This set of Wireless & Mobile Communications Interview Questions and Answers for freshers focuses on “Improving Coverage and Capacity in Cellular Systems”.
1. Which of the following techniques do not help in expanding the capacity of cellular system?
a) Sectoring
b) Scattering
c) Splitting
d) Microcell zone concept
View Answer
Explanation: As the demand for wireless service increases, the number of channels assigned to a call eventually becomes insufficient to support the required number of user. Techniques such as cell splitting, sectoring and coverage zone approaches are used in practice to expand the capacity of cellular system.
2. ________ uses directional antennas to control interference.
a) Sectoring
b) Cell splitting
c) Repeaters
d) Micro cell zone concept
View Answer
Explanation: Sectoring uses directional antenna to further control the interference and frequency reuse of channels. By decreasing the cell radius R and keeping the co-channel reuse ratio D/R unchanged, cell splitting increases the number of channels per unit area.
3. _______ allows an orderly growth of cellular system.
a) Sectoring
b) Scattering
c) Cell splitting
d) Micro cell zone technique
View Answer
Explanation: Cell splitting allows an orderly growth of cellular system. By defining new cells which have a smaller radius than the original cells, capacity increases due to additional number of channels per unit area.
4. Which of the following technology distributes the coverage of the cell and extends the cell boundary to hard-to-reach places?
a) Cell splitting
b) Scattering
c) Sectoring
d) Micro cell zone concept
View Answer
Explanation: Micro cell zone concept distributes the coverage of the cell and extends the cell boundary to hard-to reach places. It is the solution for the problem of increased number of handoffs when sectoring which results in an increase of load on switching.
5. Which of the following increases the number of base stations in order to increase capacity?
a) Cell splitting
b) Sectoring
c) Repeaters
d) Micro cell zone concept
View Answer
Explanation: Cell splitting increases the number of base stations in order to increase capacity. Whereas, sectoring and zone microcells rely on base station antenna placements to improve capacity by reducing co-channel interference.
6. Which of the following trunking inefficiencies?
a) Cell splitting
b) Micro cell zone technique
c) Sectoring
d) Repeaters
View Answer
Explanation: Sectored cells experience trunking inefficiencies. Cell splitting and zone micro cell techniques do not suffer the trunking inefficiencies experienced by sectored cells. They enable the base station to oversee all handoff chores related to microcells, thus reducing the computational load at MSC.
7. The process of subdividing a congested cell into smaller cells is called _______
a) Cell splitting
b) Sectoring
c) Micro cell technique
d) Repeaters
View Answer
Explanation: Cell splitting is the process of subdividing a congested cell into smaller cells. Each small cell has its own base station and a there is a corresponding reduction in antenna height and transmitter power.
8. Cell splitting increases the capacity of a cellular system since it increases the number of times ________ are reused.
a) Cells
b) Channels
c) Transmitters
d) Mobile stations
View Answer
Explanation: Cell splitting increases the capacity of a cellular system since it increases the number of times channels are reused. But it has a limitation that handoffs are more frequent and channel assignments become more difficult.
9. Cell splitting do not maintain the minimum c-channel reuse ratio.
a) True
b) False
View Answer
Explanation: Cell splitting allows a system to grow by replacing large cells with smaller cells. It does not upset the channel allocation scheme required to maintain the minimum co channel reuse ratio Q between co-channel cells.
10. Which of the following technique is used to limit radio coverage of newly formed microcells?
a) Sectoring
b) Splitting
c) Antenna downtilting
d) Scattering
View Answer
Explanation: Antenna downtilting deliberately focuses radiated energy from the base station toward the ground (rather than toward the horizon). It is often used to limit the radio coverage of newly formed microcells.
11. Sectoring increases SIR (Signal to Interference Ratio).
a) True
b) False
View Answer
Explanation: Sectoring increases SIR so that cluster size may be reduced. SIR is improved using directional antenna. And then capacity improvement is achieved by reducing the number of cells in a cluster, thus increasing the frequency reuse.
12. Which of the following has range extension capability?
a) Sectoring
b) Repeaters
c) Scattering
d) Micro cell zone concept
View Answer
Explanation: Wireless operator needs to provide dedicated coverage for hard-to-reach areas, such as within buildings, or in valleys or tunnels. Radio transmitters used to provide such range extension capabilities are called as repeaters. They are bidirectional in nature.
13. Repeaters has one drawback of reradiating ____________
a) Frequency
b) Channels
c) Power
d) Repeater noise and interference
View Answer
Explanation: Upon receiving signals from a base station forward link, the repeater amplifies and reradiates the base station signals to the specific coverage region. Unfortunately, the received noise and interference is also reradiated by repeater on both the forward and reverse link.
14. Which of the following is not an advantage of micro cell zone technique?
a) Reduced co channel interference
b) Improved signal quality
c) Increase in capacity
d) Increasing number of base stations
View Answer
Explanation: The advantage of the zone cell technique is that co-channel interference in the cellular system is reduced since a large central base station is replaced by several low powered transmitters on the edges of the cell. Thus, signal quality is reduced and it leads to an increase in capacity.
15. In a micro cell zone concept, when a mobile travels from one zone to another within the cell, it retains the same _________
a) Power level
b) Base station
c) Channel
d) Receiver
View Answer
Explanation: As a mobile travels from one zone to another within the cell, it retains the same channel. Thus, unlike in sectoring, a handoff is not required at the MSC when the mobile travels between zones within the cell. The channels are re used in co channel cells in a normal fashion.
Sanfoundry Global Education & Learning Series – Wireless & Mobile Communications.
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