UNIT – I
PART-A
1.
|
What are the two
kinds of mobility?
User Mobility :-
refers to a user who has access to the same or similar telecommunication
services at
different places, i.e the user is mobile and the service will follow him or
her.
Device
Portability:- refers to the movement of communication devices e.g. Mobile
phones.
|
2.
|
What are the
characteristics of communication devices?
Ø
Fixed and wired.
Ø
Mobile and wired.
Ø
Fixed and wireless.
Ø
Mobile and Wireless.
|
3.
|
What are the
categories of wireless device?
Ø
Sensor.
Ø
Embedded Controllers.
Ø
Pager.
Ø
Mobile Phones.
Ø
Personal Digital assistant.
Ø
Pocket computer.
Ø Notebook/laptop.
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4.
|
Define Signal.
Signals are the physical
representation of data. Signals are functions of time and location. Users of
a communication system can only exchange data through the transmission of signals.
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5.
|
What are the
problems of wireless signals?
Ø
Path loss of radio signals
Ø
Propagation effect on signals
Ø Multipath
propagation
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6.
|
What is meant by
line-of-sight?
A straight line exists between a sender and a receiver it is called
line-of-sight.
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7.
|
Differentiate
periodic signal and aperiodic signal?
In a signal if a particular
signal pattern repeats over a time period systematically it is a periodic
signal. In a signal if the same signal pattern does not repeat itself over a
time period it is known as ‘Aperiodic’ signal.
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8.
|
Give an example for
a periodic and aperiodic signals.
a. periodic signal - x (t + T) = x(t). where - ∞ < t < + ∞
b. Aperiodic signal
-x (t + T) ≠ x (t).
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9.
|
What is delay
spread?
At the receiver, due to the
different paths with different length the signals reach the destination at
different times. This is called delay spread.
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10.
|
State Advantage of
cellular system.
Ø
Higher Capacity.
Ø
Less transmission power.
Ø
Local interface only.
Ø Robustness.
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11.
|
Tabulate two
differences between analog and digital signals.
Analog signal
1. It is a continuously varying
signal
2. Media used for signal propagation
is like
a. Space propagation
b. Copper wire media.
Digital signal
1.It is a regular sequence of
voltage pulses.
2.Media used for propagation is like
a. Copper wire medium
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12.
|
Define attenuation.
Attenuation is a reduction in
signal strength mainly at higher frequency ranges, and at receiving end this
attenuated signal has reduced voltage levels.
|
13.
|
Give the equation
for signal to noise ratio.
Signal to noise ration (SNR) = 10
log10 Noisepower/ Signalpower It
is expressed in decibel units.
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14.
|
What is the normal
operating range of frequency for cell phones and microwave transmission?
The operating
frequency range for cell phones is 825 MHz to 845 MHz (approx).
The
frequency of microwave transmissions is 2 GHz to 40 GHz.
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15.
|
Define a cell. What
are the shapes related to a cell?
The smallest geographical area
covered by wireless communication is said to be a cell. The shapes related to
a cell are:
a. Circle
b. Square
c. Hexagon
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16.
|
Define wavelength.
The wavelength of a signal
represents its distance or range it takes for one cycle. It is denoted as
‘λ’. Wavelength λ = c/f.
|
17.
|
What is a
bandwidth?
Bandwidth is the range of
frequencies and represented as BW = f2 – f1, where f1 – f2 are the first and
last frequencies of the signal graph.
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18.
|
Differentiate
between signal and data.
The term ‘data’ represents message or information where the signal is
the representation of the data, and it is also termed as information bearing
signal.
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19.
|
What is the
principle used in multiplexers?
The principle used in multiplexer
is ‘many to one’ concept. Many inputs are combined as one link or one output
from a MUX unit where a DEMUX unit at the receiver reproduces the same many
units at the end entity. Multiplexing tells how many users can share the
medium with minimum of no interference.
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20.
|
What are the
important multiplexing schemes in wireless channel?
Ø
Space Division Multiplexing
Ø
Time Division Multiplexing
Ø
Frequency Division Multiplexing
Ø
Code Division Multiplexing
|
21.
|
What are the
multiple access schemes?
a) FDMA
b) TDMA
c) CDMA
d) SDMA
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22.
|
Define guard band.
It is unused (dummy) frequency
inserted with actual spectrum to reduce adjacent channel interference to
enhance accuracy.
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23.
|
What are the types
of spread spectrum?
a) FHSS - Frequency
Hopping Spread Spectrum
b) DSSS – Direct
Sequence Spread Spectrum.
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24.
|
What are the basic
shift keying methods?
(i) Amplitude shift
keying.
(ii) Frequency
shift keying
(iii) Phase shift
keying.
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25.
|
State inverse
square law.
Even if no matter
exists between the sender and the receiver (i.e, if there is a vacuum),
the signal still
experiences the free space loss. The received power Pr is proportional to
1/d2 with d being the distance between sender and receiver.
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26.
|
Classify the radio
waves based on the frequency used.
(i) Ground wave
uses <2MHz
(ii) Sky wave uses
2-30 MHz
(iii)
Line of sight uses > 30 MHz
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27.
|
State the different
types of additional propagation effects of a signal.
(i) Blocking (or)
shadowing
(ii) Reflection
(iii) Refraction
(iv) Scattering
(v) Diffraction
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28.
|
Why is digital
modulation not enough for radio transmission?
Ø
Antenna height is based on the signal’s wavelength.
Ø
FDM can’t be applied.
Ø
Medium characteristics like path-loss, penetration of
obstacles, reflection, scattering and diffraction depend on the wavelength of
the signal.
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29.
|
What are the 3
fundamental propagation behaviors depending on their frequency?
Ø
Ground wave
Ø
Sky wave
Ø
Line of sight
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30.
|
What is multipath
propagation?
As there is the atmosphere between
the sender and the receiver the radio waves do not follow line of sight. The
propagation effects leads to channel impairment called multipath propagation.
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31.
|
What is guard
space? How are guard spaces realized between users in CDMA?
Guard space is the space between the
interference regions. Guard spaces are needed to avoid frequency band
overlapping is also called channel interference. Guard spaces are realized by
using codes with the necessary distance in code space.
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32.
|
What is the 3
difference basic schemes analog modulation?
Ø
Amplitude modulation
Ø
Frequency modulation
Ø
Phase modulation
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33.
|
What is the use of
phase lock loop (PLL)?
To receive the signal correctly,
the receiver must synchronize in frequency and phase with the transmitter.
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34.
|
What is hopping
sequence?
Transmitter and receiver stay on
one of these channels FDM and TDM. The pattern of channel usage is called the
hopping sequence.
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35.
|
What is dwell time?
The time spend on a channel with a
certain frequency is called the dwell time.
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36.
|
What are the
disadvantages of small cellular systems?
The disadvantages of cellular
systems are
1. Infrastructure
needed
2. Handover needed
3. Frequency planning
|
37
|
What are the
advantages of cellular systems?
1. Higher capacity
2. Less Transmission
power
3. Local interference
4. Robustness
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38
|
What is browsing
channel allocation and fixed channel allocation?
Cells with more traffic are
dynamically allotted more frequencies. This scheme is known
as browsing channel
allocation, while the first fixed scheme is called channel allocation.
|
39
|
What is digital
sense multiple access?
The scheme which is used for
the packet data transmission service cellular digital packet data in the AMPS
mobile phone system is also known as digital sense multiple access
(DSMA).
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40
|
What is network and
switching subsystem?
The heart of the GSM is
formed by the network and switching system (NSS). NSS
consists of the
following switches and database:
o Mobile services switching
center (MSC)
o Home location registers (HLR)
o Visitor location registers
(VLR)
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41
|
What is called
burst and normal burst?
Data is
transmitted in small portions called burs, normal burst are used for data
transmission inside
a slot (user and signaling data).
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42
|
Specify the steps
perform during the search for a cell after power on?
Primary
synchronization
Secondary
synchronization
Identification
of the scrambling code
|
43
|
Explain about
transparent mode?
The transparent mode
transfer simply forwards MAC data without any further processing. The system
then has on the FEC which is always used in the radio layer.
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44
|
List out several
services that might depend on the actual locations can be distinguished?
Follow
on services
Location
aware services
Privacy
Information
services
Support
services
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45
|
Describe lower
security, simpler to attack?
Not only can portable devices
be stolen more easily, but the radio interface is also prone to the dangers
of eavesdropping. Wireless access must always include encryption, authentication,
and other security mechanisms that must be efficient and simple to use.
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46
|
What are the
benefits of reservation schemes?
Increased no other station is allowed to
transit during this slot
Avoidance of congestion
Waiting time in clearly known
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47
|
What limits the
number of simultaneous users in a TDM/FDM system compared to a CDM
system?
TDM/FDM system has a hard
upper limit of simultaneous users. The system assigns a
certain time-slot
at a certain frequency to a user. If all time-slots at all frequencies are
occupied
no more users can
be accepted. Compare to this “hard capacity” a CDM system has so called
“soft capacity”.
The system can accept an additional user. However the noise level may then
increase above a
certain threshold where transmission is impossible.
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48
|
What is meant by
software defined radio?
A Software-defined
radio (SRD) system is a radio communication system where
components that
have typically been implemented in hardware are instead implemented using
software on a
personal computer or other embedded computing devices.
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49
|
What is the
importance of digital signals?
The signal processing is
better with digital signal formats (0’s and 1’s) where noise is
minimized. Hence
analog to digital converters are used to convert input analog signal to its equivalent
digital signal and after processing the signal is again converted to original
analog
signal with digital
to analog signal at the end entity for proper reception of the signal.
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50
|
List out some
applications can benefit from wireless networks and mobile Communications?
Vehicles
Emergencies
Business
Replacement of
wired networks
Infotainment
and more
Location
dependent services
Mobile
and wireless devices
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PART-B
1.
|
Discuss briefly the
multiplexing techniques.
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2.
|
Explain about the
signal propagation.
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3.
|
Discuss about the
cellular system.
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4.
|
List the difference
between SDMA /TDMA /FDMA/CDMA
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5.
|
What is spread
spectrum with its types.
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6.
|
Explain about the
TDMA.
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7.
|
Why CDMA is needed
and explain it with an example?
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8.
|
Why do MAC scheme
in wired network fail in wireless networks and how does the multiple access
with collision avoidance (MACA) scheme work?
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9.
|
Define modulation
and explain the method for analog modulation
techniques
in details.
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10.
|
Discuss briefly the
code division multiplexing techniques
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11.
|
Discuss briefly the
advanced phase shift keying.
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12.
|
a. Explain about
cellular wireless network.
b. Explain about
wireless transmission.
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13.
|
Consider three
users and Barker code of six bits each for the users
transmitting the
signals, introduce noise and near / far problem while
transmitting and
reconstruct the data in the receiving side providing
the proper counter
measures for the complications.
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14.
|
a. Table the
frequency bands used for wireless applications with their
ranges, propagation
models and applications.
b. Represent diagrammatically
the protocol machines for multiple access
with collision
avoidance.
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15.
|
Explain the
following
(a)
MAC
(b)
SDMA
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16.
|
Explain the various
applications of mobile computing.
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UNIT II
PART A
1.
|
Define GSM.
In early GSM was called as Groupe
Speciale Mobile was founded on 1982, lateral it was
renamed as Global
System for Mobile Communication (GSM). The primary goal of GSM is to
provide a mobile
phone system that allows user to roam throughout Europe and PSTN systems.
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2.
|
What are the
reasons for delays in GSM for packet data traffic?
The data traffics in asymmetric at
the wireless channels which means the down link
traffic volume is
much higher than the one in the uplink. The aggregated data traffic within
one routing area is usually different with the one in the other RA, in which
case will cause different traffic load on SGSN and CGSN nodes. The CGSN with
high traffic load will cause more packet delay.
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3.
|
List out the
different categories of services offered by GSM.
Bearer
Services.
Tele
Services.
Supplementary
Services.
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4.
|
What is the
frequency range of uplink and downlink in GSM network?
The frequency range
of uplink in GSM network is 890-960 MHz.
The
frequency range of downlink in GSM network is 935-960 MHz.
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5.
|
What are the two
basic groups of logical channels in GSM?
Traffic
channels (TCH).
Control
Channels (CCH).
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6.
|
What are the
control channel groups in GSM?
Broadcast
control channel (BCCH).
Common
control channel (CCCH).
Dedicated
control channel (DCCH).
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7.
|
List out the
numbers needed to locate an MS and to address the MS.
Mobile
station international ISDN number (MSISDN).
International
mobile subscriber identity (IMSI).
Temporary
mobile subscriber identity (TMSI).
Mobile
station roaming number (MSRN).
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8.
|
What is meant by
SGSN?
SGSN is Serving GPRS Support Node. It
supports the MS via the Gb interface. The SGSN is connected to a BSC via
frame relay.
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9.
|
What are the four
possible handover scenarios in GSM?
Intra-cell
handover.
Inter-cell,
intra-BSC handover.
Inter-BSC,
intra-MSC handover.
Inter
MSC handover.
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10.
|
What are the
security services offered by GSM?
Access
control and authentication.
Confidentiality.
Anonymity.
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11.
|
What is meant by
GGSN?
GGSN is Gateway GPRS Support
Node. It is the inter-working unit between the GPRS
network and
external packet data networks. The GGSN is connected to external networks via
the Gi interface and transfers packets to the SGSN via an IP-based GPRS
backbone network.
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12.
|
What is meant by
BSSGP?
BSSGP is Base Station Subsystem
GPRS Protocol. It is used to convey routing and QoSrelated information
between the BSS and SGSN.BSSGP does not perform error correction and works on
top of a frame relay network.
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13.
|
Define the protocol
architecture of DECT.
The protocol architecture of DECT
consists of three layers. They are:
Physical
Layer.
Medium
Access Layer.
Data
Link Control Layer.
Network
Layer.
The first three layers are common
for both Control Plane (C-Plane) and User Plane (UPlane). The network layer
has been specified only for U-Plane, so that user data from layer two is
directly forwarded to the U-Plane.
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14.
|
Specify the
standards offered by TETRA.
Voice+Data
(V+D).
Packet
Data Optimized (PDO).
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15.
|
How many ITU
standardized groups of 3G radio access technologies are there in IMT-2000?
IMT-DS
IMT-TC
IMT-MC
IMT-SC
IMT-FT
|
16.
|
What are the steps
perform during the search for a cell after power on?
The steps perform during the
search for a cell after power on is:
Primary
Synchronization.
Secondary
Synchronization.
Identification
of the scrambling code.
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17.
|
What are the two
basic classes of handover?
The two basic classes of handover
are:
Hard
Handover.
Soft Handover.
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18.
|
What are the two
basic transport mechanisms used by DAB?
The two basic transport mechanisms
used by DAB are:
Main
Service Channel (MSC).
Fast
Information Channel (FIC).
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19.
|
Define Elevation
Angle.
The Elevation angle is the angle
from the horizontal to the point on the center of the main beam of the
antenna when the antenna is pointed directly at the satellite.
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20.
|
What are the
factors limited the number of sub channels provided within the satellite
channel?
There are three factors
limited the number of sub channels provided within the satellite
channel. They are:-
Thermal
Noise.
Inter
modulation Noise.
Crosstalk.
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21.
|
Define Digital
cellular networks.
Digital cellular networks are the
segment of the market for mobile and wireless devices which are growing most
rapidly. They are the wireless extensions of traditional PSTN or ISDN
networks and allow for seamless roaming with the same mobile phone nation or
even worldwide.
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22.
|
What is meant by
worldwide market?
The worldwide market figures for
cellular networks are as follows. The most popular digital
system is GSM, with
approximately 70 percent market share. The remainder is split between CDMA
(12 percent) and TDMA (10 percent) systems, and other technologies.
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23.
|
Describe Mobile
services.
GSM permits the integration of
different voice and data services and the inter-working with existing
networks. Services make a network interesting for customers. GSM has defined
three different categories of services.
A mobile station MS is connected
to the GSM public land mobile network (PLMN) via the Um inter-network is
connected to transit networks.
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24.
|
What is meant by
Bearer Services?
GSM specifies different mechanisms
for data transmission, the original GSM allowing for data rates of up to 9600
bits/s for non-voice services. Bearer services permit transparent and
nontransparent, synchronous or asynchronous data transmission.
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25.
|
Define Transparent
bearer services.
Transparent bearer services only use
the functions of the physical layer to transmit data.
Data transmission
has a constant delay and throughput id no transmission errors occur.
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26.
|
What is meant by
Non-Transparent bearer services?
Non-Transparent bearer services
use protocols of layers two and three to implement error correction and flow
control. These services use the transparent bearer services, adding a radio
link protocol (RLP). This protocol comprises mechanisms of high-level data
link control (HDLC).
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27.
|
Define Tele
services.
GSM mainly focuses on
voice-oriented tele services. These comprise encrypted voice
transmission,
message services, and basic data communication with terminals as known from
the PSTN or ISDN.
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28.
|
Define
Supplementary services.
GSM providers can offer
supplementary services. Similar to ISDN networks, these services offer
various enhancements for the standard telephone service, and may vary from
provider to provider. Typical services are user identification, call
redirection or forwarding of ongoing calls.
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29.
|
Explain the GSM
Sub-Systems.
A GSM system consists of three
subsystems, the radio sub system (RSS), the network and switching subsystem
(NSS) and the operation subsystem (OSS). Generally a GSM customer only notices
a very small fraction of the whole network the mobile stations (MS) and some antenna
masts of the base transceiver stations (BTS).
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30.
|
Define Radio
subsystem.
The radio subsystem (RSS)
comprises all radio specific entities, the mobile stations (MS) and the base
station subsystem (BSS). It has the connection between the RSS and NSS via
the A interface (solid lines) and the connection to the OSS via the O
interface (Dashed lines).
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31.
|
What is meant by
Base station subsystem (BSS)?
A GSM network comprises many
BSSs, each controlled by a base station controller (BSC). The bss performs
all functions necessary to maintain radio connections to an MS,
coding/decoding of voice and rate adaptation to/from the wireless network
part, besides a BSC, the BSS contains several BTSs.
|
32.
|
Define Base transceiver
station (BTS).
A BTS comprises all radio
equipment, antennas, signal processing, amplifiers necessary for radio
transmission. A BTS an form a radio cell or, using sectorized antennas,
several cells and is connected to MS via the Um interface and to the BSC via
the Abis interface.
|
33.
|
Define Base station
controller (BSC).
The BSC basically manages the BTSs.
It reserves radio frequencies, handles the handover from one BTS to another
within the BSS, and performs paging of the MS. The BSC also multiplexes the
radio channels onto the fixed network connections at the A interface.
|
34.
|
What is meant by
Mobile station (MS)?
The MS comprises all user
equipment and software needed for communication with a GSM network. An MS
consists of user independent hard and software and of the subscriber identity
module (SIM), which stores all user specific data that is relevant to GSM. MS
can be identified via the international mobile equipment identity (IMEI), a
user can personalize any MS using his or her SIM.
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35.
|
List out the
Network and switching subsystem.
Mobile
services switching center (MSC)
Home
location registers (HLR)
Visitor
location registers (VLR)
|
36.
|
List out the
Operation subsystems in GSM.
Operation
and maintenance center (OMC)
Authentication
centre (AuC)
Equipment
identity registers (EIR)
|
37.
|
Define Radio
Interface.
GSM implements SDMA implements
SDMA using cells with BTS and assigns an MS to a BTS. Furthermore, FDD is
used to separate downlink and uplink. Media access combines TDMA and FDMA.
|
38.
|
What are the
services offered by Tele services.
Emergency
number
Short
message service (SMS)
Enhanced
message service (EMS)
Multimedia
message service (MMS)
Group fax
|
39.
|
Define Protocols.
The main interest lies in the
Um interface, as the other interfaces occur between entities in a fixed
network. Layer 1, the physical layer, handles all radio-specific functions.
This includes the creation of bursts according to the five different formats,
multiplexing of bursts into a TDMA frame, synchronization with the BTS,
detection of idle channels, and measurement of the channel quality on the
downlink.
|
40.
|
What are the
numbers needed to locate an MS and to address the MS?
o Mobile station international
ISDN number (MSISDN)
o International mobile
subscriber identity (IMSI)
o Temporary mobile subscriber
identity (TMSI)
o Mobile station roaming number
(MSRN)
|
41.
|
What are the two
basic reasons for a handover?
The mobile station moves out of
the range of a BTS or a certain antenna of a BTS respectively. The received
signal level decreases continuously until it falls below the minimal
requirements for communication. The error rate may grow due to interference,
the distance to the BTS may be too high. The wire infrastructure may decide
that the traffic in cell is too high and shift some MS to other cells with a
lower load (if possible). Handover may be due to load balancing.
|
42.
|
Define HSCSD.
A straightforward improvement
of GSM’s data transmission capabilities is high speed circuit switched data
(HSCSD), which is available with some providers. In this system, higher data
rates are achieved by bundling several TCHs. An MS requests one or more TCHs
from the GSM network, i.e., it allocates several TDMA slots within a TDMA
frame.
|
43.
|
What is meant by
GPRS?
The next step toward more flexible
and powerful data transmission avoids the problems of
HSCSD by being
fully packet-oriented. The general packet radio service (GPRS) provides
packet
mode transfer for
applications that exhibit traffic patterns such as frequent transmission of
small
volumes according
to the requirement specification.
|
44.
|
Define DECT.
Fully digital cellular network
is the digital enhanced cordless telecommunications (DECT) system specified
by ETSI. DECT is also a more powerful alternative to the digital system CT2,
which is
mainly used in the
UK and has even been selected as one of the 3G candidates in the IMT-2000
family.
|
45.
|
What is meant by
System Architecture?
A global network
connects the local communication structure to the outside world and
offers its services
via the interface D1. Global networks could be integrated services digital
networks (ISDN),
public switched telephone networks (PSTN), public land mobile networks (PLMN)
or packet switched
public data network (PSDDN).
|
46.
|
Define Protocol
Architecture.
The DECT protocol
reference architecture follows the OSI reference model. The physical
layer, medium
access control, and data link control for both the control plane (C-plane)
and the user
plane (U-plane).
|
47.
|
What are the three
physical channels used for the data transmission?
1) Dedicated
physical data channel (DPDCH)
2) Dedicated
physical control channel (DPCCH)
3) Dedicated
physical channel (DPCH)
|
48.
|
What is meant by
UMTS?
UMTS (Universal
Mobile Telecommunications service) is a third-generation(3G) broadband,
packet-based
transmission of text, digitized voice and multimedia at data rates up to 2
megabits per second. UMTS offers a set of services to mobile computer and
phone users, no matter where they are located in the world.
|
49.
|
Why Intra-cell
handover procedure is needed for cellular system?
Within a cell,
narrow band interference could make transmission at a certain frequency
impossible. The BSC
will decide to change the carrier frequency.
|
50.
|
Give the major
difference between DECT and GSM.
The cell diameter
and cell capacity is the major difference between the two.
GSM: 70 km is the
cell diameter can handle upto one lakh people in within 1 km2.
DECT: 300 m is the
cell diameter service offered to be 10,000 people in within 1 km2.
|
51.
|
List out the
advantages of MEO.
Needs 12 satellites to cover the earth.
They move slowly relative to the earth’s
rotation.
They have simple system design.
Based on the inclination, they can cover
large population hence needs only few handovers.
|
52.
|
What are the
different managements under GSM protocol architecture?
Mobility management
Connection management
Radio resource management
Message transfer
|
53.
|
List some
applications of Satellite.
Whether Forecasting.
Military purposes
Radio and TV Broad casting
For navigation
|
54.
|
Differentiate hard
and soft handover.
Hard handover:
Existing connection must be broken before a
new connection is established.
Intra cell handover.
There is a short break in transmission
which can be noticed by the user.
Soft handover:
A new connection is established before the
old one is released.
Used in UMTS.
|
55.
|
State the different
types of transport modes and the channels used to carry packets in Digital
Audio Broadcasting.
Types of transport
modes:
Stream mode
Packet mode
Types of channels:
Main service channel
Fax information channel
|
PART-B
1.
|
Explain
the functional architecture of a GSM system.
|
2.
|
Discuss
about Digital video broadcasting.
|
3.
|
Discuss
about Digital audio broadcasting.
|
4.
|
Explain
Satellite networks in detail.
|
5.
|
Explain
DECT.
|
6.
|
Explain in details the functioning of GPRS.
|
7.
|
Compare
GEO, MEO and LEO
|
8.
|
Sketch the data
network in your campus. How many hosts are there and how large is the user
population? What is the speed of the access link to the Internet? How so you
gain access to the Internet? How much does home access to the Internet costs?
|
9.
|
Consider a mobile
user who is migrating from a place to another place provide him a seamless
service by satellite system, also sketch the architecture.
|
10.
|
Discuss
the importance of DECT Protocol Layers
|
11.
|
How is
routing carried out in GSM networks?
|
12.
|
Explain
in detail about the General Packet Radio Service (GPRS)
|
13.
|
List
the various handovers carried out in GSM and explain any one of them in
detail.
|
14.
|
How is
Mobility Management done in GSM ?
|
UNIT
III
PART
A
1.
|
What is WLAN?
WLANs is to replace
office cabling, to enable ether less access to the internet and, to
introduce a higher
flexibility for ad-hoc communication in e.g., group meetings.
|
2.
|
List out the
advantages of WLANs.
a. Flexibility
b. Planning
c. Design
d. Robustness
e. Cost
|
3.
|
List out
disadvantage of WLANs.
a. Quality of
service
b. Proprietary
solutions
c. Restrictions
d. Safety and security
|
4.
|
List out WLANs to
ensure their commercial success.
a. Global operation
b. Low power
c. License free
operation
d. Robust
transmission technology
e. Simplified
spontaneous cooperation
f. Easy to use
g. Protection of
investment
h. Safety and
security
|
5.
|
List out two
different basic transmission technologies can be used to transmission
technologies can be
used to set up WLANs.
a. Infra red
b. Radio
transmission
|
6.
|
Define intra red.
Infra red
technology uses diffuse light reflected at walls, furniture, etc. or directed
light if a line of
sight (LOS) exists between sender and receiver. Senders can be simple light
emitting diodes
(LEDs) or laser diodes. Photodiodes act as receivers. Details about infra red
technology, such as
modulation, channel impairments etc.
|
7.
|
List the advantages
of infra red.
a. Infra red
technologies are its simple and extremely cheap senders and receivers
which are
integrated into nearly all mobile devices available today.
b. PDA’s laptops,
notebooks, mobile phones etc. Have an infra red data association
(IrDA) interface.
Version 1.0 of this industry standard implements data rates of up
to 115 kbit/s,
while IrDA1.1 defines higher data rates of 1.152 and 4 Mbit/s.
c. No licenses are
needed for infra red technology and shielding is very simple.
Electrical devices
do not interfere with infra red transmission.
|
8.
|
List the
disadvantages of Infra red.
a. It has low
bandwidth compared to other LAN technologies. Typically IrDA devices
are internally
connected to a serial port limiting transfer rates to 115 kbit/s.
b. Even 4 Mbit/s is
not a particularly high data rate. However, their main disadvantage
is that infra red
is quite easily shielded. Infra red transmission cannot penetrate
walls or is quite
shielded.
c. Infra red
transmission cannot penetrate walls or other obstacles. Typically, for good
transmission
quality and high data rates a LOS, i.e., direct connection, is needed.
|
9.
|
List the advantages
of radio transmission.
a. It includes the
long-term experiences made with radio transmission for wide area
networks and mobile
cellular phones.
b. Radio
transmission can cover larger areas and can penetrate walls, furniture,
plants,
etc.
c. Additional
coverage is gained by reflection. Radio typically does not need a LOS if
the frequencies are
not too high. Furthermore, current radio based products offer
much higher
transmission takes than infra red.
|
10.
|
List the
disadvantages of radio transmission.
Shielding is not so simple, Radio
transmissi0n can interfere with other senders or
electrical devices
can destroy can destroy data transmitted via radio.
Radio transmission is only permitted
in certain frequency bands, very limited ranges
of license free
bands are available worldwide and those that are available are not
the same in all
countries.
|
11.
|
Define
infrastructure.
Infrastructure
networks not only provide access to other networks, but also include
forwarding
functions, medium access control etc. In these infrastructure based wireless
networks,
communication typically takes place only between the wireless nodes and the
access point, but
not directly between the wireless nodes.
|
12.
|
Describe ad-hoc
networks.
Ad-hoc wireless
networks, however, do not need any infrastructure to work. Each
node can
communicate directly with other nodes, so no access point controlling medium
access is
necessary.
|
13.
|
Define IEEE 802.11.
This means that the
standard specifies the physical and medium access layer
adapted to the special
requirements or wireless LANs, but offers the same interface as the
others to higher
layers o maintain interoperability.
|
14.
|
Explain System
Architecture.
Wireless networks
can exhibit two different basic system architectures of
infrastructure or
ad-hoc. It shows the components of an infrastructure and a wireless part
as specified for
IEEE 802.11. Several nodes, called stations (STAi), are connected to access
points (AP).
Stations are terminals with access mechanisms to the wireless medium and
radio contact to
the AP.
|
15.
|
Define protocol
architecture.
It is indicated by
the standard number, IEEE 802.11 fits seamlessly into the other 802.x
standards for wired
LANs. Applications should not notice any difference apart from the lower
bandwidth and
perhaps higher access time from the wireless LAN.
|
16.
|
Explain medium
access control layer.
The MAC layer has
to fulfill several tasks. First of all, it has to control medium
access, but it can
also offer support for roaming, authentication, and power conservation.
The basic services
provided by the MAC layer are the mandatory asynchronous data service
and an optional
time bounded service.
|
17.
|
Define Roaming.
Typically, wireless
networks within buildings require more than just one access
point to cover all
rooms. Each storey of a building needs its own access point(s) as quite
often walls are
thinner than floors. If a user walks around with a wireless station, the
station has to move
from one access point to another to provide uninterrupted service.
Moving
between access points is called roaming.
|
18.
|
Describe 802.11a.
Initially aimed at
the US 5 GHz U-NII (Unlicensed National Information
Infrastructure)
bands IEEE 802.11a offers up to 54 MBits/s using OFDM. The first products
were available in
2001 and can now be used in Europe. The FCC (US) regulations offer three
different 100 MHz
domains for the use of 802.11a, each with a different legal maximum
power output.
|
19.
|
Describe 802.11b.
As standardization
took some time, the capabilities of the physical layers also
evolved. Soon after
the first commercial 802.11 products came on the market some
companies offered
proprietary solutions with 11 Mbits/s. To avoid market segmentation, a
common standard,
IEEE 802.11b soon followed and was added as supplement to the original
standard described
a new PHY layer and is by far the most successful version of IEEE 802.11
available today.
|
20.
|
Define HIPERLAN.
HIPERLAN1 was
originally one out of four HIPERLANs envisaged, as ETSI decided to
have different
types of networks for different purposes. The key feature of all four
networks is their
integration of time sensitive data transfer services.
|
21.
|
Explain WATM.
Wireless ATM does
not only describe a transmission technology but tries to specify a
complete
communication system. While many aspects of the IEEE WLANs originate from the
data communication
community, many WATM aspects come from the telecommunication
industry.
|
22.
|
Define BRAN.
The broadband radio
access networks (BRAN), which have been standardized by the
European
telecommunications standards institute (ETSI), could have been an RAL for
WATM.
|
23.
|
List out BRAN has
specified four different network types.
a. HIPERLAN 1 b.
HIPERLAN/2
c. HIPERACCESS d. HIPERLINK
|
24.
|
Describe history
Bluetooth.
The history of
Bluetooth starts in the tenth century, when Harald Gormsen, King of
Denmark, erected a
rune stone in Jelling, Denmark, in memory of his parents. The stone has
three sides with
elaborate carvings. One side shows a picture of Chris, as Harald did not
only unite Norway
and Denmark, but also brought Christianity to Scandinavia. Harald has
the
common epithet of ‘Blatand’, meaning that he had a rather dark complexion.
|
25.
|
Define IEEE 802.15.
In 1999 the IEEE
established a working group for wireless personal area networks
(WPAN) with similar
goals to Bluetooth. The working group was divided into several
subgroups
focusing on different aspects of WPANs.
|
26.
|
What are the
advantages of WLANS?
Flexibility
Planning
Design
Robustness
Cost
|
27.
|
Mention some of the
disadvantages of WLANS.
Quality of service
Proprietary solutions.
Restrictions
Safety and Security
|
28.
|
Mention the design
goals of WLANS.
Global operation
Low power
License-free operation
Robust transmission technology
Simplified spontaneous cooperation
Easy to use
Protection of investment
Safety and security
Transparency for applications.
|
29.
|
What is the
difference between infrastructure and ad-hoc networks?
Infrastructure-based
wireless networks:
Communication takes
place only between the wireless nodes and the access
point, but not directly
between the wireless nodes.
Ad-hoc wireless
networks:
Communication takes
place directly with other nodes, so no access point
controlling medium
access is necessary.
|
30.
|
Give the primary
goal of IEEE802.11.
The primary goal of
the standard was the specification of a simple and robust WLAN
which offers
time-bounded and asynchronous services.
|
31.
|
Mention the
features of infrared transmission.
Simple
Extremely cheap
licenses are not needed
Electrical devices do not interfere
|
32.
|
What are the
disadvantages of infrared transmission?
Low bandwidth
Cannot penetrate walls or other
obstacles.
|
33.
|
Mention the
features of radio transmission.
Cover large areas.
Can penetrate walls, furnitures.
Does not need a LOS.
Higher transmission rates.
|
34.
|
What are the
disadvantages of radio transmission?
Shielding is not so simple.
Can interfere with other senders.
Limited ranges of license-free bands.
|
35.
|
Define frequency
hopping spread spectrum.
FHSS allows for the
coexistence of multiple networks in the same area by Separating
different networks
using different hopping sequences.
|
36.
|
Define random back
off time.
If the medium is
busy, nodes have to wait for the duration of DIFS, entering a
contention phase
afterwards. Each node now chooses a random back off time within a
contention window
and delays medium access for this random amount of time.
|
37.
|
What is Traffic
Indication Map?
The TIM contains a
list of stations for which unicast data frames are buffered in the
access point.
|
38.
|
What is Delivery
Traffic Indication Map?
The access point
maintains a DTIM interval for sending broadcast/multicast frames.
The DTIM interval
is always a multiple of the TIM interval.
|
39.
|
What is Ad-hoc TIM?
All stations
announce a list of buffered frames during a period when they are awake.
destinations
are announced using ATIMs.
|
40.
|
What is meant by
roaming?
If a user walks
around with a wireless station, the station has to move from one
access point to
another to provide uninterrupted service. Moving between access points is
called
roaming.
|
41.
|
Mention the
features of HIPERLAN1.
Ability to forward data packets
using several relays.
Extend
communication beyond radio range.
|
42.
|
What are the three
phases of medium access in EY-NPMA?
Prioritization.
Contention
Transmission
|
43.
|
Mention the
elements of Bluetooth core protocols.
Radio
Base band
Link manager protocol
Logical link control and adaptation
protocol
Service discovery protocol
|
44.
|
What is the purpose
of sniff state?
The sniff state has
the highest power consumption. The device listens to the piconet
at a reduced rate.
|
45.
|
What is the use of
hold state?
The device does not
release its AMA but stops ACL transmission. A slave may still
exchange SCO
packets.
|
46.
|
What is the purpose
of park state?
In this state the
device has the lowest duty cycle and the lowest power
consumption. The
device releases its AMA and receives a parked member address. The
device is still a
member of the piconet, but gives room for another device to become active.
|
47.
|
State the modes
possible when the slave is in connection state in Bluetooth.
Active
Sniff
Hold
Park
|
48.
|
What are elements
available under link security of Bluetooth technology?
(1) Authentication
(2) Key management (3) Encryption
|
49.
|
What is a LMP?
It is “link manager
specification” that is responsible for radio link between the master
and slave in
Bluetooth. This protocol also involves message exchanges in the form of
LMPPDU’s.
|
50.
|
List three security
services under LMP.
a) Authentication
b) Change link key
c) Encryption
|
PART-B
1.
|
Explain
in detail the system architecture of IEEE 802.11 (16)
|
2.
|
With a
focus on security, what are the problems of WLAN?
|
3.
|
What
are the advantages and problems of forwarding mechanism in Bluetooth networks
regarding power saving and network stability?
|
4.
|
Explain the MAC layer in IEEE802.11 (16)
|
5.
|
Discuss in detail about IEEE802.11a. (16)
|
6.
|
Explain Channel control sub layer in HIPERLAN (16)
|
7.
|
What is meant by Bluetooth? Describe architecture of
BLUE TOOTH. (16)
|
8.
|
Explain the service offered by IEEE802.11 standard. (16)
|
9.
|
Explain how power management is done in IEEE 802.11 infrastructure based
and ad hoc networks. (16)
|
10.
|
Discuss how to increase the quality of service in an ad hoc network. (16)
|
11.
|
Detail the time-bounded service on top of the standard DCF mechanism
where ad hoc networks cannot use the function.
|
12.
|
The channel access control sublayer of HIPERLAN offers a connectionless
data transfer service to the higher MAC layer. Justify the above
statement with
related references.
|
13.
|
Discuss the functionalities and support provided by
L2CAP.
|
UNIT
IV
PART
A
1.
|
Define mobile IP.
Mobile IP includes
detailed descriptions of classical internet protocols is given in stevens
(1994). Many new
approaches related to internet protocols, applications, and architectures can
be found in Kurose.
|
2.
|
List out the
several entities and terms needed to understand mobile IP.
Mobile node (MN)
Correspondent node (CN)
Home network
Foreign network
Foreign agent (FA)
Care of address (COA)
a) Foreign agent
COA
b) Co-located COA
Home agent (HA)
|
3.
|
Describe IP packet
delivery.
A correspondent
node CN wants to send an IP packet to the MN. One of the
requirements of
mobile IP was to support hiding the mobility of the MN. CN does not need to
know anything about
the MN’s current location and sends the packet as usual to the IP address
of MN.
|
4.
|
What is meant by
agent discovery?
One initial problem
of an MN after moving is how to find a foreign agent. How does the
MN discover that it
has moved? For this purpose mobile IP describes two methods:
Agent advertisement
Agent solicitation
|
5.
|
Define four
addition message needed in optimization.
The optimized
mobile IP protocol needs four additional messages.
a. Binding request
b. b. Binding
update
c. Binding
acknowledgement
d. d. Binding
warning
|
6.
|
Define IPV6.
Comparing to IP
version 4, IP version 6 makes life much easier. Several mechanisms that
had to be specified
separately for mobility support come free in IPv6. One issue is security with
regard to
authentication, which is now a required feature for all IPv6 nodes. Every
IPv6 node
can send binding
updates to another node so the MN can send its current COA directly to the CN
and HA.
|
7.
|
List out micro
mobility problems presents a comparison of the three approaches.
a. Cellular IP
b. Hawali
c. Hierarchical
mobile IPv6 (HMIPv6)
|
8.
|
Explain DHCP.
The dynamic host
configuration protocol is mainly used to simplify the installation and
Maintenance of
networked computers. If a new computer is connected to a network, DHCO can
provide it with all
the necessary information for full system integration into the network, e.g.,
addresses of a DNS
server and the default router, the subnet mask, the domain name and IP
Address.
|
9.
|
What is meant by
mobile ad-hoc network?
There may be
several situations where users of a network cannot rely on an
Infrastructure. The
ad-hoc setting up of a connection with an infrastructure is not the main
issue
Here. These
networks should be mobile and use wireless communications.
|
10.
|
Define routing.
Routing is needed
to find a path between source and destination and to forward the
Packets
appropriately. In wireless networks using an infrastructure, cells have been
defined.
Within a cell, the
base station can reach all mobile nodes without routing via a broadcast.
|
11.
|
List out some
fundamental differences between wired networks and Ad-hoc Wireless
Networks related to
routing.
a. Asymmetric links
b. Redundant links
c. Interference and
d. Dynamic topology
|
12.
|
Define DSDV.
Destination
sequence distance vector (DSDV) routing is an enhancement to distance
vector routing for
ad-hoc networks. Distance vector routing is used as routing information
protocol (RIP) in
wired networks. It performs extremely poorly with certain network changes
due to the count to
infinity problem.
|
13.
|
What are the
requirements of mobile IP?
Compatibility
Transparency
Scalability and efficiency
Security
|
14.
|
Mention the
different entities in a mobile IP.
Mobile Node
Correspondent Node
Home Network
Foreign Network
Foreign Agent
Home Agent
Care-Of address
Foreign agent CO A
Co-located COA
|
15.
|
What do you mean by
mobility binding?
The Mobile Node
sends its registration request to the Home Agent. The HA now sets up a
mobility binding
containing the mobile node’s home IP address and the current COA.
|
16.
|
Define a tunnel.
A tunnel
establishes a virtual pipe for data packets between a tunnel entry and a
tunnel
endpoint. Packets
entering a tunnel are forwarded inside the tunnel and leave the tunnel
unchanged.
|
17.
|
What is
encapsulation?
Encapsulation is
the mechanism of taking a packet consisting of packet header and data
putting
it into the data part of a new packet.
|
18.
|
What is
decapsulation?
The reverse
operation, taking a packet out of the data part of another packet, is called
decapsulation.
|
19.
|
Define an outer
header.
The HA takes the
original packet with the MN as destination, puts it into the data part of
a new packet and
sets the new IP header in such a way that the packet is routed to the COA.The
new header is
called the outer header.
|
20.
|
Define an inner
header.
There is an inner
header which can be identical to the original header as this case for IPin-
IP encapsulation,
or the inner header can be computed during encapsulation.
|
21.
|
What is meant by
generic routing encapsulation?
Generic routing
encapsulation allows the encapsulation of packets of one protocol suite
into the payload
portion of a packet of another protocol suite.
|
22.
|
What is the use of
network address translation?
The network address
translation is used by many companies to hide internal
resources and to
use only some globally available addresses.
|
23.
|
Define triangular
routing.
The inefficient
behavior of a non-optimized mobile IP is called triangular routing. The
triangle
is made up of three segments, CN to HA, HA to COA\MN, and MN back to CN.
|
24.
|
What is meant by a
binding cache?
One way to optimize
the route is to inform the CN of the current location by caching it in
a
binding cache which is a part of the local routing table for the CN
|
25.
|
Define binding
request.
Any node that wants
to know the current location of an MN can send a binding request
to the HA. The HA
can check if the MN has allowed dissemination of its current location. If the
HA is
allowed to reveal the location it sends back a binding update.
|
26.
|
What is known as
Binding update?
This message sent
by the HA to CNs reveals the current location of the MN.The message
contains the fixed
IP address of the MN and the COA.The binding update can request an
acknowledgement.
|
27.
|
Explain binding
acknowledgement.
If requested, a
node returns this acknowledgement receiving a binding update message.
|
28.
|
Define binding
warning.
If a node
decapsulates a packet for a MN, but it is not the current FA for this MN,
this
node sends a
binding warning. The warning contains MN’s home address and a target node
address.
|
29.
|
Explain cellular
IP.
Cellular IP
provides local handovers without renewed registration by installing a single
cellular IP gateway
for each domain, which acts to the outside world as a foreign agent.
|
30.
|
What are the
advantages of cellular IP?
Manageability
Efficiency
Transparency and Security
|
31.
|
What is known as
mobility anchor point?
HMIPv6 provides
micro-mobility support by installing a mobility anchor point, which is
responsible for a
certain domain and acts as a local HA within this domain for visiting MNs.
|
32.
|
Explain destination
sequence distance vector routing.
Destination
sequence distance vector routing is an enhancement to distance vector routing
for ad-hoc networks
and is used as routing information protocol in wired networks.
|
33.
|
What are the two
things added to the distance vector algorithm?
Sequence Numbers
Damping
|
34.
|
How the dynamic
source routing does divide the task of routing into two separate problems?
Route discovery
Route Maintenance
|
35.
|
State the
requirements of mobile IP.
i. Compatibility
ii. Transparency
iii. Scalability
and efficiency
iv Security
|
36.
|
What is COA? How is
it assigned?
Care-or address
(COA): The COA defines the current location of the MN from an IP point of
view.
There are two
different possibilities for the location of the COA:
Foreign agent COA
Co-located COA
|
37.
|
How does a MN
identify that it has moved?
Mobile IP describes
two methods: agent advertisement and agent solicitation, which are in
fact router
discovery methods plus extensions.
|
38.
|
What are the
contents of mobility binding?
Mobility binding
containing the mobile node’s home IP address and the current COA.
Additionally, the
mobility binding contains the lifetime of the registration which is
negotiated during the registration process.
|
39.
|
List the types of
encapsulation.
IP-in-IP encapsulation
Minimal encapsulation
Generic routing
encapsulation
|
40.
|
What are the
messages used for mobile IP optimization?
Binding request
Biding update
Binding acknowledgement
Binding warning
|
41.
|
State the reasons
for reverse tunneling.
Firewalls
Multi-cast
TTL
|
42.
|
State any 4
features of IPv6.
a. No special
mechanisms as add-ons are needed for securing mobile IP registration.
b. Every IPv6 node
masters address auto configuration – the mechanisms for acquiring a COA
are already built
in.
c. Neighbor
discovery as a mechanism mandatory for every node is also included in the
specification;
special foreign agents are no longer needed to advertise services.
d. Combining the
features of auto configuration and neighbor discovery means that every
mobile node is able
to crate or obtain a topologically correct address for the current point of
attachment.
e. Every IPv6 node
can send binding updates to another node, so the MN can send its current
COA directly to the
CN and HA.
|
43.
|
State the
advantages of cellular IP.
Manageability:
Cellular IP is mostly self-configuring, and integration of the CIPGW into a
firewall
would facilitate
administration of mobility-related functionality.
|
44.
|
State the
disadvantages of cellular IP.
Efficiency : Additional network load is
induced by forwarding packets on multiple paths.
Transparency: Changes to MNs are required.
Security : Routing tables are changed based
on messages sent by mobile nodes. Additionally, all systems in the network
can easily obtain a copy of all packets destined fro an MN by sending
packets with the
MN’s source address to the CIPGW.
|
45.
|
State the
advantages of Hawaii.
Security : Challenge-response extensions
are mandatory. In contrast to Cellular IP, routing
changes are always
initiated by the foreign domain’s infrastructure.
Transparency : HAWAII is mostly transparent
to mobile nodes.
|
46.
|
State the
disadvantages of Hawaii.
Security : There are no provisions
regarding the setup of IPSec tunnels.
Implementation : No private address support
is possible because of co-located COAs.
|
47.
|
State the
advantages of HMIPv6.
Security : MNs can have (limited) location
privacy because LCOAs can be hidden.
Efficiency : Direct routing between CNs
sharing the same link is possible.
|
48.
|
State the
disadvantages of HMIPv6.
Transparency : Additional infrastructure
component (MAP).
Security : Routing tables are changed based
on messages sent by mobile nodes. This requires
strong
authentication and protection against denial of service attacks. Additional
security
functions might be
necessary in MAPs.
|
49.
|
State the uses of
mobile ad hoc networks.
Instant infrastructure
Disaster relief
Remote areas
Effectiveness
|
PART
B
1.
|
What are the requirements of a mobile IP?
|
2.
|
Describe Dynamic host configuration protocol.
|
3.
|
Discuss the routing algorithm in ad-hoc network.
|
4.
|
What are the entities in mobile IP?
|
5.
|
Discuss how optimization in achieved in mobile IP.
|
6.
|
Explain tunneling and
encapsulation in mobile IP.
|
7.
|
Explain how dynamic source routing protocols handles
routing with an example.
|
8.
|
Discuss and detail the differences in topology reorganization in DSDV and
DSR routing protocols.
|
9.
|
What are the general problems of mobile IP regarding security and support
of quality of service?
|
10.
|
Name the inefficiencies of mobile IP regarding data forwarding from a
correspondent node to a mobile node. What are optimizations and what
additional problems do they cause?
|
11.
|
What are the types of registration in mobile IP? Explain.
|
12.
|
Explain the different routing techniques available for mobile ad hoc
network
with an example.
|
13.
|
Explain the agent discovery process in mobile IP.
|
14.
|
Explain the different approaches available for IPv6 to support mobility.
|
15.
|
Compare the features of wired network with ad hoc network related
to routing.
|
UNIT
V
PART
A
1.
|
What is slow start?
TCP’s reaction to a
missing acknowledgement is necessary to get rid of congestion
quickly. The
behavior TCP shows after the detection of congestion is called slow start.
|
2.
|
What is the use of
congestion threshold?
The exponential growth
of the congestion window in the slow start mechanism is
dangerous as it
doubles the congestion window at each step. So a congestion threshold is set
at
which the
exponential growth stops.
|
3.
|
What led to the
development of Indirect TCP?
• TCP performs poorly
together with wireless links
• TCP within the
fixed network cannot be changed.
This led to the
development of I-TCP which segments a TCP connection into a fixed part
and a wireless part.
|
4.
|
What is the goal of
M-TCP?
The goal of M-TCP
is to prevent the sender window from shrinking if bit errors or
disconnection but
not congestion cause current problems. It wants
• To provide
overall throughput
• To lower the
delay
• To maintain
end-to-end semantics of TCP
• To provide a more
efficient handover.
|
5.
|
What do you mean by
persistent mode?
Persistent mode is
the state of the sender will not change no matter how long the
receiver is
disconnected. This means that the sender will not try to retransmit the data.
|
6.
|
What are the
characteristics of 2.5G/3.5G wireless networks?
Data rates
Latency
Jitter
Packet loss
|
7.
|
What are the
configuration parameters to adapt TCP to Wireless environments?
Large Windows
Limited Transmit
Large MTU
Selective Acknowledgement
Explicit Congestion Notification
Timestamp
No header compression
|
8.
|
State the
requirements of WAP.
Interoperable
Scalable
Efficient
Reliable
Secure
|
9.
|
Name the layers of
WAP.
Transport layer
Security layer
Transaction layer
Session layer
Application layer
|
10.
|
Name some ICMP
messages.
Destination unreachable
Parameter problem
Message too big
Reassembly failure
Echo request/reply
|
11.
|
What is WTP? What
are its classes?
WTP stands for
Wireless Transaction Protocol. It has been designed to run on very thin
clients such as
mobile phones. It has three classes.
Class 0: provides unreliable message
transfer without any result message.
Class 1: provides reliable message
transfer without exactly one reliable result
message.
Class 2: provides reliable message
transfer with exactly one reliable result message.
|
12.
|
What is WSP?
The Wireless
Session Protocol has been designed to operate on top of the datagram
service WDP or the
transaction service WTP. It provides a shared state between a client and a
server to optimize
content transfer.
|
13.
|
Name some features
of WSP adapted to web browsing.
HTTP/1.1 functionality
Exchange of session headers
Push and pull data transfer
Asynchronous request
|
14.
|
What is WML?
The Wireless Markup
Language is based on the standard HTML known from the www and
on HDML. WML is
specified as an XML document type.
|
15.
|
What are the
features of WML?
Text and Images
User interaction
Navigation
Context Management
|
16.
|
What are the
advantages of WML Script over WML?
WML Script offers
several capabilities not supported by WML:
Validity check of user input
Access to device facilities
Local user interaction
Extension to the device software
|
17.
|
Name the libraries
specified by WML Script.
Lang
Float
String
URL
WML Browser
Dialogs
|
18.
|
What are the
classes of libraries?
Common network services
Network specific services
Public services
|
19.
|
Name the operations
performed by PAP.
Push access
Protocol performs the following operations:
• Push submission
• Result
notification
• Push cancellation
Status query
• Client
capabilities query
|
20.
|
What are the
components of WAP2.0?
The protocol
framework of WAP2.0 consists of four components:
• Bearer networks
• Transport
services
• Transfer services
• Session services
|
21.
|
State any 4
improvements to the classical TCP.
1. Indirect TCP 2.
Mobile TCP
3. Snooping TCP 4.
Fast retransmit / Fast recovery.
|
22.
|
State any 2
advantages of I-TCP.
I-TCP does not require any changes in the
TCP protocol as used by the hosts in the fixed
network or other
hosts in a wireless network that do not use this optimization.
Due to the strict partitioning into two
connections, transmission errors on the wireless link,
i.e., lost packets
cannot propagate into the fixed network.
|
23.
|
State any 2
disadvantages of I-TCP.
The loss of the end-to-end semantics of TCP
might cause problems if the foreign agent
partitioning the
TCP connection crashes.
In practical use,
increased handover latency may be much more problematic.
|
24.
|
State any 2
advantages of S-TCP.
The end-to-end TCP semantic is
preserved. No matter at what time the foreign agent
crashes (if this is
the location of the buffering and snooping mechanisms), neither the
correspondent host
nor the mobile host have an inconsistent view of the TCP connection as
is possible with
I-TCP.
The correspondent host does not need
to be changed; most of the enhancements are in the
foreign agent.
|
25.
|
State any 2
disadvantages of S-TCP.
Snooping TCP does not isolate the behaviour
of the wireless link as well as I-TCP.
Using negative acknowledgements between the
foreign agent and the mobile host assumes
additional
mechanisms on the mobile host. This approach is no longer transparent for arbitrary
mobile hosts.
|
26.
|
State any 2
advantages of M-TCP.
It maintains the TCP end-to-end semantics.
The SH does not send any ACK itself but forwards
the ACKs form the
MH.
If the MH is disconnected, it avoids
useless retransmissions, slow starts or breaking connections
by simply shrinking
the sender’s window to 0.
|
27.
|
State any 2
disadvantages of M-TCP.
As the SH does not act as proxy as in
I-TCP, packet loss on the wireless link due to bit errors is propagated to
the sender.
M-TCP assumes low bit error rates, which is
not always a valid assumption.
|
28.
|
State any 2
advantages of Transmission / time out freezing.
The advantage of this approach is
its simplicity. Only minor changes in the mobile host’s
software already
result in a performance increase. No foreign agent or correspondent host has
to be changed.
The main disadvantage of this scheme
is the insufficient isolation of packet losses.
|
29.
|
State any 2
advantages of Transmission / time out freezing.
o The advantage of
this approach is that it offers a way to resume TCP connections even
after longer
interruptions of the connection.
o It is independent
of any other TCP mechanism, such as acknowledgements or sequence
numbers, so it can
be used together with encrypted data.
|
30.
|
State any 2 disadvantages
of Transmission / time out freezing.
Not only does the software on the
mobile host have to be changed, to be more effective the
correspondent host
cannot remain unchanged.
All mechanisms rely of the
capability of the MAC layer to detect future interruptions.
Freezing the state
of TCP does not help in case of some encryption schemes that use
timedependent
random numbers.
These schemes need resynchronization after interruption.
|
31.
|
State any 2
advantages of selective retransmission.
The advantage of this approach is
obvious: a sender retransmits only the lost packets. This
lowers bandwidth
requirements and is extremely helpful in slow wireless links.
The gain in efficiency is not
restricted to wireless links and mobile environments. Using
selective
retransmission is also beneficial in all other networks.
|
32.
|
State any 2
disadvantages of selective retransmission.
More buffer is necessary to
re-sequence data and to wait for gaps to be filled.
But while memory sizes and CPU
performance permanently increase, the bandwidth
of the air
interface remains almost the same.
Therefore, the higher complexity is
no real disadvantage any longer as it was in the
early days of TCP.
|
33.
|
State any 2
advantages of Transaction oriented TCP.
The obvious
advantage for certain applications is the reduction in the overhead which
standard TCP has
for connection setup and connection release.
|
34.
|
State any 2
disadvantages of Transaction oriented TCP.
This solution no
longer hides mobility. Furthermore, T/TCP exhibits several security problems.
|
35.
|
Who have formed the
WAP forum?
Ericsson, Motorola,
Nokia, and Unwired Planet.
|
36.
|
State the features
of WAP Forum solutions.
All solutions must
be:
interoperable
scalable
efficient
reliable
secure
|
37.
|
State the layers in
WAP architecture.
1. Transport layer
2. Security layer
3. Transaction
layer
4. Session layer
5. Application
layer
|
38.
|
State any 4 WAP
working groups.
1. WAP architecture
working group
2. WAP wireless
protocol working group
3. WAP wireless
security working group
4. WAP wireless
application working group
|
39.
|
What are the
service primitives available in T-SAP?
1. T_D Unit
data.req(DA, DP, SA, SP, UD)
2. T_D Unit
data.ind(SA, SP, UD)
3. T_DError.ind(EC)
DA – destination
address SA – Source Address
DP – destination
port SP – Source Port
UD –
user data EC – Error code.
|
40.
|
What are the
different security levels offered by WTLS?
1.
Privacy 2. data integrity 3. authentication
|
41.
|
What are the different
services offered by WTP?
1. Class 0 –
unreliable message transfer without any result message.
2. Class 1 –
reliable message transfer without any result message.
3.
Class 2 – reliable message transfer with exactly one result message.
|
42.
|
How is reliability
achieved in WTP?
1. duplicate
removed
2. retransmission
3. acknowledgements
4. unique
transaction identifier.
|
43.
|
What are the types
of PDU exchanged between WTP entities?
1. invoke PDU.
2. ack PDU
3. result PDU.
|
44.
|
What are the
functions of WSP?
1. session
management
2. Capability
negotiation
3. content encoding
|
45.
|
State the features
of WSP/B.
1. HTTP1.1
functionality
2. exchange of
session headers
3. Push & Pull
data transfer
4. Asynchronous
requests.
|
46.
|
List any 4 basic
features of WML.
1. Text and images
representation.
2. User interaction
3. Navigation
4. Context
management.
|
47.
|
List any 4
capabilities of WML script.
1. Validity check
of user input
2. Access to device
facilities
3. Local user
interaction
4. Extension to the
device software
|
48.
|
What are the
standard libraries available for WML script?
1. Lang.
2. Float
3. String
4. URL
5. WML Browser
6. Dialogs
|
49.
|
What are the
libraries available for WTA?
1. Common network
services
2. Network specific
services
3. Public services.
|
50.
|
State the component
present in protocol framework in WAP 2.0
Bearer network
Transport service
Transfer service
Session service.
|
PART
B
1.
|
Explain in detail about traditional TCP in details. (16)
|
2.
|
Explain classical TCP improvements and snooping TCP
|
3.
|
Explain the function of the components of the WAP
architecture.
|
4.
|
Explain the concept of wireless markup language.
|
5.
|
Explain wireless application protocols with the it’s
version WAP 2.0 in detail.
|
6.
|
Describe the operation
of the window flow control mechanism
|
7.
|
What are the major difference between WAP 2.0 and WAP 1.x? What
influenced the WAP 2.0 development?
|
8.
|
Explain the features of S-TCP.
|
9.
|
Explain the function of WDP. (16)
|
10.
|
Explain the services offered by WSP.
|
11.
|
Explain the services offered by WTA with an example.
|
12.
|
Explain the following:
a. Indirect TCP.
b. Snooping TCP.
c. Performance enhancing proxies.
|
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