data rate of MS1at Spot 1
(DRDA
1) is achieved by:
DRDA
1=B·log2(1 + P0+P1
N0
).(3)
3) MS2at Spot 2 in an area overlapped by the cell coverage
areas of three ONU-BSs: Similar to the case at Spot 1, other
wireless signals are regarded as a part of ICI. Then, the
achievable data rate of MS2at Spot 2 under a TA environment
(DRTA
2) is given by:
DRTA
2=B·(log2(1 + P0
P1+P2+N0
)+ (4)
log2(1 + P1
P0+P2+N0
)+log2(1 + P2
P0+P1+N0
)).
Unlikely, the achievable data rate of MS2at Spot 2 under
a DA environment (DRDA
2) is given by:
DRDA
2=B·log2(1 + P0+P1+P2
N0
).(5)
IV. MATHEMAT I C A L MODELS FOR CELL PLANNING
Cell planning in the integrated network is for achieving
target performance gains under limited environments including
the optimal placement and number of network devices, and
fiber layout (the number of ONU-BSs (n) and the distance
between ONU-BSs (d)). Particularly, under a limited region
of the integrated network, the more collaborative ONU-BSs
produce the better wireless downlink transmission perfor-
mance, but it inevitably demands a longer total length of the
deployed optical fibers and thus a higher total deployment
cost of the integrated network has to be followed [4], [5].
Therefore, in order to evaluate the total deployment cost and
the total achievable data rate supported by the integrated
network, the following models (e.g., IV.A. cost model for
the integration architecture and IV.B. transmission model for
WiMAX systems) will be presented, and then a cost-efficient
cell planning method will be shown with a new cost efficiency
evaluator.
A. Cost Model for the Integration Architecture
The total deployment cost for the integrated network in-
cluding the OLT, the splitter, ONU-BSs, and optical fibers
is given by the following factors: (a) the cost of the OLT,
(COLT ) including uplink line card costs, downlink line card
costs, fixed costs for a router, and site rentals; (b) the cost of
trenching and laying fibers between the OLT and the splitter
(per kilometer) (CA
inst) including ducts and tubes; (c) the cost
of the optical splitter (Cs); (d) the cost of trenching and laying
fibers between the splitter and ONU-BSs (CB
inst) including
ducts and tubes; and (e) the cost of ONU-BSs (CN) including
site rentals. Since there is no relationship between the wireless
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812 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 28, NO. 6, AUGUST 2010
downlink transmission performance and the locations of the
OLT and the splitter, optimizing the locations are not included
in a part of the cost model, and thus the location of splitter
is voluntarily set to the center of in the integrated network.
With the aforementioned considerations and assumptions, a
mathematical model is presented as follows [4].
•Parameters:
◦x0,y0: Position coordinates of the OLT.
◦xs,ys: Position coordinates of the splitter.
◦xi,yi: Position coordinates of the ith ONU-BS.
◦α: The cost of the OLT including uplink line card costs,
downlink line card costs, router costs, and site rentals. For
simplicity, the cost of every line card is identical.
◦β: The cost of each splitter port. For simplicity, the cost
of every outlet port is identical.
◦γ: The cost of an ONU-BS including site rentals.
◦δ: The cost of trenching and laying fibers (per kilometer).
For simplicity, fibers are deployed under roads and thus site
rentals for fibers are not included.
◦θ: The cost of fiber cable including ducts and tubes (per
kilometer).
•Var i ab l es:
◦DCO (=(x0−xs)2+(y0−ys)2): The distance from
the OLT to the splitter.
◦Di(=(xs−xi)2+(ys−yi)2): The distance from the
splitter to the ith ONU-BS.
Depending on the number of ONU-BSs and the distance
between ONU-BSs, the total deployment cost of the integrated
network (CT) is given by:
CT(n, d)=COLT +CA
inst +Cs+CB
inst +CN(6)
=α+(δ+θ)DCO +
n
i
β+
n
i
((δ+θ)·Di+γ),
where nis the number of ONU-BSs, and dis the distance
between ONU-BSs. Therefore, one of the performance metrics
with respect to the number of ONU-BSs and the distance
between ONU-BSs, the total deployment cost of the integrated
network can be obtained.
B. Transmission Model for WiMAX Systems
A radio propagation model for WiMAX systems, based
upon a large-scale propagation model by path-loss power law,
is adopted to analyze DA and TA performances. Thus, the
average signal power received from the ith ONU-BS to the
location of an MS (x, y)(PA
i(x, y)) is obtained as [25]:
PA
i(x, y)=K·(di
d0
)e,(7)
where diis the distance from the ith ONU-BS (xi,yi)to
the location of an MS (=(x−xi)2+(y−yi)2), d0is the
reference distance, Kis an arbitrary constant (which depends
on the transmitted power, the transmitter, receiver antenna
gain, and the frequency), and eis the path-loss exponent (=2
in free space).
Under a DA environment, two or more collaborative ONU-
BSs may communicate with a single MS simultaneously, and
thus the SINR of an MS under a DA environment at the
location (x, y)(γDA(x, y )) is given by:
γDA(x, y)= iPA
i(x, y)
N0
,(8)
where N0is the channel noise power.
In contrast, the SINR of an MS from the ith associated
ONU-BS under a TA environment at the location (x, y )
(γTA(x, y)) is given by:
γTA
i(x, y)= PA
i(x, y)
j(j=i)PA
j(x, y)+N0
.(9)
Under a DA environment, there is only one chance to send
data from all of the collaborative ONU-BSs to an MS in an
overlapped cell coverage area. Therefore, through Shannon’s
result, the achievable data rate at the location of an MS (x, y)
under a DA environment (DRDA(x, y)) is expressed as:
DRDA(x, y)=B·log2(1 + γDA(x, y)),(10)
where Bis the bandwidth of the channel in Hz.
Differing from a DA environment, all of the ONU-BSs
can transmit wireless signals to their associated MSs in an
overlapped cell coverage area. So, the achievable data rate
at the location of an MS (x, y )under a TA environment
(DRTA(x, y)) is given by:
DRTA(x, y)=
i
B·log2(1 + γTA(x, y)).(11)
Then, for evaluation of the wireless downlink transmission
performance, the total achievable data rate supported by the
integrated network is given by:
DRT(n, d)=∞
−∞ ∞
−∞
DR(x, y)dxdy, (12)
where nis the number of ONU-BSs, dis the distance
between ONU-BSs, and DR(x, y)is either DRDA(x, y)or
DRTA(x, y)according to each transmission environment. As
a result, one of the performance metrics with respect to the
number of ONU-BSs and the distance between ONU-BSs, the
total achievable data rate supported by the integrated network,
can be obtained.
C. Cost Efficiency Evaluator
For measuring cost efficiency of the integrated network
(i.e., the total achievable data rate supported by the integrated
network over the total deployment cost of the integrated
network under predefined nand d), we introduce a cost
efficiency evaluator (Z(n, d)):
Z(n, d)= DRT(n, d)
CT(n, d),(13)
where nis the number of ONU-BSs (decided by the required
region of the network coverage area), and dis the distance
between ONU-BSs (decided by applying this evaluator).
Now, we can optimally conduct a cost-efficient cell planning
in consideration of cost efficiency of the integrated network.
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KIM et al.: DISTRIBUTED ANTENNA-BASED EPON-WIMAX INTEGRATION AND ITS COST-EFFICIENT CELL PLANNING 813
(e) 19 ONU-BSs:
Octagon
d
(a) 4 ONU-BSs:
Diamond
d
(b) 6 ONU-BSs:
Triangle
d
(d) 9 ONU-BSs:
Diamond
d
(c) 7 ONU-BSs:
Octagon
d
Cell coverage area
The location of the splitter
Fig. 3. Basic examples of network topologies (d: the distance between
ONU-BSs).
V. P ERFORMANCE EVA L U AT I O N
A. Assumptions
To analyze the performance of a DA environment regarding
the wireless downlink transmission performance and total
deployment cost compared to that of a TA environment, it is
assumed that the size of the area to be evaluated is divided by
discrete rectangular units (each unit of area (U)). According
to a predefined number of ONU-BSs, the shape of the network
topology is set variously in consideration of several cases of
wireless downlink transmission and cost, as shown in Fig. 3.
To illustrate, in cases where the number of ONU-BSs is 3,
6, or 10, the network topology is organized by a triangular
shape. Also, in cases where the number of ONU-BSs is 4,
9, or 16, the network topology is organized in a diamond
shape. Lastly, in cases where the number of ONU-BSs is 7
or 19, an octagonal shape is adopted as the network topology.
Based upon the system parameters in Table V-A, only wireless
downlink transmission performance is put into consideration
because there is no difference of wireless uplink transmission
performances between under DA and TA environments. In
each network topology, the ONU-BS providing the strongest
RSS under a TA environment is selected as the associated
ONU-BS without concerning about handovers of MSs.
B. Evaluation Metrics for Wireless Downlink Transmission
Performance
To express enhancement degree of the wireless downlink
transmission performance under both DA and TA environ-
ments, two evaluation metrics are defined as follows:
(i) The total achievable data rate supported by an
ONU-BS (DRA); this can be obtained from dividing the
total achievable data rate supported by the integrated network
(DRT(n, d)from Equ. (12)) by the number of ONU-BSs.
Namely, this metric is for showing the total achievable data
rate supported by an ONU-BS in the integrated network under
apredefined condition.
TAB L E I
SYSTEM PARAMETERS
Symbol Description Value Unit
PTx Transmitter output power 64 watts
PL
FS Path loss 34.5+35log10DLdB
FSShadow fading None -
GTx,A Tx antenna gain 10 dBi
GRx,A Rx antenna gain 0dBi
NTx Number of Tx antennas 1 -
NRx Number of Rx antennas 1 -
SRx Receiver sensitivity -90 dBm
BW Channel bandwidth 107Hz
DSOFDM symbol duration 102.9 µs
TSUseful symbol time 91.4 µs
TGGuard time (12.5%)11.4 µs
DL:UL -28:9 -
PN0Noise power -104 dBm
Atot Total evaluated area 100km·100km -
UBasic unit of area 100m·100m -
AMIN Minimum position coordinates in Atot 0 -
AMAX Maximum position coordinates in Atot 1000 -
SINRcRequired SINR for coverage 8dB
DRA(n, d)= DRT(n, d)
n,(14)
where nis the number of ONU-BSs and dis the distance
between ONU-BSs.
(ii) The total available size of a cell coverage area
supported by an ONU-BS (CCA); the total available size of
network coverage area (CCT) is given by counting the number
of units of an area whose SINR is greater than SINRc(this
threshold value decides that each Ucan be recognized as a
part of network coverage area) in the integrated network.
CCT=
AMAX
x=AMIN
AMAX
y=AMIN
(CCT+1),for γ(x, y)≥SINRc,
(15)
where γ(x, y)is γDA(x, y )or γTA(x, y)according to each
transmission environment, and the initial value of CCTis set
to 0.
Then, CCA(n, d)is obtained from dividing CCTby n
within it. In other words, this metric is for presenting
CCA(n, d)in the integrated network under a predefined
condition.
CCA(n, d)= CCT(n, d)
n,(16)
where nis the number of ONU-BSs and dis the distance
between ONU-BSs.
C. Wireless Downlink Transmission Performance and Cost
Efficiency
The total available size of a cell coverage area supported
by an ONU-BS (CCA) and the total achievable data rate
supported by an ONU-BS (DRA) are shown in Figs. 4
and 5, respectively. As expected, in the overall range of d
except the distances of more than 6 km, the CCAunder
a DA environment is much greater than that under a TA
environment. This implies that some areas out at the edge of
a overlapped cell coverage area, whose SINR are lower than
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814 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 28, NO. 6, AUGUST 2010
1 2 3 4 5 6 7 8 9 10
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Distance between ONU−BSs (km)
CCA (U)
DA (n=6)
DA (n=10)
DA (n=15)
TA (n=6)
TA (n=10)
TA (n=15)
(a) Triangle network topology
1 2 3 4 5 6 7 8 9 10
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Distance between ONU−BSs (km)
CCA (U)
DA (n=4)
DA (n=9)
DA (n=16)
TA (n=4)
TA (n=9)
TA (n=16)
(b) Diamond network topology
1 2 3 4 5 6 7 8 9 10
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Distance between ONU−BSs (km)
CCA (U)
DA (n=7)
DA (n=19)
TA (n=7)
TA (n=19)
(c) Octagon network topology
Fig. 4. Comparison of DA and TA environments regarding the total available
size of a cell coverage area supported by an ONU-BS (CCA) (n: the number
of ONU-BSs).
SINRc, could be transferred to a part of a network coverage
area, as presented in Fig. 2. In addition, the DRAunder a DA
environment is better than the DRAunder an TA environment.
This is mostly due to the fact that neighbor ONU-BSs can
take a much more aggressive modulation and coding ratio,
although doing so will definitely consume resources from all
of the collaborative ONU-BSs. As a result of the observation
of the positive effects on CCAand DRA, the best performance
can be achieved under situations where the distance between
1 2 3 4 5 6 7 8 9 10
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2x 1011
Distance between ONU−BSs (km)
DRA (bps/cell)
DA (n=6)
DA (n=10)
DA (n=15)
TA (n=6)
TA (n=10)
TA (n=15)
(a) Triangle network topology
1 2 3 4 5 6 7 8 9 10
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2x 1011
Distance between ONU−BSs (km)
DRA (bps/cell)
DA (n=4)
DA (n=9)
DA (n=16)
TA (n=4)
TA (n=9)
TA (n=16)
(b) Diamond network topology
1 2 3 4 5 6 7 8 9 10
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2x 1011
Distance between ONU−BSs (km)
DRA (bps/cell)
DA (n=7)
DA (n=19)
TA (n=7)
TA (n=19)
(c) Octagon network topology
Fig. 5. Comparison of DA and TA environments regarding the total
achievable data rate supported by an ONU-BS (DRA) (n: the number of
ONU-BSs).
ONU-BSs is similar with the diameter of the cell coverage
area of an ONU-BS (e.g., about 5 km).
Fig. 6 presents the total deployment cost of the integrated
network according to the number of ONU-BSs (n)andthe
distance between ONU-BSs (d), which is achieved through
Equ. (6). To begin with, the following cost factors are assumed
for the evaluation: the cost of the OLT including site rentals
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KIM et al.: DISTRIBUTED ANTENNA-BASED EPON-WIMAX INTEGRATION AND ITS COST-EFFICIENT CELL PLANNING 815
1 2 3 4 5 6 7 8 9 10
0
1
2
3
4
5
6
7x 106
Distance between ONU−BSs (km)
Total deployment cost ($)
n=19
n=16
n=15
n=10
n=9
n=7
n=6
n=4
Fig. 6. Total deployment cost of the integrated network ($) (n: the number
of ONU-BSs).
(α)is$28,000, the cost of each splitter port (β)is$100, the
cost of an ONU-BS including site rentals (γ)is$40,000, the
cost of trenching and laying fiber is (δ)$16,000/km,and
the cost of fiber including duct and tube (θ)is$4,000/km
[26], [27]. When d increases, the cost also increases due to
increasing the cost of trenching and laying fibers. Hence, it
is revealed that the total deployment cost is mainly affected
by the total length of deployed optical fibers in the integrated
network.
Fig. 7 presents cost efficiency evaluator (Z), which eval-
uates the cost efficiency of the integrated network in con-
sideration of the total achievable data rate supported by the
integrated network over the total deployment cost of the
integrated network, under DA and TA environments. Since the
total achievable data rate supported by the integrated network
depending on djust increases until reaching a certain degree
(e.g., when dis about 5km, as presented in Fig. 5) and the total
deployment cost linearly increases due to the increase of the
total length of deployed optical fibers, the maximum point of
Zis mostly d=between 2 to 4 km under a DA environment.
On the other hand, under a TA environment, the maximum
point of Zis d=5, because interferences from other wireless
downlink signals decrease significantly. However, from this
point, the Zdecreases due to the fact that there is increased
total deployment cost of the integrated network and no change
in the total achievable data rate supported by the integrated
network.
D. Case Study under the Required Size of Network Coverage
Area
Based on Z, a case study (Fig. 8) that finds the optimal
solution under the required size of network coverage area is
conducted to examine the DA-based integration architecture
about the average spectral efficiency of MSs for wireless
downlink transmission and the total deployment cost of the
integrated network. In particular, the cost efficiency improve-
ment by initiating cooperative transmission among DAs of
ONU-BSs is investigated. Fundamentally, this solution is
1 2 3 4 5 6 7 8 9 10
0
0.5
1
1.5
2
2.5 x 106
Distance between ONU−BSs (km)
Z (bps/$)
n=4
n=6
n=7
n=9
n=10
n=15
n=16
n=19
Maximum point
(a) A DA environment
1 2 3 4 5 6 7 8 9 10
0
0.5
1
1.5
2
2.5 x 106
Distance between ONU−BSs (km)
Z (bps/$)
n=4
n=6
n=7
n=9
n=10
n=15
n=16
n=19
Maximum point
(b) A TA environment
Fig. 7. Comparison of DA and TA environments regarding cost efficiency of
the integrated network (Z) (maximum point: the highest cost efficiency under
each n).
found with the following consideration; since the diameter of
a single ONU-BS is about 4.5km under the system parameters
shown in Table I, the distance between ONU-BSs is limited to
4km so that every cell coverage area is continuously connected
with cell coverage areas of other ONU-BSs. In addition, this
is conducted with varying the required region of a network
coverage area from 5000 to 20000U. In the overall range of
the required region, the total deployment cost under a DA
environment are positively enhanced compared to that under
a TA environment while keeping reasonable spectral efficiency
due to the effect of the increased SINR based upon the ONU-
BS cooperation. To exemplify, when the required region of
network coverage area is set to 5000U, the distance between
ONU-BSs under a DA environment is 4 and smaller than that
of a TA environment. Specifically, when the required region
of network coverage area is larger, the number of ONU-BSs
or the distance between ONU-BSs under a DA environment is
more decreased than that under a TA environment. This means
that increasing the overlapped cell coverage areas causes
increasing of the positive effects of a DA environment.
VI. CONCLUSION
In this paper, we proposed a Distributed Antenna (DA)-
based EPON-WiMAX integration architecture with a cost-
efficient cell planning for enhancement of cost efficiency of the
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816 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 28, NO. 6, AUGUST 2010
5000 10000 15000 20000
0
1
2
3
4
5
6
7
8
A required region of network coverage area (U)
Spectral efficiency (bps/Hz)
DA
TA
(a) The average spectral efficiency of MSs for wireless downlink transmis-
sion
5000 10000 15000 20000
0
0.5
1
1.5
2
2.5
3
3.5
4x 106
A required region of network coverage area (U)
Total deployment cost ($)
DA
TA
(4,4)
(4,3)
(9,4)
(10,4)
(15,4)
(10,4)
(15,4)
(19,4)
(n,d)=(the number of ONU−BSs, the distance between ONU−BSs)
(b) Total deployment cost of the integrated network
Fig. 8. Comparison of DA and TA environments regarding spectral efficiency
and the total deployment cost perspectives under a required region of network
coverage area.
integrated network. Fundamentally, the proposed DA-based
integration architecture can enlarge the available network
coverage area and provision the achievable data rate than
a TA environment, and thus it can support more Mobile
Stations (MSs). Then, a DA environment could generate more
revenue without increasing operating expenditure (OPEX)
due to similar conditions including power consumption, form
factor, etc. Besides, a cost-efficient cell planning with a case
study presented the enhanced total deployment cost gain
of the integrated network with a similar level of spectral
efficiency of Mobile Stations (MSs) for wireless downlink
transmission under a required region of network coverage
area, as a part of applying the proposed DA-based integration
architecture. Therefore, the DA-based integrated network is
expected to be one of the promising solutions for modern
broadband access networks supplying quad-play services. In
addition, the study for the DA-based integration architecture
can make the synergy effect between optical and wireless
sides to each other in consideration of two key issues: the
wireless downlink transmission performance for multicast and
broadcast services (MBSs) in wireless networks and total
deployment cost efficiency in optical networks.
ACKNOWLEDGMENT
This work was supported in part by the Development Man-
made Disaster Prevention Technology grant funded by the Ko-
rea Government (NEMA; National Emergency Management
Agency) (No. Nema−09−MD−06), the MKE (Ministry of
Knowledge Economy), Korea, under the ITRC (Information
Technology Research Center) support program supervised
by the NIPA (National IT Promotion Agency)(NIPA-2010-
(C1090-1011-0013)), and the IT R&D program of MKE
KEIT [2009-F-057-01, Large-scale wireless-PON convergence
technology utilizing network coding].
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Min-Gon Kim is a research engineer with Public
and Original Technology Research center, Daegu
Gyeongbuk Institute of Science and Technology
(DGIST). Before joining DGIST, he received his
BS degree from Ajou University, Korea, in 2004,
and his Ph.D degree (Integrated MS and Ph.D pro-
gram) from Korea Advanced Institute of Science and
Technology (KAIST), Korea, in 2009, respectively.
As a part of his research experience, he worked for
research development laboratory at Miritek in 2005,
where he researched implementation of testbed for
optical networks. Besides, he visited the Center for the Ultra-Broadband
Information Network (CUBIN), University of Melbourne, Australia, for
overseas exchange program in 2008 for integration of optical and wireless
access networks. He was nominated Marquis Who’s Who in the World 2009
and 2010. His research interests are management and applications of wireless
networks including practical applications of WPAN, mobility management of
WLAN, and management enhancement and extension WMAN.
Gangxiang Shen (S’98-M’99) is a Lead Engineer
with Ciena US. Before he joined Ciena, he was
an Australian Postdoctoral Fellow (APD) and ARC
Research Fellow with ARC Special Research Center
for Ultra-Broadband Information Networks, Depart-
ment of Electrical Engineering, University of Mel-
bourne, Australia. He received his Ph.D. from the
Department of Electrical and Computer Engineering,
University of Alberta, Canada, in January 2006.
He received his M.Sc. from Nanyang Technolog-
ical University in Singapore and his B.Eng. from
Zhejiang University in P. R. China. His research interests are in network
survivability, optical networks, and wireless networks. He has authored and
co-authored more than 40 peer-reviewed technical papers. He is also a
recipient of the Izaak Walton Killam Memorial Award of University of
Alberta, the Canadian NSERC Industrial R&D Fellowship, etc. His personal
URL is http://www.gangxiang-shen.com/.”
JungYul Choi received his B.S degree from Inha
University, South Korea, in 2000, and his M.S and
Ph.D degrees from Information and Communica-
tions University (currently merged to Korea Ad-
vanced Institute of Science and Technology), South
Korea, in 2002 and 2006, respectively. He has been
working for Network R&D Laboratory, KT Cor-
poration (formally, Korea Telecom) since 2006. He
has authored around 20 reviewed technical journal
papers, and holds around ten patents in areas of
telecommunications networks. He was nominated
Marquis Who’s Who in the World 2009, and International Engineer of the
Year for 2010 from IBC. He has been a reviewer of technical journal papers
such as IEEE Infocom, IEEE Communications Letters, IEICE Transaction on
Communications, IEICE Transaction on Information and Systems, Elservier
Journal of Visual Communication and Image Representation, and ETRI
Journal. His research interests are in Next-Generation Networks, Future
Networks, wired/wireless convergence, and network economics.
Bokrae Jung received the B.S. degree in Informa-
tion and Communications Engineering from Yeung-
nam University, Gyeongsan, Korea, in 2003, and
the M.S. degree in School of Engineering in Ko-
rea Advanced Institute of Science and Technology
(KAIST), Daejeon, Korea, in 2006, where He is cur-
rently working toward Ph.D. degree in Department
of Information and Communications Engineering.
He worked in WDM-PON Technology Team at
ETRI, Korea from April to December, 2005. He
spent six months in the Center for Ultra-Broadband
Information Networks (CUBIN), the University of Melbourne, Australia, for
an overseas exchange program from 2007 to 2008, where he studied optical
and wireless converged networks.
Hong-Shik Park received the B.S. degree from
Seoul National University, Seoul, S. Korea in
1977, and the M.S. and Ph.D. degrees from Ko-
rea Advanced Institute of Science and Technology
(KAIST), Daejeon, S. Korea all in Electrical En-
gineering in 1986 and 1995, respectively. In 1977
he joined Electronics and Telecommunications Re-
search Institute (ETRI) and had been engaged in
development of TDX digital switching system fam-
ily including TDX-1, TDX-1A, TDX-1B, TDX-10,
and ATM switching systems. In 1998 he moved to
Information and Communications Univ., Daejeon, Korea as a faculty. Cur-
rently he is a professor of the Dept. of Electrical and Electronics Engineering,
KAIST, Daejeon, S. Korea. From 2004 he is a director of BcN Engineering
Research Center sponsored by KEIT, Korea. His research interests are network
architecture and protocols, traffic engineering, and performance analysis of
telecommunication systems. He is a member of the IEEE, IEEK and KICS,
S. Korea.
Minho Kang received the BSEE, MSEE, and Ph.D.
degrees from Seoul National University, University
of Missouri-Rolla, and University of Texas at Austin
in 1969, 1973, and 1977, respectively. From 1977
to 1978, he was with AT&T Bell Laboratories,
Holmdel, NJ. Moreover, from 1978 and 1989, he
was a Department Head and a Vice President at
Electronics and Telecommunications Research In-
stitute (ETRI). Also, he served as the Electrical
and Electronics Research Coordinator at the Korean
Ministry of Science and Technology from 1985 and
1988. After that, he was an Executive Vice President at Korea Telecom (KT) in
charge of R&D, quality assurance, and overseas business development groups
from 1990 to 1998. In 1999, he joined the Information and Communications
University (ICU) as a professor and served as Dean of Academic and Student
Affairs. He was the Director of the OIRC from 2000 to 2009. Now, he
joins a professor and served as a vice-president of the college of information
science &technology, Korea Advanced Institute of Science and Technology
(KAIST), Daejeon, Republic of Korea. He was awarded the Order of Merit-
DongBaekJang by Korean Government and Grand Technology Medal by
21st Century Management Club in 1983 and 1991, respectively for the
contribution of optical communications technology development. In 2007 and
2008, He was awarded the COIN Award 2007 and ICU Best Research Award,
respectively. He served as the Study Group Chairman at the Asia Pacific Tele-
community of Bangkok during 1996-1999, is a member of National Academy
of Engineering in Korea, and is a senior member of IEEE. He is an author of
Broadband Telecommunications Technology, published in 1993 and revised
in 1996 by Artech House. He is also an associate editor of IEEE Optical
Communication and Networks Magazine.
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