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Right choice is (b) Antenna of DIFFERENT heights

Best EXPLANATION: Umbrella cell approach is POSSIBLE by using different antenna heights and different power levels. By using this approach, it is possible to provide large and small CELLS which are co-located at a single LOCATION.

The correct CHOICE is (b) Footprint

To explain I would SAY: Actual radio coverage of a cell is known as the footprint. It is DETERMINED from field measurements or propagation prediction models. Although the real footprint is amorphous in nature, a regular cell shape is needed for SYSTEMATIC SYSTEM design.

Right CHOICE is (c) Erlang C

The best I can EXPLAIN: Erlang C is also KNOWN as Blocked Calls Delayed. In this trunked system, a queue is provided to hold calls which are blocked. If a CHANNEL is not available immediately, the call REQUEST may be delayed until a channel becomes available.

The correct choice is (a) MSC

Easiest explanation: Each TIME a call request is made, the serving base station REQUESTS a channel from the MSC. The switch then ALLOCATES a channel to the requested cell following an algorithm that takes into ACCOUNT the likelihood of FUTURE blocking within the cell.

Correct option is (c) Channel

The best I can explain: 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.

Correct CHOICE is (C) Antenna downtilting

Easy 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.

The correct choice is (b) CALL request rate and holding TIME

The explanation: The TRAFFIC INTENSITY offered by each user is equal to the call request rate multiplied by the holding time. Each user generates a traffic intensity A=λH ERLANG. Here, H is the average duration of a call and λ is the average number of call requests per unit time for each user.

Correct OPTION is (d) CELLS using same frequency

To explain I would say: DUE to frequency reuse concept, there are SEVERAL cells that use the same set of frequencies. These cells are called co-channel cells. And the INTERFERENCE between these cells is called co-channel interference.

Right OPTION is (c) OVERLAPPING regions or gaps are left

The explanation: Circle is the first natural choice to represent the coverage area of a base station. But while adopting this shape, adjacent CELLS cannot be OVERLAID upon a map without leaving gaps or creating overlapping regions.

Correct choice is (b) Repeaters

To explain I would say: 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.

Right option is (d) Erlang

Explanation: The MEASURE of traffic INTENSITY is given by Erlang. It is defined as the ratio of the time during which a facility is cumulatively occupied to the time this facility is AVAILABLE for occupancy. Telecommunication operators are vitally INTERESTED in traffic intensity as it dictates the amount of equipment they must supply.

Correct answer is (d) REDUCE total CARRIED traffic

Explanation: Guard CHANNEL is a concept for handling priority in handoff. Here, a fraction of the total available channels in a cell is reserved exclusively for handoff requests from ongoing calls. This METHOD has the disadvantage of reducing the total carried traffic, as fewer channels are allocated to ORIGINATING calls.

The correct option is (C) A small GEOGRAPHICAL area

Explanation: Cell is a small GEOGRAPHIC area in a cellular system. Each cellular BASE station within a cell is allocated a GROUP of radio channels that could be used in another cell.

The CORRECT answer is (b) False

The best I can explain: Cellular concept is a SYSTEM level idea that replaces a single high power transmitter to many low power TRANSMITTERS. High power transmitters lead to large cell, and THUS it was IMPOSSIBLE to use the same frequencies throughout the systems. But, it is possible with low power transmitter.

Correct answer is (b) 10 SECONDS

Best explanation: In first generation ANALOG CELLULAR SYSTEM, the typical time to make a handoff once the signal level is below the threshold, is about 10 seconds. This requires the value for threshold to be 6 DB to 12 dB.

Right answer is (d) INCREASE storage and computational load on system

Explanation: DYNAMIC channel assignment requires the MSC to collect real time data on channel occupancy, traffic distribution and RSSI of all channels on continuous basis. This INCREASES the storage and computational load on the system but provides the advantage of increased channel utilization and decreased probability of BLOCKED call.

The CORRECT option is (C) Blocked

The BEST I can explain: As any call attempt within a cell can be served by unused channels in fixed CHANNEL strategy. If all the channels in that cell are occupied, the call is blocked and subscriber does not receive any SERVICE.

The CORRECT option is (B) GROUP of cells

The BEST I can explain: Cluster is group of N cells. These cells use the complete set of frequency available for the cellular system at that location.

Right answer is (a) Cell splitting

The best I can explain: 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.

Right OPTION is (C) ERLANG

The BEST I can explain: The fundamentals of trunking theory were developed by Erlang. He was a Danish mathematician. He embarked on the study of how a large population could be accommodated by a LIMITED number of servers in late 19th century.

Correct option is (a) Locator receiver

The EXPLANATION is: Locator receiver is a spare receiver in each base STATION. It is used to scan and determine signal STRENGTHS of MOBILE USERS which are in neighbouring cells.

Correct option is (d) Make before break

For EXPLANATION: Soft handoff is one in which the channel in the source cell is RETAINED and USED for a while in parallel with the channel in the target cell. In this CASE, the connection with the receiver target is established before the connection to the source is broken, hence this HANDOVER is called make-before-break.

The CORRECT answer is (a) Largest area

To explain: For a given distance between the center of a polygon and its farthest perimeter POINTS, the hexagon has the largest area. Thus, by using the hexagon geometry, the FEWEST NUMBER of cells can cover a GEOGRAPHIC region.

Right CHOICE is (b) False

To elaborate: In a trunked radio system, each user is ALLOCATED a channel on a per call basis. Upon termination of the call, the previously occupied channel is immediately returned to the pool of available channels. It is a method for a system to provide NETWORK ACCESS to many clients by SHARING a set of lines or frequencies instead of providing them individually.

The correct choice is (b) False

The best 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.

Right answer is (a) Base station in a different cluster

The explanation is: INTERFERENCE is a major limiting FACTOR in the performance of cellular radio systems. Sources of interference includes another mobile in the same cell, a CALL in progress in neighbouring cell, other base stations OPERATING in the same frequency band, or any non-cellular system which INADVERTENTLY leaks energy into the cellular frequency band.

The CORRECT CHOICE is (a) Request rate

The best I can explain: Request rate is the average NUMBER of call requests per unit time. It is denoted by λ. Unit for request rate is second-1. It can also be defined as the ratio of traffic INTENSITY of each user and the holding time.

Correct CHOICE is (b) Channels

To elaborate: 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.

Right choice is (a) HOLDING TIME

Easy explanation: Average time of a typical call is called holding time. It is denoted by H (in seconds). It is used to MEASURE the traffic intensity PER user. The time over which a call may be maintained within a CELL, without handoff is called dwell time.

Correct ANSWER is (a) True

To explain I would SAY: Interference is more SEVERE in rural areas. It happens due to the GREATER RF noise floor and the LARGE number of base stations and mobiles.

Correct ANSWER is (a) 150 CHANNELS

Easiest explanation: Total bandwidth is 30 MHz. And the channel bandwidth is 50 KHz/duplex channel (25KHz*2). Therefore, total available channels are 600 channels (30,000/50). For 4 cell REUSE factor, total number of channels available per cell will be 150 channels (600/4).