7/29/2019 EE and CCA analysis for macrocell Network

1/6

r Cfr uur Cu rk

Energy Efficiency and Cell Coverage Area

Analysis for Macrocell Networks

Ayad Atiyah Abdulkafi, Sieh Kiong Tiong, Johnny KohElectrical epartment, College of Engineering,Universiti Tenaga Nasional (UNITEN), Malaysiaal.ayad@yahoo.com, siehkiong@uniten.edu.my

Ab The issues of energy eciency and environmentalprotection are becong critical issues for both xed andwireless network operators worldwide. For wireless networkoperators, the challenge generally lies on providing maximumenergy eciency with largest possible coverage area. In thispaper we rst investigate the parameters affecting energyeciency and the cell coverage area. We later analyze therelationship between area power consumption and

transssion range (cell radius), transssion power,frequency band, shadowing and the path-loss exponent. Fromthe analysis, optimal inter site distance that utilizing nmumarea power consumption can be obtained for dierentpercentage requirement of coverage area corresponding tomum transit power that achieves this degree of coverage.The optimal inter site distance is deterned for macrocellwithout the impact of shadowing to be equal about 1250m withmnmum area power consumption of 526 Wkm. With theeffect of shadowing, the optimal inter site distance andmum area power consumption are 1050 m and 777Wkm respectively.

Keywodscopoet; acocel etwok; eegy effcecy;

cel ovege aeaI. NTRODUCTION

Besides minimizing the environmental impact of theindustry which becomes an increasingly important item onthe global political agenda, cellular network operators arestriving to reduce the energy consumption of their networksfor economical reasons. The costs for running a network arelargely affected by the energy bill and significant savings incapex and opex can be realized through reduced energyneeds. According to [1], about 57% of network energy isconsumed by the BSs (Base Stations). The explosive demandfor high data rate of mobile users has caused BSs to be the

dominant total energy consumer within the mobile cellulnetworks. ue to this, most studies on energy efciency inmobile cellul radio networks focus on the BS side. Existingmobile and cellular wireless network architectures aredesigned to provide large coverage areas, which oen facechallenges in catering the expected throughput requirementat the cell edge. This is mainly due to the increase in theinter-cell interference, as well as to constraints on thetransmit power of the mobile devices [2]. In thesearchitectures, the locations of the macro BSs are carefullychosen by network planning. BS settings are objectivelyconfigured to maximize the coverage while controlling theinterference between BSs. Generally, the improvements can

be achieved via two approaches. The first approach is byreducing the power consumption of BS (either by using morepower-efficient hardware or by using more advanced

97147009/1/$100 01 IEEE 1

avid Chieng, Alvin TingWireless Communication Cluster, MIMOS Berhad,Malaysia

{ht.chieng, kee.ting} @mimos.my

soware to adapt power consumption to the raic situation).The second approach is by adopting intelligent networkdeployment strategies by means of using small, low powerBSs since the later is able to signicantly decrease the powerconsumption compared to high power macro BSs due tosimple reason whereby BS closer to mobile users lowers the

required transmit power due to advantageous path loss

conditions [3].In principle, gains achieved in one area arecomplimentary to gains achieved in the other, i.e., if thedeployment is optimized with respect to a certain coverage,additional energy saving might be realized through siteoptimization. Interdependencies, however, do exist if siteoptimization aects the link budget, for instance if thereceiver sensitivity , which is a target minimum receivedpower level below which performance becomes unacceptable and it is denoted as Pn is lowered throughimproved RF components. [4].

In [2], the energy eiciency of downlink of a two-tierheterogeneous networks, i.e. a network of macrocell BSs

overlaid by randomly distributed picocell BSs is analyzed inorder to address the exponential increase in data traicdriven by a new generation of wireless devices. Theevaluation performance of the two-tier networks in terms ofenergy efficiency and fairness of resource allocation iscarried out using analytical expressions of successprobabilities for each tier when a disjoint set of subchannels.

In [3] a potential improvement of the ea powerconsumption achievable with network layouts featuringvarying numbers of micro sites in addition to conventionalmacro sites for given system performance tgets under fullload conditions is evaluated. They provide a framework tooptimize cellular network deployments with respect to the

average number of micro sites per macro cell as well as themacro cell size. Anyway, the effect of equency band,different shadowing and the receiver sensitivity on the cellcoverage ea e not considered. Most existing literaturesinvestigate deployment strategies with respect to specralefficiency, coverage, or outage probability without focusingon all pameters that aecting the coverage. In this paper,we focus on the pameters. In addition, we characterize anetwork's power consumption in Watts per unit area forgiven coverage requirements and optimize the BS cell radiuswith respect to these factors. We also provide simple modelsfor overall energy consumption of a network. From theanalysis we found that optimal inter site distance thatachieves minimum area power consumption can be obtained

based on coverage degree and the corresponding minimumtransmit power that achieves this degree of coverage with

7/29/2019 EE and CCA analysis for macrocell Network

2/6

and without the impact of shadowing. With a 95% coveragedegree, the optimal inter site distance that achieves minimumarea power consumption is determined for macro BS with2.4 GHz, a =4 and minimum receiver sensitivity ofPmin= -70dBm, to be equal about 250m and the corresponding cell

radius 72.7m with minimum area power consumption of526 W/km. For same pameters above and with standddeviation of shadow fading of 4 dB, the optimal cell radius,optimal inter site distance and mum area powerconsumption e 606.2 m, 1050 m and 778.7 Wkm

respectively.

The remainder of this paper is organized as follows.Section II describes the wireless network architecture, andthe power consumption module. The simulation results andanalysis e presented in Section III, as well as an illustrationof the trade-off between network energy efciency andoptimal inter site distance selection with and withoutshadowing is demonstrated. Finally, conclusions e drawnand the future work is described.

II. SYSTEM MOEL AN ERFORMANCEMETRICS

Cellular systems designed for a given average receivedpower PxR at cell boundary. Cell coverage area dictatesthe percentage of locations within the cell withPx Pmi

In order to compute the cell coverage area under pathloss and shadowing, we consider a BS inside a circular cellof a given radius R. The percentage of area within a cellwhere the received power exceeds the minimum requiredpower Pmin is obtained by taking an incremental area dA atradius rfrom the BS in the cell, as shown in Fig. 1 [5].

A. Propagao ModeCommonly, deterioration of signal quality due to

propagation is related to three dierent causes: path loss,shadowing, and multi path. A basic signal propagation modelcapturing path loss as well as shadowing is formulated as [5]

1

Where PIX P r and a denote transmit and receivepower, propagation distance, and path loss exponent,respectively. The random viable is used to model slowfading eects and commonly follows a log-normal

distribution, i.e., the variable g follows a normaldisribution. K can set to the free-space path gain at distancer assuming omnidirectional antennas. Where r is typicallyassumed to be 110 m indoors and 10100 m outdoors.Alternatively, K also can be determined by measurement atr or optimized (alone or together with a) to minimze themean-square error (MSE) between the model and theempirical measurements [4, 5]. The required transmit poweris calculated as a function of cell range for fixed coveragerequirement C by using (1). Here, coverage is defined as

h o howg

Fig. 1. Contours of constant received power

the max cell range Rmx where the user satisfies minimumrequired power Pmin Neglecting the effect of shadowing and

with D =. R the required transmit power of macro BS canbe written as:

2

Where Pmin denotes the receiver sensitivity and D is the intersite distance.

The transmit power of each site is calculated based on acel coveage reuirement fr macrocell without shadwing[4, 6]. Combined path loss and shadowing leads to outageand amoeba-like cell shapes as shown in Fig.. The standard

deviation of the shadowing varies with equency, antennaheights and the environment.

B. Ce Coverage Areas

The cell coverage ea C also known as the useful eacan be defined as the fraction of cell ea where receivedpower is above a given level Pmin , and the closed-form for Ccan be written as [5]

C= Q(a)+exp .

Pmn PxR b 1 Where

3

Note that a we he e mmum reeved pwerequals the average power at the cell boundy Pmi =PR)and PR) = PIX + . g K a . g (r) is thereceived power at the cell boundy (distanceR from the BS)due to path loss alone. f is the standd deviation of

7/29/2019 EE and CCA analysis for macrocell Network

3/6

shadow fading. The outage probability of the cell is definedas the percentage of ea within the cell that does not meet its

nimum power rquirement Pmin; that is, P0"'= p( Prir)