THE COPPERBELT UNIVERSITY
SCHOOL OF ENGINEERING
ELECTRICAL ENGINEERING DEPARTMENT
ET 571 – MOBILE COMMUNICATION
TERM TEST 1
DURATION: 2hours
DATE: 18th November, 2016
INSTRUCTIONS: ATTEMPT TWO QUESTIONS INCLUDING QUESTION 3
Question 1
i.
What co-channel reuse coefficient?
[2 marks]
ii.
Draw a cluster of hexagonal cells, which has a cluster size of N=4. Assuming that you can choose from a
range of frequencies fi, i = 1, 2, …, show what frequency is to be used in each cluster cell and in each cell
of 2 neighbor clusters (with same cluster size).
[2.5 marks]
iii.
If the cell range is R=1000 m, what is the value of the re-use distance?
[2.5 marks]
iv.
What is the value of the Signal-to-Interference ratio (SIR) in decibels for this cluster size, in an environment
with the path loss factor n=4?
v.
[3 marks]
What is the cluster size (N) in the figure below? If the cell range is R=100 m, what is the value of the reuse distance? What is the value of the signal-to-interference ratio (SIR) in decibels for this cluster size, in
an environment with the path loss exponent n=3?
[10 marks]
Question 2
a)
A GSM900 MHz operator has 12 carriers and uses a cluster size of 4. How much traffic (per cell) can the
operator serve with 2 % blocking probability. (The network is ideal with spatially homogeneously
distributed traffic and equal-sized cells.)
b)
[4 marks]
To meet the increasing capacity, demand the operator opens a GSM1800 MHz network with 36 carriers
given the same coverage using same base stations as the GSM900 MHz network and having the same reuse
factor. Determine how large total traffic the operator can now serve with 2 % blocking probability? Assume
dual-band mobiles that can switch between GSM frequencies.
[5 marks]
c)
A busy mining town has a population of 620, 000 people and an area 9 square kilometers. Of its population,
70% are in employment and two thirds of them own mobile handsets. During lunch time break, a quarters
of the employees with mobile handsets make a call of atleast 30 second to their family. If the grade of
service acceptable is 1%, and given a cluster size of 4 and that 196 channels are available,
i. Calculate the total carried traffic and the offered load per cell
ii. Determine the cell radius required for a cellular system in the town
[6 marks]
[5 marks]
Question 3
You are a mobile operator and the regulator has just give you a license to build a GSM 900 cellular system (the
application cost for the license being ZMW500). The license is to cover 140 square kilometers. Assume a base
station cost ZMW500,000 and the MTSO cost ZMW1.5 million. An extra ZMW500,000 is needed to advertise
and start the business. You have convinced the bank to loan you ZMW6 million, with the idea that in four years
you will have earned ZMW10 million in gross billing revenue, and will have paid off the loan.
a) How many base stations will you be able to install for ZMW6 million.
[5 marks]
b) Assuming the earth is flat and subscribers are uniformly distributed on the ground, what assumption can
you make about the coverage area of each cell site? Further, what is the major radius of each of these cells
if hexagonal mosaic is used?
[5 marks]
c) Assume that the average customer will pay ZMW50 per month over a 4 year period. Assume also that on
the first day you turn your system on, you have a certain number of customers which remain fixed
throughout the year. On the first day of each new year the number of customers using your system doubles
and then remains fixed for the rest of the year. What is the minimum number of customers you must have
on the first day of service in order to have earned ZMW10 million in gross revenues by the end of the fourth
year of operation?
[5 marks]
d) Base on your answer in (c) above, how many users per square km are needed on the first day of service in
order to reach the ZMW10 million mark after the 4th year?
[5 marks]
Erlang B Table
No. of
Trunks
(N)
1
2
3
4
5
6
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
Erlang B Table
0.5%
1%
1.5%
2%
3%
5%
0.005
0.105
0.349
0.701
1.13
1.62
2.16
2.73
3.33
3.96
4.61
5.28
5.96
6.66
7.38
8.10
8.83
9.58
10.3
11.1
11.9
12.6
13.4
14.2
15.0
15.8
16.6
17.4
18.2
19.0
19.9
20.7
21.5
22.3
23.2
24.0
24.8
25.7
26.5
27.4
28.2
29.1
29.9
30.8
31.7
32.5
33.4
34.2
35.1
36.0
0.010
0.153
0.455
0.869
1.36
1.91
2.50
3.13
3.78
4.46
5.16
5.88
6.61
7.35
8.11
8.88
9.65
10.4
11.2
12.0
12.8
13.7
14.5
15.3
16.1
17.0
17.8
18.6
19.5
20.3
21.2
22.0
22.9
23.8
24.6
25.5
26.4
27.3
28.1
29.0
29.9
30.8
31.7
32.5
33.4
34.3
35.2
36.1
37.0
37.9
0.02
0.19
0.53
0.99
1.52
2.11
2.73
3.40
4.08
4.80
5.53
6.27
7.03
7.81
8.59
9.39
10.19
11.00
11.82
12.65
13.48
14.32
15.16
16.01
16.87
17.72
18.59
19.45
20.32
21.19
22.07
22.95
23.83
24.72
25.60
26.49
27.39
28.28
29.18
30.08
30.98
31.88
32.79
33.69
34.60
35.51
36.42
37.34
38.25
39.17
0.020
0.223
0.602
1.09
1.66
2.28
2.94
3.63
4.34
5.08
5.84
6.61
7.40
8.20
9.01
9.83
10.7
11.5
12.3
13.2
14.0
14.9
15.8
16.6
17.5
18.4
19.3
20.2
21.0
21.9
22.8
23.7
24.6
25.5
26.4
27.3
28.3
29.2
30.1
31.0
31.9
32.8
33.8
34.7
35.6
36.5
37.5
38.4
39.3
40.3
0.031
0.282
0.715
1.26
1.88
2.54
3.25
3.99
4.75
5.53
6.33
7.14
7.97
8.80
9.65
10.5
11.4
12.2
13.1
14.0
14.9
15.8
16.7
17.6
18.5
19.4
20.3
21.2
22.1
23.1
24.0
24.9
25.8
26.8
27.7
28.6
29.6
30.5
31.5
32.4
33.4
34.3
35.3
36.2
37.2
38.1
39.1
40.0
41.0
41.9
0.053
0.381
0.899
1.52
2.22
2.96
3.74
4.54
5.37
6.22
7.08
7.95
8.83
9.73
10.6
11.5
12.5
13.4
14.3
15.2
16.2
17.1
18.1
19.0
20.0
20.9
21.9
22.9
23.8
24.8
25.8
26.7
27.7
28.7
29.7
30.7
31.6
32.6
33.6
34.6
35.6
36.6
37.6
38.6
39.6
40.5
41.5
42.5
43.5
44.5
No. of
Trunks
(N)
Erlang B Table
0.5%
1%
1.5%
2%
3%
5%
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
36.9
37.7
38.6
39.5
40.4
41.2
42.1
43.0
43.9
44.8
45.6
46.5
47.4
48.3
49.2
50.1
51.0
51.9
52.8
53.7
54.6
55.5
56.4
57.3
58.2
59.1
60.0
60.9
61.8
62.7
63.6
64.5
65.4
66.3
67.2
68.1
69.0
69.9
70.8
71.8
72.7
73.6
74.5
75.4
76.3
77.2
78.2
79.1
80.0
38.8
39.7
40.6
41.5
42.4
43.3
44.2
45.1
46.0
46.9
47.9
48.8
49.7
50.6
51.5
52.4
53.4
54.3
55.2
56.1
57.0
58.0
58.9
59.8
60.7
61.7
62.6
63.5
64.4
65.4
66.3
67.2
68.2
69.1
70.0
70.9
71.9
72.8
73.7
74.7
75.6
76.6
77.5
78.4
79.4
80.3
81.2
82.2
83.1
40.08
41.00
41.92
42.84
43.77
44.69
45.62
46.54
47.47
48.40
49.33
50.26
51.19
52.12
53.05
53.99
54.92
55.86
56.79
57.73
58.67
59.61
60.55
61.49
62.43
63.37
64.32
65.26
66.20
67.15
68.09
69.04
69.99
70.93
71.88
72.83
73.78
74.73
75.68
76.63
77.58
78.53
79.48
80.43
81.39
82.34
83.29
84.25
85.20
41.2
42.1
43.1
44.0
44.9
45.9
46.8
47.8
48.7
49.6
50.6
51.5
52.5
53.4
54.4
55.3
56.3
57.2
58.2
59.1
60.1
61.0
62.0
62.9
63.9
64.9
65.8
66.8
67.7
68.7
69.6
70.6
71.6
72.5
73.5
74.5
75.4
76.4
77.3
78.3
79.3
80.2
81.2
82.2
83.1
84.1
85.1
86.0
87.0
42.9
43.9
44.8
45.8
46.7
47.7
48.7
49.6
50.6
51.6
52.5
53.5
54.5
55.4
56.4
57.4
58.4
59.3
60.3
61.3
62.3
63.2
64.2
65.2
66.2
67.2
68.1
69.1
70.1
71.1
72.1
73.0
74.0
75.0
76.0
77.0
78.0
78.9
79.9
80.9
81.9
82.9
83.9
84.9
85.8
86.8
87.8
88.8
89.8
45.5
46.5
47.5
48.5
49.5
50.5
51.5
52.6
53.6
54.6
55.6
56.6
58.6
59.6
60.6
61.6
62.6
63.7
64.7
65.7
66.7
67.7
68.7
69.7
70.8
71.8
72.8
73.8
74.8
75.8
76.9
77.9
78.9
79.9
80.9
82.0
83.0
84.0
85.0
86.0
87.1
88.1
89.1
90.1
91.1
92.2
93.2
94.2