# Assignments ```Mobile Communication (ETEC-314)
Assignments
Assignment No. 1
1. What do you mean by interference? How it affects the performance of a cellular system?
2. What are the components of a cellular system?
3. Why hexagonal shape is preferred over other cell shapes in cellular networks?
4. What is effect of antenna height?
5. Explain foliage loss.
6. What is frequency reuse distance? What are the parameters on which it depends?
7. Explain co-channel interference reduction factor. How it can be minimized?
8. Obtain the relation for signal to interference ratio for a 7-cell cluster in cellular system.
9. Explain different performance criterion of a cellular system with special emphasis on grade
of service.
10. Explain Uniqueness of mobile radio environment.
11. Explain Point to Point model.
12. In a mobile radio environment the average cell site antenna height is about 60 m , the
mobile antenna height is about 4 m, and the communication path length is 4 Km. Calculate

Incident angle

Elevation angle at the antenna of mobile unit

Elevation angle at the location of mobile unit
Assignment No.2
1. What is Cell Splitting? How is it advantageous?
2. What is meant by Handoff? Why is it required?
3. How many full duplex channels are required in each cell for a cellular system with 6
clusters, 7 cells per cluster and a total capacity of the system being 1050 full duplex
channels?
4. What gives rise to the constant standard deviation along a path loss curve? Explain with
diagram.
5. Explain the gain and pattern relationship of antenna.
6. Explain Umbrella pattern antennas.
7. Explain propagation over water loss.
8. Explain the advantages and disadvantages of the two-ray ground reflection model in the
analysis of path loss.
9. List five ways of increasing the coverage and capacity of cellular system.
10. Prove that for a hexagonal geometry, the co-channel reuse distance is Q = √3N where,
N = i2 + ij + j2
11. Suppose 5 cells originally cover a congested service area with 80 channels/cell. Find its
channel capacity. Now, if cell splitting is done with new radius exactly half, find its new
channel capacity. Assume path loss exponent n = 4.
12. Determine depth loss for a signal with frequency 1 GHz, at a distance of 10 Km.What will
be the far field distance for a base station antenna with largest antenna dimension D =
0.5m, frequency of operation f = 900 MHz ? If frequency of operation is changed to f =
1800 MHz, then find far field distance?
Assignment No.3
1. Describe the term Bandwidth Efficiency.
2. What are the types of error control methods?
3. Explain about error detection and correction capabilities of hamming codes.
5. A (15,5) linear cyclic has a generator polynomial,
G (p) = p10+p8+p5+p4+p+1
(a) Draw the block diagram of an encoder and syndrome calculator for this code.
(b) Find the code polynomial for message polynomial M(p) = p4+p2+1 (in systematic
form)
6. What is constraint length for convolution encoders?
7. Define the following terms
a. Code Word
b. Code Rate
c. Hamming Distance
d. Hamming Weight
e. Block Length
8. Explain the linearity property of Block codes.
9. Give a short note on concatenated turbo codes.
10. Write short note on Vocoders.
Assignment No. 4
1. How the grouping of channels into subsets is done in frequency management?
2. Differentiate between soft and hard handoff.
3. Explain Mobile high gain antennas.
4. How omni-directional and directional antennas are arranged in system configuration to
reduce the interference?
5. Explain the formula of dropped call rate in detail.
6. What is the role of BSC and MSC in handoff?
7. Distinguish b/w dropped call and terminated call.
8. Define :

Forced handoff

Paging channel
9. What are the types of cell-site antenna? Compare them according to geographical area of a
cell.
10. Give all the differences b/w fixed and non-fixed channel assignment.
11. If 25 MHz of total spectrum is allocated for a duplex wireless cellular system and each
simplex channel has 25 KHz RF bandwidth, find:
No. of duplex channels

Total no. of channels/site, if N = 4 cell reuse is used.
12. If Pt = 10W, Gt = 0db, Gr = 0db, fc = 900 MHz. Find P6 in watts at a free space distance of
1Km.
Assignment No. 5
1. Why we prefer TDMA in digital cellular system?
2. The GSM TDMA system uses a 48.6kbps data rate to support three users per frame. Each
user occupies two of the six time slot per frame. What is the raw data rate provided for
each user?
3. Explain QPSK modulation technique in detail. Why do we prefer MSK over QPSK?
4. What are the advantages of digital modulation techniques over analog modulation
techniques?
5. What is orthogonality? How OFDM proves to be a better modulation technique over
others?
6. For a PCM system with following parameters : -


Maximum decoded voltage at the receiver = 2.25 V

Minimum dynamic range = 46 dB
Determine (a) the minimum sample rate (b) minimum no. of bits used in the PCM code (c)
resolution (d) quantization error
7. Explain all the setup channels in GSM architecture.
8. Explain three types of multiple access techniques. Why CDMA technique is more secure
over others?
9. What are training bits and why they are used in GSM burst architecture?
10. What is IS 95 CDMA network? How it is different from its competing TDMA based GSM
technology?
11. Explain how orthogonality and auto-correlation properties are helpful in designing the
spreading sequences without interference in CDMA systems?
12. What is Fraunhofer distance? How it influences to find the coverage area of long distance
propagation?
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