ITCE417: Mobile and Wireless Networking

Department of Computer Engineering
College of Information Technology
University of Bahrain
ITCE417: Mobile and Wireless Networking
Lab 2: Link Budget Calculation
Introduction
A link budget is accounting of all the gains and losses from the transmitter, through the medium (free
space, cable, waveguide, fiber, etc.) to the receiver in a telecommunication system. It accounts for the
attenuation of the transmitted signal due to propagation, as well as the antenna gains. In this lab, we
will perform a simple link budget calculation using the following formula:
Link budget (dBm) = Transmit Power (dBm) + Gains (dB) – Losses (dB)
Objectives
Learn how to calculate the link budget for wireless communication systems.
Figure 1: Example plot for users distributed in circular cell with BS in centre
Procedure
First, check the function files supplied with this lab sheet, which are:
a. Main script “Lab 2 “
b. Script with function “GenerateCell”
c. Script with function “CalculatePL”
d. Script with function “CalculatingLinkBudget”
Step1: lab2
This is the main script that call all functions explained in steps 2-4. The following is snapshot of the
main script that you need to complete.
Figure 2: “Lab 3” main script code
Step2: GenerateCell
This script creates one cell only with radius 500m. Then distribute 50 users within the vicinity of this
cell at random distances. Assume the BS is placed at the origin point (0,0). The ‘GenerateCell’ function
should return the coordinates of the users in two-dimensional matrix with size (N * 2), where N is the
number of users, and the distance of each user from the BS stored in a vector of size N*1. The following
is part of the code that you need to complete !
Figure 3: “GenerateCell” script code
Step 3: CalculatePL
After calculating the distance, calculate the pathloss between BS and users in by calling the
“CalculatePL” function. Use the Log-Distance pathloss model to evaluate the PL assuming small; cells
case:
PL (dB)= PL(d0) + 10nlog(d/d0) + χ0
Where PL(d0) is given by 20log10(4πd0/λ), assume d0 =1m since it is a small cell and the path loss
exponent n=2. χ0 is the shadowing effect which can be calculated using ‘randn*σ’. The notation σ
denotes the log-normal shadowing which is assumed to be 8 dB. This function returns a vector of PL
values for all users, so the size of returned vector is N*1. Check the code below to complete !
Figure 4: “CalculatePL” script code
Step 4: Calculating Link Budget
Finally, calculate the link budget by calling the function” “CalculatingLinkBudget” using the
following formula
Link budget (dBm) = Transmit Power (dBm) + Antenna Gain (dB) – PL (dB)
Assuming small cells are deployed, the transmit power is given by 20 dBm and the antenna gain is 10
dBi. The functions returns the link budget values for all users. The following figure demonstrate the
function code that you need to complete.
Figure 5: “Calculating Link Budget” script code
Report
Include the following in your report:
1. Objectives.
2. A snapshot of the script code for each function and discuss the line of codes you added.
3. Plot the users and BS locations as in figure 1.
4. Plot the LinkBudget for all users, such that the X axis of the graph represents the distance of the
user and the Y axis represents the LinkBudget in dB. Explain how distance affect link budget
according to the graph.
5. Explain the importance of calculating the link budget.