Anna University, Chennai
SRINIVASAN ENGINEERING COLLEGE
PERAMBALUR-621212.
DEPARTMENT OF INFORMATION TECHNOLOGY
IT1403 MOBILE COMPUTING
UNIT I-
WIRELESS COMMUNICATION FUNDAMENTALS
1. What are the disadvantages of small cells?
a) Infrastructure b) Handover
c) Frequency
2. What are the benefits of reservation schemes?
a) Increased no other station is allowed to transit during this slot b) Avoidance of congestion.
c) Waiting time in clearly known.
3. Differentiate between free space loss and path loss.
| Free space loss | Path loss |
| 1) Even if no matter exists between the sender and the receiver, signals still experience free space loss. | 1) If there exists any matter between the sender and the receiver, then it experiences the path loss. |
| 2) There is a gradual degradation in the strength of the signal with the distance traveled. | 2) There is a sudden decrease in the strength of the signal due to obstacles in the path. |
4. Define multipath propagation
Radio waves emitted by the sender can either travel along a straight line, or they may be reflected at a large building or scattered at smaller obstacles. This leads to one of the most severe radio channel impairments called multipath propagation.
5. Define dwell time.
The time spent in a channel with a certain frequency is called the dwell time.
6. Why CSMA/CD scheme fails in wireless networks?
CSMA/CD is not really interested in collisions at the sender, but rather in those at the receiver. The sender applies carrier sense and detects an idle
medium. The sender starts sending but a collision happens at the receiver due to a second sender. The sender detects no collision and assumes that the data has been transmitted without errors, but a collision might actually have destroyed the data at the mission. The power in the area of the transmitting antenna is several magnitudes higher than the receiving power.
7. Define hidden terminal.
The transmission range of A reaches B but not C. The transmission range of C reaches B but not A. B reaches A and C. A cannot detect C and vice versa.
A starts sending to B, but C does not receive this transmission. C also wants to send something to B and senses the medium. The medium appears to be free, the carrier sense fails. C also starts sending, causing a collision at B. But A can’t detect this collision at B and continues with its transmission. A is hidden for C and vice versa.
8. What is orthogonal and autocorrelation thickness?
Orthogonal: Two vectors are called orthogonal if their inner product is 0. E.g.) the two vectors are(2,5,0) & (0,0,17): (2,5,0)* (0,0,17)=0+0+0. Autocorrelation: The barker code (+1, -1, +1, +1, -1, +1, +1, +1, -1, -1, -1) for example has a good autocorrelation (i.e.) the inner product with itself is large the result is 11.
9. Mention the merits and demerits of spread spectrum.
Merits:
=>The main advantage is the resistance to narrowband interference.
=>coexistence of several signals without co-ordination.
=>robustness against narrowband interference.
=>relative high frequency.
=>characteristics like background noise.
Demerits:
*Increase in complexity of receivers that have to despread a signal.
*Large frequency band that is needed due to the spreading of the signal.
10. Why can waves with a very low frequency follow the earth’s surface ? Why are they not used for data transmission in computer networks?
The waves with low frequencies follow the earth’s surface and can propagate long distance. Generally, the lower the frequency, the better the penetration.
Low frequency waves are bent by the atmosphere due to refraction. High frequency waves follow straight line of sight. This enables direct communication with satellites or microwave link on the ground.
11. Why don’t radio waves always follow a straight line? Why is reflection both
useful and harmful?
We have a line of sight between the sender and the receiver of the radio signals. Mobile phones are typically used in big cities with skyscrapers, on mountains, inside buildings, while driving through an alley, etc.
Here several effects occur in addition to the attenuation caused by the distance between the sender and the receiver.
Reflection is useful because,
It helps transmitting signals as soon as no line of sight exists.
Reflection is harmful because,
The reflected signal is not as strong as original, as objects can absorb some of the signal’s power.
12. What are the 3 fundamental propagation behaviors depending on their frequency?
Ground wave
Sky wave
Line of Sight
13. What’s the use of Phase Lock Loop (PLL)?
To receive the signal correctly, the receiver must synchronize in frequency and phase with the transmitter
14. What is OVSF?
Using orthogonal code separation of data streams of a sender UMTS uses so-called orthogonal variable spreading factor codes (OVSF).
15. Explain about transparent mode?
The transparent mode transfer simply forwards MAC data without any further processing .The system then has to rely on the FEC which is always used in the radio layer.
16. Specify the steps to be performed during the search for a cell after power on?
Primary synchronization
Secondary synchronization
Identification of the scrambling code.
17. 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 fixed channel allocation.
18. 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).
19. What is called burst and normal burst?
Data is transmitted in small portions called bursts. Normal burst are used for data transmission inside a slot.
20. What is frequency hopping spread spectrum and mention their variants?
The total available bandwidth is split into many channels of smaller bandwidth plus guard spaces between the channels, hopping take place between the transmitter and receiver staying on one of these channels. This is known as Frequency hopping spread spectrum.
Two variants
Slow hopping
Fast hopping
21. What do you mean by spread factor?
It determines the bandwidth of the resulting signal in direct sequence spread spectrum
S = tb/tc
tb – user bit duration; tc – chip duration
22. What are the types of antennae?
Theoretical
Real
Directional
Multi-element
Smart
23. What are the different considerations for a signal to be propagated?
Transmission Range
Detection Range
Interface Range
24. Mention the several effects when a signal is propagated.
Blocking or Shadowing
Reflection
Refraction
Scattering
Diffraction
UNIT-II
TELECOMMUNICATION NETWORKS
1) What are the different types of handovers used in GSM?
Intra-cell handover: Within a cell, narrow-band interference could make transmission at a certain frequency impossible. The BSC could then decide to change the carrier frequency.
Inter-cell, intra-BSC handover: This is a typical handover scenario. The mobile station moves from one cell to another, but stays within the control of the same BSC.
Inter-BSC, intra-MSC handover: As a BSC only controls a limited number of cells. GSM also has to perform handovers between cells. This has to be controlled by the MSC.
Inter MSC handover: A handover could be required between two cells belonging to different MSCs. Now both MSCs perform the handover together.
2) What is meant by Inclination angle and Elevation angle?
Inclination angle is defined as the angle between the equatorial plane and the plane described by the satellite orbit.
Elevation angle is defined as the angle between the center of the satellite beam and the plane tangential to the earth’s surface.
3) Write the different types of orbits used in the satellite systems?
Geostationary earth orbit(GEO) Medium earth orbit(MEO)
Low earth orbit(LEO) Highly elliptical orbit(HEO)
4) What are different broadcast patterns available to send the data?
Flat disk Skewed disk Multi-disk
5) What is the need of SIM?
The need for SIM is that one can personalize any MS using his or her SIM i.e. user-specific mechanisms like charging and authentication are based on the SIM not on the device itself.
6) How authentication is performed in GSM systems?
Authentication is based on the SIM, which stores the individual authentication key Kj, the user identification IMSI and the algorithm used for authentication A3.
The VLR sends the random value RAND to the SIM. Both sides network and subscriber module perform the same operation with RAND and the Kj called A3. The MS sends back the SRES (signed response) generated by the SIM. The VLR can now compare both values. If they are the same, the VLR accepts the subscriber, otherwise the subscriber is rejected.
7) Draw the UMTS architecture
Uu Iu
UE UTRAN CN
UTRAN- the UTRAN network
UE-User requirement
CN-Core network
Uu-Interface that connects UE and UTRAN Iu - Interface that connects UTRAN and CN
8) What is meant by footprint?
A footprint can be defined as the area on earth where the signals of the satellite can be received.
9) What the two basic transport mechanisms of DAB?
Main service channel (MSC): It carries all user data. The MSC consists of common interleaved frames (CIF) i.e, data fields of 55,296 bits that are sent every 24 ms. A CIF consists of capacity units (CU) with a size of 64 bits which form the smallest addressable unit within a DAB system.
10) What is MOT? Give its primary goal.
DAB faces a broad range of different receiver capabilities. So to solve this problem it defines a common standard for data transmission, the multi-media object transfer (MOT) protocol.
The primary goal of MOT is the support of data formats used in other multi- media systems.
11) What is SUMR?
An important register in satellite networks is the satellite user mapping register (SUMR). This stores the current position of satellites and a mapping of each user to the current satellite through which communication with a user is possible.
12) Give the two basic reasons for a handover in GSM.
The mobile station moves out of the range of a BTS or a certain antenna of a BTS. The received signal level decreases continuously until it falls below the minimal requirements for communication. The error rate may grow due to interference. All these effects may diminish the quality of the radio link.
The wired infrastructure may decide that the traffic in one cell is too high and shift some MS to other cells with a lower load. Handover may be due to load balancing.
13) Give the security services offered by GSM.
Access control and authentication
Confidentiality
Anonymity
14) What is the primary goal of GSM?
The primary goal of GSM was to provide a mobile phone system that allows users to roam throughout Europe and provides voice services compatible to ISDN and other PSTN systems.
15) Differentiate GSM and DECT.
| GSM | DECT |
| 1. Global systems for mobile communications | 1. Digital enhanced cordless telecommunications |
| 2. Range is up to 70km. | 2. Range is limited to about 300m. |
16) What are the two new network elements in GPRS architecture?
Gateway GPRS support node (GGSN): It is the inter-working unit between the GPRS network and external packet data networks (PDN). Serving GPRS support node (SGSN): It supports the MS.
17) Describe about MAC layer in DECT architecture.
The medium access control (MAC) layer establishes, maintains and releases channels for higher layers by activating and deactivating physical channels. MAC multiplexes several logical channels onto physical channels. Logical channels exist for signaling network control, user data transmission, paging or sending broadcast messages. Additional services offered include segmentation/reassembly of packets and error control/error correction.
18) Give the full form for the following:
a) CKSN
b) EIR
c) DTMF
d) MOC
a) CKSN- Ciphering key sequence number b) EIR- Equipment Identity Register
c) DTMF- Dual Tone multiple frequency d) MOC- Mobile originated call
19) Describe the three subsystems of GSM.
Radio subsystem (RSS): It comprises all radio specific entities i.e. the mobile stations (MS) and the base station subsystem (BSS).
Networking and switching subsystem (NSS): The heart of the GSM system is formed by the NSS. This connects the wireless network with standard public networks.
Operating subsystem (OSS): It monitors and controls all other network entities.
20) What are the applications of satellites?
Weather forecasting
Radio and TV broadcast satellites
Military satellites
Satellites for navigation
UNIT III WIRELESS LAN
1. List the advantages of Wireless LANs
Flexibility
Planning
Design
Robustness and
Cost
2. List the disadvantages of Wireless LANs Quality of service Proprietary solutions Restrictions
Safety and security
3. What are the advantages and disadvantages of infra red technology?
Advantages:
It is simple and extremely cheap
No licenses are needed
Shielding is very simple
Electrical devices do not interfere with infra red transmission.
Disadvantages:
It has low bandwidth compared to other LAN
technologies.
It cannot penetrate walls or other obstacles.
For good transmission quality and high data rates a
LOS, i.e., direct connection is needed.
4. Explain briefly about an infrastructure network
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.
5. Explain briefly about an Ad-hoc network
Ad-hoc wireless networks do not need any infrastructure to work. Each node can communicate directly other nodes, so no access point controlling
medium access is necessary. Nodes within an ad-hoc network can only communicate if they can reach each other physically, i.e., if they are within each others radio range.
6. What are the basic tasks of the MAC layer?
Medium access Fragmentation of user data Encryption
7. What are the basic services provided by the MAC layer?
Asynchronous data service (mandatory)
Time-bounded service (optional)
8. List the basic access mechanisms defined for IEEE 802.11
The mandatory basic method based on a version of CSMA/CA
An optional method avoiding the hidden terminal problem
A contention-free polling method for time bounded service.
9. What is the basic idea of IEEE 802.11 power management?
The basic idea is to switch off the transceiver whenever it is not needed. Switching off the transceiver should be transparent to existing protocols and should be flexible enough to support different applications. The power saving includes two states for a station: Sleep and awake, and buffering of data in senders.
10. What are the techniques used for MAC management?
Synchronization
Power management
Roaming
Management information base(MIB)
11.Define beacon?
Beacon frame is used to convey timing information within a BSS.It contains a timestamp and other management information used for power management and roaming.The timestamp is used by the node to adjust its local clock.
12.What are the handovers in hiperLAN?
The handovers in hiperLAN are
*Sector handover
*Radio handover
* Network handover
13.Distinguish infrastructure and adhoc networks?
| Infrastructure networks | adhoc networks |
| Communication takes place only between a wireless node and an access point | Communication takes place only between two wireless nodes |
| The wireless node is simple as functionality is based on the access point | The wireless node is complex |
| Can forward messages across networks | Can forward messages only within the specified range |
14.Why is physical layer in IEEE802.11 subdivided ? What are its sublayers?
The physical layer in IEEE802.11 is subdivided because a sublayer has to be dependant on the upper layers (architecture dependant)and the other has to be medium dependant. The two sublayers are namely,
*Physical layer convergence protocol
* Physical medium dependant sublayer
15.Define MSDU lifetime?
MSDU lifetime is used to provide time bounded service which specifies
the maximum time that can elapse between sending and receiving a MSDU. It has a range of 0-16000 ms.
16.What are the elements in core protocols in Bluetooth?
The elements in core protocols in Bluetooth are,
*Radio
*Baseband
*Link Manager protocol
*Logical Link control and adaptation protocol
*Service discovery protocol
1 7.What are the low power states in Bluetooth?
The low power states in Bluetooth are
*Sniff state
*Hold state
*Park state
18.Define SDP?
SDP stands for Service discovery protocol.SDP defines the discovery of services enabled by a SDP server which has some information about the list of services available called the service record.
19.What is EY-NPMA?
EY-NPMA stands for Elimination-yield non preemptive priority multiple access which is the heart of channel access providing priorities and different access mechanisms.
20.What do you mean by ESSID?
ESSID means Extended Service Set Identifier.It is the name of the
network and is used to separate two networks.Without knowing ESSID it is impossible to participate in a WLAN.
UNIT IV
MOBILE NETWORK LAYER
1.What are the two possibilities for the location of the Care-of address(COA)?
Foreign agent COA:The COA could be located at the Foreign Agent.i.e;the COA is an IP address of the FA.The FA is the tunnel end-point and forwards packets to the Mobile Node.
Co-located COA:The COA is co-located if the MN temporarily acquired an additional IP address which acts as COA.This address is now topologically correct, and the tunnel end point is at the MN.Co-located addresses can be acquired using services such as DHCP
2.What are the three alternatives for the implementation of Home Agent(HA)?
The HA can be implemented
*on a router that is responsible for the home network.
*on an arbitrary node in the subnet
*again on the router.But here the router acts as a manager for MNs belonging to a virtual home network.
3.What is 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 suiteThis encapsulation supports other network layer protocols in addition to IP.
4.What are the four additional messages in optimized mobile IP Protocol?
Binding request
Binding update
Binding acknowledgement
Binding warning
5.What are the disadvantages of Cellular IP?
Efficiency:Additional network load is induced by forwarding packets on multiple paths
Transparency: Changes to Mobile Nodes are required
Security:Routing tables are changed based on messages sent by mobile nodes
6.What is the function performed by Mobility anchor point(MAP)?
MAP is responsible for a certain domain and acts as a local Home Agent within this domainfor visiting Mobile Nodes.The MAP receives all packets on behalf of the Mobile Node,encapsulates and forwards them directly to the Mobile Node’s current address.As long as a Mobile Node stays within the domain of a MAP,the globally visible COA does not change.
7.What is the use of dynamic host configuration protocol?
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, DHCP can provide it with all the necessary information for full system integration into the network.
8.What is meant by destination sequence distance vector?
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 in wired networks.DSDV adds sequence numbers and dambling to the distance vector algorithm.
9.What do you mean by dampling in DSDV?
Transient changes in topology that are of short duration should not destabilize the routing mechanisms.Advertisements containing changes in the topology currently stored are therefore not disseminated further.A node waits with dissemination if these changes are probably unstable.Waiting time depends on the time between the first and best announcement of a path to a certain destination.
10. How does Dynamic source routing divide the task of routing?
problems:
Dynamic source routing divides the task of routing into two separate
Route discovery:A node only tries to discover a route to a destination if it has to send something to this destination and there is currently no known route.
Route maintenance:If a node is continuously sending packets via a route,it has to make sure that the route is held upright.As soon as a node detects problems with the current route,it has to find an alternative.
11.What is the goal of a mobile IP?
The goal of a mobile IP can be summarized as: supporting end-system mobility while maintaining scalability,efficiency,and compatibility in all respects with existing applications and Internet protocols.
12.What is the use of Mobile Node?
A mobile node is an end-system or router that can change its point of attachment to the internet using mobile IP.The MN keeps its IP address and can continuously communicate with any other system in the internet as long as link-layer connectivity is given.Mobile nodes are not necessarily small devices such as laptops with antennas or mobile phones; a router onboard an aircraft can be a powerful mobile node.
13.What are the services provided by a foreign agent(FA)?
The FA can provide several services to the MN during its visit to the foreign network.The FA can have the Care-of address acting as tunnel point and forwarding packets to the MN.The FA can be the default router for the MN. FAs can also provide security services.
14.What are the entities and terminologies in mobile IP?
Mobile Node
Correspondent node
Home network
Foreign network
Foreign agent
Care-of address
Home agent
15.What are encapsulation and decapsulation?
Encapsulation is the mechanism of taking a packet consisting of packet header and data and putting it into the data part of a new packet.The reverse operation, taking a packet out of the data part of another packet,is called decapsulation.Encapsulation and decapsulation are the operations typically performed when a packet is transferred from a higher protocol layer to a lower layer or from a lower to a higher layer respectively.
16.What are the problems associated with reverse tunneling?
Firewalls
Multi-cast
TTL
17.What are 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 for an MN by sending packets with the MN’s source address to the cellular IP gateway.
18.What are the advantages of HAWALI?
Security: Challenge-response extensions are mandatory.In contrast to Cellular IP,routing changes are always initiated by the foreign domain’s infrastructure.
Transparency: HAWALI is mostly transparent to mobile nodes.
19. What are the disadvantages of HAWALI?
Security: There are no provisions regarding the setup of
IPSec tunnels.
Implementation: No private address support is possible because of co-located Care-of Addresses
20.What is the use of sequence numbers in DSDV?
Each routing advertisement comes with a sequence number.Within ad-hoc networks,advertisements may propagate along many paths.Sequence numbers help to apply the advertisements in correct order.This avoids the loops that are likely with the unchanged distance vector algorithm
UNIT V
TRANSPORT AND APPLICATION LAYERS
1. What is the function of transport layer in WAP?
The transport layer offers a bearer independent, consistent datagram-oriented service to the higher layers of the WAP architecture. Communication is done transparently over one of the available bearer services.
2. What is the use of WCMP?
The wireless control message protocol provides error handling mechanisms for WDP. WCMP is used for diagnostic and informational purposes. It is used by WDP nodes and gateways to report errors.
3. What are the advantages of WTP?
WTP offers several advantages to higher layers, including an improved reliability over datagram services, improved efficiency over connection-oriented services and support for transaction-oriented services such as web browsing.
4. How is reliability achieved in WTP?
WTP achieves reliability using duplicate removal, retransmission, acknowledgements and unique transaction identifiers.
5. What are the service primitives offered by WTP?
The three service primitives offered by WTP are
o TR-Invoke to initiate a new transaction
o TR-Result to send back the result of a previously initiated transaction
o TR-Abort to abort an existing transaction.
6. What are the features offered by WSP?
WSP offers certain features for content exchange between cooperating clients and servers:
Session management
Capability negotiation
Content encoding.
7. What are the features offered by WSP/B?
In addition to the general features of WSP, WSP/B offers the following features adapted to web browsing:
HTTP/1.1 functionality
Exchange of session headers
Push and pull data transfer
Asynchronous requests
8. What is meant by WML?
The wireless markup language(WML) is based on the standard HTML known from the www and on HDML. WML is specified as an XML document type. WML follows a deck and card metaphor.
9. What are the capabilities of WMLScript?
WMLScript offer several capabilities:
Validity check of user input
Access to device facilities
Local user interaction
Extension to the device software
10. Define WTA
Wireless telephony application (WTA) is a collection of telephony specific extensions for call and feature control mechanisms, merging data networks and voice networks.
11. Define XHTML
XHTML is the extensible hypertext mark-up language developed by the w3c to replace and enhance the currently used HTML.
12. What do you mean by MMS?
The multimedia messaging service (MMS) transfers asynchronous multi-media content. MMS supports different media types such as JPEG, GIF, text and AMR coded audio. There is no fixed upper bound for the message size. Depending on the network operator and device capabilities typical sizes are 30-100 Kbytes.
13. What are the two functions of transport layer in the internet ?
1) Checksumming over user data.
2) Multiplexing/Demultiplexing from /to applications.
14. Distinguish TCP& UDP ?
| TCP | UDP |
| 1) Connection oriented protocol | Connection less protocol |
| 2) TCP is network friendly | UDP is not network friendly |
| 3) TCP guarantees in-order delivery or reliable data transmission using Retransmission techniques. | Does not pull back in case of congestion to send packets in to an already congested network. |
15. What is congestion & how it is identified in TCP?
When there is a temporary overload at some point in the transmission path it is referred to as congestion. Congestion result in packet loss. If acknowledgement does not arrive in time or if any acknowledgement is missing, TCP assumes network congestion.
16. How congestion is controlled in TCP?
TCP shows a behavior after congestion is called slow start. The sender has a congestion window & congestion threshold for receiver. For each acknowledgement the window size is increased exponentially until the congestion threshold & then it increases linearly (by 1). When congestion occurs the
threshold is reduced to half its current size.
17. State whether standard TCP alone support mobile users or wireless links and why?
No, standard TCP alone cannot support wireless links because wireless links have much higher error rates compared to wired links. The link layer may try to correct errors which results in higher delays and mobility (Handover between access points) may result in packet loss. In both cases standard TCP goes into slow start state.
18. State some of the classical solutions to improve the efficiency of TCP in wireless?
1) Indirect TCP (I-TCP)
2) Snooping TCP
3) Mobile TCP(M-TCP)
4) Fast retransmit/font recovery
5) Transmission/time –out freezing
6) Selective retransmission
7) Transaction oriented TCP.
19. What is indirect TCP?
Indirect TCP segments a TCP connection in 2 parts
Fixed part
Wireless part.
20. What are the steps to be taken by I-TCP when hand over take place?
1) The old proxy must forward buffered data to new proxy
2) After registration with new foreign agent, the new foreign agent informs the old one about its location to enable packet forwarding.
3) The sockets of proxy must mitigate to the new foreign agent located in the access point.
16 MARKS - KEYPOINTS
1.Explain in detail about Signal Propagation.
Path loss of radio signals
Ground wave
Sky wave
Line-of-sight
Additional Signal propagation effects
Blocking (or) Shadowing, Reflection, Refraction, Scattering, Diffraction
Multi-path propagation
Delay Spread
Intersymbol Interference
Short-term fading, long-term fading
Doppler Shift
2. Write a brief note about multiplexing.
Space division multiplexing
Guard space
disadvantages
Frequency division multiplexing
Adjacent Channel Interference
disadvantages
Time division multiplexing
Guard spaces
Co-channel Interference
Advantages, disadvantages
Code division multiplexing
Guard spaces- orthogonal codes
Advantages, disadvantages
3. What is modulation? Explain in detail.
Introduction
Digital modulation, Analog modulation
Antennas
Frequency division Multiplexing
Medium Characteristics
Spectral efficiency, Power efficiency, Robustness
Amplitude Shift Keying
Advantages, disadvantages, Applications
Frequency Shift Keying
Binary FSK
Continuous Phase Modulation
Phase Shift Keying
Binary PSK
Phase lock loop
Advanced Frequency Shift Keying
Minimum Shift Keying, Gaussian MSK
Advanced Phase Shift Keying
Quadrature PSK
Reference signal
Differential QPSK
Quadrature Amplitude Modulation
Multi-carrier modulation
Advantages
4. Briefly demonstrate the concept of spread spectrum.
Direct Sequence Spread Spectrum
Chipping Sequence
Pseudo-noise Sequence
Spreading factor
DSSS transmitter & receiver
Frequency hopping Spread Spectrum
Hopping Sequence
Dwell Time
Slow & Fast Hopping
FHSS transmitter & receiver
5. Describe in detail about cellular systems.
Base Station, cell
Advantages
Higher capacity, less transmission power, local interference only, Robustness
Disadvantages
Infrastructure needed, Handover needed, Frequency planning
Clusters, sectorized antennas, Borrowing Channel Allocation(BCA),
Fixed Channel Allocation(FCA), Dynamic Channel Allocation(DCA)
6. Describe the mobile services provided by GSM in detail.
Bearer Services
Transparent & Non- transparent Bearer Services
Tele Services
Telephony
Emergency number
Short Message Service
Enhanced Message Service
Multimedia Message Service
Group 3 fax
Supplementary Services
Typical services
7. Explain in detail about the GSM architecture.
Radio Subsystem
Base Station Subsystem
Base Transceiver Station
Base Station Controller
Mobile Station
Subscriber Identity Module
Personal Identity Number, PIN Unblocking
Key
Network and Switching Subsystem
Mobile Services Switching center
Home Location register
Visitor Location register
Operation Subsystem
Operation and Maintenance center
Authentication center
Equipment Identity Register
8. Briefly explain about GPRS
GPRS concepts
Time slots
PTP packet transfer service
QoS profile
Delay
GPRS architecture
GSN
Mobility management
9. Give a detailed explanation about DECT
System architecture
Global network
Local network
Home database, visitor database
Protocol architecture
Physical layer
Medium access control layer
Data link control layer
Network layer
10. Explain briefly about Satellite systems
History
SPUTNIK
SYNCOM
INTELSAT1
Applications
Weather forecasting, Radio & TV broadcast satellites, military satellites, satellites for navigation.
Global telephone backbone, connections for remote or
developing areas, global mobile communication
Basics
Routing
Fg=Fc
Inclination angle, elevation angle
Footprint
GEO(Geostationary Earth Orbit) Advantages, disadvantages
LEO(Low Earth Orbit)
Advantages, disadvantages
MEO(Medium Earth Orbit)
Advantages, disadvantages
HEO(Highly Elliptical Orbit) Advantages, disadvantages
Localization
Home Location register(HLR)
Visitor Location register (VLR)
Satellite user mapping register(SUMR)
Handover.
Intra-satellite, inter-satellite, Gateway, Intersystem handover
11. Explain the types of broadcasting in detail.
Digital Audio Broadcasting (DAB)
Transport mechanisms
Main Service Channel
Fast Information Channel
Multi-media object Transfer protocol
Header core, Header extension, Body Object repetition, Interleaved objects, segment repetition, Header repetition
Digital Video Broadcasting (DVB)
Contents of DVB
Network Information Table, Service Description table, Event Information table, Time and date table
DVB Data Broadcasting
Data pipe, Data Streaming,, multiprotocol encapsulation, data carousels, object carousels.
DVB for high-speed Internet access
12. Give a detailed description about the physical layer of IEEE 802.11
Frequency hopping Spread Spectrum
Functions
Synchronization, Start frame delimiter, PLCP_PDU length word, PLCP signaling field, Header error check
Direct Sequence Spread Spectrum
Synchronization, Start frame delimiter, signal, Service, Length, Header error check
Infra red
13. Make a detailed description about MAC management.
Synchronization
Timing Synchronization function
Beacon
Beacon transmission in
Infrastructure network
Ad-hoc network
Power management
Sleep & awake states
Power management in
Infrastructure network
Traffic indication map
Delivery Traffic indication map
PS(power saving) poll
Ad-hoc network
Ad-hoc Traffic indication map
Roaming
Steps
Scanning
Passive & active scanning
Association request
Association response
Updation of database
14. Explain briefly about HIPERLAN1
Phases
Prioritization
Elimination
Yield
Transmission
Quality of Service support and other specialities
MSDU Lifetime
Power Conservation
Encryption, decryption
15. Give a short description of the Bluetooth architecture
Networking
Piconet
Scatternet
Protocol stack
Core specifications, profile specifications
Core protocols
Link manager protocol, Logical link control &
adaptation protocol, service discovery protocol
Cable replacement protocol, telephony control protocol specification
Host controller interface
16. What are the advantages and disadvantages of WLANs? Explain.
Advantages
Flexibility
Planning
Design
Robustness
Cost
Disadvantages
Quality of service
Proprietary solutions
Restrictions
Safety and security
17. Briefly explain about the goals, assumptions and requirements of mobile IP.
Quick ‘solutions’
Requirements
Compatibility
Transparency
Scalability and efficiency
Security
18. Give a detailed note about tunneling and optimization in mobile IP.
Tunneling & Encapsulation
IP-in-IP encapsulation
Minimal encapsulation
Generic routing encapsulation
Optimization
Triangular routing, binding cache
Four additional messages Binding request Binding update
Binding acknowledgement
Binding warning
Reverse tunneling
Firewalls
Multi-cast
TTL
19. Explain the concept of routing in MANET
Fundamental differences between wired & wireless ad-hoc networks
Asymmetric links
Redundant links
Interference
Dynamic topology
Problems with ad-hoc routing
Need for algorithms with high dynamic topology
Information from lower layers essential
Centralized approaches will not work
Efficient routing capabilities are needed
Notion of connection with certain characteristics will not work
Flooding
20. Write short notes on DSR and DSDV
Dynamic Source Routing (DSR)
2 phases in routing
Route discovery
Route Maintenance
Basic operation
Optimization of the basic algorithm
Approaches for Route Maintenance
Destination Sequence Distance Vector (DSDV)
Sequence numbers
Damping
Routing table
21. Give a detailed explanation about Agent Discovery and registration of mobile IP.
Agent advertisement.
Agent advertisement message
Agent advertisement packet
Type
#addresses Lifetime Preference
Length, bits
Agent solicitation
Three solicitations: one per second
Decrease solicitations exponentially
Registration
22. Give a detailed view of traditional TCP.
Congestion Control
Dropped packet
Retransmission of missing packet
Slow Start
Congestion window
Congestion threshold
Exponential growth
Fast retransmit/ Fast recovery
Implications on mobility
Error rates
Packet loss
23. Explain indirect TCP in detail.
Socket and state migration after handover of a mobile host
Advantages
No change in TCP protocol
Transmission errors on wireless links cannot propagate into the fixed network
Different solutions can be tested without jeopardizing the stability of the internet
Uses precise time-outs to guarantee retransmissions as fast as possible
Partitioning allows the use of different transport layer
protocol
Disadvantages
Loss of end-to-end semantics of TCP might cause problems
Increased handover latency may be problematic
FA must be a trusted entity.
24. Give a detailed description about Mobile TCP.
2 parts
Unmodified TCP
Optimized TCP
Persistent mode
Bandwidth manager
Advantages
Disadvantages
25. Describe in detail about WAP architecture
Bearer services
Transport layer Service Access point (T-SAP)
Security layer
Security SAP (SEC-SAP)
Transaction layer
Transaction SAP (TR-SAP)
Session layer
Session-SAP (S-SAP)
Application layer
Integration of www and mobile telephony applications
Integration of WAP components
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