Computer and Communications Protocols
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ELE3040: Computer and Communications Protocols, Coursework
Submission deadline: 21th March 2023, 4pm [20% of total marks]
Question 1 [60 marks]
The free-space path loss (FSPL) equation can be expressed as
= � 4�2
The last term = � 4�2 corresponds to the propagation loss in the free-space. Unfortunately,
this model is not accurate enough in most cellular networks. Your first task is to find in the literature
the Hata model for small to medium sized city, large city, suburban area and open area (rural). Then,
you should plot (using MATLAB) LFS, LHata for distances [1km, 10km] and carrier frequency
900MHz. Assume that the height of the mobile station is 1m and that of the base station is 8m.
Repeat your simulations for frequency 1800MHz. What kind of observation can you make for the
impact of frequency?
Question 2 [40 marks]
Sliding window protocol with window size of 7 frames are used between the data link layers of
machines A and B. Assume that machine B sends an ACK (acknowledgement) for every frame it
receives without error, and it sends a NAK (negative acknowledgement) for every frame it receives
with error. This corresponds to a receiver window size of 1 frame. Assume also that no frames are
lost in the transmission medium. For the scenario shown in the figure on the right hand side, write
the numbers of the data frames indicated by a, b, c, d, e, f, g, and write the numbers of the ACKs
indicated by h, i, j, k, l, m, n, and also explain what kind of process does the receiver perform on
the frames indicated by p for each of the following cases:
a) For the Go-back-N method. [20 marks]
b) For the Selective Repeat AQR method. [20 marks]
2
Format and Deadlines
The report should typically consist of no more than 6 typed pages – marks will be deducted
for excessively long-winded reports. This report constitutes 20% of the total marks for this
module and you should allocate the effort to it accordingly.
The reports are to be submitted on Canvas before 21st March 2023, 4pm. Marks will be
deducted for every day after this date.