Calculate FSPL in dB for 5Km and 10Km for 5.8GHz and 2.4GHz frequencies

Learn how to calculate Free Space Path Loss (FSPL) in dB for a distance of 5Km and 10Km for two different frequencies 5.8GHz and 2.4GHz. Understand the formula and calculations involved.

A.
Calculate the FSPL in dB for a distance of 5Km and 10Km for two different frequencies 5.8GHZ, 2.4GHz
and construct a table as follows:
FSPL(dB)
Distance (Km) 2.4GHz 5.8GHZ
5
10
FSPL – free space path loss is proportional to the distance and frequency. In other words, FPSL is
proportional to the square of the frequency of the radio signal and as well as it is proportional to the
square of the distance between the transmitter and the receiver.( Idc-onlinecom. 2019.)
The FSPL in dB for a distance of 5Km and 10Km for two different frequencies 5.8GHZ, 2.4GHz is
calculated as follows:
Formula:
FPSL (dB) = 20 log10 (d) + 20 log10 (f) +32.45
The FSPL in dB for a distance of 5Km and for the frequency of 2.4GHz is calculated as follows:
For 2.4GHz,
At, d=5 Km
FPSL (dB) = 20 log10 (5) + 20 log10 (2.4G) +32.45
= 13.9794 + 187.60 + 32.45
= 234.02 dB
The FSPL in dB for a distance of 10Km and for the frequency of 2.4GHz is calculated as follows:
At, d=10 Km
FPSL (dB) = 20 log10 (10) + 20 log10 (2.4G) +32.45
= 20 + 187.60 + 32.45
= 240.05 dB
For 5.8GHz,
The FSPL in dB for a distance of 5Km and for the frequency of 5.8GHz is calculated as follows:
At, d=5 Km

FPSL (dB) = 20 log10 (5) + 20 log10 (5.8G) +32.45
= 13.9794 + 195.268 + 32.45
= 241.697 dB
The FSPL in dB for a distance of 5Km and for the frequency of 5.8GHz is calculated as follows:
At, d=10 Km
FPSL (dB) = 20 log10 (10) + 20 log10 (5.8G) +32.45
= 20 + 195.268 + 32.45
= 247.718 dB
Below is a table summarizing the FPSL in dB for given distance of 5Km and 10Km for two different
frequencies 5.8GHZ, 2.4GHz
FSPL(dB)
Distance (Km) 2.4GHz 5.8GHZ
5 234.02 241.697
10 240.05 247.718
B.
For the information given below, calculate the link budget analysis for the wireless system, which will
involve calculating the following:
Received power
Link margin
Distance: 5Km
Frequency: 5.8GHz
Link type: point-to-point, line-of-sight
Tx power: +23dBm
Antenna gain: 24dBi
Assume negligible loss for cabling and connectors
Receiver sensitivity: -72dBm
It is being estimated that, if the received power is more than that of the link margin, the link budget is
said to be sufficient enough to send the data under perfect conditions. (Quoracom. 2019)
Link margin is the difference between the received power and the receiver sensitivity. In other words,
the amount by which the received power exceeds the receiver sensitivity is called the link margin.

Link budget analysis:
First, we need to calculate the received power. In order to calculate it, we need to know transmitter
power, the gain of the antenna and the losses. And then, we have to calculate the link margin and are
done by knowing received power along with the received sensitivity.
Formulae:
Received Power (dBm) = transmitted Power (dBm) + Gain (dB) – Losses (dB)
Gains (dB) = Transmit Antenna gain + Receiver Antenna Gain
The received power can be calculated as,
Received Power (dBm) = 23 +24–0 = 47 dBm
The link margin can be calculated as,
Link Margin = Received Power – Received Sensitivity
Link Margin = -47 – (-72) = 25 dBm
The link budget analysis for the wireless system is given by the formula,
Link budget = Received power – FPSL
Link budget can be calculated as follows,
Link Budget = 47 – 241.697
= -194.697 dBm
C.
For the calculated link margin at 5Km what can you say about the availability/reliability of the link based
on the following Table which shows the relationship between the available link margin and link
availability as a percentage of the time.
Time availability (Percentage) Link /Fade Margin
90 8
99 18
99.9 28
99.99 38
99.999 48
At this point, we need to ensure that, the obtained link margin is enough for a reliable link. As per
calculation, we have obtained the link margin of more than 20dB:

In order to calculate the link margin, we need to know, received power as well as the received sensitivity.
The obtained received power is 47dBm and the given received sensitivity is 72dBm.( Ques10com. 2019.)
The link margin can be calculated as,
Link Margin = Received Power – Received Sensitivity
Link Margin = -47 – (-72) = 25 dBm
The link margin seems to be sufficient at 5km to transmit the data and ensure better than 99% link
availability based on the Rayleigh’s Fading Model.
The obtained link margin is of 25dB. From the given table, it’s clear that our link margin lies between the
ranges of 18 to 28. And the availability of time in percentage may range from 99 to 99.9.
References:
Idc-onlinecom. 2019. Idc-onlinecom. [Online]. [29 May 2019]. Available from: http://www.idc-
online.com/technical_references/pdfs/electronic_engineering/Free_Space_Loss.pdf
Quoracom. 2019. Quoracom. [Online]. [29 May 2019]. Available from: https://www.quora.com/Why-is-
the-received-power-negative-in-wireless-communication
Ques10com. 2019. Ques10com. [Online]. [29 May 2019]. Available from:
http://www.ques10.com/p/2681/explain-link-budget-analysis-and-requirements-of-1/
Researchgatenet. 2019. ResearchGate. [Online]. [29 May 2019]. Available from:
https://www.researchgate.net/publication/320465087_LINK_MARGIN_FOR_WIRELESS_RADIO_CO
MMUNICATION_LINK