International Journal of Engineering Trends and Technology (IJETT) - Volume4 Issue8- August 2013
Network Audit and Quality Check Of Live BTS Sites: A Practical Survey
Tushar Saxena#1, J.S.Jadon*2
#1
#2
M.Tech, AITEM, Amity University, Noida, India.
Associate professor, AITEM, Amity University, Noida, India.
ABSTRACT GSM network is always susceptible to
various issues and faults. A BTS site consists of
certain parameters which are required to be
measured timely. This brings the need of network
audit. Network audit is necessary to judge the
network performance and maintain QOS standards.
The network audit identifies the inconsistencies or
the limitations in current BTS site or sites. The
parameters are SWR, return loss and cable loss.
SWR and return loss are interrelated and cable loss
is the loss in the feeder cable which is going from
BTS to GSM antenna. This paper is presented as
the part of the live BTS quality check for different
non showcase sites. In this paper real BTS sites are
evaluated and different issues, trials, punch points
and improvements have been summarized and
observations have been listed to relate together the
aspects of network improvement which will affect
the QoS of love cellular network. The measurement
was carried out with the aid of the Anritsu site
master instrument model S325D. This Anritsu site
master instrument is capable of determining the
voltage standing wave ratio in a transmission line.
Index terms GSM, BTS, E tilt, M tilt, MS etc.
I.
INTRODUCTION
GSM network usually called as ‘cellular network’ (as
the whole coverage area is divided into different cells
and sectors) is comprised of a mobile Station (MS)
which is connected to the Base Transceiver Station
(BTS) via air interface. BTS also contains the
equipment called Transceiver (TRX or sometimes
TRU), which is responsible for the transmission and
reception of several radio frequency (RF) signals to
and from the end users. BTS is further connected to
the base station controller (BSC) through an Abis
interface. BSC handles radio resource management
and handovers of the calls from one BTS to the other
BTS in it. BSC is then connected to Mobile
Switching Centre (MSC). Every subscriber demands
for congestion free network with no call drops and
blocking[1]. To satisfy the subscriber demand, RF
optimization teams aims to ensure minimum
blocking/congestion over air interface in order to
provide better QoS to guarantee significant network
performance. RF Optimization teams analyze the
ISSN: 2231-5381
performance and evaluate quality of service offered
by the existing network. Since the deployment of
GSM network, it has been observed practically that
there are many phenomena and issues which have
been neglected in literature/available text but they
severely influence the network performance[2].
II.
NETWORK BASICS
There are different terminologies that one should
know while talking about network audit and Quality
check. There are different manufacturers of BTS
equipments like ericsson, NSN and ZTE but a single
telecom circle uses the BTS of only one manufacturer
for a given circle. The telecom BTS can be of three
types as indoor BTS, outdoor BTS and tower top
BTS. Indoor BTS are placed inside prefab or concrete
shelter with air conditioning as a much needed
requirement. Outdoor BTS are installed at open over
a foundation generally of 5”x6”. Tower top BTS can
be mounted on wall, tower or a pole. The telecom
towers have GSM antennas, microwave antenna and
3G antennas as well. 3G antennas are present only on
the 3G network sites. To maintain the balance
between the coverage and capacity, GSM antennas
are given with E and M tilts. E tilts are given to
increase the coverage of the antennas and M tilts are
given to increase the capacity of an antenna. The
telecom tower can be GBT or ground based tower
usually of height of 30 meters to 50 meters from the
ground and RTT or roof top towers which are
mounted over a building usually in urban areas where
there is no space for GBT. Height of rtts aree
generally depends on the height of the building and
usually ranges from 7 meters to 15 meters. The
survey includes 100 NS or non showcase sites to be
audited.
III.
EVALUATION PROCESS
GSM network performance and QoS evaluation are
the most important steps for the mobile operators as
the revenue and customer satisfaction is directly
related to network performance and quality. The
entire project consists of mainly SWR and
corresponding return loss and cable loss for each
sector’s transmitter and receiver. The hardware tool
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International Journal of Engineering Trends and Technology (IJETT) - Volume4 Issue8- August 2013
anritsu’s site master S325D is used to calculate the
parameters for every live telecom site.
A. Voltage standing wave ratio
The ratio of the maximum voltage to the minimum
voltage amplitude in a transmission line is called the
Voltage Standing Wave Ratio (VSWR). In many
practical circumstances this parameter can be readily
measured and then used as indication of the
transmission line performance[3]. The voltage
standing wave ratio can be related to the magnitude
of the reflection coefficient. If the reflection
coefficient is given by A, then the maximum voltage
in the standing wave is :
VSWR = (1+|A|) / (1-|A|)
Where A is the ratio of reflected voltage and incident
voltage.
The VSWR is always a real and positive number,
smaller the VSWR is, better the antenna is matched
to the transmission line and the more power is
delivered to the antenna. The minimum value of the
VSWR is 1.0 indicating that no power is reflected
from the antenna, which is ideal. In practical scenario
the VSWR of 1.30 is the maximum value. There was
a margin given by the telecom company for 0.2 and if
the VSWR exceeds 1.5 then it will damage the TRX.
B. Return Loss
Return Loss can be stated as the measure of the
reflected energy from a transmitted signal. It is
commonly expressed in positive value of dB scale.
More the value, the less energy is reflected. Return
loss is generated as the result of the varying
impedance of the channel. These variations can
generate through the connectors with high or low
impedance values. The average input impedance of
the patch cables can be significantly different from
the horizontal cable's average impedance. The
impedance of the cables may have certain variations
at specific points due to the instability of the cable
design.
RL(dB)
=
10LOG(Pr/Pt)
VSWR may vary because of certain reasons like
rainfall when rainwater get inside the connector, if
there are more twists and turns in the cable etc.
VSWR is a linear measurement and is useful when
large reflections are needed to display whereas return
loss is a logarithmic measurement when small
reflections are needed to display.
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C. Working with Site Master
By using the Anritsu site master instrument, the
measurement is done in such a way that the Anritsu
site master is connected to the transmission line
which in this case was coaxial cable. The
measurement setup is shown in Figure 2. The Anritsu
site master instrument needs to be calibrated before
the measurements were taken. The first process in
calibration is to select the desire frequency range
which in this case 1800 MHz. The following steps
were taken in selecting the frequency range.
- Press the ON button to switch on the device.
Press the soft key FREQ from the main
menu.
- Press Soft key F1 from the main menu.
- Enter the lower frequency limit (1710-1785)
in MHz for the antenna system by using the
up/down arrow and press ENTER.
- Press the soft key F2 from frequency menu.
- Enter the higher frequency limit (18051880) in MHZ for the antenna system by
using the UP/down arrow and press ENTER.
- Check the new frequency start and stop
indication in the FREQ (MHz) scale in the
display area.
The further actions in calibration are to perform the
following.
- Turn on the calibration by pressing the start
key.
- Choose the type of calibration and press
ENTER.
- Follow the onscreen instructions.
After the calibration, site master is connected to
the transmitter as shown in Figure 1. Firstly it is
connected to the TX and then connected to the
RX for every sector without removing the other
end.
TRX
Connector
Site master
Fig. 1 Site master arrangements
IV.
OBSERVATION
Total of 100 sites were visited and audited but in this
paper data of only 30 sites are presented. The
different non showcase sites of Haryana state of India
are taken from different cities like ambala, jagadhari,
sonipat, jind, rohtak and pehowa.
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International Journal of Engineering Trends and Technology (IJETT) - Volume4 Issue8- August 2013
A. Ambala
TABLE 1
VSWR of TX and RX for Ambala
TABLE 3
VSWR of TX and RX for Sonipat
VSWR
TX
VSWR
RX
BWLA66A
BWLA66B
BWLA66C
DEV111A
DEV111B
DEV111C
HGL187A
HGL187B
HGL187C
KMK182A
KMK182B
KMK182C
KSN570A
KSN570B
1.25
1.24
1.14
1.29
1.23
1.24
1.25
1.19
1.14
1.26
1.18
1.11
1.17
1.2
1.28
1.3
1.24
1.22
1.25
1.27
1.2
1.14
1.15
1.12
1.3
1.25
1.29
1.14
KSN570C
1.23
1.26
Site ID
Cell ID
BWLA66
BWLA66
BWLA66
DEV111
DEV111
DEV111
HGL187
HGL187
HGL187
KMK182
KMK182
KMK182
KSN570
KSN570
KSN570
B. Jagadhari
TABLE 2
VSWR of TX and RX for Jagadhari
Site ID
Cell ID
BSPR22
BSPR22
BSPR22
DRW168
DRW168
DRW168
KHDR84
KHDR84
KHDR84
KNH508
KNH508
KNH508
RNPR87
RNPR87
RNPR87
BSPR22A
BSPR22B
BSPR22C
DRW168B
DRW168C
DRW168D
KHDR84A
KHDR84B
KHDR84C
KNH508A
KNH508B
KNH508C
RNPR87A
RNPR87B
RNPR87C
C. Sonipat
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Site ID
Cell ID
VSWR
TX
VSWR
RX
AMP562
AMP562
AMP562
APR558
APR558
APR558
JHAK57
JHAK57
JHAK57
JHR534
JHR534
JHR534
RAJU57
RAJU57
RAJU57
AMP562A
AMP562B
AMP562C
APR558A
APR558B
APR558C
JHAK57A
JHAK57B
JHAK57C
JHR534A
JHR534B
JHR534C
RAJU57A
RAJU57B
RAJU57C
1.26
1.19
1.25
1.27
1.3
1.15
1.19
1.29
1.2
1.3
1.15
1.24
1.28
1.17
1.19
1.3
1.15
1.24
1.22
1.23
1.28
1.15
1.2
1.2
1.23
1.28
1.29
1.17
1.3
1.15
D. Jind
TABLE 4
VSWR of TX and RX for Jind
VSWR
TX
VSWR
RX
1.2
1.28
1.28
1.3
1.28
1.24
1.2
1.17
1.29
1.22
1.22
1.23
1.28
1.25
1.24
1.29
1.25
1.24
1.29
1.19
1.14
1.14
1.26
1.17
1.24
1.29
1.2
1.3
1.31
1.24
Site ID
Cell ID
VSWR
TX
VSWR
RX
GNG231
GNG231
GNG231
JIND03
JIND03
JIND03
JIND04
JIND04
GNG231A
GNG231B
GNG231C
JIND03A
JIND03B
JIND03C
JIND04A
JIND04B
1.3
1.15
1.24
1.15
1.19
1.3
1.24
1.22
1.23
1.28
1.29
1.28
1.15
1.23
1.29
1.14
JIND04
JIND04C
1.29
1.2
JIND05
JIND05A
1.2
JIND05
JIND05B
1.3
JIND05
JIND05C
1.15
KLWA75 KLWA75A 1.24
KLWA75 KLWA75B 1.22
KLWA75 KLWA75C 1.19
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1.2
1.23
1.28
1.29
1.14
1.15
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International Journal of Engineering Trends and Technology (IJETT) - Volume4 Issue8- August 2013
E. Rohtak
PHWA36 PHWA36A
PHWA36 PHWA36B
TABLE 5
VSWR of TX and RX for Rohtak
V.
Site ID
Cell ID
VSWR
TX
VSWR
RX
BLAB30
BLAB30
BLAB30
BYAN19
BYAN19
BYAN19
NIGA68
NIGA68
NIGA68
RTHK10
RTHK10
BLAB30A
BLAB30B
BLAB30C
BYAN19A
BYAN19B
BYAN19C
NIGA68A
NIGA68B
NIGA68C
RTHK10A
RTHK10B
1.14
1.26
1.17
1.26
1.17
1.19
1.2
1.3
1.15
1.29
1.2
1.24
1.26
1.29
1.27
1.3
1.15
1.2
1.23
1.28
1.2
1.2
RTHK10
RTHK10C
1.3
SUND27 SUND27A 1.14
SUND27 SUND27B 1.26
SUND27 SUND27C 1.17
1.23
1.24
1.26
1.22
1.23
1.14
1.26
GRAPHS
1.34
1.33
1.32
1.31
1.3
1.29
1.28
1.27
1.26
1.25
1.24
1.23
1.22
1.21
1.2
1.19
1.18
1.17
1.16
1.15
1.14
1.13
1.12
1.11
1.1
VSWR TX
VSWR RX
1.29
F. Pehowa
Fig 2: Sites at AMBALA
TABLE 6
VSWR of TX and RX for Pehowa
Site ID
Cell ID
VSWR
TX
PHWA01
PHWA01
PHWA01
PHWA01
PHWA14
PHWA14
PHWA14
PHWA15
PHWA15
PHWA15
PHWA15
PHWA34
PHWA34
PHWA34
PHWA01A
PHWA01B
PHWA01C
PHWA01D
PHWA14A
PHWA14B
PHWA14C
PHWA15A
PHWA15B
PHWA15C
PHWA15D
PHWA34A
PHWA34B
PHWA34C
1.29
1.2
1.3
1.15
1.24
1.22
1.23
1.28
1.17
1.19
1.27
1.3
1.15
1.24
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VSWR
RX
1.2
1.2
1.23
1.28
1.29
1.14
1.26
1.17
1.3
1.15
1.22
1.23
1.28
1.29
1.34
1.33
1.32
1.31
1.3
1.29
1.28
1.27
1.26
1.25
1.24
1.23
1.22
1.21
1.2
1.19
1.18
1.17
1.16
1.15
1.14
1.13
1.12
1.11
1.1
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VSWR
TX
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International Journal of Engineering Trends and Technology (IJETT) - Volume4 Issue8- August 2013
Fig 3: Sites at Jagadhari
1.34
1.33
1.32
1.31
1.3
1.29
1.28
1.27
1.26
1.25
1.24
1.23
1.22
1.21
1.2
1.19
1.18
1.17
1.16
1.15
1.14
1.13
1.12
1.11
1.1
VSWR TX
VSWR RX
1.34
1.33
1.32
1.31
1.3
1.29
1.28
1.27
1.26
1.25
1.24
1.23
1.22
1.21
1.2
1.19
1.18
1.17
1.16
1.15
1.14
1.13
1.12
1.11
1.1
VSWR TX
VSWR RX
Fig 6: Sites at Rohtak
Fig 4: Sites at Sonipat
1.34
1.33
1.32
1.31
1.3
1.29
1.28
1.27
1.26
1.25
1.24
1.23
1.22
1.21
1.2
1.19
1.18
1.17
1.16
1.15
1.14
1.13
1.12
1.11
1.1
VSWR TX
VSWR RX
Fig 5: Sites at Jind
ISSN: 2231-5381
1.34
1.33
1.32
1.31
1.3
1.29
1.28
1.27
1.26
1.25
1.24
1.23
1.22
1.21
1.2
1.19
1.18
1.17
1.16
1.15
1.14
1.13
1.12
1.11
1.1
VSWR
TX
Fig 7 : Sites at PEHOWA
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International Journal of Engineering Trends and Technology (IJETT) - Volume4 Issue8- August 2013
VI.
OTHER MEASUREMENTS
There are various other measurements to be done like
E and M tilt of GSM antennas, azimuth of the GSM
antennas, height of the antennas and tower, height of
the microwave antennas and their azimuth, presence
of lightning arrestor. Capacity of air conditioning unit
in case of indoor BTS, capacity of rectifier and
SMPS modules, Dg set and presence of different
working infra alarms.
VII.
CONCLUSION
In this work, the VSWR, return loss and cable loss
values were measured in the investigated and the
different VSWR values are plotted against various
sites in different zones of Haryana state of India.
BTS and the result of the study showed that the
VSWR values are within the acceptable range during
the time of this survey indicating that the level of
mismatch are minimum.
Refrences
1. Kechagias, S.Papaoulakis, N.Nikitopoulos, D.
Karambalis:
“A
Comprehensive
Study
on
Performance Evaluation of Operational GSM and
GPRS Systems under Varying Traffic Conditions”.
IST Mobile and Wireless telecommunications
Summit, 2002, Greece.
2. S. Kyriazakos, G. Karetsos, E. Gkroustiotis, C.
Kechagias, P. Fournogerakis “Congestion Study and
Resource Management in Cellular Networksof
present and Future Generation”, IST MobileSummit
2001, Barcelona, Spain, 9-12 September 2001.
3. Aleksandra N . “Modern Approaches in modeling
of Radio propagation environment” IEEE
communication surveys USA, 2000.
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