CUSTOMER_CODE
SMUDE
DIVISION_CODE
SMUDE
EVENT_CODE
SMUJAN15
ASSESSMENT_CODE MCA5032_SMUJAN15
QUESTION_TYPE DESCRIPTIVE_QUESTION
QUESTION_ID
23973
QUESTION_TEXT Explain GSM channels in detail
SCHEME OF
EVALUATION
1 .types:
Traffic channels.
Broadcast channels
Common control channels.
Dedicated control channels.
2.Traffic channels (TCH):
(2.5marks)
Combination of voice and data signals that exit within a communication
channel.
Either half or full rate
Full –rate: raw rate of 22.8Kbps,with a useable rate of 9.6kbps for
data.
Half-rate: raw rate of 11.4kbps,useable 4.8kbps for data.
3.Broadcast channels(BCH):
(2.5marks)
Used in operation of GSM.
3 parts
1)BCCH(The broadcast control channel): logical broadcast channel
used by base station in GSM network to send information about the
identity of the network
2)FCCH(The Freequency correction Channel):used by GSM base
stations.
3)SCH(Synchronisation channel):downlink broadcast channel of the
base stations of GSM network. provide information about mobile
stations needed.
4.common control channels:
(2.5marks)
Used for sending and receiving command messages between devices.
Alert devices about incoming call ,for accessing control.
A)PCH(paging channel): transmits paging message at certain time
interval. B)AGCH(Access Grant Channel): ,c)RACH(Random
Access channel):the base station receives a response from the mobile
station through RACH.
5.Dedicated control channels:
(2.5marks)
i.Communication channels that transfer signalling messages to specific
devices in a GSM network.
ii.3 dedicated channels are there a)stand alone dedicated control
channel(SDCCH) .b)slow associated control channel(SACCH) .c)fast
associated control channel(FACCH) .
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
23975
QUESTION_TEXT
Explain the features, advantages and disadvantages of different
generations of Wireless Communication System.
SCHEME OF
EVALUATION
First Generation or 1G:
Features:
*Narrow band analogue communication system
*Facilitates voice calls and sending text messages
*Connection oriented and circuit switching method is used to
exchange information
Advantages:
*Is easier to establish and understand
*Cost involved in establishing a 1G network was less
Disadvantages:
*Power consumption is high so the equipment needed large batteries
*1G network could only be used for making calls and sending text
messages
*Multimedia services are not provided in 1G as high speed data
transmission was not possible.
(2.5 marks)
Second generation or 2G
Features:
*Power consumption is high so the equipment needed large batteries
*1G network could only be used for making calls and sending text
messages i.e. the network was only used for transmitting voice and
not data
*Multimedia services are not provided in 1G as high speed data
transmission was not possible.
Advantages:
*Establishment of digital transition thus leading to introduction of
services such as SMS and email
*Increased security by greatly reducing SIM forgery
*Lower power emission from network help reducing health
problems
Disadvantages:
*Under slightly worse conditions, analog will experience static,
while digital has occasional dropouts.(2.5 marks)
Third generation or 3G
Features :
*Facilitate global roaming.
*Supports Wide Band Voice Channels
*Low disturbances in the form of noise experienced
*Video on demand can be activated on 3G systems
*Supports video conferencing
Advantages :
*3G is suitable for high data transmission at a faster rate
*3G supports multimedia applications like video conferencing
Disadvantages :
*Limited mobility with less than 10 miles per hour
*High power consumption requires large batteries.
(2.5 marks)
Fourth Generation or 4G
Features :
*Inbuilt multimedia support
*Television connectivity
*Faster data transmission rate
Advantages :
*4G will be based on packet switching only thus requiring low
latency data transmission
*4G allow seamless mobility
*4G will offer very high data rates
Disadvantages:
*A major issue in 4G systems is to make the high bit rates available
in a larger portion of the cell.
(2.5 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
23977
QUESTION_TEXT What are the attributes of speech codec? Explain briefly.
SCHEME OF
EVALUATION
The important speech attributes are:
*Transmission bit rate
*Complexity
*Delay
*Bandwidth(2 marks)
Transmission bit rate: The bit rate indicates level or the rate or
exploiting the “speech model” in the coder. It usually measured as the
average number of bits per second. The lower the bit rate, the greater is
the reliance on the speech production model. You can use fixed-rate or
variable-rate speech coders depending on system and design
constraints.
Delay: This is the measure of the time taken for an input sample to be
processed at the encoder, transmitted and decoded at the decoder. The
quality of a conversation is affected directly by the significant delay. If
delay is excessive, it affects a two-way communication
Complexity: the computational complexity and memory requirements
of a speech coder decide the cost and power consumption of the
hardware on which it is implemented. In most cases, real-time
operation is required at least for the decoder.
Quality: it is the measure of degradation of the decoded speech with
the original one. The quality of the decoded speech should be such that
it should be acceptable for the target application. The quality decreases
when the bit rate is less. The most widely used and ITU-T defined
subjective measure of quality is the Man Opinion Score (MOS).(2
marks each)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
73082
QUESTION_TEXT Write a note on history and evolution of wireless communication system.
SCHEME OF
EVALUATION
The term “wireless” refers to a method of communication using radio waves.
It is also used to mean any type of operation that is implemented without the
use of wires, such as "wireless remote control" regardless of the specific
technology used for communication. It is believed that the world’s first,
wireless telephone conversation occurred in 1880, when Alexander Graham
Bell and Charles Sumner Tainter invented telephone for voice
communication wirelessly through modulated light beams. (3 marks)
In 1888, physicist Heinrich Rudolf Hertz from Hamburg, Germany produced
the first radio wave. This radio wave became the media for communication by
1894. During that time telegraph wires were used to receive the radio signals
from one point to another. (2 marks)
An Italian scientist Marchese Guglielmo has expanded the range to 9 miles
and 31 miles across the English Channel to France by 1901. He is awarded
Nobel Prize in Physics in 1909 for his contribution to wireless telegraphy. (2
marks)
The radio waves were used officially for data transmission during World War
II in the battle field by United States. In 1971, Norman Abramson and his
team at the University of Hawaii have developed the first radio
communications network for exchanging data among computers. This
network is known as “Alohanet”. The Alohanet was the first Wireless Local
Area Network (WLAN). The Alohanet WLAN was comprised of seven
computers that communicated to each other. In 1972, Alohanet was first
connected with the telephone systems for communications between
computers and telephone.(3 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
120035
QUESTION_TEXT
Explain the system operations of GSM.
For explaining mobile telephone initialization – frequency
synchronization, timing synchronization, overhead information
acquisition
(5 marks)
SCHEME OF
EVALUATION
For explaining updating location
For explaining waiting for calls, cell resection, system access,
mobile call origination, transferring calls
(2 marks)
Between call sites, mobile assisted handoff, receiving a call on a
mobile telephone, conversation mode, authentication
(3 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
120041
QUESTION_TEXT
List and explain all the additional WLAN requirements for data
transmission in wireless medium that effect implementation of
physical and MAC layers.
SCHEME OF
EVALUATION
i.
Number of nodes
ii.
Throughput
iii.
Serve multimedia
iv.
Collocated network operation
v.
Saving energy
vi.
Robustness and security
vii.
Dynamic topology
viii. Compliance with standards
ix.
Handoff roaming support
x.
Effect of propagation delay
(10X1=10 marks)