Mobility Management

Mobility management is nothing but the technique in which uninterrupted signal connectivity is maintained, when a mobile device changes location from cell Ci to Cj or from network Ni to network Nj . Following are the two important points to ensure constant connectivity:
1. Infrastructure management that connects two or more cells or networks.
2. Location management and registration management by handoff when mobile devices move from one cell to another cell.
The technique of mobility management is as shown in following diagram:

Mobility Management is one of the major functionality of a GSM or a UMTS network. Mobile devices inform the cellular network, whenever it moves from one location area to another. Mobiles devices detects the location area codes. When a mobile finds that the location area code is different from its last update, it performs another update by sending to the network, a location update request, together with its previous location, and its Temporary Mobile Subscriber Identity (TMSI) as well. Thus a subscriber enjoys an uninterrupted access to the network. Roaming is the fundamental mobility management procedures of all cellular networks. Roaming is referred as the ability for a customer to automatically make and receive voice calls, send and receive data, or access other services, including home data services, when travelling outside the geographical coverage area of the home network, by means of using a visited network. This can be possible by using a communication terminal. Roaming is always technically supported by mobility management, authentication, authorization as well as billing procedures.

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This article is the topic of unit " Communication Technologies-II " from RTMNU MBA 3 rd sem IT syllabus notes.Further topics will be covered in upcoming blogs For more notes you can also refer to other links as given below:

1. http://rtmnupervasivecomp.blogspot.com
2. http://rtmnuittrends.blogspot.com
3. http://www.rtmnunetworkingtechnology.blogspot.com

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Grid Computing

Grid computing is simply means that the different things to different users. A grid is a collection of machines called as nodes, resources, or clients. Some resources may be used by all users of the grid, while some of them have certain restrictions. Thus grid computing can be defined as pervasive computing in which individual users gain access to computing resources as per their requirements with no information about the location of these resources and technologies hardware, operating system used. Therefore, grid computing can be defined as path of integrating various technologies as well as solutions. Although various kinds of resources on the grid may be shared and used, they are usually accessed by executing application or job. Jobs are programs that are executed at a specific point on the grid. In some cases these job are not executed in parallel due to some restrictions on them else they are executes in parallel. For example, some time some jobs require the output of another jobs. Initially grid computing is implemented internally for particular company or organization. However, nowadays, cross-organizational grids are also being implemented and are important part of business optimization and computing.

Benefits of grid computing:

 Grid computing consists of open standards for Web services and interfaces that make services, or computing resources, available over the network.
 There are many aspects to grid computing that are typically controlled by sophisticated software’s. These software ranges in capabilities as well as availability.
 Grid computing takes the advantage of various computing resources in such a way which is not previously possible.
 They can take advantage of underutilized resources to minimizing additional costs in business or organization.
 Grid computing uses parallel processing in order to make many applications economically feasible and help in finishing them as soon as possible.
 Grid computing makes more resources available to organizations which enhances resource balancing, reliability, and manageability.
 The basic security components such as authentication, authorization, and confidentiality used to make data secured while processing within the grid.

Grid topologies:

There are three types of Grid topologies:Intragrid, extragrid and intergrid which are as shown below:

From fig. it is cleared that intragrid consist of basic set of services within a single organization only, extragrid is a combination of two or more intragrids and intergrids consist of dynamic integration of applications, resources, and services with patterns, customers and organizations.

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This article is the topic of unit " Communication Technologies-II " from RTMNU MBA 3 rd sem IT syllabus notes.Further topics will be covered in upcoming blogs For more notes you can also refer to other links as given below:

1. http://rtmnupervasivecomp.blogspot.com
2. http://rtmnuittrends.blogspot.com
3. http://www.rtmnunetworkingtechnology.blogspot.com

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Cluster computing

There is an enormous requirement of processing power in many enterprises in order to manage their desktop applications, databases and knowledge management. The solution for this is nothing but cluster computing. Cluster computing is thus referred as the use of multiple computers, typically PCs or UNIX workstations, multiple storage devices in order to provide a single highly available system. Cluster computing is used in many areas such as in hosting websites, in managing game server and in big and/or complex projects in which large mathematical calculations are to be executed.

Definitions:
• Cluster computing is defined as the technique of linking two or more computers into a network by using the advantages of the parallel processing power of those computers.
• Cluster computing is a form of computing in which a group of computers are connected with each other and acts like a single entity.

Benefits:
Benefits of computer clusters are as follows:
1) Helps in reducing the cost.
2) Parallel processing power of clustering are very effective and faster.
3) Provides improved network technology.
4) Computer clusters can be easily expanded by adding more nodes into a network as per the requirements.
5) If a node fails in network then its operation can be simply transferred to another node within cluster, ensuring that there is no interruption in service.

Types of computer clusters:
There are three types of computer cluster which are as follows:

Load-balancing clusters:
It divides the workload efficiently between the available nodes. Thus by distributing the workload, it ensures the optimization of limited processing power.

High availability clusters:
Whenever the problems arise due to mainframe failure in the organizations then high availability clusters are used. It ensures 24/7 access to computational power. In business where data processing is time sensitive, this feature of high availability clusters becomes important.

High performance clusters:
They are designed to perform functions that requires node to communicate as they perform their tasks. E. g, when calculating results from one node will affect future results from another.

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This article is the topic of unit " Communication Technologies-II " from RTMNU MBA 3 rd sem IT syllabus notes.Further topics will be covered in upcoming blogs For more notes you can also refer to other links as given below:

1.http://rtmnupervasivecomp.blogspot.com

2.http://rtmnuittrends.blogspot.com

3.http://www.rtmnunetworkingtechnology.blogspot.com

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Network security and privacy

Security is needed in order to maintain privacy. Thus network must provide security to the data whenever transmitted from one end point to another end point. The desirable properties of secure communication are confidentiality, authentication, message integrity and non repudiation.

Cryptography technique is generally used in order to provide security to the data while transmitting over network. Thus cryptography keeps information secure from getting into the unauthorized hands or intruders . Basically, Cryptography is the process in which plain text is first encrypted and then transmitted over the network and is then recovered into plain text at destination by using decryption. Process of Cryptography is as shown in following figure.

Encrypted data is referred as cipher text. Various cryptography algorithms are available and are used for encryption as well as decryption of data transmitted over the communication channel. Algorithm uses one or more keys. there are two types of keys: Public key which is publicly available and private key which is known to belonging person only. Intruders may present in between the communication channel. Encryption or decryption algorithms are classified into two types as symmetric and/or asymmetric algorithms. These algorithms help in achieving confidentially and privacy.

Network security can also be achieved by using digital signature and digital certificate. Digital signature and digital certificate are useful in verification of records. A DSA (digital signature algorithm) is used to sign a digital document. Digital signature is used to identify the sender. It specifies that the particular document belong to the person who signed the document. Once a document is signed by a particular person then he cannot say that the document does not belong to him/her. Digital certificate is an electronic certificate issued by a certificate authority. Digital certificate includes digital signature.

In this manner, security is provided to data over the network.

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This article is the topic of unit " Communication Technologies-II " from RTMNU MBA 3 rd sem IT syllabus notes.Further topics will be covered in upcoming blogs For more notes you can also refer to other links as given below:

1.http://rtmnupervasivecomp.blogspot.com

2.http://rtmnuittrends.blogspot.com

3.http://www.rtmnunetworkingtechnology.blogspot.com

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CDMA

Concept:

As per the previous discussion, CDMA stands for Code Division Multiple Access. It is a multiplexing access method in which multiple users are allocated different codes to access the same channel. Where channel is the set of frequencies and code is nothing but the sequence of n symbols (0 or 1). Mobile telephony systems which use CDMA are referred as CDMA systems.

CDMA uses cellular network and is used for long distance communication. The initial evolution of CDMA was as 2.5 G. Nowadays CDMA supports high data rate and is thus considered as 3G. It transmits not only voice but also data and multimedia streams.

Features:
The important features of CDMA systems are:
1. It is more robust for multi-path delay.
2. Signals from each mobile station are coded with two or three codes.
3. It gives higher quality voice and data transmission with small bit error rate.
4. It has soft handover.
5. It performs power control by open loop or close loop methods.

CDMA codes allow unique identification of signals from different sources and transmit these signals through the same time, space and frequency slots without interference. Thus it is necessary that CDMA codes should not correlate with each other. The various types of codes are used and are discussed below.

Types of Codes:

1. Autocorrelation Codes:
An autocorrelation code is a multi-bit code which is used for coding the symbols before transmitting, allows the receiver to correlate and extract the symbols automatically. Barker codes and Pseudo-noise (PN) codes are the examples of autocorrelation codes. Barker code gives strong autocorrelation where as PN code gives strong peak with few, low and non-zero values which may results in interference with the users using same spread. Long M-sequence PN code has strong autocorrelation and is used as scrambling code. A short PN code also has strong autocorrelation. for example, in WCDMA short PN code is used.

2. Orthogonal Codes:
Two codes used for coding are referred as orthogonal when there is no effect of interference between two sets of signals on the received output. Orthogonal code do not show the strong autocorrelation property and thus requires the synchronization between transmitter and receiver. It gives zero cross-correlation. Examples of this code are Best code and Walsh code.
Best codes are optimized codes which allows significant correlation and do not create interference in between different channels. Whereas Walsh code are generated from Hadamard matrix with all pairs of rows are orthogonal. Walsh code is used in IS-95/cdmaOne. This code is used for channelization due to orthogonality property. Following table gives information about the different CDMA standards.

Different CDMA standards:

Conclusion:
Here we discussed about concept, features, types of codes used in different CDMA standards and different CDMA standards with their properties and uses also.

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This article is the topic of unit " Communication Technologies-II " from RTMNU MBA 3 rd sem IT syllabus notes.Further topics will be covered in upcoming blogs For more notes you can also refer to other links as given below:

1. http://rtmnupervasivecomp.blogspot.com/

2. http://rtmnuittrends.blogspot.com/

3. http://www.rtmnunetworkingtechnology.blogspot.com/

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Wireless Medium Access

Here we talk about the access to transmission media in wireless networks through various modulation methods and controlling the access by multiplexing the modulated signals.
When no of signals from different sources attempt to access a wireless medium simultaneously, it creates a problem of receiving the signals from each radio carrier distinctly. To overcome these problem, communication system receives the different signals from various terminals in the presence of signals divided into different cells, time slot , frequencies and codes called as SDMA, TDMA, FDMA, and CDMA signals respectively . The big challenge is to control the collision between the signals from one wireless station and other wireless station.
Whenever different wireless stations from different cells transmits signals then it uses SDMA i.e Space division multiple access which is as shown in following figure. It avoids the problem of collision but there is a limit to the number of cells which can be formed among the wireless stations using direct antennae. Hence SDMA does not resolve the interference issue completely.



When wireless stations are located in same cell transmitting the signals access access the medium using m different time slots is referred as TDMA i.e time division multiple access when there are m slots in TDMA communication system which is as depicted in following figure.

When the wireless stations in same cell access the transmission medium uses different ratio carrier frequencies then is called as FDMA i.e frequency division multiple access as shown in figure.

Suppose wireless stations in same cell uses same time-slot and frequency then the only choice is CDMA i.e code division multiple access. It access the transmission medium using distinct codes.
GSM communication standards uses TDMA and FDMA where as some CDMA-based standards are also available such as IS-95, WCDMA, CDMA2000 etc.

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This article is the topic of unit " Communication Technologies-II " from RTMNU MBA 3 rd sem IT syllabus notes.Further topics will be covered in upcoming blogs For more notes you can also refer to other links as given below:

1. http://rtmnupervasivecomp.blogspot.com/

2. http://rtmnuittrends.blogspot.com/

3. http://www.rtmnunetworkingtechnology.blogspot.com/

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GSM

GSM is developed in 1982 by Groupe Speciale Mobile. Global Service Mobile (GSM) communication is one of the most popular second generation mobile communication standard which basically uses cellular network.
GSM operates in frequency ranges such as 900MHz, 1800 MHz and 1900 MHz. Easy international roaming in GSM network is enabled by triband phones operating in GSM 900/1800/1900.GSM gives integrated services for data as well as voice.
Basically Services provided by GSM are divided into three different types such as teleservices, supplementary services and bearer service which are as shown in following figure.




Teleservices are the services provided to user by mobile service network. It is a point-to-point service which means a service is from one terminal provided to another terminal. Teleservices provides many services some of them are SMS, MMS, Fax, Voice communication at full data rate 13.4 kbps, emergency numbers for emergency calls etc.
Whereas GSM also provides some additional services that are available by subscription only called as supplementary services. Caller line forwarding, caller line identification at connected terminal, closed group formation, multiparty groupings, call holding, l waiting and barring calls from specified numbers or groups etc are some of the examples of supplementary services.
Bearer services are the services which are responsible for transmission of voice and data in terms of digital format over the network. Bearer services are transparent which uses only physical layer protocol for transmission or non-transparent which uses physical layer, data link layer and flow control layer protocol for transmission. Bearer services are also categorized depending on synchronous data transfer, asynchronous data transfer or synchronous data packet transfer.

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This article is the topic of unit " Communication Technologies-II " from RTMNU MBA 3 rd sem IT syllabus notes.Further topics will be covered in upcoming blogs For more notes you can also refer to other links as given below :

1. http://rtmnupervasivecomp.blogspot.com/

2. http://rtmnuittrends.blogspot.com/

3. http://www.rtmnunetworkingtechnology.blogspot.com/

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Mobile Communication

Mobile Computing is the process in which the set of distributed computing system participate, connect, and synchronize through mobile communication protocols. Mobile computing is also referred as pervasive computing when a set of computing devices, systems, or networks have the characteristics such as transparency, application aware adaptation and environment sensing ability.

Pervasive computing is nothing but the next generation of computing in which information and communication technology is used. Pervasive computing devices are very tiny or even invisible devices such as mobile phones. Mobile computing systems have large number of applications; for example, mobile computing has recently made Mobile TV which to make TV viewing on tiny cell phones easier and cheaper. A Smartphone is a mobile phone with additional computing functions such as SMS, MMS, E-Mail, Address Book, Web Browsing, Calendar, Bluetooth, Speaker Phone etc. BlackBerry 7130e is the example of Smartphone. Another application of mobile computing is enterprise solutions which provide business solutions for corporations and enterprises.

An innovative application of mobile computing is the iPod-Nano from Apple. The Apple iPods made it possible to listen to one’s favorite tunes anytime and anywhere. It can be also used for viewing photo albums, slide shows, and video clips etc. An additional example is the Sony Network Walkman. It can store and play 33 hours of music without charging the battery and stores music equivalent to 11 CDs.

A further important application is Mobile-Cheque. A mCheque is mobile –based payment system. This service is activated through text-message exchanges between a customer, a retailer and mobile service provider. It basically transfers money from customer account to retailer account. Mobile Commerce is one more application with much wider scope in which mobile devices are used to obtain stock quotes, for booking cinema, train, flight and bus tickets etc.

Mobile computing is also widely used today in the Supply Chain Management. Though mobile computing is useful in many areas, it has some limitations. Battery recharging requirements is biggest constraints of mobile computing. Interference in wireless signals affects the quality of service. There may be the problem related to connection such as link delays or connection losses while communication is going on. The problem may arise related to connection stability and data security also.

for more detail on mobile computing refer following mobile computing ppt :

mobile computing ppt : Mobile Computing.pptx

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This article is the topic of unit " Communication Technologies-II " from RTMNU MBA 3 rd sem IT syllabus notes.Further topics will be covered in upcoming blogs For more notes you can also refer to other links as given below:

1. http://rtmnupervasivecomp.blogspot.com/

2. http://rtmnuittrends.blogspot.com/

3. http://www.rtmnunetworkingtechnology.blogspot.com/

)