Wireless Networks and Communication - Networking Assignment Solution

This document provides a detailed solution to a networking assignment focusing on wireless networks and communication. The solution addresses various aspects, including digital signal modulation techniques like two-level amplitude shift keying and frequency shift keying, and calculations related to frequency modulation. It also covers error detection using Cyclic Redundancy Check (CRC) and provides a practical example of CRC calculation. Furthermore, the assignment explores the concept of spreading the input signal using a PN bit stream, and it concludes with an explanation of why hexagonal cell shapes are preferred in cellular networks. The solution includes figures and references to support the explanations.

Wireless networks and communication

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Answer 1
The digital signal= 110101
a. Two-level amplitude shift keying
b. Two-level Frequency Shift Keying
c. Two-level Phase Shift Keying

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d. Differential Phase shift keying
e. Four level Amplitude Shift Keying
f. Four level Phase Shift Keying

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g. Eight level Amplitude Shift Keying
Answer 2
The given data and facts in the question are highlighted below:
Fc= 1000 KHz
Fd= 50 KHz
M= 16
L= 4 bits
The below formula will help for finding total frequency:
Fi= Fc + (2i-L-M)*Fd

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It is identified that for this formula, i= 1, 2, 3, 4, …………….. 16 and putting all these values in
the above equation total frequency may be determined. The below table includes all these
values at different signals:
Fi Output (kHz)
F1 100
F2 200
F3 300
F4 400
F5 500
F6 600
F7 700
F8 800
F9 900
F10 1000
F11 1100
F12 1200
F13 1300
F14 1400
F15 1500
F16 1600
Answer 3
It is examined that frequency modulation enhances the frequency of the input signal by
adding a larger frequency signal and reduce the errors and distortions in the
communication systems. The below signal is transmitted by the source which can be
modulated using frequency modulation technique:

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Answer 4
Answer 5
CRC refers to the cyclic redundancy check which is mainly used for identifying errors from
the transmitted signals [2]. In which the signal is divided with the input pattern and
determine the error occur in the data communication systems. The below diagram shows
the process of CRC technique which includes both sender and receiver along with the
transmitted signals:
Figure: CRC process [2]

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Answer 6
Message signal= 111010110 and Pattern signal= 101110
So, dividing the message signal by pattern value error or CRC value can be determined. It is
examined that CRC is capable to find errors from the signals which help for performing
data communication effectively. Therefore, for this signal value of CRC is 01100.
Answer 7
Input value= 101
PN bit stream= 011011010110
T= 4*Tc
Transmitted signal= Input signal + PN stream
Here, the input signal after spreading is 111100001111
So, the Transmitted signal is 100111011001
Answer 8
The major reason for selecting hexagonal cell shape is that it is capable to cover the entire
area without overlapping which cannot be done in the square and circle cells [2]. Moreover,
in terms of effectiveness and reliability hexagonal cell shape is more appropriate as

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compared with the circle and square shapes. From the previous investigation, it is found
that circular and square shapes cannot be used in the cellular networks because of the gaps
present between the base station and antennas.

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References
[1].S., Li, Y., Deng, X., Gao, H., Li, L., Guo and, Z. Dong, “Generalized Segmented Bit-
Flipping Scheme for Successive Cancellation Decoding of Polar Codes With Cyclic
Redundancy Check,” IEEE Access, vol. 7, no. 5, pp. 83424-83436, 2019.
[2].R., Diaz-Salmeron, G. Ponchel and, K., Bouchemal, “Hierarchically built hyaluronan
nano-platelets have a symmetrical hexagonal shape, flattened surfaces, and
controlled size," European Journal of Pharmaceutical Sciences, vol. 133, no. 6,
pp.251-263, 2019.