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8/3/2019 Fifth Practical Assignment (BEMPENIS M., 09099225)
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Oxford Brookes University ASSESSED COURSEWORK School of Technology
TO BE COMPLETED BY STUDENT(S)
Department: School of Technology
Module No: P00240 Module Title: Broadband Wireless Networks
Assignment Title or No: 5
th
Practical AssignmentIf this is a group assignment, please enter all group members nos., names, and if relevant, group no. or name.
Student No(s): Student Name(s): (Surname , first name)09099225 Bempenis, Michail Group:
Statement of Compliance:
We declare that the work submitted is our own and that the work we submit is fully in accordance with the
University regulations regarding assessments (see overleaf).
Student Signature(s):
signed MB Date: 23 Apr 20 10
TO BE COMPLETED BY SCHOOL
Received by: Date Received by School:
Markers Name: Markers Signature:
Weighting of this assignment as a % of the whole module:
Areas of achievement:
Areas for further development:
Grade / mark (unmoderated): Date:
FORM: LT1 Assessed Coursework Coversheet Version: September 2009
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Table of Contents
1. Measurement Equations and Results............1
Broadband Wireless Networks
Title: 5th Coursework (Experiment 3-Wireless Sensor
System using Zigbee)
Student Name: Bempenis MichailStudent Number: 09099225
Course: MSc in Wireless Communication SystemsDate of submission: 23 April 2010
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2. Experimental Results and Analysis........ 23. Calculation of Theoretical Range........... 54. Conclusions...............8
References.........9
List of Abbreviations
DSR Dynamic Source Routing
FSPL
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1. Measurement Equations and Results
Thermistor B parameter equation is given by the following equation [1]:
+=
2RT
1RTln
B
1
2T
1
1T
1
(Equation 1), where
RT1: Thermistor resistance at temp T1 (K)
RT2: Thermistor resistance at temp T2 (K)
B: A constant for the Thermistor
Assuming that:
B=3380
T1: reference temperature=298.15K
RT1: Thermistor resistance at temperature T1=10K
T2: temperature to be measured (related to RT2)
We re-arrange the above expression by multiplying all parts of equation 1 with
T1*T2*B to get an expression for T2 in terms of T1, RT1, RT2 and B as follows:
+=2RT
1RTln2T1T1BT2BT
1BT]2RT
1RT
ln1TB[2T=-
2RT
1RTln1TB
1BT2T
-
=
or
2RT
1RTln33.11
33802T
-
=
for the above assumed values.
(Equation 2)
Regarding that the total voltage of 10k and RT in
series is +5V as illustrated in Figure1-1, we can write
an expression for Vadc which is related to voltage of
RT as follows:
5/Vadc=(RT+10k)/RT
Vadc=5*[RT/(RT+10k)] (in volts) (Equation 3)
Given that Vdigital=Vadc*1024/5V
Vdigital=1024*[RT/(RT+10k)]
(Equation 4)
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Then regarding that the above value is divided by 4 in order to be sent over the
Zigbee link, we can give an expression of RT in terms of Vdigital by rearranging the
equation 4 above as follows:
Vdigital*RT+Vdigital*10k=256*RT
Vdigital*10k=(256-Vdigital)*RT
RT=(10k*Vdigital)/(256-Vdigital) (Equation 5)
Now, substituting equation 5 into equation 2 we get an equation for T2 in terms of T1,
RT1, B and Vdigital as follows:
2
1ln1-
12
RT
RTTB
BTT =
digital
digital
V256
kV10
1RTln1TB
1BT2T
-
=
( )=
digital
digital
kV10
V2561RTln1TB
1BT2T
-
(Equation 6)
2. Experimental Results and Analysis
Setting the co-ordinator in room R2.22 and loading the Arduiro programming
environment, we tried to experimentally find the maximum range of the Zigbee link by
performing a great deal of walkabout tests both at ground and 1st floor areas of
School of Technology building. Additionally, one member of the group was watching
the results from Arduino programming environment on the screen of the PC located
in room 2.22. In Figure 2-1 below we present a typical row of data as derived from
the loaded software.
1st floor
At the 1st floor we followed the route: R2.12 R2.15 R2.16 R2.24 R2.27
R2.39 R2.37 R2.44, as illustrated in Figure 2-2 below. On the same time we
3
igure 1-1: RT and 10k in series
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were recording values of T2 for specific locations as typical ones can be shown in
Table 2-1 below.
2
1st floor
Location T2
R2.22 23.64
R2.06 22.63
R2.16 21.96R2.43 22.30
R2.27 22.97
R2.37 22.97
Figure 2-1: Typical row of data derived fromprogramming environment
Table 2-1: Recorded T2 values atspecific locations on the 1st floor of
the building
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Figure 2-2: First floor path and co-ordinator location
At this point it has to be noted that for the whole route on the 1 st floor we were having
established Zigbee link between end device and co-ordinator.
On the other hand, when end device reach the stairwells towards the ground floor,
the communication between end device and co-ordinator was lost (stop of row data
on the Com window of software on screen of PC), and apparently we confirmed that
no communication link could be achieved when the end device would be located on
the ground floor without relay device in between.Consequently, we confirmed that the maximum range situation between end device
and co-ordinator can be achieved on the whole of 1st floor and could be considered
approximately about 40m regarding the relative dimension figures of the building.
Ground floor
Having found the locations (stairwells) where communication link was broken off, we
then placed the relay at these locations in order to perform the second part of the
experiment which referred to the maximum range from end device to relay and relayto co-ordinator respectively.
We so firstly located the relay out of R1.129 room. We confirmed that
communication between end device-relay-co-ordinator established, and we followed
the route towards RLT2 where the link interrupted. At this point it has to be noted that
distance between relay and end node is roughly estimated about 25m.
Based on the same philosophy, we also located the relay outside R1.20 and
followed two different routes towards R1.117 and on the other hand towards R1.54
where in both cases the already established link was lost. It is also noted at this point
1
C
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that the distance between end node and relay was roughly measured to be about
20m and 25m respectively.
In Figure 2-3 below path on ground floor, relay positions (R), and connection lost
points (X) are clearly illustrated.
Figure 2-3: Path of ground floor, relay positions (R), and connection lost points (X)
From all above mentioned we can conclude that maximum range from end device to
relay is approximately 20-25m and maximum range between relay to co-ordinator is
about 25-30m respectively.
3. Calculation of Theoretical Range
To calculate the theoretical range we firstly found the receiver sensitivity of the
Series 2 Xbee transceiver to be -92dBm [1] as it can be seen from Figure 3-1.
Regarding that Xbee transmitter is 2.5mW or equal to 10*log2.5=3.98dBm, we can
calculate the theoretical range by using the ITU indoor path loss equation (3-1)
derived from [2], as follows:
L=20*logf+N*logd+P f(n)-28 (3-1), where
L: the total path loss in dB
f: frequency of transmission in MHz
N: the distance power loss coefficient
n: number of floors between the transmitter and receiver
Pf(n): the floor loss penetration factor
2
RRX
X
X
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Figure 3-1: Arduino Xbee Shield Wireless Module Specifications
The distance power loss coefficient, N is the quantity that expresses the loss of
signal power with distance. This coefficient is an empirical one and some values are
provided in Table 3-1 below [2]. So regarding that the experimental device operates
at 2.4GHz and in an office area environment we adopt as proper value that one of
N=30 as highlighted in Table 3-1.
Frequency Band Residential Area Office Area Commercial Area
900 MHz N/A 33 20
1.2 GHz N/A 32 22
1.3 GHz N/A 32 22
1.8 GHz 28 30 22
4 GHz N/A 28 22
5.2 GHz N/A 31 N/A
Table 3-1: Distance power loss coefficient (N) values
The floor penetration loss factor is an empirical constant dependent on the number of
floors the waves need to penetrate. Some values are tabulated in Table 3-2 below.
So regarding that the experimental device operates at 2.4GHz and in an office area
environment we adopt as proper formula highlighted in Table 3-2. Regarding that co-
ordinator was located at the first floor of the building (room 2.22), in case of 1 st floor
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range calculation floor loss penetration factor takes the value of Pf(0)=15-11=4, as
n=0, and for the ground floor Pf(1)=15-0=15.
Frequency
Band
Number of
Floors
Residential
Area Office Area Commercial Area900 MHz 1 N/A 9 N/A
900 MHz 2 N/A 19 N/A
900 MHz 3 N/A 24 N/A
1.8 GHz n 4n 15+4(n-1) 6 + 3(n-1)
2.0 GHz n 4n 15+4(n-1) 6 + 3(n-1)
5.2 GHz 1 N/A 16 N/A
Table 3-1: Floor penetration loss factor
Having calculated all relevant inputs of equation (3-1) above, we then calculate the
maximum theoretical range for both 1st floor and ground floor cases.
1st floor (n=0)
Considering that maximum losses take place at the maximum range, Lmax has to
meet the following equation (3-2):
PR=PT-Lmax(1) (3-2)
-92dBm=3.98dBm-[20*log2400+30*logd max(1)+Pf(0)-28]
-92dBm=3.98dBm-43.6-30*logdmax(1)
52.38=30logdmax(1)
logdmax(1)=1.746 dmax(1)=55.71m
Ground floor (n=1)
Similarly for the ground floor we have:
PR=PT-Lmax(0)
-92dBm=3.98dBm-[20*log2400+30*logd max(0)+Pf(1)-28]
-92dBm=3.98dBm-54.6-30*logdmax(0)
41.38=30logdmax(0) logdmax(0)=1.379 dmax(0)=23.93m
4. Conclusions
Regarding the experimental and theoretical results we can make the following
conclusions:
The theoretical ranges derived from calculations are longer than practical ones,
but not a great deal.
It was confirmed that ITU model for indoor attenuation tends to give realistic
results both for the same floor range calculations and different floors respective
calculation.
The movement between floors seems to affect dramatically the relevant range,
considering that range on the same floor is more than double of that one achieved in
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two different floors case. This observation is confirmed by both theoretical
calculations (53.71/23.93=2.33) and experimental results (40/20=2)
References
1. Arduino Xbee Shield Wireless Module. Robotshop. Available at:
http://www.robotshop.com/Arduino-Xbee-Shield-Wireless-Module.html
(Accessed: 21 April 2010).
2. ITU Model for Indoor Attenuation.Wikipedia. Available at:
http://en.wikipedia.org/wiki/ITU_Model_for_Indoor_Attenuation (Accessed: 21
April 2010).
2
http://www.robotshop.com/Arduino-Xbee-Shield-Wireless-Module.htmlhttp://en.wikipedia.org/wiki/ITU_Model_for_Indoor_Attenuationhttp://en.wikipedia.org/wiki/ITU_Model_for_Indoor_Attenuationhttp://www.robotshop.com/Arduino-Xbee-Shield-Wireless-Module.html