Second International Conference on Electrical Engineering

25-26 March 2008

University of Engineering and Technology, Lahore (Pakistan)

978-1-4244-2293-7/08/$25.00 ©2008 IEEE.

Performance Analysis of 3G and WiMAX as

Cellular Mobile Technologies Sadia Murawwat and Kazi Ahmed

Asian Institute of Technology

P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand sadiamurawwat@yahoo.com

kahmed@ait.ac.th

Abstract__In this paper, performance analysis of

802.16/WiMAX and 3G technologies is done considering both as a

cellular mobile technology. The performance measures used for

this analysis are path loss, signal to noise ratio, coverage range of

a cell and capacity in terms of number of user supported. An

example scenario is considered as a reference. Different

parameters for this scenario are assumed and adopted from

literature.

This paper evaluates the potential of WiMAX as a cellular

technology in comparison to existing cellular networks evolving

from Analog (1G), Digital (2G), Digital network with high speed

(2.5G) and transmission with high data rate (3G). At the end

concluding that there is trade off between different network

parameters.

Keywords-Performance Analysis, WiMAX, 3G, Broadband,

Cellular networks.

I. INTRODUCTION

3G mobile technologies support high bandwidth

communications in addition to voice. It is based on one of the

several standards included under the ITU's IMT-2000. ETSI

developed two standards for IMT-2000, one of them is UMTS

and other is CDMA2000 [1].While WiMAX, based on the

IEEE 802.16 standard, offers full mobility of cellular networks

with high broadband speeds. Both fixed and mobile versions of

WiMAX are there to provide broadband wireless services. All

these technologies of cellular mobile networks are evolving to

meet different user requirements.

So, a competition between cellular phone services and

broadband access technologies is around.

II. REFERENCE CELLULAR SCENARIO

We take a reference scenario for an urban interference

limited network. Two different cases have been considered; in

Case1, we have taken 3.5 MHz bandwidth in 3.5 GHz

frequency band for WiMAX and 2 MHz bandwidth in 2.1GHz

frequency band for 3G. In Case2, we consider the same

frequency bandwidth for both technologies and study its effects

on path loss, signal to noise ratio, capacity and the cell ranges

for both cases. Case 1:

GHzf

HzGf

G

WiMAX

1.2

5.3

3

Case 2:

GHzf

HzGf

G

WiMAX

2

2

3

Cell layout

We consider the deployment of WiMAX and 3G as cellular

network in our reference area, which is divided into hexagonal

cells. Each cell has the Base Station (BS) providing coverage

to the surrounding region and the mobile users are uniformly

distributed over the area. Fig.1 shows the scenario under study

and the relevant parameters are mentioned in Table .I

BS

and

mobile

users

Fig.1. Hexagonal cellular structure

Parameters Values

Different parameters considered for the said scenario are

given in Table1.

TABLE I

PARAMETER VALUES OF REFERENCE SCENARIO

Parameters Values Cell layout Hexagonal

Frequency reuse

pattern

1x1

MS distribution Random uniform

Frequency band WiMAX 2-11GHz

3G 1900MHz, 2100MHz

Propagation model WiMAX Modified Hata Model,

Path loss Model for WiMAX

3G Hata Model, Free space

Model, Dual slope Model,

Walfish-Ikegami Model

BS power WiMAX +47.7dBm

3G +30 dBm

Slow fading st. dev. 8 dB

MS power +24dBm

BS antenna gain +17dBi

MS antenna gain 0 dBi

BS antenna height 35 m above ground

MS antenna height 2 m above ground

Noise power -138.41 dBm

Noise figure 7dB

Duplexing FDD, TDD

Frame length WiMAX 10ms

3G 10ms

Data Rate WiMAX 1-9.7Mbit/s

3G 2Mbit/s (Fixed/indoor)

144kbit/s (veh. speed)

384kbits/s (pedestrian)

Modulation techniques

and coding rate

WiMAX BPSK ½, QPSK ½, QPSK

¾, 16 QAM ½16 QAM ¾, 64

QAM 2/3, 64 QAM ¾ (all

WiMAX Modes)

3G QPSK

Bandwidth/channel WiMAX 1.25-28 Mbits/s

3G 2, 5, 10 Mbits/s

Spectral efficiency WiMAX 3.1-3.8 bit/s/Hz

3G 0.192 bit/s/Hz

Using above mentioned parameters, performance analysis of

both cellular technologies including WiMAX and 3G is done

under section III. Results and discussions based on coverage

and capacity are described in section IV.

III. PERFORMANCE PARAMETERS

The performance of any cellular network depends on various

parameters and network conditions. Following are some

parameters considered for analysis:

A. Propagation model

Maximum distance between the BS and user is calculated

using different path loss models, Path loss attenuation is due to

many effects such as free space loss, refraction, diffraction,

reflection, aperture medium coupling loss and absorption also

affected by terrain contours, different environments ,

propagation medium, the distance between the transmitter and

the receiver and height and location of antennas. a. Propagation model for WiMAX

For finding the loss variations with the increasing distance

from the base station, the IEEE 802.16 path loss and shadow

fading model is given by [2] is used.

PL= A + 10 γ log10 (d / d0) + ΔPLf + ΔPLh + s

(1)

Three propagation environments have been considered:

Terrain Type A, B and C. We take type C: Flat terrain with

light tree densities Second model use the Hata formula

proposed in [3] developed for frequencies below 2 GHz. To

use it for higher frequencies, the original formula has been

extrapolated to frequencies up to 6 GHz in [4]

b. Path Loss Models for 3G

Different path loss models have been studied and analyzed

for 3G in literature. First model used for analysis is the

modified Hata model for frequencies above 1500MHz and

distance is 1-20km as mentioned in [5].Other includes free

space, dual slope formula and Walfish-Ikegami model that

includes ground reflections is more practical than others as it is

based on measurements [4].

B. Signal to Noise Ratio and Received Power (Pr)

Signal to Noise Ratio (SNR) is the ratio of signal power to

noise power attenuating the signal. There is a minimum

acceptable value of SNR for receiving a quality signal.

Required SNR for different PHY mode are mentioned in

IEEE802.16 standards.

The received power and SNR is given in [5]

nrttr PFLGGPdBP )( (2)

IPPdBSNIR nr)( (3)

The necessary received power (m in)rPis [5]

FfPSNRdBP cnr log10)((min) (4)

The maximal distance between BS and MS is determined

using the maximal signal to noise ratio (SNR) a MS should

receive to avoid data loss. With the maximal SNR, the

maximal distance a MS should have from its BS is calculated.

Pr is the received power and Pt is the transmit power, Gr and

Gt are transmitting and receiving gain. L is the path loss

calculated using different propagation models mentioned above.

F is the noise figure of receiver. With the maximal SNR, the

maximal distance a user should have from its base station is

calculated.

C. Spectrum Efficiency

IEEE 802.16 uses OFDM with 256 point transform,

designed for the NLOS operation in 2-11GHz frequency band.

From the basic assumptions of the PHY layer, the basic OFDM

parameters are calculated. Different OFDM parameters used

are mentioned in [6]

The WiMAX throughput given in [7] is used taking B is the

bandwidth in use 3.5 MHz; sampling rate, n, taken is (8/7),

256; NFFT is the length of Fast Fourier Transformation, 192;

Nused is the number of used carriers, code rate is the rate of

channel coding and m is the modulation efficiency.

Spectrum Efficiency= Effective throughput /Bandwidth (5)

Using different PHY modes given in Table.1 certain amount of

data can be carried by a single OFDM symbol.

D. Coverage Area

The maximum distance served by different modulation

techniques mentioned in Table.1 is calculated, this distance is

determined using the maximal Signal to Noise Ratio, a user

should receive to avoid data loss. The area served by a certain

PHY mode which is a certain fraction of the whole reference

area is considered. As we have considered a hexagonal cell so

the coverage area of BPSK ½ mode having maximum radius is

calculated. 2 2

1/ 2 1/ 2

33

2BPSK BPSK QPSKA r r

(6)

Area of annulus formed by two circles is: 2 2

ring outer innerA r r (7)

Fig.2. Adaptive modulation ranging different coverage areas in WiMAX

The cell layout of our reference scenario is hexagonal and

the radius of cell is r km, so the area of a single cell is:

2

_ ( )

33

2hexa cell WCDMAA r

(8)

There are many factors which limit the coverage area of a

cell like voice requirement, path loss, minimum signal to noise

ratio and interference. The surface area is planned based on

above mentioned equations.

E. Capacity

Capacity is the number of users served by a given system.

The number of users is limited by the minimum signal to noise

ratio required. The number of user using certain

modulation/coding schemes for respective surface area is

derived.

min0

max)/(

1..

NEm

R

BM

b

tot

(9)

Where Mmax is the maximum number of user supported

min0 )/( NEb is the required ratio of energy and noise, m is the

modulation efficiency and R is the data rate of transmission.

For the calculated distance between transmitter and receiver,

we find the coverage area and respective number of users in

that region. Results are shown in next section.

IV. RESULTS AND DISCUSSION

This section deals with the results of performance analysis

and related discussion on efficiency of WiMAX and 3G

cellular networks. First, the path loss and coverage issues

considering different models are evaluated. Then its effects on

signal to noise ratio, spectrum efficiency and capacity are

presented. Finally a comparison of various cases is considered.

We evaluated six path loss models as listed in Table. 1. To

study their impact on coverage area prediction of a base station,

two path loss models for WiMAX are considered and four for

3G as shown in Fig. (3)

Comparison of Path loss Models for 3G and WiMAX

0

50

100

150

200

250

0 5 10 15 20 25 30

d(km)

los

s(d

B)

WiMAX model(f=3500MHz)

Hata Model(f=3500MHz)

Hata Model(f=2100MHz)

Free SpaceModel(f=2100MHz)

Dual Slope Model(f=2100MHz)

Walfish-Ikegami(f=1900MHz)

Fig. 3. Path loss models for WiMAX and 3G

In case of 3G network, carrier frequency is same for both

cases so path loss is also invariable, with cell radius 1.5 km the

path loss calculated is 146 dB. In WiMAX cell having cell

radius 20 km its value is 197 dB for case1 and 183 dB for

case2, resulting in fact that with increase in frequency high

path loss is observed as compared to low frequencies.

Behavior of signal to noise ratio with changing cell radius is

shown in Fig.4. There is a minimum acceptable value of SNR

for receiving a quality signal. This required SNR for different

PHY modes of WiMAX are mentioned in IEEE802.16

standards. For these values we have calculated the cell ranges

supported by a base station implementing all PHY modes of

WiMAX.

SNR vs Distance

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

d(km)

SN

R(d

B)

3G

WIMAX(Hatamodel)WiMAX Model

Fig. 4.Cell ranges versus SNR for WiMAX and 3G

Spectrum efficiency refers to the amount of information that

can be transmitted over a given bandwidth in a specific digital

communication system. It is a measure of how efficiently a

limited frequency spectrum is utilized by the physical layer [8].

Comparison of spectral efficiencies for WiMAX and 3G

0

1

2

3

4

5

6

BPSK 1/2 QPSK 1/2 QPSK 3/4 16 QAM ½ 16 QAM ¾ 64 QAM 2/3 64 QAM 3/4

Sp

ectu

m e

ffic

ien

cy

(b

its/

sec/H

z)

Case 1

case2

3G (QPSK)

Fig. 5. Spectral efficiencies of WiMAX and 3G

Simple capacity estimations for WiMAX/ IEEE 802.16 and

3G system are calculated Number of users supported by 3G in

1.5 km radius is found to be 27 and for WiMAX considering

64QAM(3/4) its value is 24 while, cell radius is 6 km. But the

data rates values based on OFDM considerations are almost

three times, as WiMAX supports high data rate transmissions.

Comparison of user served (WiMAX: Case1 & 2)

0

5

10

15

20

25

30

35

40

BPSK1/2 QPSK1/2 QPSK3/4 16QAM1/2 16QAM3/4 64QAM2/3 64QAM3/4

Modulation Schemes

Percen

tag

e(%

)

PercentageUser(Case1)

PercentageUser(case2)

Fig. 6.Users supported in WiMAX cell: Case1& 2

The number of user supported decreases as higher

modulation technique is used. For BPSK(1/2) and QPSK(1/2)

the user supported in Case2 is large than Case1, while for all

other techniques percentage of user in case2 is more than user

for Case1 due to high path loss and interferences.

Maximum cell radius supported by different PHY modes of

WiMAX is calculated using path loss and SNR requirements,

this distance limits the coverage area supported by different

modulation techniques and the number of user served. Result

shows that higher modulation technique serves less coverage

area and less number of users. 64QAM serve 1.92 while BPSK

serve 39.4 percentage of area.

In comparison of percentage area and percentage users of

Case 1, uptil PHY mode using QPSK (3/4) large number of

users are accommodated in small area but, as the radius

increases than 14.5 km the number of users decreases in

contrast to the coverage area due to more interference and

losses at higher frequencies. In Case 2, uptil PHY mode using

QPSK (3/4) less number of users are accommodated in large

area. As the radius increases than 34 km due to less signal to

noise ratio requirement, the number of user increases in

contrast to the coverage area.

Four different cases studied for analytical comparison of

WiMAX and 3G are:

Case 1: Considering a cell of WiMAX network with all PHY

modes. All parameters used for calculations are described

previously.

Case 1(a): In this case we consider the maximum radius

supported by the WiMAX cell using BPSK scheme having

radius 20 km and data rate is 1 Mbit/s.

Case 1(b): In this we consider the radius supported by 64

QAM scheme of the WiMAX cell having radius 6km and data

rate is 9.7 Mbit/s.

Case 2: Implementing all techniques of WiMAX technology

on low frequencies and lower data rates.

Case 3: Considering a cell of 3G cellular network with 1.5km

radius and data rate 384 kbit/s.

Number of users supported/ km with data rate 0.384Mbits/s for

different cases

0

20

40

60

80

100

120

140

160

Case 1(a) Case 1(b) Case 2 Case 3

Use

rs/

km

Number of users

Fig. 7.Comparing cases in terms of capacity

This comparative analysis shows that the capacity of

WiMAX cell is almost four times of the capacity of the 3G

cellular network in terms of the number of user. An interesting

result obtained is that if we implement all the technologies and

PHY modes in 3G networks, it gives the maximum efficiency

than the individual 3G or WiMAX network. The system

capacity amazingly increased in both cases 3G and WiMAX

network.

V. CONCLUSION

Different cases for finding the coverage and capacity of

cellular mobile network are considered for WiMAX and

3G.We find the optimum radius of a WIMAX cell. It is

observed that this radius is dependent on the PHY mode that is

in use. Different PHY modes implemented give different

spectral efficiencies, coverage and capacity of a cell. Due to

adaptive modulation the cell radius increases with different

data rates. Our results show that there is a tradeoff between the

cell radius and the data rates provided to the user. We find that

BPSK is providing cell radius of 20 km while data rate for the

user at the cell edge is 1Mbits/s and the number of users

supported are 260. While 64QAM is providing less coverage,

only 6 km but the data rate is almost 9.7 Mbit/s and the users

supported are 27.

In comparison to 3G and WiMAX number of users served

by WiMAX is four times more than the 3G cellular networks.

In fact, only broadband capabilities are not enough for

technology to mature. Standardization of mobile version

802.16e is still in progress. Network mobility and management

issues are still to discover.

Moreover, our work verifies and provides numerical facts

regarding the WiMAX and 3G cellular network comparison

issues, which are only theoretically discussed in literature.

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