mobile computing complete introduction

Mobile Computing

R. DENIS, Assistant Professor,

PG Department of Computer Science,

Sacred Heart College (Autonomous),

Tirupattur.

What Is Mobile Computing?• 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.

Comparison to Wired Net.• 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

Why Go Mobile?

• Enable anywhere/anytime connectivity • Bring computer communications to areas without pre-existing infrastructure • Enable mobility • Enable new applications • An exciting new research area

Mobile Computing Vs Wireless NetworkingMC –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.

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).

New Forms of Computing

Mobile Computing Functions

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User Mobility Network Mobility

Bearer MobilityDevice Mobility Session Mobility

Service MobilityHost Mobility

Types of Wireless Devices

• Laptops

• Palmtops

• PDAs

• Cell phones

• Pagers

• Sensors

Apple’s Newton

The Palm Motorola Marco The Pocket PC

Applications for mobile computing

Enable the business initiatives by supporting mobility of CustomersSuppliers 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-portalSpecialized applications

Location sensitive appsWireless sensor network appsMobile agent apps

Two views: Mobile applications are fundamentally new applications.Mobility is another dimension of the existing applications

Mobile Computing - Characteristics– 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.

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.

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

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

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

Network cells (2)

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

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

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

the Internet

Cellular network components

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

Components of a cellular phone (MSU – Mobile Subscriber Unit)

• radio transceiver – low power radio transmitter and receiverantenna, 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

Global System for

Mobile Communication (GSM)

GSM ServicesSystem Architecture of GSMGSM Security

What is GSM?

GSM Services

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GSM Supplementary Services

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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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• 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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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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• 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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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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• Core Network:• The core network is the equivalent of the GSM

Network Switching Subsystem (NSS).

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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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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

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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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Reservation Based Schemes

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Key Mechanism in Mobile IP

Three basic Mechanisms are used,Discovering the care of addressRegistering the care of addressTunnelling to the care of address

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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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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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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

mobile computing complete introduction

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