EC2401- Wireless Communication
VII semester
EC2401 - WIRELESS COMMUNICATION
2MARKS:
UNIT 1
1.1.What is meant by frequency reuse?
If an area is served by a single Base Station, then the available spectrum can be divided
into N frequency channels that can serve N user...
1.1.What is meant by frequency reuse?
If an area is served by a single Base Station, then the available spectrum can be divided
into N frequency channels that can serve N users simultaneously. If more than N users are to
be served, multiple BSs are required, and frequency channels have to be reused in different
locations. Since spectrum is limited, the same spectrum has to be used for different wireless
connections in different locations. This method of reusing the frequency is called as
frequency reuse.
1.2. What are the trends in cellular radio systems?
The trends in personal cellular radio systems are:
i. PCS – Personal Communication Services
ii. PCN – Personal Communication Networks
1.3. What do you mean by forward and reverse channel?
Forward channel is a radio channel used for transmission of information from base
station to mobile.Reverse channel is a radio channel used for transmission from mobile to
base station.
1.4. What is the function of control channel? What are the types?
The function of control channel is to transmit call setup, call request, call initiation
and Control. There are two types of control channels,
i. Forward control channel
ii. Reverse control channel
1.5. What is channel assignment? What are the types?
For efficient utilization of radio spectrum a frequency reuse scheme with increasing
capacity and minimizing interference is required. For this channel assignment is used. The
types of channel assignment are:
i. Fixed channel assignment
ii. Dynamic channel assignment.
1.6. What is fixed channel assignment?
If the channels in each cell are allocated to the users within the cell, it will be called as
fixed channel assignment. If all channels are occupied, the call will be blocked.
1.7. What is dynamic channel assignment?
If the voice channels are not allocated permanently in a cell, it will be called as
dynamic channel assignment. In this assignment, channels are dynamically allocated to users
by the MSC.
Prepared by A.Devasena., Associate Professor., Dept/ECE Page 1
, EC2401- Wireless Communication VII semester
1.8. Define MS, BS and MSC.
MS – Mobile station. A station in the cellular radio service intended for use.
BS – Base Station. A fixed station in a mobile radio system used for radio
communication with MS.
MSC – Mobile Switching Centre. Mobile switching centre coordinates the routing of
calls in large service area. It connects the base station and mobiles to PSTN. It is also
called as MTSO(Mobile telephone switching office.
1.9. Define hand off and mode of hand off.
A handoff refers to the process of transferring an active call or data session from one
cell in a cellular network to another or from one channel in a cell to another. A well-
implemented handoff is important for delivering uninterrupted service to a caller or data
session user. Modes of hand off are:
i. MCHO – Mobile Controlled Hand off
ii. NCHO – Network Controlled Hand off
iii. MAHO – Mobile Assisted Hand off
1.10. Write the types of hand off.
Types of handoff are:
i. Hard hand off – Mobile monitors BS and new cell is allocated to a call with strong
signal.
ii. Soft hand off – MS with 2 or more calls at the same time and find which is the
strongest signal BS, the MSC automatically transfers the call to that BS.
1.11. Define Cell, Cluster.
For a large geographic coverage area, a high powered transmitter therefore has to be
used. But a high power radio transmitter causes harm to environment. Mobile communication
thus calls for replacing the high power transmitters by low power transmitters by dividing the
coverage area into small segments, called cells.
Each cell uses a certain number of the available channels and a group of adjacent cells
together use all the available channels. Such a group is called a cluster.
1.12. What do you mean by foot print and dwell time?
The region over which the signal strength lies above this threshold value x dB is
known as the coverage area of a BS and it must be a circular region, considering the BS to be
isotropic radiator. Such a circle, which gives this actual radio coverage, is called the foot
print of a cell.The time over which a call may be maintained within a cell without hand off is
called the dwell time.
1.13. What are the major types of cellular interference?
The major types of cellular interferences are as follows
i. CCI – Co-channel interference is the interference between signals from co-channel
cells.
ii. ACI – Adjacent channel interference resulting from signals which are adjacent in
frequency to the desired signal.
Prepared by A.Devasena., Associate Professor., Dept/ECE Page 2
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