 Open Access
 Total Downloads : 559
 Authors : Sonia Sharma, Sunita Parashar
 Paper ID : IJERTV3IS070080
 Volume & Issue : Volume 03, Issue 07 (July 2014)
 Published (First Online): 03072014
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Analysis of Path Loss Models at 3.3GHz to Determine Efficient Handover in Wimax
Sonia Sharma
M. Tech Scholar, Department of Computer Science & Engineering
H.C.T.M, Kaithal, Haryana, India
Sunita Parashar
Associate Professor, Department of Computer Science & Engineering
H.C.T.M, Kaithal, Haryana, India
ABSTRACT – Wimax stands for Worldwide Interoperability for Microwave Access and operate in 2.3GHz, 2.5GHz, 3.3GHz, 3.5GHz (licensed) and 5.8GHz (unlicensed) frequency bands. Path loss models can be used to find Received Signal Strength (RSS) which is an important factor in deciding handover. If RSS is less than a particular threshold value then handover decision is to be taken. For our analysis we have taken Free space Propagation, ECC33, COST 231 Hata, COST 231 WI and SUI models compared w.r.t. different environment (high density, medium density and low density) and different height of receiving antenna (2m, 6m, and 10m). Then RSS value are calculated in three environment and comparing RSS with particular threshold we determine which of these models is suitable for avoiding number of handover.
Keywords: ECC33, SUI, COST 231 Hata, COST 231 WI, RSS,
Handover

INTRODUCTION
One of important feature of wimax is to provide support for mobility and handover is one of important factor in mobility support. So it is required that handover process in wimax be efficient. Number of handover depends on the size of the cell if size of cell is small then number of handover will increase which in turn increase load on network and handover delay. RSS is very useful in deciding for handover, received signal strength can be calculated using path loss values for different propagation models. Path loss is reduction in signal strength when it is transmitted in from of
signal reduces due to interaction between electromagnetic waves and environment. Path loss models uses set of mathematical equations and algorithms for prediction of path loss values. Such models are categorized into three categories
i.e. deterministic (uses physical law leading propagation of waves), Empirical (based on measurements and observations) and stochastic (uses series of random variables) models. In our study we use only empirical models which are described as follow.
A.) Freespace path loss model
This model is used for finding path loss when there is lineofsight between transmitter and receiver. Equation for finding path loss is given [1] by:
PL(dB) 20log10(d) 20log10( f ) 32.45 (1)
Where, f is frequency of signal in MHz, d Is distance
from transmitter in km.
B.) COST 231 Hata model
COST 231 Hata model is introduced as an extension of Hata model. This model cannot be used for measurement on 2.5GHz and 3.5GHz, but correction factors are taken to predict the path loss in this higher frequency range. The basic path loss equation [1] for this COST231 Hata Model can be expressed as:
PL(dB) 46.3 33.9 log 10( f ) 13.82 log 10(hb)
electromagnetic waves between transmitter and receiver and

ah
(44.9 6.55(h )) log
(d ) c
(2)
measured in decibel (dB). In this paper our aim is to compare m
b 10 m
free space path loss, ECC33, COST 231 Hata, COST 231 WI and SUI model in different environment and with different receiver antenna height, determining model with minimum path loss in each environment, calculating RSS from path loss values, finding model with RSS greater than a threshold value such model can be adopted to minimize number of handover (frequent handover).
Section 2 gives a brief introduction of path loss models that we have taken for our study. Section 3 gives our simulated results and analysis (using MATLAB). Conclusions are drawn in section 4.


PATH LOSS MODELS Electromagnetic waves are used for transmitting
information between transmitter and receiver. Strength of
Where, d is distance between transmitter and receiver in (km), f is signal frequency (MHz), hb is height of transmitter antenna (m), cm is correction factor its value is 0dB for suburban and rural area and 3dB for urban area. ahm For urban area is given as:
ahm 3.20(log 102(11.75hr)) 4.79 (3)
for, f 400MHz
ahm For suburban and rural area is given as:
ahm (1.11log 10( f ) 0.7)hr (1.5log 10( f ) 0.8)
(4)
Where, hr is height of receiver antenna in m.
C.) COST 231 WI Model
This is COST 231 WalfischIkegami model and used as an extension of COST Hata model. It is used for frequencies that are above 2000MHz. path loss in case of LOS condition between transmitter and receiver is given by [1]:
PL(dB) 42.64 26log10(d) 20log10( f ) (5)
PL(dB) A 10 log 10(d / d 0) Xf Xh S
for, d d0 (15)
Where, d is distance between transmitter and receiver in km, Xf is correction factor for frequencies above 2GHz, Xr is correction factor for receiving antenna height in meter, S is correction factor for shadowing, its value in urban is 10.6, 9.6
in suburban and 8.2 in rural area.
In case of NLOS condition path loss is:
PL(dB) L0 LRTS Lmsd (6)
A 20log10(4d 0 / ) (16)
Where, is wavelength in meter and d 0 is reference
Where, L0 is attenuation in free space and given as:
distance of 100 meter. Path loss exponent is given by:
L0 32.45 20log10(d) 20log10( f ) (7)
a bhb (c / hb) (17)
LRTS is rooftop to street diffraction.
Here hb is height of transmitter antenna in meter. a, b, c are
LRTS 16.9 10 log 10(w) 10 log 10( f )
constants. Value of constants a, b and c is given in table 1 for

20 log 10(Hm) Lori
(8)
different terrain
Hm hroof hb and Lori is given as follow:
Table 1: Parameter of SUI model [3]
Lori 10 0.345
2.5 0.075( 35)
4 0.114( 55)
for 0 35
Parameter
A
B
C
a
4.6
4.0
3.6
b
0.0075
0.0065
0.005
c
12.6
17.1
20
for 35 55
for 55 90
(9)
Lmsd is multi screen diffraction loss.
Lmsd lbsh ka kd log 10(d ) kf log 10( f )
Frequency correction factor and correction factor for receiver antenna height are given by:

9 log 10( f ) 9 log 10(B) for Lmsd 0
Xf 6.0log10( f / 2000) (18)
0 for Lmsd 0 (10)
Xh 10.8log10(hr / 2000) for typeA and B
lbsh 18log 10(1 hb) for hb hroof
Xh 20.0log10(hr / 2000) for typeC (19)
0
ka 54 0.8hb ,
hb hroof (11)
for hb hroof and
d 0.5km
Where, f is frequency in MHz and hr is receiver antenna height in meter.
E.) ECC33 Model
International Telecommunication Union extended Hata Okumura model up to 3.5GHz. Such extended model is
54 0.8hb(dist / 0.5), for hb hroof and
known as ECC33 model i.e. Electronic Communication Committee. In such model path loss is given by equation [4]:
kd 18
d 0.5km
hb hroof
(12)
PL(dB) Afs Abm Gb Gr (20)
18 15(hb/hroof)
hb hroof
(13)
Where, Afs is attenuation in free space in dB,
Abm is basic
kf 4 0.7( f / 925 1)
for suburban areas
median path loss in dB, Gb is gain factor for transmitter
4 1,5( f / 925 1)
for urban areas (14)
antenna height in dBm, Gr is gain factor for receiver antenna
where, w is street width in meter and B is building to building
distance in meter.
height in dBm. These factors are given as follow:
Afs 92.4 20 log 10(d ) 20 log 10( f )
(21)
D.) SUI (Standard University Interim) Model
Abm 20.41 9.83 log 10(d) 7.894 log 10(f)
SUI model is used in frequency band of 2.5GHz to 2.7GHz. But their use on higher frequencies is possible by introducing correction factors. SUI models are divided into three types of terrains namely A, B and C. Type A is related with maximum path loss and is also known as urban area. Type C is related with minimum path loss and also known as
rural area. Type B is related with suburban area. The basic
9.56( log 10(f))2
Gb log 10(hb / 200)
[13.958 5.8(log 10(d ))2Gr [42.57 13.7 log 10( f )]
(22)
(23)
path loss equation [3] is given by:
[log 10(hr ) 0.585] (24)Where, d is distance between transmitter and receiver in
km, f is frequency in GHz, hr
is receiver antenna height in
meter, hb
is transmitter antenna height in meter.
F.) Received signal Strength (RSS) calculation:
This is power of radio signal received from base station. If received signal strength is below a threshold point then handover process is to be initiated to maintain ongoing communication. Equation used to measure RSS from path loss for various model is given as:
RSS PT GT GR PL CL
(25)
Where, RSS is receiver signal strength in dBm, PT is transmitter power in dBm, GR is receiver antenna gain, GT is transmitter antenna gain, and CL is loss factor for cables and connectors.


OUR RESULTS AND ANALYSIS
For our simulation, our operating frequency is 3300MHz (3.3GHz) which is licensed frequency band of WiMAX and mostly used in Asian regions. Distance is variable from 250m to 6km. Other parameters taken are suitable for Asian regions and obtained from study of various research papers.
Table 2: values for simulation parameters
Parameter
Name
Urban
area
Suburban
area
Rural area
Transmitter
Height
40m
30m
20m
Receiver
Height
2m,6m,
and10m
2m, 6m,
and 10m
2m,6m,
and10m
Frequency
3.3GHz
3.3 GHz
3.3GHz
Distance between
transmitter and receiver
Varies from 250m
6km
Varies from 250m6km
Varies from 250m6km
Shadowing
factor
10.6dB
9.6dB
8.2dB
Street width
25m
25m
——
orientation
angle
30
degree
40
degree
Not allowed
Transmitter
power
43dBm
43dBm
43dBm
Receiver
power
30dBm
30dBm
30dBm
A.) Analysis in urban (High Density Area):
For analysis distance is variable from 250m to 6km. Results are shown in Fig. 1, 2 and 3
Fig. 1: Simulation of models in urban environment at 2m height of receiver antenna
Fig. 2: Simulation of models in urban environment at 6m height of receiver antenna
Fig. 3: Simulation of models in urban environment at 10m height of receiver antenna
Urban Environment
200
COS
T 231
Hata
COS
Path loss at 2m
receiver antenna height
Path loss at 6m receiver antenna height
Path loss at 10m receiver antenna height
161.8
179.1 135.2 164.6
156.3
127.7
144.4
154.1
161.4
130.1
155.4
156.8
T
231
WI
SUI
ECC
33
0
20
40
60
80
100
120
140
160
180
Path Loss (dB)
Fig. 4: Analysis of path loss at reference distance of 3km in urban area
Bar chart showing our analysis at reference distance of 3km is shown in Fig. 4. From this we find that SUI model is showing lowest path loss (135.2dB to 127.7dB) with different receiver antenna height. ECC33 model is showing highest path loss of 179.1dB at 2m receiver antenna height and COST WI is showing highest path loss 156.3dB at 10m receiver antenna height. SUI is showing lowest variation in path loss values with change in height of receiver antenna and ECC33 is showing largest variations. COST 231 Hata model is showing moderate path loss value (161.8dB to 154.1dB). Free space model is not analysed here because it is showing same value of path loss in all environment and at all receiver antenna heights.
B.) Analysis in Suburban (medium density) area
For analysis in suburban area we consider same distance and receiver antenna height as in urban area. Results of simulation are shown in Fig. 5, 6 and 7.
Fig. 5: Simulation of models in suburban area at 2m height of receiver antenna
Fig. 6: Simulation of models in suburban area at 6m height of receiver antenna
Fig. 7: Simulation of models in suburban area at 10m height of receiver antenna
Bar chart showing our analysis at reference distance of 3km between transmitter and receiver is shown in Fig. 8
Suburban Environment
200
Path Loss (dB)
180
160
140
120
100
80
60
40
20
125.5
147.2
154
130.7
181.5
160
Path loss at 2m receiver antenna height
COS T 231 WI
SUI
ECC 33
COS T 231
Hata
0
Path loss at 6m receiver antenna height
157.8
150.8
145.7
123.1
146.8
134.3
Path loss at 10m receiver antenna height
Fig. 8: Analysis of path loss models at reference distance of 3km in suburban area
From our analysis we find that SUI model is showing minimum path loss (130.7dB to 123.1dB). ECC33 is showing maximum value of path loss (181.5dB to 146.8dB). COST 231 WI and Hata are showing moderate values of path loss.
C.) Analysis in rural (low density) area
In rural area ECC33 model is not valid and COST 231 WI model operates in lineofsight condition because this model do not have specific parameters for rural areas. Results of simulation are shown in Fig. 9, 10 and 11.
Fig. 9: Simulation of models in rural area at 2m height of receiver antenna
Fig. 10: Simulation of models in rural area at 6m height of receiver antenna
Fig. 11: Simulation of models in rural area at 10m height of receiver antenna
Path loss at 2m
receiver antenna height
Path loss at 6m receiver antenna height
Path loss at 10m receiver antenna height
163
158.7 125.3
125.3
144.8
137.3
125.3
149.2
150.1
COS
T 231 WI
ECC
33 SUI
231
Hat a
Rural Environment
180
160
140
120
100
80
60
40
20
0
COS
T
Path Loss (dB)
Fig. 12: Analysis of path loss models in rural area at reference distance of 3 km
Bar chart showing our result of analysis is shown in Fig. 12. We find that i rural are SUI model is showing path loss value (158.7dB to 144.8dB). COST 231 WI model is showing minimum path loss of 125.3dB in lineofsight condition (minimum as compared to all other models).
D.) Analyzing Handover by calculating Received Signal Strength
Here we are analyzing handover based on RSS calculated from Path Loss value of models taking 6m receiver antenna height and variable distance from 1km to 6km. Threshold from BS is 86dB. Transmitter Antenna gain is 17.5dBi.
Table 3: Parameter RSS
Power of transmitter
43
dBm
Cable and connector loss factor (A)
3.5dB
1.) RSS for Urban Environment
Fig. 13: Simulation of RSS for models in urban Environment
Values for RSS of various models from 1km to 6km are accumulated in Table 4 from this we analyze that that RSS value is highest for SUI (47.1dBm to 83.0dBm) less than threshold point (86.0dB) so SUI model is best for spanning greater distance leading to cell of larger size and reducing number of handover. Deciding handover by comparing RSS with threshold will also reduces handover delay.
Table 4: RSS values for path loss models from 1km to 6km in urban area
Distance
RSS
forECC 33 (dBm)
COST 231 HATA
(dBm)
RSS
for SUI (dBm)
RSS for COST 231 WI (dBm)
1km
76.3
79.4
47.1
77.2
2km
87.7
89.8
61.0
88.6
3km
94.4
95.8
69.1
95.3
4km
99.1
100.1
74.8
100.1
5km
102.8
103.5
79.3
103.7
6km
105.8
106.2
83.0
106.8
2.) RSS for Suburban Environment
Results of simulation for SUI, Cost hata, COST 231 WI and ECC33 model for determining Received Signal Strength are shown below in Fig. 14. In this simulation receiver antenna height is taken as fixed and this is 6km.
Fig. 14: Simulation of RSS for models in suburban environment
Values for RSS of various models from 1km to 6km are accumulated in Table 5, from this we analyze that that RSS value is highest for SUI (43.7dBm to 77.7dBm) so SUI model is best for reducing number of handover and leads to efficient performance and COST 231 WI model have minimum RSS (115.4dBm) for 6km which is worst for handover.
Table 5: RSS values for path loss models in suburban environment
Distance
RSS
RSS
RSS
RSS for
(km)
for
for
for SUI
COST 231
ECC
Cost
(dBm)
WI(dBm)
33
231
(dBm)
hata
(dBm)
1km
78.0
69.4
43.7
85.8
2km
89.9
80.0
56.8
97.3
3km
96.8
86.2
64.5
104.0
4km
101.8
90.6
70.0
108.7
5km
105.6
94.0
74.2
112.4
6km
108.7
96.8
77.7
115.4
3.) RSS for Rural Environment
Result of simulation for SUI, Cost hata and COST 231 WI model for determining RSS are:
Fig. 15: simulation of RSS for models in rural environment
Values for RSS of various models from 1km to 6km are accumulated in Table 6, from this we analyze that that RSS value is highest for COST 231 WI (74.8dBm) greater than threshold point (86dB).
Table 6: RSS values for path loss models in rural environment
Distance (km)
RSS for
COST 231
Hata (dBm)
RSS for SUI (dBm)
RSS for
COST 231 WI (dBm)
1km
71.8
66.7
54.6
2km
82.7
80.3
62.4
3km
89.1
88.2
67.0
4km
93.7
93.8
70.3
5km
97.2
98.2
72.8
6km
100.1
101.7
74.8

CONCLUSIONS
We conclude that path loss value changes with different environments, height of transmitter and receiver antenna and distance between transmitter and receiver. No single model is suitable for all environments. Although SUI model is showing minimum path loss values for Urban and suburban areas but not in rural area reason for this is that we have take height of transmitter 20m in rural and presence of term (c / hb) in path loss exponent factor increases path loss value
in rural area for SUI model. In rural area COST 231 WI is showing better result. Received signal Strength for SUI model in urban and suburban areas is greater than threshold point up to 6km so this model can leads to cell of larger size by spanning more distance as compared to other models, without reducing RSS below threshold point and thereby reducing number of handover. That will makes handover process efficient.
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