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ISE MVJCE 2014-15

INFORMATION SCIENCE AND ENGINEERING

SEMESTER 8

10IS831-WIRELESS NETWORK AND MOBILE COMPUTING

Author Details:Name: Vanshika RastogiDesignation: Asst. ProfessorDepartment: ISE

WIRELESS NETWORK AND MOBILE COMPUTING-10IS831

ISE MVJCE 2014-15

UNIT-1

MOBILE COMPUTING ARCHITECTURE

1. What is mobile computing????

Mobile Computing is a technology that allows transmission of data, voice and video via a computer or any other wireless enabled device without having to be connected to a fixed physical link.

Nomadic computing, another name for mobile computing, is the use of portable computing devices (such as laptop and handheld computers) in conjunction with mobile communications technologies to enable users to access the Internet and data on their home or work computers from anywhere in the world.

Mobile computing can also be defined as a computing environment over physical mobility. The user of the mobile computing environment will be able to access data, information or any other logical object from any device in any network while on the move.

To make mobile computing environment ubiquitous, it is necessary that the communication bearer is spread over both wired and wireless network.

Mobile computing is used in different contexts with different names; like; virtual home environment, pervasive computing, ubiquitous computing, nomadic computing, global service portability, wearable computers.

2. Mobile Computing Functions

User mobility: user is free to move from one location to the other while using the same service.

Network mobility: deals with two types of use-cases. In one, the user moves from one location to another while using the same service seamlessly. Example, a user was using a Wi-Fi connection at a place and then moves to another place on another internet connection but continuing the same online service. In the other use-case, the network itself is mobile.

Bearer mobility: the user is allowed to move from one bearer to another while using the same service. Example, A device is connected to a mobile network using GPRS. The device comes into range of a Wi-Fi network. The device decides to change to the Wi-Fi network and creates a bearer to access the Wi-Fi network. The device then moves all the existing connections across to the Wi-Fi bearer. In the final step the device disconnects from the GPRS network.


ISE MVJCE 2014-15

Device mobility: user is able to move from one device to another while using the same service. Example, a software engineer is working from home on his laptop and then comes to office and works on the computer on the same application.

Service mobility: user is free to move from one service to another. Example, the user is writing a mail or a paper, for that he need some information from internet, so he opens another browser or tab and switches among the two without any problem.

Host mobility: the user device can act as a server or a client.

Fig.1.1: Mobile Computing Functions

3. Segments for mobile computing functions

User with device: this means that this could be a fixed device like a desktop computer or any portable device like mobile phone.

Network: whenever a user uses a mobile or any portable device, he may use different network at different places.

Gateway: this acts as an interface between different transports bearers. These gateways convert one bearer to another.

Middleware: this handles the presentation and rendering of the content on a particular device.

Content: this is the domain where the origin server and content is.

4. Different networks

Mobile computing uses different types of networks. These can be fixed telephone networks, GSM, GPRS, ATM, Frame Relay, ISDN, CDMA, Dial-up, WiFi, Bluetooth, Ethernet, Broadband etc.

Wireline Networks Designed over wire or tangible conductors.


ISE MVJCE 2014-15

Fixed telephone networks over copper and fiber-optic is used in this network.

These networks are generally public networks that cover wide areas. Wireless Networks

The term wireless networking refers to technology that enables two or more computers to communicate using standard network protocols, but without network cabling.

Wireless networking is a method by which homes, telecommunications networks and enterprise (business) installations avoid the costly process of introducing cables into a building, or as a connection between various equipment locations.

They are also called mobile networks. Examples, GSM, CDMA, GPRS etc. In a wireless network, other than the radio interface, rest of the network is

wireline and is generally called PLMN(Public Land Mobile Network). Ad hoc Networks

An ad-hoc network is a local area network (LAN) that is built spontaneously as devices connect.

Instead of relying on a base station to coordinate the flow of messages to each node in the network, the individual network nodes forward packets to and from each other.

In Latin, ad hoc literally means "for this," meaning "for this special purpose" and also, by extension, improvised or impromptu.

Bearers Bearer service or data service is a service that allows

transmission of information signals between network interfaces. for different types of networks, there are different types of transport

bearers. These can be TCP/IP, HTTP, dial-up connection.

5. Architecture for Mobile Computing

The network centric mobile computing architecture uses three-tier architecture as shown in the figure 1.2.

In the three-tier architecture, the first layer is the user interface or the presentation layer. This deals with the user facing device handling and rendering.

This layer provides a user system interface where the services like session, text input etc. reside.

The second tier is Process management or Application Tier. This layer is specifically for application programs or for process management where business logic and rules are executed.

The third layer is the Database Management or Data Tier. This layer provides the increased performance, flexibility, maintainability, reusability and scalability while handling the complexity from the user.


ISE MVJCE 2014-15

fig.1.2: three-tier architecture for mobile computing

6. Three-Tier Architecture

While designing a system for mobile computing, need to make the system in a manner that it may be used through any network, bearer, agent and device.

So, it is required to have the server connected to a ubiquitous network like the internet.

Through web browser, server can be accessed from any device. The below fig. 1.3 shows the three-tier architecture for mobile computing.

Fig.1.3: the mobile computing architecture

Presentation (Tier-1) This is the user-facing system in this tier. This layer consists of user applications and systems.


ISE MVJCE 2014-15

All these user applications run on the client’s device and offer all the user interfaces.

This is basically the user interface layer. This tier includes web browsers, WAP browsers and customized client programs. The agent software in the client’s device is an internet browser. These agents can

perform various tasks for the client.

Application (Tier-2) This is the engine for the ubiquitous applications. It performs the business logic of processing user input, obtaining data, and

making decisions. It includes technologies like CGI, Java, JSP, PHP. This layer is independent of presentation and database layer. In addition to the business logic, there are a few management functions that need

to be performed. These decisions may include network management, security, and data store

access. For implementing these functions different middleware software is used. Middleware framework is software that resides in between the operating system

and user facing software. Middleware software can be divided into the following categories: Message-oriented Middleware(MOM)

It loosely connects different applications through asynchronous exchange of messages.

It works over a networked environment without having to know what platform or processor the application is using.

MOM system provides a message queue between two interoperating applications.

If the destination system is out of service or busy, the message is made to be there in the temporary location until the message gets processed.

MOM is generally asynchronous, peer-to-peer, and works in public/publish manner.

One of the examples of MOM is Message Queue from IBM, better known as MQ Series.

Transaction Processing (TP) Middleware It provides tools and an environment for developing transaction based

distributed applications. TP is used in data management, network access, security systems, delivery

order processing, airline reservations, etc. These systems can provide service to thousands of clients in a distributed

environment. TP middleware also include features like, restarting failed processes,

dynamic load balancing, to ensure consistency of distributed data. It is independent of the database architecture.

Communication Middleware


ISE MVJCE 2014-15

This is basically used to connect one application to another through some communication middleware, like, telnet.

Distributed Object and Components One of the examples of this is CORBA (Common Object Request Browser

Architecture). CORBA simplifies many common network programming tasks that are

used in a net-centric application environment. CORBA is useful in many situations because of the easy way that CORBA

integrates machines from many vendors, with different sizes ranging from mainframes through minis and desktop to hand-held and embedded systems.

Transcoding Middleware It is used to transcode the data from one format to another format to meet

the need of the client. Example, we need to access any website from our mobile phone, and our

phone supports WAP, so we need to transcode the HTML pages to WML. Technically, transcoding is used for content adaptation to fit the need of

the device. Content adaptation is required to meet the network bandwidth needs.

Internet Content Adaptation Protocol The most important task for web servers is to provide the data to millions

of connected clients. Majority of the servers are designed keeping desktops in consideration. There are servers with the other protocols also. ICAP, is a protocol aimed at providing simple object-based content

vectoring for HTTP services. ICAP does the transcoding for HTTP messages. This works in a similar way to executing a “remote procedure call” on a

HTTP request. The protocol allows ICAP clients to pass HTTP messages to ICAP servers

for some sort of transformation. The server executes the transformation and then sends the transformed

message back to the client. There are two major components in ICAP architecture:

What are the various semantics for the transformation? How do I ask for content adaptation?

How is the policy for the transformation being managed? What kind of adaptation do I need to ask for and from where? How do I define and manage the adaptation?


ISE MVJCE 2014-15

Fig 1.4: Typical data flow in an ICAP environment

ICAP works at the edge part of the network. When an application is delivered from an edge device, end users find that

the applications execute more quickly and are more reliable also. Typical data flow in an ICAP environment is shown above;

A user agent makes a request to an ICAP-capable surrogate (ICAP client) for an object on an origin server.

The surrogate sends the request to the ICAP server. The ICAP server executes the ICAP resource’s service on the

request and sends the modified request, or a response to the ICAP client.

The surrogate sends the request, different from the original client’s request to the origin server.

The origin server responds to the request. The surrogate sends the reply to the client.

In future ICAP servers might be available to even provide services like; Language translation based on clients requirements. Virus checking for the requested content. Content filtering based on sensor rating. Wireless protocol translation. Transcoding or image enhancement. Image magnification. Content filtering based on copyright/digital signature.

Web Services Web services provide a standard means of communication and

information exchange among different software applications. The basic architecture includes web services capable of :

Exchanging messages Describing web services Publishing and discovering web service descriptions

The web service architecture defines the standards for exchange of messages between the service requester and service provider.

Data (Tier-3)


ISE MVJCE 2014-15

This layer is used to store data needed by the application and acts as a collection of both, temporary and permanent data.

The data can be stored in form of any database or data warehouse. Database Middleware

For mobile computing environment, the business logic should be independent of the device compatibility.

Also advised that the business logic should be independent from the database.

Database middleware does this for the business logic to be independent and transparent of the database technology.

This middleware works between the application program and the database. They are also referred to as database connectors. Examples, ODBC, JDBC etc.

SyncML It is a protocol for synchronization of data access from different nodes. Benefit of using this is the resources are managed at centralized level. The ability to access and update information on the move is the key to the

pervasive nature of mobile computing.

7. Design Considerations For Mobile Computing The mobile computing environment needs to be context-independent and context-

sensitive. “Context” refers to the information that helps determine the state of an object. The object can be anything, a place, a person, a device, a physical or a

computational object or any other entity being tracked by the system. In mobile computing environment, context data is captured so that decisions can

be made about how to adapt content or behavior to suit this context. Mobility implies that the attributes that are associated with the mobile devices and

users will change constantly. There are many ways in which content and behavior can be adapted: Content with context awareness: each application needs to be build with context

awareness. There are different services for different client context (devices). For example, the bank offers mobile banking application through internet, PDA, mobile phones. The three devices will have different links to access these services.http://www.mybank.com/inter.html, http://www.mybank.com/mbank.com, http://www.mybank.com/wap.wml

Content switch on context: another way to provide intelligence for the adaptation of content within service. This adaptation is transparent to the client. In this case, the service will remain same for internet, PDA or mobile phone.

Content transcoding on context: another way is to provide an underlying middleware platform that performs the adaptation of the content based on the context and behavior of the device. This adaptation is transparent to the client as well as to the application. In this case, the service may be in either HTML or XML, the middleware platform transcodes the code from html (or xml) to html, and wml on the move.


http://www.mybank.com/wap.wml

http://www.mybank.com/mbank.com

http://www.mybank.com/inter.html

ISE MVJCE 2014-15

Fig. 1.5: The Content Architecture with Respect to Mobile Computing

There are different types of contexts that can enhance the usability, reliability, and security of the service:

Client Context Manager: It is the human nature to make use of the implicit situational information of

the surrounding environment. Interpret the context about the current situation and then only react. When we are using some content on the PC in any organizational

environment, we face no problem, as it assumes the context to be safe. Mainly the applications are developed keeping the PC and the browsers

company in mind. While, the mobile computing applications, needs to be operated in dynamic

environment. This is mainly because of the different devices used and different supporting

networks. Thus, need a platform that is able to respond to the changes to the device

capability, user preferences, enterprise policy, network policy and many other environmental factors.

Therefore, a Client-Context Manager is needed to gather and manage the information pertaining to the client device, user, network and the surrounding environment of the device.

This information is provided by the Awareness Modules, which are sensors of various kinds, can be a hardware sensor or a software sensor or a combination of the two.


ISE MVJCE 2014-15

The hardware sensor is used to identify the precise location of a user, whereas the software sensor is used to determine the type of user agent.

The Awareness Module can be within the device, network or in the middleware.

A system is context-aware if it can extract, interpret and use context-related information to adapt its functionality to the current context.

The challenge lies in the complexity of capturing, representing, filtering and interpreting contextual data.

The context information needs to be represented in a format that can be understood by the machine.

All these requirements leads to three aspects of context management: Context sensing: the way in which context data is received. Context representation: The way in which context information is

stored and transported. Context interpretation: the way in which meaning is obtained from

the context representation. W3C has proposed a standard for the context information, called,

“Composite Capabilities/Preference Profiles (CC/PP)”. This standard describes the device capabilities and user preferences. CC/PP is based on RDF (resource description framework). CC/PP profile contains a number of attribute names and the associated values

that are needed by an application to determine the appropriate form of resource to deliver it to the client.

This helps in describing their capabilities to the origin server. CC/PP is designed in such a way that an origin server or proxy can perform

some sort of content to device matching. CC/PP is designed to suit an adaptation algorithm. The steps are as follows:

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 an 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.

Policy Manager It is responsible for controlling policies related to mobility. Policy is a set of rules, these rules needs to be for different conditions. Considering mobility, it means that the data or the information can be

viewed from outside the four walls of the organization also. Although, organizations have policies regarding the disclosure of the

information. The policy manager for the mobile computing will be able to define

policy for documents/services and assign roles to users. Each role will have certain responsibilities, rules, rights with them.


ISE MVJCE 2014-15

Semantic Web Policy manager states the rules for mobile computing, but how to

make the machine understand these policies and react in the expected way?

Semantic web is the solution to all this, also to how to find which content is required and which is not.

They are built on syntaxes that uses URI’s to represent data. Security Manager

It provides a secure connection between the client and the origin server.

Depending on the security policy, the security manager ensures security with respect to:

o Confidentialityo Integrityo Availabilityo Non-repudiationo Trust

Platform for Privacy Preference Project (P3P) It is an engineering standard defined by W3C. It enables the web sites to express their privacy practices in a

standardized format so that they can be retrieved and interpreted by the user agents.

With P3P, the user does not need to go through the privacy policies. It provides a technical mechanism to inform the user about the

privacy policy. This helps the user in deciding about the release of information.

Adaptability Manager It is responsible for adapting the content, behavior, and other aspects

according to context and policy. It may take any number of actions depending on the information

passed to it by the context manager. Content Adaptation and Transcoding

In certain situation, services may be used from any device through any network, so the content should be able to adapt to these dynamic situations.

Content adaptation can be performed either at the client level or at the server level or at the agent level.

For good adaptation, need to consider the requirements of the entire web page.

Content adaptation needs to consider the following attributes:o Physical capabilities of the deviceo Logical capabilities of the deviceo Effective network bandwidtho Payload

Transcoding can be classified as the following:o Spatial transcoding, is the transcoding in space or dimension.


ISE MVJCE 2014-15

o Temporal transcoding, copes with the reduction of the number of frames in the time scale.

o Color transcoding, something requested for monochrome client.

o Object or semantic transcoding, comprises of different techniques based on computer vision techniques.

Server side content adaptation is achieved through the use of InfoPyramid.

It creates context-aware content through static transcoding. It is used to store multiple resolutions and modalities of the

transcoded content. In case of client side adaptation, the adaptation is done by the agent

application. The agent application does the adaptation based on the capabilities. It is effective for static images.

Content Rating and Filtering We need a way to filter the content or to identify the type of content. W3C has proposed a standard called PICS (Platform For Internet

Content Selection) for rating the web content. Based on this rating the content can be filtered. It is a set of technical specifications for the meta-data that helps

software and rating services to work together. The RSACI (Recreational Software Advisory Council Internet) has a

PICS-compliant rating system called Resaca. Web pages that are rated by Resaca have the labels for the content. The motivation for PICS was concern over children accessing

inappropriate material. W3C is working to extend this service and mainly focusing on to the

areas of:o Digital signatureo Intellectual Property Rights Managemento Privacyo Personalization

Content Aggregation There are four parties involved in the process of communication: end

user (EU), Content Provider (CP), Content Aggregator (CA), Internet Service Provider (ISP) or the wireline or wireless network operator (NO).

The NO has the routers, cache, gateways, and other nodes to offer the services.

Here, anybody can become the requester and the responder. There are two types of parameters to decide the type of content, i.e.,

static and dynamic. The static adaptation parameters can be adapted before the service

begins. The dynamic adaptation parameter is required with every request.


ISE MVJCE 2014-15

From the content aggregator’s perspective, the service may be classified into two categories:

o Single service request: works at the user level and only for one user at a time.

o Group Service request: this works for a group of users. Seamless Communication

The basic aim of ubiquitous system is that the system is available and accessible anywhere and at anytime.

Seamless communication combines seamless handoffs and seamless roaming.

Handoff refers to the process of transferring an ongoing call or data session from one channel connected to the core network to another channel.

Whereas, Roaming helps ensure that a traveling wireless device (typically a cell phone) is kept connected to a network without breaking the connection.

The main challenge for handoff is that it has to work on while a session is going on.

Seamless communication offers users freedom to roam around the different wireless networks.

In seamless communication, the following aspects need to be maintained:

o Authentication across network boundaries.o Authorization across network boundaries.o Billing and charging data collectiono End-to-end data security across roamingo Handoff between wireless access points.o Roaming between networkso Session migrationo IP mobility

Autonomous Computing The essence of autonomous computing is self-management, which is

the combination of the following function:o Self-configurableo Self-optimizingo Self-healingo Self-protectingo Self-upgradable

Context Aware Systems The role of the context manager is to maintain information

pertaining to location, mobile devices, network, users, the surrounding environment or any other related information.

Description of these information is as follows:o Location information: this helps in identifying the location

of the user. This can be achieved either through the device


ISE MVJCE 2014-15

or through the network. This can be done either through GPS or GSM.

o Device information: this helps in knowing about the features of the device. This helps in determining the resource capability and the user interface capability.

o Network information: the user may move from one network to another, these networks can be heterogeneous in nature. This helps in determining the capability of the network.

o User information: this is needed to identify the user. Keeping the security in mind, this help in ensuring that the user is genuine and who he claims to be.

o Environment information: this includes ambient surrounding awareness. At certain point, we may need to know the temperature, elevation, moisture, which are important for sensor networks.

GPS The Global Positioning System (GPS) is a space-based satellite

navigation system that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.

The system provides critical capabilities to military, civil and commercial users around the world. It is maintained by the United States government and is freely accessible to anyone with a GPS receiver.


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