Question

Section A (40pt). In this section you decide whether a given statement is true (T) or false (F). Place letter T within the parenthesis if the statement is true; otherwise, place F. In this section, when we mention "cellular system," we refer to those which is not a CDMA-based system. 1. Base station decides which mobile needs to handoff and manages the handoff process 2. In an FDD system, the frequency band is split into multiple frequency channels and each channel is used by only one mobile 3. )If the system has C channels, then the maximum traffic is A C Erlangs 4. If a system has 25 channels, then the maximum traffic of 50 Erlang would be allowed 5. ()The smaller GoS, the smaller total allowed traffic in the system 6. ()If total traffic is A 10 Erlang in a wireless system and if each user has Au -0.5 Erlang traffic, then the maximum number of mobiles in this system can be upto 20 mobiles 7. The farther the cells that make use of the same frequency channels, the higher the co-channel interference 8. ( ) Assume the grade of service is 3%. This means that, the system may block upto 3 calls out of 100 calls at the busiest time 9. Microcell zone concept tries to reduce the system complexity by reducing the number of handoffs 10.( As the mobile moves within a system which employs microcell concept, the mobile is served by the closest base station but its currently used channel is not changed 11. ( Let dr be the far-field distance of a given antenna. Then the Friis' formula can be used for estimating received power levels for distances that is smaller than de 12. Electromagnetic wave may change its direction and speed by through reflection, refraction, and diffraction 13. (T) When we look at a straw which is half-way inserted into a glass of water, the straw seems to be broken at the surface of the water. This is due to refraction.

Answer 1

1.True(base station decides the handoff between mobiles)

2.False(the same frequency is used by other cell, if that band of frequency is free)

3.False(maximum traffic is grater than the no of channels by a factor)

4.False(maximum traffic should not be double the no of channels)

5.True(Grade of Service indirectly proportional to traffic in system)

6.True

7.True(same ferquency of a particular cell can be used by farther cell)

8.True

9.False(microcell concept increases the system complexity)

10.True(mobile is served as closest base station always in a microcell concept)

11.True

12.True(EMW changes its speed and direction when it strikes a medium)

13.True(this is due to refraction)