Lecture Slides

1. Mobile Computing
R. DENIS,
Assistant Professor,
PG Department of Computer Science,
Sacred Heart College (Autonomous),
Tirupattur.

2. What Is Mobile Computing?
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• What is computing?
Operation of computers
• What is the mobile?
That someone /something can move or be moved easily and quickly from place
to place
• What is mobile computing?
Users with portable computers still have network connections while they move
• A simple definition could be:
Mobile Computing is using a computer (of one kind or another) while on the move
• Another definition could be:
Mobile Computing is when a (work) process is moved from a normal fixed position
to a more dynamic position.
• A third definition could be:
Mobile Computing is when a work process is carried out somewhere where it
was not previously possible.

3. Comparison to Wired Net.
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• Wired Networks
- high bandwidth
- low bandwidth variability
- can listen on wire
- high power machines
- high resource machines
- need physical access(security)
- low delay
- connected operation
• Mobile Networks
- low bandwidth
- high bandwidth variability
- hidden terminal problem
- low power machines
- low resource machines
- need proximity
- higher delay
- disconnected operation

4. Why Go Mobile?
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• Enable anywhere/anytime connectivity
• Bring computer communications to areas without
pre-existing infrastructure
• Enable mobility
• Enable new applications
• An exciting new research area

5. Mobile Computing Vs Wireless Networking
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MC –Denotes accessing information and remote computational services while on the move.
WN –Provides the basic communication infrastructure necessary to make this possible.
Mobile Computing:
Mobile computing is based on wireless networking.
Subsumes (counts, lists) the area of wireless networking.

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Wireless Networking:
It helps one to invoke computing services on remote servers while on the move:
like., Office, home, conference, hotel…etc.,
It is an important intergradient (component) of mobile computing.
It’s classified into two basic types:
1. Extension of Wired Networks.
-It uses fixed infrastructure
- Base stations to provide single hop wireless communication.
-With a wired network.
2. An ad hoc Network.
-It does not use any fixed infrastructure.
-It’s based on Multi-hop Wireless communication.
-It’s also known as Mobile Ad hoc Network(MANET).

7. New Forms of Computing
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8. Mobile Computing Functions
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User Mobility
Network Mobility
Bearer Mobility
Device Mobility
Session Mobility
Service Mobility
Host Mobility

9. Types of Wireless Devices
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• Laptops
• Palmtops
• PDAs
• Cell phones
• Pagers
• Sensors
Apple’s Newton

10. The Palm
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Motorola Marco The Pocket PC

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19. Applications for mobile computing
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Enable the business initiatives by supporting mobility of
Customers
Suppliers and Businesses
Employees
Mobile computing applications
Wireless messaging (e.g., SMS)
Mobile ecommerce (M-Commerce) and its variants
Positional commerce (p-commerce) .
Voice commerce (v-commerce).
Television commerce (T-Commerce)
Mobile ebusiness applications (MEBAs), e.g., M-CRM, M-portal
Specialized applications
Location sensitive apps
Wireless sensor network apps
Mobile agent apps
Two views:
Mobile applications are fundamentally new applications.
Mobility is another dimension of the existing applications

21. Mobile Computing - Characteristics
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– Mobile devices
• Laptops
• Palmtops
• Smart cell phones
– Requirements
• Data access:
– Anywhere
– Anytime
• Nomadic users
– Constraints
• Limited ressources
• Variable connectivity:
– Performance
– Reliability
Ubiquity
Location Awareness
Adaptation
Broadcast
Personalization
Ability of a user to perform computations from anywhere and at any time.
Can provide information about the current location of a user to a tracking station. GPS
Implies the ability of a system to adjust bandwidth fluctuation without
inconveniencing the user.
Efficient delivery of data can be made simultaneously to hand reads of mobile users.
Services in a mobile environment can be easily personalized according to a user’s
profile.

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Three tiers.
Presentation Tier:
•User Interface.
•The users to issue requests and to present the result to the them meaningfully..
•Run on a client’s Computer.
•This layer includes web browser and customized client programs.
Application Tier:
•It’s make logical decisions and performing calculation.
•It’s move data between the presentation layer and data layers.
•It performs the processing of user input,obtaining information and then making decisions.
•Implemented using technologies. (ex:java,.net,..etc.,)
•Implementation and functionality should be database independent.
•Implemented on a fixed server.
Data Tier:
•responsible for providing the basic facilities of data storage ,access ,and manipulation.
•information is stored and retrieved from this database.
•implemented on affixed server.

24. Cellular systems generations
• 1G (first generation) – voice-oriented systems based on analog technology; ex.: Advanced
Mobile Phone Systems (AMPS) and cordless systems
• 2G (second generation) - voice-oriented systems based on digital technology; more efficient
and used less spectrum than 1G; ex.: Global System for Mobile (GSM) and US Time
Division Multiple Access (US-TDMA)
• 3G(third generation) – high-speed voice-oriented systems integrated with data services; ex.:
General Packet Radio Service (GPRS), Code Division Multiple Access (CDMA)
• 4G (fourth generation) – still experimental, not deployed yet; based on Internet protocol
networks and will provide voice, data and multimedia service to subscribers

25. Frequency reuse
• is a method used by service providers to improve the efficiency of a
cellular network and to serve millions of subscribers using a limited radio
spectrum
• is based on the fact that after a distance a radio wave gets attenuated and
the signal falls bellow a point where it can no longer be used or cause any
interference
• a transmitter transmitting in a specific frequency range will have only a
limited coverage area
• beyond this coverage area, that frequency can be reused by another
transmitter

26. Network Cells
• the entire network coverage area is divided into cells based on the principle of
frequency reuse
• a cell = basic geographical unit of a cellular network; is the area around an
antenna where a specific frequency range is used; is represented graphically as
a hexagonal shape, but in reality it is irregular in shape
• when a subscriber moves to another cell, the antenna of the new cell takes over
the signal transmission
• a cluster is a group of adjacent cells, usually 7 cells; no frequency reuse is
done within a cluster
• the frequency spectrum is divided into subbands and each subband is used
within one cell of the cluster
• in heavy traffic zones cells are smaller, while in isolated zones cells are larger

27. Network cells (2)

28. Types of cells
• macrocell – their coverage is large (aprox. 6 miles in
diameter); used in remote areas, high-power transmitters and
receivers are used
• microcell – their coverage is small (half a mile in diameter)
and are used in urban zones; low-powered transmitters and
receivers are used to avoid interference with cells in another
clusters
• picocell – covers areas such as building or a tunnel

29. Other cellular concepts
• handover = moving a call from one zone (from the transmitter-
receiver from one zone) to another zone due to subscriber’s
mobility
• roaming = allowing the subscriber to send/receive calls outside
the service provider’s coverage area

30. Cellular services
• voice communication
• Short Messaging Service (SMS)
• Multimedia Messaging Service (MMS)
• Global Positioning System (GPS)
• Wireless Application Protocol (WAP) – to access
the Internet

31. Cellular network components

32. Cellular network components (2)
• BTS (Base Transceiver Station) – main component of a cell and it connects the
subscribers to the cellular network; for transmission/reception of information it uses
several antennas spread across the cell
• BSC (Basic Station Controller) – it is an interface between BTSs and it is linked to
BTSs by cable or microwave links; it routes calls between BTSs; it is also
connected to the MSC
• MSC (Mobile Switching Center) – the coordinator of a cellular network, it is
connected to several BSCs, it routes calls between BSCs; links the cellular network
with other networks like PSTN through fiber optics, microwave or copper cable

33. Components of a cellular phone
(MSU – Mobile Subscriber Unit)
• radio transceiver – low power radio transmitter and receiver
antenna, usually located inside the phone
• control circuitry – formats the data sent to and from the BTS;
controls signal transmission and reception
• man-machine interface – consists from a keypad and a
display; is managed by the control circuitry
• Subscriber Identity Module (SIM) – integrated circuit card
that stores the identity information of subscriber
• battery, usually Li-ion, the power unit of the phone

34. Global System
for
Mobile Communication
(GSM)
GSM Services
System Architecture of GSM
GSM Security
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35. What is GSM?
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36. What is GSM?
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37. GSM Services
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38. GSM Supplementary Services
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39. GSM Supplementary Services
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40. GSM Supplementary Services
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50. GSM Security
• Security in GSM is broadly supported at three levels:
• Operator’s level
• Customer’s level
• System level
• These three levels help to oversee aspects such as correct
billing to the customer, avoiding fraud, protecting services and
ensuring anonymity.
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51. • Authentication
• The purpose of authentication is to protect the network
against unauthorized use.
• Confidentiality
• A GSM network protects voice, data and sensitive signaling
information against eavesdropping on the radio path.
• Anonymity
• A GSM network protects against someone tracking the
location of a user or identifying calls made to or from the
user by eavesdropping on the radio path.
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58. Universal Mobile Telecommunication (UMTS)
• The UMTS was developed mainly for countries with GSM
networks
• It is expected that all GSM networks will be upgraded to
UMTS networks.
• In these networks, coverage is provided by a combination of
various cell sizes, ranging from “in building” pico cells to
global cells provided by satellites.
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59. • The UMTS networks are different from the 2G networks in the
following respects:
• High speech quality:
• In addition to speech , the UMTS supports the advanced data and
information services and can be called a true multimedia network.
• Higher data rate:
• The UMTS supports 2Mbps data rate, which is much higher than that
supported by the 2G mobile systems.
• Virtual home environment:
• A user roaming from his network to other UMTS networks will not feel
any discomfort.
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60. UMTS Network Architecture:
• The UMTS network architecture can be divided into three
main elements:
• User Equipment (UE):
• The User Equipment (UE) is the name by which a cell
phone is referred to.
• Radio Network Subsystem(RNS):
• The RNS is the equivalent of the BSS in GSM.
• It provides and manages the wireless interface for the
overall network.
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61. • Core Network:
• The core network is the equivalent of the GSM Network
Switching Subsystem (NSS).
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62. MAC Protocols
(Medium Access Protocol)
• The primary responsibility of a MAC protocol is to enforce
discipline
• In the access of a shared channel when multiple nodes contend to
access the same channel.
• The MAC protocol is a sublayer of the data link layer protocol and it
directly invokes the physical layer protocol.
• At the same time, two other objectives of any MAC protocol are
• Maximization of the utilization of the channel
• Minimization of average latency of transmission
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63. Properties Required of MAC Protocols:
• The design of a MAC protocol depends upon the specific environment and the specific
design requirements.
• In a general sense a good MAC protocol needs to possess the following features:
• It should implement some rules that help to enforce discipline
• It should help maximize the utilization of the channel
• Channel allocation needs to be fair.
• It should be capable of supporting several types of traffic having different maximum
and average bit rates.
• It should be robust in the face of equipment failures and changing network conditions.
• At present, IEEE 802.11 has emerged as a popular and standard MAC protocol for
wireless network.
• Wireless networks can be divided mainly into categories:
• Infrastructure-based wireless network
• Infrastructure-less wireless network 63

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Random Assignment Schemes
• There are number of random
assignment schemes that are
used in MAC protocols.
• ALOHA
• Pure ALOHA
• Slotted ALOHA
• CSMA
• CSMA/CD
• CSMA/CA

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85. Reservation Based Schemes
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93. Key Mechanism in Mobile IP
Three basic Mechanisms are used,
 Discovering the care of address
 Registering the care of address
 Tunnelling to the care of address
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94. Discovering the care of address
o Each mobile node uses a protocol to identify the respective home
and foreign agents
o Discovery process consists of following important steps
 The mobile agents advertise their presence by periodically broadcasting the agent
advertisement messages
 The mobile node receiving the msg. observes whether it is from home or foreign
agent.
 If the MN doesn’t wants to wait for adv. It can send solicitation msg . That will be
responded by the agent.
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95. Registering the care of address
o If a MN discovers that it is on the home network, it
operates without requiring any mobility services.
o Else it goes for the registration process
 MN on new n/w sends registration req. msg to its FA, which
consist of Permanent IP and IP of the HA
 FA takes node forwards it to its HA registration req. msg which
consist of Permanent IP of MN and IP of FA
 HA updates the mobility binding by associating the care of
address of the mobile with its home address
 Then HA sends ack to FA
 FA in turn updates its visitors list
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96. Tunnelling to the care of address
• Takes place to forward an IP datagram from the home agent to
the care of address which involves
 When a HA receives a packet addressed to a mobile host it forwards the
packet to the care of address (COA) using IP within IP (Encapsulation)
 Using the above method the HA inserts a new IP header in front of the
IP header of any datagram
 Destination address is set to the care of address
 Source address is set to the home agents address
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