CUSTOMER_CODE
SMUDE
DIVISION_CODE
SMUDE
EVENT_CODE
OCTOBER15
ASSESSMENT_CODE MIT4033_OCTOBER15
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
23976
QUESTION_TEXT
Discuss the basic services offered by GSM PLMN.
SCHEME OF
EVALUATION
Dual – Tone multi Frequency (DTMF): The automatic answering
machines used in wireless telephone network needs a controlling
mechanism. For this purpose the GSM PLMN uses a tone signaling
service called Dual-Tone multi-frequency.
Facsimile group III: Standard Fax machines need to be connected to a
telephone using analog signals, so a special fax converter needs to be
installed in the GSM system. This will help the fax to be connected to
the GSM and thus communicate with any other analog fax in the
network.
Short message Services (SMS): the SMS allows subscribers to send a
message consisting of fixed maximum length of alphanumeric characters
among mobile stations. If the user’s mobile is switched off or out of
coverage area, the messages is stored and offered back to the user when
the mobile is powered on or re-entered the coverage area of the network.
Cell broadcast: A message whose maximum length is 93 characters can
be broadcasted to all the users who are in particular geographical region.
This facility is primarily used for network management especially when
traffic congestion is reported.
Voice mail: This service provides a method of answering unattended
calls automatically. These answering machines are located within the
network and calls are forwarded to the subscriber’s voice mail box if it is
not attended during a stipulated time.(2 marks each)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
73085
QUESTION_TEXT
Write procedure followed by different components of the network to complete
a call from the PSTN subscriber to a mobile station.
SCHEME OF
EVALUATION
1. The PSTN subscriber dials the mobile telephone number using Mobile
Station ISDN number (MSISDN). A connection request is made to the mobile
stations home GMSC (Gateway Mobile Switching Centre).
2. The home GMSC finds the respective HLR of the called mobile station
and sends a query to the HLR for information about the serving MSC/VLR of
the called mobile station.
(2 marks)
3. The HLR translates MSISDN into IMSI, and determines which MSC/VLR
is currently serving the MS.
4. The HLR requests a Mobile Subscriber Roaming Number (MSRN) from
the serving MSC/VLR of the called mobile station.
(2 marks)
5. The MSC/VLR returns an MSRN via HLR to the GMSC.
6. The GMSC routes the call to the concerned MSC/VLR.
7. The MSC/VLR searches its record to find the current LA of the mobile
station and a paging message is sent to the BSC of the controlling the LA.
(3 marks)
8. The BSC’s uses PCH to page the mobile station.
9. When the mobile station detects the paging message, it sends a request
on RACH for a SDCCH.
10. The BSC provides a SDCCH via AGCH.
(3 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
73086
QUESTION_TEXT
Write brief note on any five air interface channels.
SCHEME OF
EVALUATION
1. Frequency correction channel (FCCH): FCCH is used to correct the MS
frequency. (1 mark)
2. Synchronization channel (SCH): SCH which is used in the MS frame
synchronization and BTS identification. (2 marks)
3. Broadcasting channel (BCH): BCH is the one-point-to-many-points
unidirectional control channel from BTS to MS, which is used to broadcast all kinds of
information to MS. (2 marks)
4. Broadcasting Control Channel (BCCH): Which is used to broadcast cell
information.it is also used to indicate the configuration of the common control
channels(CCCH). CCCH is the one-point-to-many-points bidirectional control channel,
which is mainly used to carry signalling information necessary for the access
management function, and it can also carry other kinds of signalling. CCCH is
commonly used by all MSs of the network. (4 marks)
5. Paging channel (PCH): Which is used by BTS to page MS. (1 mark)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
73087
QUESTION_TEXT
Write any five comparisons between WiMAX and Wi-Fi.
SCHEME OF
EVALUATION
1. Wi-Fi is based on IEEE 802.11 standard whereas WiMAX is based on
IEEE 802.16. However both are IEEE standards.
2. Wi-Fi uses unlicensed spectrum to provide access to a local network
whereas Wimax does not.
(2 marks)
3. Wi-Fi typically provides local network access for around a few hundred
feet with speeds of up to 54 Mbps, a single WiMAX antenna is expected to
have a range of up to 40 miles with speeds of 70 Mbps or more. (3 marks)
4. WiMAX and Wi-Fi have quite different quality of service
(QoS) mechanisms:
a. WiMAX uses a QoS mechanism based on connections between the base
station and the user device.
b. Wi-Fi uses contention access - all subscriber stations that wish to pass
data through a wireless access point (AP) are competing for the AP's attention
on a random interrupt basis. (2 marks)
5. Wi-Fi is intended for LAN applications. WiMAX is designed to efficiently
support from one to hundreds of Consumer premises equipment’s (CPE)s, with
unlimited subscribers behind each CPE. Although Wi-Fi and WiMAX are
designed for different situations, they are complementary. WiMAX network
operators typically provide a WiMAX Subscriber Unit which connects to the
metropolitan WiMAX network and provides Wi-Fi within the home or business
for local devices (e.g., Laptops, Wi-Fi Handsets, smartphones) for connectivity.
(3 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
120042
QUESTION_TEXT
Explain any five characteristics of Ultra Wide Band Technique.
i.
Low power consumption
ii.
High data rates
iii.
Interference immunity
iv.
High security
v.
Reasonable range
SCHEME OF EVALUATION
(5X2=10 marks)