1.Explain
about Concept of cell splitting?
Cell splitting
is the process of. subdividing a congested cell into smaller cells,
each with its own base station and a corresponding reduction in antenna height
and transmitter power. • Cell splitting increases the. capacity of a cellular
system since it increases the number of times that channels are reused.
2.Types
of co channel interference?
Repeated use of the
same frequency channels in different co-channel cells produces co-channel
interference. Non-co-channel interference (NCCI) - Non-co-channel interference
is due to signals that are adjacent in the frequency to the desired
signal.
3.Channel sharing?
In telecommunication,
frequency sharing or channel sharing is the assignment to or use of the
same radio frequency by two or more stations that are separated geographically
or that use the frequency at different times.
4.What is omni cell and
sectorized cell ?
Omni cells:
An omni cell is a cell where the
antenna transmits omni-directional. The coverage area of an omni cell is in
principle a hexagon/circle, but in reality a rough pattern.
Sector cells:
A sector cell is a cell where the
antenna transmits directional.
Examples of sector cell types are:
- 2-sector cells
(e.g. for highways)
- 3-sector cells.
2. Explain about frequency Reuse concept?
Frequency reusing is the concept of
using the same radio frequencies within a given area, that are separated by
considerable distance, with minimal interference, to establish communication.
Frequency reuse offers the following
benefits −
Allows communications within cell on a
given frequency
Limits escaping power to adjacent cells
Allows re-use of frequencies in nearby
cells
Uses same frequency for multiple
conversations
10 to 50 frequencies per cell
3.a)Explain about permeance criteria of
cellular mobile communication?
The system should serve an area as large as possible.
The transmitted power would have to be very high to illuminate weak spots with
sufficient reception, a significant added cost factor. The higher the
transmitted power, the harder it becomes to control interference.
b) Explain about
cellular traffic?
Mobile radio networks
have traffic issues that do not arise in connection with the fixed line PSTN.
Important aspects of cellular traffic include: quality of service targets,
traffic capacity and cell size, spectral efficiency and sectorization, traffic
capacity versus coverage, and channel holding time analysis. Trunking
Cellular radios rely on trunking to
accommodate a large number of users in a limited radio spectrum. Each user is
allocated a channel on need/per call basis and on termination of the cell, the
channel is returned to the common pool of RF channels.
Grade of Service (GOS)
Because of trunking, there is a
likelihood that a call is blocked if all the RF channels are engaged. This is
called ‘Grade of Service’ “GOS”.
Cellular designer estimates the maximum
required capacity and allocates the proper number of RF channels, in order to
meet the GOS. For these calculations, ‘ERLANG B’ table is used.
