MOBILE COMPUTING (TCS-054)Anurag Malik Associate Professor Shivanshu Rastogi Assistant Professor

CE & IT Dept. M.I.T Moradabad B.Tech VIII CS / IT UNIT I Recommended Books:1. 2. 3.

4.

J. Schiller, Mobile Communications, Addison Wesley A. Mehrotra, GSM System Engineering Asok K. Talukder, Mobile ComputingTechnology, Applications & Service Creation, TMH Raj Kamal,Mobile Computing, Oxford University Press1

Mobile Computer A computer which you can take with you all around. You can do all the things which can be done with a desktop computer. You should be able to use same software, which you use on a desktop computer. Mobile computer - How? One possibility is to have a standalone computer capable of storing large amount of software and data files, processing power to support the required applications. Modern day laptop computer are something like this. Whenever you are static, connect to internet through an access point and you can do the file transfer, telnet, web browsing etc.. While on the move, connectivity is desired for using software which require cooperation of at least two machines.2

Mobile Computing

Mobile computing is a generic term describing one's ability to use technology while moving, as opposed to portable computers, which are only practical for use while deployed in a stationary configuration. Using a computing device while in transit. Mobile computing implies wireless transmission, but wireless transmission does not necessarily imply mobile computing. Fixed wireless applications use satellites, radio systems and lasers to transmit between permanent objects such as buildings and towers.

Mobile computing device Acts as a terminal Have wireless connectivity to the network Whatever command or application you run is executed on a remote server. Mobile computing device acts as remote terminal. Issues in mobile computing networks Nature of medium Mobility Portability3

Wireless characteristics

Variant Connectivity

Low bandwidth and reliability

Frequent disconnections

predictable or sudden Broadcast medium

Asymmetric Communication Monetarily expensive

Charges per connection or per message/packet

Connectivity is weak, intermittent and expensive4

What is Mobility

Mobility means different things to different people. Some people are quite happy being able to get around town. Others view the world in terms of time distance-Obviously, range of motion is an important aspect of mobility. Another factor in mobility is ease of access. What might be considered mobile in one context is quite immobile in another. A more pertinent example of mobility is the ever decreasing size of cellular telephones. What was once considered a "mobile phone" had to be transported in a vehicle. This continuing decrease in size and weight of handsets has greatly increased the mobility of cellular subscribers. We define mobility as the ability to send and receive communications anytime anywhere. Mobility means that both source and destination devices, applications and people are free of the constraints imposed by physical location.5

Mobility Characteristics

Location changes location management - cost to locate is added to communication Heterogeneity in services bandwidth restrictions and variability Dynamic replication of data data and services follow users Querying data - location-based responses Security and authentication System configuration is no longer static6

Two aspects of Mobility

Mobility

User Mobility : a user communicates, anytime, anywhere using any access technology Device Portability : A device can connect to the network anytime and anywhere.Wireless X X

Mobile X X

Example Stationary computer Notebook in ahotel Wireless LAN in buildings Cellular Phone

The demand for mobile communication creates the need for integration of wireless networks into existing fixed networks:In the local range: standardization of IEEE 802.11 (Wireless LAN, WLAN considering existing wired standards like Ethernet) In Wide area range: e.g. Internetworking of GSM and ISDN IN the Internet protocols: Mobile IP as enhancement of normal IP7

Portability Characteristics

Resource constraints Mobile computers are resource poor Reduce program size interpret script languages (Mobile Java?) Computation and communication load cannot be distributed equally Small screen sizes Asymmetry between static and mobile computers Battery power restrictions transmit/receive, disk spinning, display, CPUs, memory consume power Battery lifetime will see very small increase need energy efficient hardware (CPUs, memory) and system software planned disconnections - doze mode Power consumption vs. resource utilization 8

Mobile Computing Functions

User Mobility: User should be able to move from one physical location to another location and use the same service. E.g. user moves from London to New Delhi and uses Internet to access the corporate application the same way the user uses in home office. Network Mobility: User should be able to move from one Network to another network and use the same service. E.g. user moves from London to New Delhi and uses the same GSM phone to access the corporate application through WAP. In home Network he uses this services over GPRS whereas in Delhi he access it over the GSM Network. Bearer Mobility: User should be able to move from one bearer to another and use the same service. E.g. user was using a service though WAP bearer in his home N/W in Bangalore. He moves to Coimbatore, where WAP is not supported, he switch over to voice or SMS bearer to access the same application. (switching from BSNL to Vodafone on roaming)

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Mobile Computing Functions

Device mobility: User should be able to move from one device to another and use the same service. E.g. could be sales representatives using their desktop computer in home office. During the day while they are on the street they would like to use their Palmtop to access the application. Session Mobility: A user session should be able to move from one useragent environment to another. E..g. could be a user was using his service through a CDMA iX network. The user entered into the basement to park the car and got disconnected from the CDMA n/w. User goes to home office and starts using the desktop. The unfinished session in the CDMA moves from the mobile device to the desktop computer. Service Mobility: User should be able to move from one service to another. E.g. a user is writing a mail. To complete the mail user needs to refer to some other information. In a desktop PC, user simply opens another service (browser) and moves between them using the task bar. User should be able to switch amongst services in small footprint wireless devices like in the desktop. (In a browser we use HTTP to open yahoo. COM page and POP3 or SMTP to send & receive mail ) Host Mobility: The user device can be either a client or server. When it is a server or host, some of the complexities change. In case of host mobility the mobility of IP needs to be taken care of.10

WHY WIRELESS NETWORK Advantages Spatial flexibility in radio reception range Ad hoc networks without former planning No problems with wiring (e.g. historical buildings, fire protection, esthetics) Robust against disasters like earthquake, fire and careless users which remove connectors! Disadvantages Generally very low transmission rates for higher numbers of users Often proprietary, more powerful approaches, standards are often restricted Consideration of lots of national regulations, global regulations are evolving slowly Restricted frequency range, interferences of frequencies11

Types of Wireless NetworksCellular Networks Base stations distributed over the area to be covered Each base station covers a cell Need of an infrastructure network connecting all base stations Used for mobile phone networks and data networks like Wireless LAN Mobile Ad-Hoc Networks (MANETs) Self-configuring network of mobile nodes Each node serves as client and router No infrastructure (base stations) necessary, direct connections between any pair of nodes E.g. Bluetooth Mesh Networks Enhancement of above concepts: Ad-hoc network with infrastructure Allow a whole mesh of connections between wireless nodes Increased fault tolerance E.g. used in WiMAX 12

Classification of Wireless Network

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Wireless Personal Area Network (WPAN)

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Wireless Local Area Network (WLAN)

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Wireless Metropolitan Area Network (WMAN)

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Wireless Wide Area Network (WWAN)

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Frequencies For Communication

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Limitations of Mobile Environmentsy

Limitations of the Wireless Network y heterogeneity of fragmented networks y frequent disconnections y limited communication bandwidth Limitations Imposed by Mobility y lack of mobility awareness by system/applications y route breakages Limitations of the Mobile Computer y short battery lifetime y limited capacities24

y

y

Mobile Applications

Vehicles transmission of news, road condition etc ad-hoc network with near vehicles to prevent accidents Emergencies early transmission of patient data to the hospital ad-hoc network in case of earthquakes, cyclones military ... Traveling salesmen direct access to central customer files consistent databases for all agents mobile office

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Mobile Applications

Web access outdoor Internet access intelligent travel guide with up-to-date location dependent information Location aware services find services in the local environment, e.g. printer Information services push: e.g., stock quotes pull: e.g., nearest cash ATM Disconnected operations mobile agents, e.g., shopping Entertainment ad-hoc networks for multi user games

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Mobile Computing ArchitecturePresentation Tier Application Tier Java Server PagesRMI

Data Tier

Internet ExplorerSOAP

iPlanet Web Server

IBM WebSphere BEA WebLogic JBOSS IIOP iPlanet Jakarta SOAP Enterprise Java Beans SQL XML Servlets JDBC

XML Data Stores Database

Netscape NavigatorIIOP

Jigsaw

XSLT

Opera

Apache

HTML

LIB WWWXML

Zeus

WML / HDML

Applications & Web Services ZOPE CGI (C. Perl, Python)

Aggregation Service Data Feeds

Java URL ClassHTTP

RPC ZEND PHP

XML

LynxHTTPS

Lotus Domino mail and Documents

JavascriptRoxen XML MS Transaction Server COM Applications Adapter Pike Equipment MS Exchange MS Commerce Server

WAP Browser

J2MEVoice

Internet Information Server

COM

Legacy Applications

ASP

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Mobile Computing Architecture

To design a system for mobile computing, we need to keep in mind that the system will be used through any network, any bearer, any agent and any device. The three tier architecture is better suited for an effective networked client/server design It provides increased performance, flexibility, maintainability, reusability and scalability while hiding the complexity of distributed processing from the user. Centralized process logic makes administration and change management easier by localizing changes in central place and using it throughout the systems. The network-centric mobile computing architecture uses a three-tier architecture. User Interface or Presentation Tier :This layer deals with user facing device handling and rendering. This tier includes a user system interface where user services (such as session, text input, dialog and display management) reside. This is the layer of agent applications and systems. These applications run on the client device and offer all the user interfaces. This tier is responsible for presenting the information to the end user. Humans generally use visual and audio means to receive the information from machines (laptop, cell phones, paltops, tablet PC, touch screen.) The visual presentation will relate to rendering on a screen which includes Web browsers like Mozila, lynx, Internet Explorer and Netscape Navigator, WAP browsers.

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Mobile Computing Architecture Process Management or Application Tier : This layer is for application programs or process management where business logic and rules are executed. This layer is capable of accommodating hundreds of users. In addition to ensure reliable completion tier controls transactions and asynchrono, queuing to ensure reliable completion of transactions. It performs the business logic of processing user input, obtaining data, and making its presentation decisions. In certain cases, this layer will do the transcoding of data for appropriate rendering in this layer. It includes technology like CGIs, Java, JSP, .NET services, PHP or ColdFusion, deployed in products like Apache, WebSphere, WebLogic, iPlanet , Pramati, JBOSS or ZEND and database-independent. A few additional management functions (decisions on rendering, network management, security, datastore access etc.) need to be performed which are implemented using different middleware software. A middleware framework is defined as a layer of software, which sits in the middle between the OS and the user facing software. The different types of middleware are: 1. Message-Oriented Middleware 2. Database Middleware 3. Transaction Processing Middleware 4. Transcoding Middleware 5. Communication Middleware 6. Distributed Object & components29

Mobile Computing ArchitectureDatabase Management or Data Tier : This layer is for database access and management. It is used to store data needed by the application and acts as a repository for both temporary and permanent data. The data could be stored in any form of datastore or database (relational, legacy, text). The data can also be stored in XML format for interoperability with other system and data sources. JBoss :- A popular open source Java application server that supports the J2EE 1.3 specifications. Runs under any J2SE 1.3 or later Java virtual machine. Based on an JMX core where other pieces of the system are plugged in. Supports JNDI, Servlet/JSP (Tomcat or Jetty), EJB, JTS/JTA, JCA, JMS. Also supports Clustering (JavaGroups), Web Services (Axis), and IIOP integration (JacORB). iPlanet was a product brand that was used jointly by Sun Microsystems and Netscape Communications Corporation when delivering software and services as part of a nonexclusive cross marketing deal. iPlanet Directory Server ,iPlanet Web Server ,iPlanet Web Proxy Server, iPlanet Portal Server , iPlanet Portal Search,iPlanet Application Server ,iPlanet Messaging Server , iPlanet Calendar Server, iPlanet Meta Directory, iPlanet Instant Messaging Server . The Apache HTTP Server, commonly referred to simply as Apache a web server notable for playing a key role in the initial growth of the World Wide Web. Apache was the first viable alternative to the Netscape Communications Corporation web server (currently known as Sun Java System Web Server), and has since evolved to rival other Unix-based web servers in terms of functionality and performance. The majority of all web servers using Apache are Linux web servers.

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Mobile Computing ArchitectureZope is a free and open-source, object-oriented web application server written in the Python programming language. Zope stands for "Z Object Publishing Environment." It can be almost fully managed with a web-based user interface. Zope publishes on the web Python objects that are typically persisted in an object database, ZODB. Basic object types, such as documents, images, and page templates, are available for the user to create and manage through the web. Specialized object types, such as wikis, blogs, and photo galleries, are available as third-party add-ons (called products), and there is a thriving community of small businesses creating custom web applications as Zope products. Zend Framework is a simple, straightforward, open-source software framework for PHP 5 designed to eliminate the tedious details of coding and let you focus on the big picture. Its strength is in its highly-modular MVC design, making your code more reusable and easier to maintain. The Roxen WebServer, from the Swedish company Roxen Internet Software, is a viable alternative for those who find Apache inappropriate for their needs. Although Apache dominates the internet web server market, it has some weak points: it lacks a built-in SQL database backend, flexible administration tools and easy SSL certificate management. All of these features can be found, however, in the Roxen WebServer. In fact, Roxen includes so many additional features that it seems more like an application server than an ordinary web server. PHP is a scripting language originally designed for producing dynamic web pages. It has evolved to include a command line interface capability and can be used in standalone graphical applications. Jakarta Struts is incredibly useful in helping you create excellent Web applications. When you use Jakarta Struts, your applications should work more effectively and have fewer bugs. Just as important (because your time is important), Struts should save you hours and hours of programming and debugging.

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Mobile Computing ArchitectureWebLogic server is based on Java 2 Platform, Enterprise Edition (J2EE), the standard platform used to create Java-based multi-tier enterprise applications. J2EE platform technologies were developed through the efforts of BEA Systems and other vendors in collaboration with the main developer, Sun Microsystems. Because J2EE applications are standardized modules, WebLogic can automate many system-level tasks that would otherwise have demanded programming time. Pike is an outliner that's been custom-fitted to plug into Manila sites. You can create and edit stories with Pike. You can use it to edit your home page. And you can also use it to edit the myriad of templates that define how a Manila site is rendered. It's both a writing and design tool. Pike is as easy to use as a web browser but has the common features that web writers and designers need. WebSphere is a set of Java-based tools from IBM that allows customers to create and manage sophisticated business Web sites. The central WebSphere tool is the WebSphere Application Server (WAS), an application server that a customer can use to connect Web site users with Java applications or servlets. Servlets are Java programs that run on the server rather than on the user's computer as Java applets do. Servlets can be developed to replace traditional common gateway interface (CGI) scripts.

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Mobile Computing Architecture

HTTPS (HTTP over SSL or HTTP Secure) is the use of Secure Socket Layer (SSL) or Transport Layer Security (TLS) as a sublayer under regular HTTP application layering. HTTPS encrypts and decrypts user page requests as well as the pages that are returned by the Web server. The use of HTTPS protects against eavesdropping and man-in-the-middle attacks. HTTPS was developed by Netscape. HTTPS and SSL support the use of X.509 digital certificates from the server so that, if necessary, a user can authenticate the sender. Unless a different port is specified, HTTPS uses port 443 instead of HTTP port 80 in its interactions with the lower layer, TCP/IP. HTTPS encrypts and decrypts the page requests and page information between the client browser and the web server using a secure Socket Layer (SSL). IIOP (Internet Inter-ORB Protocol) is a protocol that makes it possible for distributed programs written in different programming languages to communicate over the Internet. SOAP (Simple Object Access Protocol) is a way for a program running in one kind of operating system (such as Windows 2000) to communicate with a progam in the same or another kind of an operating system (such as Linux) by using the World Wide Web's Hypertext Transfer Protocol (HTTP) and its Extensible Markup Language (XML) as the mechanisms for information exchange. Since Web protocols are installed and available for use by all major operating system platforms, HTTP and XML provide an already at-hand solution to the problem of how programs running under different operating systems in a network can communicate with each other. SOAP specifies exactly how to encode an HTTP header and an XML file so that a program in one computer can call a program in another computer and pass it information. It also specifies how the called program can return a response. The Extensible Markup Language (XML) is a general-purpose specification for creating custom markup languages. It is classified as an extensible language, because it allows the user to define the mark-up elements. XML's purpose is to aid information systems in sharing structured data, especially via the Internet ,to encode documents, and to serialize data; in the last context, it compares with text-based serialization languages such as JSON and YAML HTTP, short for HyperText Transfer Protocol, is the protocol for transferring hypertext documents that makes the World Wide Web possible.

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Mobile Computing Architecture

Remote Method Invocation (RMI) is the process of activating a method on a remotely running object. RMI offers location transparency in the sense that it gives the feel a method is executed on a locally running object. Java RMI (Remote Mathod Invocation) provides a mechanism for supporting distributed computing. remote procedure call, a type of protocol that allows a program on one computer to execute a program on a server computer. Using RPC, a system developer need not develop specific procedures for the server. The client program sends a message to the server with appropriate arguments and the server returns a message containing the results of the program executed. Microsoft COM (Component Object Model) technology in the Microsoft Windows-family of Operating Systems enables software components to communicate. COM is used by developers to create re-usable software components, link components together to build applications, and take advantage of Windows services. The family of COM technologies includes COM+, Distributed COM (DCOM) and ActiveX Controls. Java database connectivity (JDBC) is the JavaSoft specification of a standard application programming interface (API) that allows Java programs to access database management systems. The JDBC API consists of a set of interfaces and classes written in the Java programming language. Using these standard interfaces and classes, programmers can write applications that connect to databases, send queries written in structured query language (SQL), and process the results. SQL (Structured Query Language) is a database computer language designed for the retrieval and management of data in relational database management systems (RDBMS), database schema creation and modification, and database object access control management. SQL is a programming language for querying and modifying data and managing databases. SQL was standardized first by the ANSI and (later) by the ISO

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Typical Application : Road traffic

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World Wide Web and Mobility

HTTP/ HTML have not been designed for mobile applications/devices HTTP Characteristicsstateless, connection oriented overheads big protocol headers, uncompressed content transfer

HTML Characteristicsdesigned for computers with high performance, color high-resolution display, mouse, hard disk typically, web pages optimized for design, not for communication; ignore endsystem characteristics

Adaptations for Mobile WWWEnhanced browsers and/or servers Client proxy: pre-fetching, caching, off-line use Network proxy: adaptive content transformation for connections Client and network proxy New protocols/languages: WAP/WML

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Early Wireless Communication

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History Of Wireless Communication 1896 - Guglielmo Marconi First demonstration of wireless telegraphy (digital!) Long wave transmission, high transmission power necessary (>200kw) 1907 - Commercial transatlantic connections Huge base stations (30 100m high antennas) 1915 - Wireless voice transmission New York - San Francisco 1920 - Discovery of short waves by Marconi Reflection at the ionosphere Smaller sender and receiver, possible due to the invention of the vacuum tube (1906, Lee DeForest and Robert von Lieben) 1926 - Train-phone on the line Hamburg - Berlin Wires parallel to the railroad track

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History Of Wireless Communication 1928 - Many TV broadcast trials (across Atlantic, color TV, TV news) 1933 - Frequency modulation (E. H. Armstrong) 1958 - A-Netz in Germany Analogue, 160MHz, connection setup only from the mobile station, no Handover, 80% coverage, 1971 11000 customers 1972 - B-Netz in Germany Analogue, 160MHz, connection setup from the fixed network too (but location of the mobile station has to be known) available also in Austria, Netherlands and Luxembourg, 1979 13000 customers in Germany 1979 - NMT at 450MHz (Scandinavian countries) 1982 - Start of GSM-specification Goal: pan-European digital mobile phone system with roaming 1983 - Start of the American AMPS (Advanced Mobile Phone System, analog) 1984 - CT-1 standard (Europe) for cordless telephones39

History Of Wireless Communication 1986 - C-Netz in Germany Analog voice transmission, 450MHz, hand-over possible, digital signaling, automatic location of mobile device Was in use until 2000, services: FAX, modem, X.25, e-mail, 98% coverage 1991 - Specification of DECT Digital European Cordless Telephone (today: Digital Enhanced Cordless Telecommunications) 1880-1900MHz, ~100-500m range, 120 duplex channels, 1.2Mbit/s data transmission, voice encryption, authentication, up to several 10000 user/km2, used in more than 50 countries 1992 - Start of GSM In Germany as D1 and D2, fully digital, 900MHz, 124 channels Automatic location, hand-over, cellular Roaming in Europe - now worldwide in more than 170 countries Services: data with 9.6kbit/s, FAX, voice, ...

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History Of Wireless Communication 1994 - E-Netz in Germany GSM with 1800MHz, smaller cells As E-plus in Germany (1997 98% coverage of the population) 1996 - HiperLAN (High Performance Radio Local Area Network) ETSI, standardization of type 1: 5.15 - 5.30GHz, 23.5Mbit/s Recommendations for type 2 and 3 (both 5GHz) and 4 (17GHz) as wireless ATM-networks (up to 155Mbit/s) 1997 - Wireless LAN IEEE 802.11 IEEE standard, 2.4GHz and infrared, 2Mbit/s Already many (proprietary) products available in the beginning 1998 - Specification of GSM successors UMTS (Universal Mobile Telecommunication System) as European proposals for IMT-2000 Iridium: 66 satellites (+6 spare), 1.6GHz to the mobile phone41

History Of Wireless Communication1999 - Standardization of additional wireless LANs IEEE standard 802.11b, 2.4-2.5GHz, 11Mbit/s Bluetooth for piconets, 2.4Ghz, 0 D4.c4 4 d4 D2.c2 2 d2

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Idea of Communication with Coding TechniqueChip Sequence

C1[+1, +1, +1 , +1]

C2[+1, -1, +1 , -1]

C3[+1, +1, -1 , -1]

C4[+1, -1, -1 , +1]

Bit 0 1 -1[ -1, -1, -1 , -1] [-1, +1, -1 , +1]

Bit 0 2 -1

[ -1 , -1, -3 , +1 ] Communication Channel[0 , 0 , 0 , 0 ] [+1 , -1 , -1 , +1]

3 Silent

0

4

+1 Bit 1

Data Representation in CDMA Data Bit 0 -1 Data Bit 1 +1 Silent -> 0100

CDMA Coding scheme

Each user is associated with a different code, say v. If the data to be transmitted is a digital zero, then the actual bits transmitted will be v, and if the data to be transmitted is a digital one, then the actual bits transmitted will be v. For example, if v=(1,1), and the data that the user wishes to transmit is (1, 0, 1, 1) this would correspond to (v, v, v, v) which is then constructed in binary as ((1,1),(1,1),(1,1),(1,1)). For the purposes of this article, we call this constructed vector the transmitted vector. Each sender has a different, unique vector v chosen from that set, but the construction method of the transmitted vector is identical. Now, due to physical properties of interference, if two signals at a point are in phase, they add to give twice the amplitude of each signal, but if they are out of phase, they "subtract" and give a signal that is the difference of the amplitudes. Digitally, this behavior can be modeled by the addition of the transmission vectors, component by component.

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CDMA Coding scheme

If sender0 has code (1,1) and data (1,0,1,1), and sender1 has code (1,1) and data (0,0,1,1), and both senders transmit simultaneously, then this table describes the coding steps: Step Encode sender0 Encode sender1 encode0=vector0.data0 encode0=(1,-1).(1,-1,1,1) encode0=((1,-1),(-1,1),(1,-1),(1,-1)) signal0=(1,-1,-1,1,1,-1,1,-1) encode1=vector1.data1 encode1=(1,1).(-1,-1,1,1) encode1=((-1,-1),(-1,-1),(1,1),(1,1)) signal1=(-1,-1,-1,-1,1,1,1,1)

0 vector0=(1,-1),data0=(1,0,1,1)=(1,-1,1,1) vector1=(1,1),data1=(0,0,1,1)=(-1,-1,1,1)

1 2 3 4

Because signal0 and signal1 are transmitted at the same time into the air, they add to produce the raw signal: (1,-1,-1,1,1,-1,1,-1) + (-1,-1,-1,-1,1,1,1,1) = (0,-2,-2,0,2,0,2,0)

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CDMA Coding scheme

This raw signal((0,-2,-2,0,2,0,2,0)) is called an interference pattern. The receiver then extracts an intelligible signal for any known sender by combining the sender's code with the interference pattern, the receiver combines it with the codes of the senders. The following table explains how this works and shows that the signals do not interfere with one another: Step Decode sender0 Decode sender1

0 1 2 3 4

vector0=(1,-1), pattern=(0,-2,-2,0,2,0,2,0) vector1=(1,1), pattern=(0,-2,-2,0,2,0,2,0) decode0=pattern.vector0 decode1=pattern.vector1 decode0=((0,-2),(-2,0),(2,0),(2,0)).(1,-1) decode1=((0,-2),(-2,0),(2,0),(2,0)).(1,1) decode0=((0+2),(-2+0),(2+0),(2+0)) decode1=((0-2),(-2+0),(2+0),(2+0)) data0=(2,-2,2,2)=(1,0,1,1) data1=(-2,-2,2,2)=(0,0,1,1)

Further, after decoding, all values greater than 0 are interpreted as 1 while all values less than zero are interpreted as 0. For example, after decoding, data0 is (2,-2,2,2), but the receiver interprets this as (1,0,1,1).103

CDMA Coding scheme

We can also consider what would happen if a receiver tries to decode a signal when the user has not sent any information. Assume signal0=(1,-1,-1,1,1,-1,1,-1) is transmitted alone. The following table shows the decode at the receiver:

Step Decode sender0 Decode sender1 0 vector0=(1,-1), pattern=(1,-1,-1,1,1,-1,1,-1) vector1=(1,1), pattern=(1,-1,-1,1,1,-1,1,-1) 1 decode0=pattern.vector0 decode1=pattern.vector1 2 decode0=((1,-1),(-1,1),(1,-1),(1,-1)).(1,-1)) decode1=((1,-1),(-1,1),(1,-1),(1,-1)).(1,1) 3 decode0=((1+1),(-1-1),(1+1),(1+1)) decode1=((1-1),(-1+1),(1-1),(1-1)) 4 data0=(2,-2,2,2)=(1,0,1,1) data1=(0,0,0,0)

When the receiver attempts to decode the signal using sender1s code, the data is all zeros, therefore the cross correlation is equal to zero and it is clear that sender1 did not transmit any data.104

Synchronous CDMA They use orthogonal codes. completely reject arbitrarily strong signals using different codes, due to the orthogonality of these systems It cant use the spectrum more efficiently in mobile telephony applications. No such flexibility in allocation of resources. There are a fixed number of orthogonal codes, timeslots or frequency bands that can be allocated for CDM, Synchronous CDMA is ideally not suited to a mobile network where large numbers of transmitters each generate a relatively small amount of traffic at irregular intervals

Asynchronous CDMA It use unique "pseudo-random" or "pseudo-noise" (PN) sequences. This is not true for Asynchronous CDMA; rejection of unwanted signals is only partial. It can use the spectrum more efficiently in mobile telephony applications. offers a key advantage in the flexible allocation of resources There is no strict limit to the number of users that can be supported in an Asynchronous CDMA system Asynchronous CDMA is ideally suited to a mobile network where large numbers of transmitters each generate a relatively small amount of traffic at irregular intervals

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Advantages

Can share a common bandwidth without interfering each other. Flexible network planning (planning is no longer needed) Greater coverage (larger area for a given amount of power ) High capacity (greater coverage capacity) Cost (larger profit for providers due to increased capacity, less infrastructure) Clarity Customer satisfaction (privacy, better call quality longer battery life dueto less power consumption, prevent cross talks)

Compatibility (dual mode analog and digital)106

Disadvantages

Poor Synchronization Difficulty to satisfy synchronization requirements. Self jamming Self jamming is a steep deterioration of performance as a result of poor synchronization. Poor synchronization causes partial-correlation with the codes of other users and the result will be a vast increase of the interference. Near-far problem power control is necessary for mitigating the Near-far problem. There are some factors for imperfect power control such as: feedback delays, imperfect power estimates, traffic conditions, errors in the feedback channel. Network complexity Complex network support is needed for implementing soft handoff, and also for countering multipath and fading effects. Throughput Low throughput efficiency for large number of users.107

CDMA ApplicationsA p p lic a t io n s :G P S O n e P o s it io n L o c a t io n T e c h n o lo g y P o s itio n lo c a tio n c o n c e p t a p p lic a tio n s . 1. 2. 3. 4. G e t d ir e c tio n s o n th e m o v e L o c a te a lo s t p e t P r o v id e tr a ff ic a n d n a v ig a tio n s e r v ic e s L o c a te V e h ic le s a n d A s s e ts c o n c e p ts a p p lic a tio n s

h t t p ://w w w .s n a p t r a c k .c o m /im p a c t /in d e x .js p

Q t v S t r e a m in g V id e o a n d A u d io S u p e r io r p la y b a c k r a te s in a f u lly in te g r a te d s o f tw a r e s o lu tio n

2 D a n d 3 D G a m in g E n g in e L if e - lik e a n im a tio n in 2 D a n d 3 D e n v ir o n m e n ts .

h t t p ://w w w .c d m a t e c h .c o m /s o lu t io n s /m u lt im e d ia .js p

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GSM Vs. CDMAGSM is a widely spread standard GSM provided by BSNL, AIRTEL, ESCOTEL etc GSM users are almost 8 times in number than CDMA users worldwide GSM is far better than CDMA in voice quality GSM base stations consumes more power than CDMA and also covers a less distance cell size in GSM is small compared to GSM. CDMA is a patented technology CDMA provided by Reliance CDMA users are almost 8 times less in number than GSM users worldwide CDMA is poor than GSM in voice quality CDMA base stations consumes less power than GSM and also covers a large distance cell size in CDMA is larger compared to GSM.

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GSM Vs. CDMAIt covers a large area of more than 25 user cannot go beyond a short Kms. distance charging area (SDCA) which is roughly a radius of 25 km. GSM offers slower data download CDMA offers faster data download

On a GSM phone your account On a CDMA phone, your account information along with your contact information is programmed into your list and other personal data are stored cellular phone on a SIM card (Subscriber Identity Module) Maximum 384kbps practice). download speed (around 140kbps of Maximum download speed of about in 2mb/s (about 700kbps in practice)

Europe, South Africa, Australia, and CDMA is mostly used in America and many Middle and Far East countries some parts of Asia have chosen to adopt GSM110

GSM Vs. CDMAIt uses TDMA. It is 2nd generation Its year of first use was 1991 Roaming is worldwide Battery life is very good due to simple protocol, good coverage and mature, power efficient chipsets Hard Handoff It uses CDMA It is 3rd generation Its year of first use was 2000 Roaming is limited Battery life lower due to high demands of CDMA power control and young chipsets Soft Handoff

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GPRS

General Packet Radio Service (GPRS) is a Mobile Data Service available to users of Global System for Mobile Communications (GSM) and IS-136 mobile phones. It provides data rates from 56 up to 114 Kbps. GPRS data transfer is typically charged per kilobyte of transferred data, while data communication via traditional circuit switching is billed per minute of connection time, independent of whether the user has actually transferred data or has been in an idle state. GPRS can be used for services such as Wireless Application Protocol (WAP) access, Short Message Service (SMS), Multimedia Messaging Service (MMS), and for Internet communication services such as email and World Wide Web access. 2G cellular systems combined with GPRS is often described as "2.5G", that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate speed data transfer, by using unused Time division multiple access (TDMA) channels in, GPRS is integrated into GSM Release 97 and newer releases. It was originally standardized by European Telecommunications Standards Institute (ETSI), but now by the 3rd Generation Partnership Project (3GPP). The General Packet Radio Service (GPRS) is a new nonvoice value added service that allows information to be sent and received across a mobile telephone network. It supplements today's Circuit Switched Data and Short Message Service. GPRS is NOT related to GPS (the Global Positioning System), a similar acronym that is often used in mobile contexts.

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GPRSGPRS Handset Classes: There are three different classes of devices. 1. Class A handsets can do both voice and data at the same time (simultaneously). If you were to receive a voice call will using the Internet, say, the connection would be placed on busy while you answer the call, rather than have it disconnected. 2. Class B handsets are voice and packet data capable, but not at the same time. It can only support either a voice or data service at a time. But like in Class A above, a voice call would put the data call on hold, and vice versa. 3. Class C handsets can handle only non-simultaneous data and voice calls. The user must manually select the service they wish to connect to. (SMS is also optional for Class C terminals).

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GPRS

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Classes of GPRS Services: Mobile devices can request different types of traffic to be prioritized in a attempt to give the user their desired level of connectivity. There are 4 types of classes. Precedence Class: An application can be assigned precedence classes 1,2, or 3. If an application has higher precedence (1) than another(3) then its traffic will be given a higher priority. Delay classes: Applications can request predictive delay classes which guarantee an average and 95% delay. Reliability class: application can request differing levels of reliability for its data depending on its tolerance of data loss. Throughput class: Applications can choose different profiles for throughput.

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GPRS Network System Architechture

A GSM network mainly consists of four components. Mobile Station (MS) carried by the subscriber . Base Station Subsystem (BSS) controls radio link with mobile station . Mobile Switching Center (MSC) is the central component of the NSS. Operates all switching functions for the mobiles within its jurisdiction. Interface between mobile and other (including fixed) network. Network Databases : Home Location Register and Visitor Location Register together with MSC provides the call routing and roaming capabilities of GSM. In order to integrate GPRS into the existing GSM network, two major new core network elements are introduced: the Serving GPRS Support Node (SGSN) and the Gateway GPRS Support node (GGSN). Serving GPRS Support Node (SGSN): An SGSN is responsible for the delivery of data packets from and to the mobile stations within its service area. SGSNs send queries to Home Location Registers (HLRs) to obtain profile data of GPRS subscribers. SGSNs detect new GPRS mobile stations in a given service area; and, finally, SGSNs process registration of new mobile subscribers and keep a record of their location inside a given service area.115

GPRS Network System Architechture

Gateway GPRS Support Node (GGSN) : GGSNs are used as interfaces between the GPRS backbone network and the external Public Packet Data Networks. GGSNs maintain routing information that is necessary to tunnel the Protocol Data Units (e.g IP) to the SGSNs that service particular mobile stations. Other functions include network and subscriber screening and address mapping. One or more GGSNs may support multiple SGSNs. In addition to the new GPRS components, following existing GSM network elements must also be enhanced in order to support GPRS. Base Station System (BSS): must be enhanced to recognize and send user data to the SGSN that is serving the area. Home Location Register (HLR): must be enhanced to register GPRS user profiles and respond to queries originating from SGSNs regarding these profiles.116

GPRS Network System Architecture

As can be seen, there are a number of new standardized network interfaces introduced: Gb Frame relay connection between the SGSN and the PCU within the BSS. This transports both user data and signaling messages to/from the SGSN. (SNDCP,LLC,BSSGP,NS) Gn The GPRS backbone network, implemented using IP LAN/WAN technology. Used to provide virtual connections between the SGSN and GGSN. Gi The point of connection between GPRS and the external networks, each referenced by the Access Point Name. This will normally be implemented using IP WAN technology. Gr Interface between the HLR and SGSN that allows access to customer subscription information. This has been implemented using enhancements to the existing GSM C7 MAP interface.117

To use GPRS, users specifically need:

A mobile phone or terminal that supports GPRS (existing GSM phones do NOT support GPRS) A subscription to a mobile telephone network that supports GPRS; Use of GPRS must be enabled for that user. Automatic access to the GPRS may be allowed by some mobile network operators, others will require a specific opt-in; Knowledge of how to send and/or receive GPRS information using their specific model of mobile phone, including software and hardware configuration (this creates a customer service requirement); A destination to send or receive information through GPRS. Whereas with SMS this was often another mobile phone, in the case of GPRS, it is likely to be an Internet address, since GPRS is designed to make the Internet fully available to mobile users for the first time. From day one, GPRS users can access any web page or other Internet applications- providing an immediate critical mass of uses.118

GPRS Services

Multimedia Messaging Service (MMS) Push to talk over Cellular PoC / PTT Instant Messaging and Presence -- Wireless Village Internet Applications for Smart Devices through Wireless Application Protocol (WAP) Point-to-point (PTP) service: internetworking with the Internet (IP protocols) Short Message Service (SMS) Future enhancements: flexible to add new functions, such as more capacity, more users, new accesses, new protocols, new radio networks. USB GPRS modem:USB GPRS modems use a terminal-like interface USB 2.0 and later, data formats V.42bis, and RFC 1144 and external antennas. Modems can be add in cards (for laptop) or external USB devices which are similar in shape and size to a computer mouse. GPRS can be used as the bearer of SMS. If SMS over GPRS is used, an SMS transmission speed of about 30 SMS messages per minute may be achieved. This is much faster than using the ordinary SMS over GSM, whose SMS transmission speed is about 6 to 10 SMS messages per minute

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Limitations Of GPRS

GPRS does impact a network's existing cell capacity. Only limited resources. Use for one purpose precludes simultaneous use for another. Maximum speed of 171.2 kbps only theoretically. Single user would need all 8 time slots. Network operator would never allow that. Bandwidth limited. Limited cell capacity for all users Speeds much lower in reality

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Features of GPRS

Faster data transfer rates GPRS currently supports an average data rate of 115 Kbps, but this speed is only achieved by dedicating all eight time slots to GPRS. Instead, carriers and terminal devices will typically be configured to handle a specific number of time slots for upstream and downstream data. The aggregate cell site bandwidth is shared by voice and data traffic. GPRS operators will vary in how they allocate the bandwidth. Typically, they will configure the networks to give precedence to voice traffic; some may dedicate time slots to data traffic to ensure a minimum level of service during busy voice traffic periods. Unused voice capacity may be dynamically reallocated to data traffic. Always-on connection An always-on connection eliminates the lengthy delays required to reconnect to the network to send and receive data. Information can also be pushed to the end user in real time.

Robust connectivity GPRS improves data transmission integrity with a number of mechanisms. First, user data is encoded with redundancies that improve its resistance to adverse radio conditions. The amount of coding redundancy can be varied, depending on radio conditions. GPRS has defined four coding schemes CS1 through CS4. Initially, only CS1 and CS2 will be supported, which allows approximately 9 and 13 Kbps in each time slot.If an error is detected in a frame received in the BSS, the frame may be repeatedly retransmitted until properly received before passing it on to the GPRS core network.121

Features of GPRS

Broad application support Like the Internet, GPRS is based on packet-switched data. This means that all native IP applications, such as email, Web access, instant messaging, and file transfers can run over GPRS. In addition, its faster data transfer rates enable GPRS to accommodate higher-bandwidth applications (such as multimedia Web content) not suited to slower GSM dial-up connections. GPRS is particularly well suited for applications based on the Wireless Application Protocol (WAP). Security support GPRS builds on the proven authentication and security model used by GSM. At session initiation, a user is authenticated using secret information contained on a smart card called a Subscriber Identity Module (SIM). Authentication data is exchanged and validated with records stored in the HLR network node. GPRS enables additional authentication using protocols such as RADIUS before the subscriber is allowed access to the Internet or corporate data networks.

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INTERWORKING WITH THE EXTERNAL INTERNET

Before a GPRS mobile station can use GPRS services it must obtain an address used in the packet data network (a PDP address) and create a PDP context. The context describes the characteristics of the connection to the packet data network (PDP type, PDP address, service precedence, reliability, delay, throughput and GGSN). With an active PDP context, packets from mobile station will be sent to its current SGSN first, then this SGSN encapsulates the IP packets, examines the PDP context, and routes them to appropriate GGSN. The GGSN decapsulates the packets and sends them out on the IP network. Similarly packets from the external packet data network will be routed to the GGSN first, which then queries the HLR and obtains the information where the MS is currently located in. It encapsulates the incoming packets and tunnels them to the current SGSN of the mobile user. The SGSN decapculates the packets and delivers them to MS. Each GGSN has an IP address and each mobile station has been assigned an IP address by its GGSN. Thus the MS's IP address has the same network prefix as the IP address of its GGSN. In GPRS network, user's current locations are managed in two levels: Micro mobility management tracks the current routing area or cell of the mobile station. It is performed by the SGSN. Macro mobility management keeps track of the mobile station's current SGSN and stores it in the HLR, VLR, and GGSN.

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GPRS Transmission Plane Protocol Reference Model

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GPRS Transmission Plane Protocol Reference Model

All data within the GPRS backbone, i.e. between the GSNs (SGSNGGSN), is transferred using the GTP (GPRS tunnelling protocol). GTP can use two different transport protocol, either reliable TCP for X.25 packets or the non-reliable UDP used for IP packets. To adapt to the different characteristics of the underlying networks, the Subnetwork Dependent Convergence Protocol (SNDCP) is used between an SGSN and the MS On top of SNDCP and GTP user packet data is tunneled from the MS to the GGSN and vice versa. To achieve high reliability of packet transfer between SGSN and MS, a special LLC is used, which comprises ARQ and FEC mechanisms. A Base Station Subsystem GPRS Protocol (BSSGP) is used to convey routing and QoS -related information between the BSS and SGSN. BSSGP doesnt perform error correction and works on top of Frame relay (FR) network.

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GPRS Transmission Plane Protocol Reference Model

Radio link dependent protocols are needed to transfer data over the Um interface. The Radio Link Protocol (RLC) provides a reliable link. The MAC controls access with signaling procedures for the radio channel and their maping of LLC frames onto the GSM physical channels. The radio interface at Um needed for GPRS doesnt require fundamental changes compared to standard GSM.

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GPRS: air interfaceRadio Link Control (RLC) Segmentation of the LLC-Frames in RLC blocks Block size dependent on short-term channel conditions Backward error correction and data flow control by Automatic Repeat Request (ARQ) protocol repeating not repairable RLC blocks selectively Medium Access Control ( MAC) Channel reservation contains: - one/several time slots (Packet Data Channels PDCH) of one frequency one uplink status flag (USF) per Packet Data Channel (PDCH), channel partition of up to 8 ms

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GPRS: air interface

Medium Access Control ( MAC) Reservation in the uplink (MS to BSS): MS sends reservation request on a Random Access Channel (Slotted ALOHA) BTS allocates a (split) channel and sends packet assignment MS sends data depending on the current priority (USF flag) Reservation in the Downlink (BSS to MS): BTS displays transmitting request and informs about the reserved channel MS supervises the reserved channel and receives

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GPRS: air interface

Physical Link Control adaptive forward error correction (FEC) dependent on shortterm channel conditions temporal scrambling (Interleaving) of the bursts and Mapping on reserved PDCH (Packet Data Channel) procedure to recognize overbooking situations on the physical channelSc R t SSSS/ / / l S Pr c SF T il its its Punctur its t r t (k it/s) . . . .

GPRS Channel Encoding

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GPRS Applications

Chat Textual and visual information Still & moving images Web browsing Document sharing/Collaborate working Audio Email, File Transfer

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GSM Vs. GPRSIt is circuit switched. It is not Always-on. It is packet switched. It is Always-on. Youre charged for the time the channel - Youre charged for the amount of data is reserved. thats being transported, not for the time that the unit is online. The System uses the same TDMA (Time The GPRS connection in the t610 can Division Multiple Access) link with one use as many as 4+1 time slots. out of seven time slots. Circuit switching provides the customer with a dedicated channel all the way to the destination. The customer has exclusive use of the circuit for the duration of the call, With packet switching, the operator assigns one or more dedicated channels specifically for shared use. These channels are up and running 24 hours a day, and when you need to transfer data, you access a channel and transmit your data.

The standard data rate of a GSM It provides data rates from 56 up to 114 channel is 22.8 kbps Kbps.

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HSCSD Vs. GPRSIt is circuit switched. It is not Always-on. It is packet switched. It is Always-on.supports guaranteed quality of service , Doesnt supports guaranteed quality of service better protocol for timing-sensitive ,so not a better protocol for timing-sensitive applications such as image or video transfer. applications such as image or video transfer is less bandwidth efficient with expensive is more bandwidth efficient wireless links expensive wireless links HSCSD is not as widespread as GPRS with less

GPRS is not as widespread as HSCSD

CSD is just your normal dial up where you GPRS on the other hand is the internet dial a number to connect to an internet connection provided by the mobile phone service provider and is limited to 9.6kbps on operator most networks

HSCSD utilizes up to four 9.6Kb or 14.4Kb It provides data rates from 56 up to 114 time slots, for a total bandwidth of 38.4Kb or Kbps. 57.6Kb.132

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