Client layers of the

optical layerModule 1

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Architecture for mobile computing

The first layer is User Interface or Presentation Tier.

Deals with user facing device handling and rendering

Includes a user system interface where user services reside

Second tier is the Process Management or Application Tier.

Here business logic and rules are executed.

Capable of accommodating hundreds of users

Controls transactions

Asynchronous queuing to ensure reliable completion of transactions.

Third tier is Database Management or Data Tier

For database access and design

Provides increased performance, flexibility, maintainability, reusability and scalability,

while hiding the complexity of distributed processing from the user 2

Three-tier architecture for mobile

computing

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Three-tier architecture (in detail)

To have universal access, the server is connected to a

ubiquitous network like internet.

To have access with network, an application called web

browser is required such as Internet explorer, Mozilla etc

Three layers

Presentation Tier (Tier 1)

Application Tier (Tier 2)

Data Tier (Tier 3)

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The mobile

computing

architecture

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Presentation Tier (Tier 1)

First tier

Layer of agents applications and systems.

Applications run on the client device and offer all the userinterfaces.

Responsible for presenting the information to the end user.

Humans use audio and video to receive information from themachine

Information is given to the system from keyboard(computer,laptop, cell phones ), pen (tablet, palmtop) etc

It includes web browsers

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Application Tier (Tier 2) Considered as engine of the application

Performs the business logic of the processing input, obtaining data and

making decisions.

Includes technologies like CGIs, Java, JSP, .NET services, PHP etc. deployed

in products such as Apache, Websphere etc.

Tier is presentation and database independent.

Operations such as network management, security are performed using a

middleware software

Middleware is defined as a layer of software, which sits in between the

operating system and user facing software.

Can also be defined as a software gateway connecting two independent open

objects.7

Middleware categories

Message-oriented Middleware (MOM)

Transaction processing (TP) Middleware

Database Middleware

Communication Middleware

Distributed Object and Components

Transcoding Middleware

Internet Content Adaption protocol (ICAP)

Web services

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Message-oriented Middleware (MOM)

It connects different applications through asynchronous exchange of messages.

Works over a networked environment without knowing what platform or

processor the other application is resident on.

The message can contain formatted data, requests for actions or unsolicited

response.

Provides a message queue between any two interoperating applications.

If the destination process is busy , then message is held in temporary storage

until it is processed.

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It is asynchronous, peer to peer, works in

Publish/Subscribe fashion.

In this mode, one or more objects subscribe to an event.

As event occurs it will be published by the loosely coupled

asynchronous object.

MOM will notify about this event , Is appropriate for event

driven applications

Eg: Message Queue from IBM known as MQ series

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Transaction Processing (TP) middleware It provides tools and environment for developing transaction based distributed

applications.

Inputs the data into a system at point of information source and output the

data at information sink.

Used in data management, network access, security systems, delivery order

processing, airline reservations, customer service etc

Capable of providing services to thousands of clients in a distributed client/

server environment.

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Includes features such as restarting failed process,

dynamic load balancing and ensuring consistency of data.

Independent of database architecture.

It optimises the use of resources by multiplexing many

client functions onto much smaller set of application

service routines.

Eg: MVC

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Transaction processing middleware

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Model view controller MVC Java uses MVC architecture , which is an example of TP middleware

It splits application into separate layers i.e. presentation, domain logic anddata access.

Model

domain specific representation of the information on which the application operates.

Domain logic manipulates and adds the meaning to the raw data

View

Responsible for rendering the model into a form suitable for interaction and understood bythe user

Controller

Manages the process and responds to events, typically user actions, may invoke changes inthe model 14

Communication middleware

Similar to connecting one application to another with the

help of telnet

Used in telecommunication world

User interface is through telnet

A mediation server automates the telnet protocol to

communicate with these nodes in the network.

Eg:TN5250, TN3270

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Distributed Object and Components

Eg: CORBA (Common Object Request Broker Architecture)

Open distributed computing infrastructure being standardizedby object management group.

Is vendor – independent infrastructure.

CORBA based program from any vendor on almost any computer,operating system, programming language and network caninteroperate with a CORBA based program from same oranother vendor

Handles large number of clients at high rates with highreliability.

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Transcoding Middleware

Used to transcode one format of data to another to suit the

need of the client.

To access web pages on phone, the HTML pages are transcoded

into WML pages so that mobile phone can access it.

It is used for content adaptation to fit the need of the device.

Content adaptation is also required to meet the network

bandwidth.

Content adaptation is done through proprietary protocols

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Internet Content Adaptation Protocol

(ICAP)

Contents present in the internet is accessed from differentagents and devices.

Is a protocol aimed at providing simple object based contentvectoring for HTTP services.

Lightweight protocol to do transcoding on HTTP messages.

Allows ICAP clients to pass HTTP messages to ICAP servers forsome sort of transformation.

The server sends back the transformed messages back to itsclients.

Before document is displayed for the agent, it is checked virus.

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Typical data flow in ICAP environment

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Steps performed

The user agent makes a request to an ICAP client for an objecton an object server.

The client sends the request to the ICAP server

The ICAP server executes the ICAP resource service on therequest and sends the possibly modified request or a responseto the request ICAP client

The client sends the request, possibly different from theoriginal client’s request to the original server.

The origin server responds to the request

The ICAP client sends the reply to the client.

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Services provided by ICAP servers

Virus checking for the requested content

Content filtering based on the sensor rating like PG(

parental guidance) , R (Restricted)

Local real time advertisement insertion like television

Wireless protocol translation

Image magnification for elderly

Peer to peer compression

Encryption of data and many more.

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Web services It provides a standard means of communication and information exchange among

different software applications, running on a variety of platforms or frameworks.

Is a software system identified by URL whose public interfaces and bindings are

defined using XML

The basic architecture includes web service technologies capable of:

Exchanging messages

Describing web services

Publishing and discovering web service descriptions.

Web services architecture defines the standard for exchange of messages

between the service requester and service provider.

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Service providers are responsible for publishing adescription of the services they provide

Requesters must be able to find and discover descriptionsof the services.

Software agents in the basic architecture can take on oneor all of the following:

Service requester: requests the execution of the web service

Service provider: processes a web service request

Discovery agency : agency through which a web service descriptionis published and made discoverable.

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Data (Tier 3)

Used to store data needed by the application and acts as

repository for both temporary and permanent data.

The data can be stored in any form of datastore or

database.

Data can be stored in XML format for interoperability with

other systems and data sources.

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Database Middleware Database independence helps in maintenance of the system better.

Allows the business logic to be independent and transparent of the database

technology and the database vendor.

Runs between the application program and the database.

Also called as database connectors as well.

Eg: ODBC, JDBC

With the help of these middleware's, the application will be able to access

data from any data source.

Data sources can be text files, flat files, spreadsheets or network, relational

, indexed, hierarchical, XML database etc.

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SyncML Is a protocol is an emerging standard for synchronization of data access form

different nodes.

New industry initiative to develop and promote a single common data

synchronization protocol that can be used industry wide.

Supports the naming and identification of records and common protocol

commands to synchronize local and network data.

Supports identification and resolution of synchronization conflicts.

It works over all networks used by mobile devices both wireless and wireline.

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Design consideration for mobile

computing The term context means , all the information that helps determine the state of an

object or actor

It can be a person, device , a place , a physical or computational object.

Content with context awareness

Build each application with context awareness

There are different services for different client context

Bank providing services on internet, for mobile phones and PDA

Have different URL for each type of device

Content switch on context

Provides adaptation of content within service

Transparent to the client

Here service is the same for internet , PDA and WAP

All access the bank site from same URL

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Content transcoding on context

Performs the adaptation of content based on the context and

behaviour of the device

Transparent for the client and the application

Middleware is used to perform all the operation

Middleware is intelligent to convert from HTML to XML or vice

versa as need occurs.

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Client Context Manager

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Identity information

The device will be in a position to communicate its identity without any ambiguity

Spatial information

Information related to surrounding space i.e. location, orientation, speed , elevation and

acceleration

Temporal information

Information related to time such as time of day, date, time zone, season of the year

Environmental information

Related to environment surroundings such as temperature, air quality, moisture etc

Social information

Related to social environment such as who is with you, people nearby, whether the user

is in the meeting or party. 30

Resource that are nearby

Relates to the resources accessible nearby such as devices, hosts or information sinks.

Availability of resources

Information about the device in use such as battery power , processing power, display etc

Physiological measurements

Relates to physiological state of the user such as blood pressure, heart rate, respiration rate

, tone of voice

Activity

Relates to the activity of the user such as talking, reading, walking and running.

Schedules and agendas

Relates to the schedules and agendas of the user. 31

A system is context aware of it can extract , interpret and use context relatedinformation to adapt its functionality to the current context.

Three aspects of the context management

Context sensing

The way in which the information is obtained

Context representation

The way in which the context information is stored and transcoded.

Context interpretation

The way in which the meaning is obtained from the context representation.

W3C proposed a standard for context information, i.e. Composite Capabilities/ PreferenceProfiles (CP/PP) 32

Composite capabilities/ Preference

Profiles (CC/PP)

Proposed by W3C

Model is based on RDF( Resource Description Framework) andcan be serialized using XML.

Contains a number of attribute names and associated valuesthat are used by an application to determine the appropriateform a resource to deliver to a client.

Help a client/ proxy to describe their capabilities to an originserver or other sender of resource data.

Fir different application to interoperate, some commonvocabulary is needed.

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Steps are

Device sends serialized profile model with request for content

Origin server receives serialized RDF profile and converts it into

an in-memory model

The profile for the requested document is retrieved and in-

memory model is created.

The device profile model is matched against the document

profile model

A suitable representation of the document is chosen.

Document is returned to device and presented.

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The simplest use of CC/PP

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Policy Manager

Responsible for controlling policies related to mobility

A policy is set of rules, these rules need to be followed under differentconditions.

When mobility is considered, the information will be visible from outside thefour walls of the enterprise.

Organizations will have policies regarding the disclosure of the information.

Eg: certain documents can be viewed only at the office of CEO

These kinds of policies must be transferable to mobile computing policymanager.

It will be able to define policy for the documents and assign roles to users.

Each role will have permission , prohibition, obligations associated with it.

Policy manager will have rights to read, write and execute36

Semantic Web

How to make machines understand policies and make thembehave in the expected fashion?

Semantic web addresses this need

Data is defined in the web and linked in such a way that it canbe used by the machine not for just display, but for theautomation. Security, filtering, integration and reuse of dataacross various applications.

It is generally built on syntaxes which use URLs to representdata, usually tuple based structures.

These syntax is called Resource Description Framework (RDF)syntaxes.

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Security manager

Provides a connection between the client device and the origin server.

Security manager will ensure security with respect to

Confidentiality:

The message transacted needs to be confidential

Nobody should be able to see it.

Managed by encryption eg: AES

Integrity

The message transacted needs to be tamper-resistant

No body should be able to change any part of the message

Managed using various hashing algorithms

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Availability

The system will be available

Nobody will be able to stop the service

Non-repudiation

Users of the system can be identified

Nobody after using will claim otherwise

Managed by digital signatures

Trust

There are complex issues of knowing what resources, services or agents totrust.

The system will be trusted.

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Platform for privacy preference project

(P3P)

Is an emerging standard defined by W3C

Enables web sites to express their privacy practices in standardizedformat so that they can be retrieved and interpreted as user agents.

With P3P , users need not read the privacy policies they visit

Instead key information about the content of the web is conveyed tothe user

The goal of P3P is to increase the user trust and confidence in theweb.

This informs the privacy policies about the site, hence makes the userto decide whether to release personal information or not.

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Adaptability Manager

Responsible for adapting content, behaviour and other

aspects acc. to the context and policy

May take any number of actions depending on the

information passed to the context manager

Most common action performed is transcoding of the

content so that it may be viewed on a particular device

Appending location-specific information to the document.

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Content adaption and transcoding

Content adaptation can be done at either content level in server endor the agent level in client device

Can be done in intermediate level in a middleware framework.

Content adaptation needs to consider the following attributes:

Physical capabilities of the device

Screen size, width and height in pixels, color

Logical capabilities of the device

Display image, audio, video

Effective network bandwidth

Payload

The total amount of bits can be delivered to the agent for static parts.

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Types of transcoding

Spatial

Transcoding in space or dimension

A standard frame is downscaled and reduced.

The frame is changed from one size to different size to suit the target device

Temporal

Reduction of number of frames on time scale

Downscales the no. of transferred frames to suit the target device andnetwork bandwidth

Code

Used to change the coding standard from one to another

Eg: transcoding BMP code into WBMP for wireless devices

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Types of transcoding

Color

Requested for monochrome clients

Uses less pixels and reduces bandwidth consumption

Modifies the perception of the image

Object or semantic

Comprises various techniques based on the computer visiontechniques

Extracts the valuable object from the scene, transfer them withlower amount of compression in order to maintain the both detailsand speed.

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Server side adaptation , resource requirements are

Static content size in bits

Display size such as height, width and area

Streaming bit-rate

Color requirements

Compression format

Hardware requirement such as display for images, support for

audio and video

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Transcoding done through middleware

Benefit of the middleware approach is it is totallytransparent to the device and content

Drawback is

Content providers have no control over how their content willappear to different clients

There may be legal issues like copyright

Html tags provides formatting information rather than semanticinformation

Transcoding of videos and audio is not easy

Developing a general purpose transcoding engine is very difficult.

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Content Rating and Filtering

W3C has proposed a standard called PICS (Platform for Internet Content Selection)for rating of the web content

Filtering of the content takes place based on this rating

It is set of technical specifications for labels that help software and rating to worktogether

Rating is allowed to the service provider , since it involves some amount ofsubjective judgement

Rating can be through self labelling or third part labelling of the content

PICS was concerned about children accessing the inappropriate materials , i.e metadata system, meaning that labels provide any kind of descriptive information aboutinternet material

Controlling was done using :47

Digital Signature:

Coupling the ability to make assertions with cryptographic signature block that ensureintegrity and authenticity

Intellectual Property Right Management

Using the meta-data system to label Web resources with respect to authors, owners, rightsmanagement information

Privacy (P3)

Using Meta-Data system to allow sites to make assertions about their privacy practices andfor users to express their preferences for the type of interaction they want to have withthose sites.

Personalization

Based on some policy, the content can be personalized to suit the need of user and theservice 48

Content Aggregation

Four parties

End User (EU)

Content Provider (CP)

Content Aggregator (CA)

Internet Service Provider (ISP)/ Wireless Network Operator (NO)

NO will have routers, gateways, cache etc to offer service

Any node can be responder and requester

There will be different parameters to determine the content

They can be static or dynamic parameters

Static parameter is received before the service begins

Dynamic parameter are those which are required with every request.

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Types of service (Content Aggregator ‘s

perspective)

Single Service Request

Works at user level

Works for only one user

Group service request

Works for group of users

Initiated at CA level or the NO level

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Seamless Communication

A system should be available and accessible from anywhere and

anytime and through any network or device

The user should be able to access the system when travelling.

Patient travelling from house to hospital via ambulance or

helicopter, here information has to exchange without any

interruptions.

Seamless Communication will combine seamless handoffs and

seamless roaming

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Handoff is the process which the connection to the

network is moved from one base station to another base

station within the same network

Roaming is a process in which connection to the network

is moved from one base station of one network to another

base station of another base station.

Offers freedom to roam across different wireless networks

Roaming works within homogeneous networks like GSM to

GSM or CDMA2000 to CDMA2000

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Following aspects needs to be maintained in seamlesscommunication

Authentication across network boundaries

Authorization across network boundaries

Billing and charging the data collection

End to end data security across roaming

Handoff between wireless access points

Roaming between the networks

Session migration

IP mobility

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Autonomous Computing

The purpose of autonomous system is to free users and systemadministrators from the details of the system operation and maintenancecomplexity.

System will run 24 X 7

Combination of the following functions

Self Configurable

Will configure automatically in accordance with high level policies

Self optimizing

Continuously look for ways to improve its operation with respect to cost, resourceand performance

Self Healing

Will detect, diagnose and repair localized problems resulting from bugs or failures.

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Self Protecting

It will be well defined from external attacks

Will not cascade failures to other parts of the system

Self Upgradeable

Will be able to grow and upgrade itself within the control of the

above properties.

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Context aware Systems Context manager is to maintain information pertaining to location,

mobile devices, networks, users , the environment around eachmobile device and other context information deemed relevant

Information such as

Location information

Helps to identify the location of the user/device

Can be achieved using device or through network

From device- GPS, can offer location precision of 10 feet radius

From network- timing advanced technology- precision of 100 feet radius

Device information

The know about the characteristics of the device

To determine the resource capability and the user interface capability

User-Agent parameter of HTTP we can obtain the device information56

Network information

Mobile computing environment, device moves from one network to another network

Is required to identify the capability of the network

Includes information such as security infrastructure, services offered by the networks

User information

This information is required to identify the user correctly

The system needs to ensure that the user is genuine and who he claims to be

Information can be validated through authentication independent of device or network

Environment information

Tells about the surrounding environment

Know about the temperature, elevation, moisture etc which is mainly required for sensorbased networks 57

GPS Global Positioning System , is a system that gives exact position on this earth

Funded and controlled by US Department of Defence

GPS satellites are orbiting around the earth, which transmits the signals that can be detected byanyone with a GPS receiver

Has three parts

Space segment

User segment

Control segment

Space Segment

Consists 24 satellites, each in its own orbit

Each GPS satellite takes 12 hours to orbit the earth

Each satellite is equipped with a clock to broadcast signals with respect to time

User segment

Has receivers, which can be users hand, embedded in a mobile device or mounted in a vehicle.

Receives the signal from satellite at the speed of light 58