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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P00240 (5th coursework)

09099225

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

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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

Fifth Practical Assignment (BEMPENIS M., 09099225)

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