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Subject Name: Wireless Networks and Mobile Computing Subject Code:10CS831

A study of wireline and wireless networks, ad hoc networks, and the architecture of mobile computing systems.

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Subject Name: Wireless Networks and Mobile Computing Subject Code:10CS831

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  1. Subject Name: Wireless Networks and Mobile Computing Subject Code:10CS831 Prepared By:Mrs.ThanuKurian Department:Computer Science Date:30/01/2015

  2. Networks • Wireline Networks(Fixedline) • Designed over copper wire and fiber optic Eg:fixed telephone networks and broadband networks over DSL • Wireless Networks(Mobile) • Networks used by radio taxis,cellular phone Eg:PCS(Personal Cellular System),AMPS(Advanced Mobile Phone System),GSM,CDMA • Ad hoc Networks

  3. Networks • Ad hoc Networks • A collection of nodes which can communicate with each other without any fixed connection or a central base station • In this, some devices are part of the network only for the duartion of a communication session • The term adhoc(meaning “for this purpose only”) has been applied to networks in which new devices can be quickly added using for eg using bluetooth or wireless LAN • Bearers

  4. Architecture of Mobile Computing • Transaction processing(TP)-information processing divided into individual operations called transactions • In mainframe computers many mission critical systems use TP • At the core the TP monitor software manages terminal resources and database resources • Terminal resources-VDU(Visual display unit,POS(Point of Sale terminal),printers • Database resources • Centralized mainframedistributed systems (Two-tier client server architecture) • Centralized server based architecture (Three-tier architecture)

  5. Three tier Architecture for Mobile Computing

  6. First layer(User interface /presentation layer) • Deals with user facing device handling and rendering • User services(session,textinput,dialog and display management) • Second layer(Process Management/Application tier) • Business logic and rules are executed • Controls asynchronous transactions and asynchronous queuing • Third layer(Database management/Data tier) • Database access and management

  7. Three-tier architecture

  8. Presentation(Tier-1) • User facing system(agent software) • Presents information to the end user • Includes web browsers(Mozilla,Lunx,Internetexplorer,Netscape navigator)

  9. Agent software functions as an agent for a user or another program working autonomously in a particular environment • As an applet- access some other application through http api to sophisticated applications like real time sales and inventory management • As web scraper- extracts information from websites. It transforms unstructured data on the web into structured data

  10. Application(Tier-2) • Engine of a ubiquitous application • It processes user input, obtains data and makes decisions • Includes technology like CGIs,Java,JSP,.NETservices,ColdFusion etc • Middleware is connectivity software that provides a mechanism for processes to interact with other processes running on multiple networked machines

  11. Middleware can be grouped into following categories • Message oriented middleware • Transaction Processing middleware • Database middleware • Communication middle ware • Distributed object and components • Transcoding middleware

  12. Message Oriented Middleware • A middleware framework that loosely connects different applications through asynchronous exchange of messages • MOM system provides a message queue between any two interoperating applications • If destination process busy, message is held in a temporary storage location until it is processed Eg:Message queue from IBM known as MQ services JMS(Java Message Service) in Java

  13. MOM Architecture

  14. Transaction Processing(TP) Middleware • Provides tools and an environment for developing transaction based distributed applications. • Provides services to thousands of clients in a distributed cient/server environment. • Will input data into a system and output the data and device for i/p and o/p will be different. • Maps numerous client requests through application service routines to different application tasks eg:used in data management,networkaccess,securitysystems,airline reservations

  15. Model View Controller • An eg of transaction processing system • An application is split into separate layers- • Presentation • Domain logic • data access • In MVC the data access layer is encapsulated by the model • View is responsible for rendering the model into a form suitable to be undesrstood by the user • Controller manages processes and responds to events

  16. Communication Middleware • Used to connect one application to another • Quite useful in telecommunication world • Example-Using telnet to connect one application to another • Distributed Objects and Components • Eg:CORBA(Common Object Request Broker Architecture)-An architecture for creating,distributing and managing distributed program objects in a network • Allows programs developed by different vendors to to communicate • Integrates machines ranging from mainframes through minis

  17. Transcoding Middleware • Used to transcode one format of data to another to suit the need of client Eg:If we want to access a website through a mobile phone supporting WAP,we need to transcode the HTML page toWML page so that the mobile phone can access it.

  18. Internet Content Adaptation Protocol(ICAP) • Provides simple object based content vectoring for HTTP services • A light weight protocol to do transcoding on http messages. • Similar to executing a RPC on a http request

  19. Typical data flow in an ICAP environment

  20. A user agent makes a request to the ICAP server • The surrogate sends the request to the ICAP server • The ICAP server executes the ICAP resources service on the request and sends the possible modified request or response back to the ICAP client • The surrogate sends the request,possibly different from the original client’s request,to the original server • The origin server responds to the request • The surrogate sends the reply to the client

  21. ICAP services • Suit content delivery based on network bandwidth • Suit content delivery based on device characteristics • Language translation • Virus checking for requested content • Content filtering • Local real time advertisement insertion like television • Local real time advertisement elimination for premium subscribers • Wireless protocol translation • Anonymous web usage profiling • Transcoding or image enhancement • Image magnification for the elderly • Image sixe reduction based on device display characteristics • Intelligent video condensation • Digest production/batch download of Web content • Content filtering • Peer to peer compression and encryption of data

  22. Web Services • Provides a standard means of communication and information exchange among different software applications running on a variety of platforms • Software systems interact with web service using XML based messgaes • Web service architecture defines standards for message exchange between sservice requester and service provider

  23. Data(Tier-3) • Store data • Repository for both temporary and permanent data • Range from sophisticated relational database to simple text files Database Middleware • Runs between the application program and the database • Also called database connectors. • Allows business logic to be independent and transparent of the database technology and database vendor.

  24. SyncML • A protocol for synchronization of data access from different nodes • A method to synchronize contact and calendar information between some type of handheld device and a computer(personal or network based) • Works over all networks used by mobile devices-wired and wireless

  25. Design Considerations for Mobie Computing • Context information is the information that helps determine the state of an object or information related to the surrounding environment of an actor in that environment • Mobility implies that attributes associated with devices and users will change constantly • Such changes will mean that the content and behaviour of applications should be adapted to suit to current situation

  26. Some examples are: • Content with context awareness • Different services for different client context • Content switch on context • Service is the same for internet,PDA and WAP • All access banks service through http://www.mybank.com/ • An intelligent code identifies the agent to decide what type of device or context it is • Content transcoding on context • Middleware intelligently identifies the context either from http or additional customized parameters

  27. The Content Architecture with respect to Mobile Computing

  28. Client Context Manager • Client content manager gather and maintain information in dynamic conditions-user prefernces,enterprisepolicy,network policy • All these informantion will be provided by a set of awareness modules-sensors(h/w or s/w) • Any information available at the time of an interaction can be seen as context information • Examples • Identity • Spatial information • Temporal information • Environmantal information • Social situation • Rosources that are nearby • Availlability of resources • Physiologicameasurements’activity • Schedules and agendas

  29. Context Aware System • A system is context aware if it can extract,interpret and use content related information to adapt its functionality to the current content • This leads to three aspects of context management • Context sensing-The way in which context data is obtained • Context Representation-The way in which context information is stored and transported • Context interpretation-The way in which meaning is obtained from the context represenation

  30. Composite Capabillities/Preference Profiles(CC/PP) • A standard proposed by W3C for context information for describing device capabilities and user preferences • Based on RDF(Resource Description Framework) • A CC/PP profile contains a number of attribute names and associated values • CC/PP standard defines vocabularies for different applications to interoperate

  31. CC/PP is designed in such a way that an origin server of proxy can perform some sort of content to device matching • The sequence of steps include • Device sends serialized profile model with request for content • Origin server receives and converts it into in-memory model • The profile for the requested document is retrieved and an in memory model is created • The device profile model is matched against document profile model • A suitable representation of document is chosen • Document is returned to device and presented

  32. Simplest use of CC/PP

  33. Format for RDF

  34. Example for RDF

  35. Policy Manager • Policy-set of rules to be followed • Controlling policies related to mobility • With mobility, data or information will be visible from outside the four walls of the enterprise • Mobile computing policy manager defines policy for documents/services and assign roles to users • Should assign roles to users like • Permission • Prohibition • Obligation

  36. Sematic Web • Provides a common framework that allows data to be shared and reused across application, enterprise and community boundaries • Allows to put machine understandable data on the web • Usually built on syntaxes which use URIs to represent data • These syntaxes are called RDF(Resource Description Framework)

  37. Security Manager • Provides secure connection between client device and the origin server • Security w.r.t: • Confidentiality-Nobody can see the message transacted • Integrity-Message should be tamper resistant • Availability-Nobody will be able to stop the service • Non-repudiation-Users of the system can be identified • Trust-System will be trusted

  38. Platform for Privacy Preference Project(P3P) • An emerging standard defined by W3C • Enables websites to inform users about privacy policies about the site • This will help users to decide whether to release their personal information or not.

  39. Adaptability Manager • Responsible for adapting content,behaviour and other aspects according to content and policy • A device uses services through the network. Content should adapt to the dymnamic situations- Content adaptation • Content adaptation can be at • Content level at Server end (Infopyramid) • Agent level in client device • Intermediate level in middleware

  40. Content adaptation should consider the following factors: • Physical capabilities of device eg:screen size • Logical capabilities of device required for displaying video, image, audio • Effective network bandwidth • Payload ie, no of bits that can be delivered

  41. Transcoding • Transcoding content is done so that it can be viewed on a particular device • Transcoding is classified as: • Spatial transcoding • Frame is changed from one size to another to suit the target device • Temporal transcoding • Downscales the no: of transferred frames to suit the target device • Color transcoding • Using less bits for pixels can reduce bandwidth and modify perception of images • Code transcoding • Change code from one standard to another • Object or sematictranscoding • Semantically extract valuabale objects from scene and transfer them

  42. Autonomous Computing • An autonomous system will free users and system administrators from details of system operation and maintainancecompexity • An autonomous system is • Self configurable-System configures itself automatically in accordance with high level policices • Self-optimizing-System will look for ways to improve its operation w.r.tresource,cost and performance • Self-healing-System will detect diagnize and repair localised problems resulting from bugs or failures • Self-protecting-Syetem will defend itself from attacks • Self-upgradable-Syetms will grow and upgrade itself within control of above properties

  43. Context Aware Systems • A context manager maintains information pertaining to location,mobiledevices,network,users the environment around each mobile device and any other context information • Location information-helps us to identify location of device • Device information-helps to know the characteristics of the device • Device-User-Agent parameter of HTTP protocol • Network-EIR(Equipment Identity Register)

  44. Network Information-information about the network • User Information- • Identify the user correctly • Genuine user and nobody is impersonating • Through authentication • Environment information-surrounding awareness for sensor based networks

  45. GPS(Global Positioning System) • System gives us the exact postion on the earth • Funded and controlled by US department of defence • GPS consists of three parts: • Space segment • consist of 24 satellites 11000 nautical miles above earth • Each satellite equipped with clock to let it broadcast messages • User segment • Consists of recievers in users hand,embedded in a mobie device or mounted in a vehicle • Receives satellite signals • Control segment

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