Wireless & Mobile Communications Questions and Answers Part-14

1.Which of the following trunking inefficiencies?
a) Cell splitting
b) Micro cell zone technique
c) Sectoring
d) Repeaters

Answer: c
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.

2. The process of subdividing a congested cell into smaller cells is called _______
a) Cell splitting
b) Sectoring
c) Micro cell technique
d) Repeaters

Answer: a
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.

3. 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

Answer: b
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.

4. Cell splitting do not maintain the minimum c-channel reuse ratio.
a) True
b) False

Answer: b
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

5. Which of the following technique is used to limit radio coverage of newly formed microcells?
a) Sectoring
b) Splitting
c) Antenna downtilting
d) Scattering

Answer: c
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

6. Sectoring increases SIR (Signal to Interference Ratio).
a) True
b) False

Answer: a
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.

7. Which of the following has range extension capability?
a) Sectoring
b) Repeaters
c) Scattering
d) Micro cell zone concept

Answer: b
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

8. Repeaters has one drawback of reradiating ____________
a) Frequency
b) Channels
c) Power
d) Repeater noise and interference

Answer: d
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.

9. 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

Answer: d
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.

10. 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

Answer: c
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