Seneca College
School of Information Technology Administration & Security - SITAS
DCN 706 - Wireless and Mobile
Student Name: Farhan Mahmud Ocean
Number: 152833194
Student
Lab 3: RF Power Measurements and Mathematics
Objectives: The main objective of this lab is to help you to be familiar with the following:
1. Power Measurement Units
2. Rule of 10’s and 3’s
3. Link Budget and Fade Margin
After completing this lab, you will be able to:
1. Calculate signal power level as exact value and approximate value
2. Demonstrate efficient use of Rule of 10s and 3s
3. Examine the values of Link Budget and Fade Margin
Materials Required:
1. A computer with Internet access
2. Microsoft Excel File available on the Course Website.
Notes: 1. This is individual work. You need to finish this lab and submit your work on blackboard before
the due date.
2. Edit this lab WORD document and answer the questions by using a different color (blue is preferable).
Insert the required screen shots in the same document as well.
3. After finishing your lab, write your name on the document as follows: Your First Name. Your Last Name
- Lab 3. Drop your lab in the corresponding drop box.
Part 1: Complete the following table:
Loss or Gain (dB)
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
Combination of 10s and 3s
-10
-3 -3 -3
-10 -10 +3 +3 +3 +3
-10 + 3
-3 -3
-10 -10 +3 +3 +3 +3 +3
-10 +3 +3
-3
-3 -3 -3 -3 +10
-10 +3 +3 +3
Loss or Gain (dB)
+2
+3
+4
+5
+6
+7
+8
+9
+10
+11
Combination of 10s and 3s
+3 +3 +3 +3 -10
+3
+10 -3 -3
+10 +10 -3 -3 -3 -3 -3
+3 +3
+10 -3
+10 +10 -3 -3 -3 -3
+3 +3 +3
+10
+10 +10 -3 -3 -3
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+1
+10 -3 -3 -3
+12
+3 +3 +3 +3
Part 2: In this part, you will use the Rule of 10’s and 3’s to solve three questions. Before you start
solving the questions below, read the PPTs posted on the Blackboard/Course website.
Q1: In Fig. 1, the access point is transmitting at 25 mW. The cable and connector between the
access point and the antenna creates –2 dB of signal loss. The antenna provides 17 dBi of signal
gain. Calculate the IR and EIRP values.
Figure 1
dBm mW
0
1
10
10
20
100
17
50
14
25
14 dBm = 29 mW
dBm mW
0
1
3
2
6
4
9
8
12
16
IR = 14 dBm – 2 dB = 12 dBm = 16 mW
dBm
mW
0
1
10
10
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20
100
23
200
26
400
29
800
EIRP=12dBm +17 dBi = 29 dBm = 800mW
Q2: In Fig. 2, the access point is transmitting at 250 mW. The cable and connector between the
access point and the antenna creates –5 dB of signal loss. The antenna provides 8 dBi of signal
gain. Calculate the IR and EIRP values.
Figure 2
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dBm
mW
0
1
10
10
20
100
30
1000
27
500
24
250
250mW=24dBm
IR=24-5=19dBm
EIRP=19+8=27dBm=500mW
dBm
mW
0
1
10
10
13
20
16
40
19
80
IR = 19dBm=80mW
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Q3: In Fig. 3, the access point is transmitting at 60 mW. The cable and connector between the
access point and the antenna creates –6 dB of signal loss. The antenna provides 12 dBi of signal
gain. Calculate the IR and EIRP values.
Figure 3
dBm
mW
x
60
X -3
30
X–3-3
15
X – 6 = x – 3 -3
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dBm
mW
x
60
X+3
120
X+3+3
240
X -6 + 12 = x+6 = x+3+3
IR = 15mW
EIRP = 240mW
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Part 3: Link Budget and Fade Margin
In this part you will learn about the link budget and fade margin. You will use a Microsoft Excel
file to calculate a link budget and fade margin.
1. From the BB, download the file LinkBudget.xls to your computer. Open the Excel file from your
computer.
2. In row 10, enter a link distance of 25 kilometers. Note that the path loss due to a 25 kilometer
link is now 128 dB in the 2.4 GHz frequency.
Question: How do you compare the FSPL of the three frequencies (900 MHz, 2.4 GHz, and 5.8
GHz)? Hint: See the values in the rows 12, 13, and 14 respectively.
Ans.
As the frequency of the radio wave rises, the attenuation of free-space path loss also rises.
3. In row 20, enter 128 for path loss in dB.
4. In row 23, change the radio receiver sensitivity to –80 dBm. Notice that the final received signal
is now –69 dBm, and the fade margin is only 11 dB.
5. Try increasing the “radio transmitter output power” to see how the connection would fare and
to determine how much power would be needed to ensure a fade margin of 20 dB.
Ans. The radio transmitter output power = ........29...... (dBm)
Question: The minimum value of radio transmitter to keep the communication successful is equal
to .......22........ (dBm)
You can also change the other components such as antenna gain and cable loss to ensure a fade
margin of 20 dB.
6. Now, start with the default values of the Excel File and examine the effect of different
parameters in the Excel file and make summary for yourself about the effect of each one of them
on both the Link Budget and the Fade Margin. After that answer the following questions:
A. What is the effect of increasing and decreasing the Radio Transmitter Output Power on both
Link Budget and Fade Margin? Ans.
Link Budget and Fade Margin rise mathematically as Radio Transmitter Output Power is
increased.
Link Budget and Fade Margin diminish mathematically as Radio Transmitter Output Power is
reduced.
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B. What is the effect of increasing and decreasing the Attenuation of Cables and Connectors on
both Link Budget and Fade Margin? Ans.
Increasing Reduced link budget and fading margin due to attenuation of cables and connectors
to the transmit antenna.
Decreasing The link budget and fading margin are increased by attenuating the cables and
connectors to the transmit antenna.
C. What is the effect of increasing and decreasing the Gain of Transmitting Antenna on both Link
Budget and Fade Margin? Ans.
Link budget and fading margin grow as transmitting antenna gain increases.
Link budget and fading margin are affected by the transmitting antenna's declining gain.
D. What is the effect of increasing and decreasing the Gain of Receiving Antenna on both Link
Budget and Fade Margin? Ans.
Link budget and fading margin rise as receiving antenna gain increases.
Link budget and fading margin are affected by the receiving antenna's declining gain.
E. What is the effect of increasing and decreasing the Radio Receiver Sensitivity on both Link
Budget and Fade Margin? Ans.
Fade margin and link budget are reduced by increasing radio receiver sensitivity.
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Fade margin and link budget are increased by decreasing radio receiver sensitivity.
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