Introductory contents

Greetings!!!

 

Before starting with the actual topic (i.e.) mobile computing let’s go through few of the terminologies that will be used later in the course:

 

Communication: It is a process that allows to exchage information by several methods, but the prerequisite is both communicating ends(source and destination) should understand a common language or should share a mutual understandable format of information. Communication can be seen as a process of information transmission governed by three levels of semstic rules:

---Syntactic: Formal properties of signs and symbols.

---Pragmatic: Concers with the relations b/w signs and expressions and their uses.

---Sementic: Study of relationships b/w signs and symbols including what they represent.

 

Telecommunication:  It is the transmission of signal over a distance for the purpose fo communication. This process typically involves the sending of electromagnetic waves(Wireless media) or electrical signals(Wired media) by use of electronic transmitters.Many networks can be included under this like computer networks, Public telephone n/w, radio n/w, Television n/w etc

 

Now two common technologies used for transmission or communication over the network by use of network devices are (More detailed specification can be found in Computer networks book author: Frouzan , around page no 194 )

-          Wired Technology: Provides the connecting media using which the information/data is transmitted using the electrical signals. Also known as guided media.

-          Wireless Technology : Uses the different frequencies over the available electromagnetic spectrum to transfer information/data. Also known as unguided media.

 

Wired media can be classified into two ways

-          Copper wires (Includes twisted pair cables with different CAT levels and the coaxial cables): use electrical signals to transfer data

o   Economical

o   Easy to install and maintain

o   Bandwidth vary from low to high depending upon the media used. From few kbps to few MBPS.

-          Fiber optic wires (Uses the glass fiber enabled wire): use light signals to transfer data

o   More expensive then copper wires

o   Complicated setup to install and maintainance cost is sometimes high

o   High bandwidth is achieved with the optimum level of utilization and rated in GBPS. As compare to copper wires optical fiber cables can work in three different modes: Single, step index and graded index,  In actual the mode which is used to transfer the data over the fiber optics decide that what speed does the cable is going to provide.

 

Wireless Media used the electromagnetic spectrum and are basically classified into three categories

-          Radio waves (3kh to 1ghz)

-          Micro waves (1 ghz to 300 ghz)

-          Infrared waves (300 ghz to 400 thz)

 

All of the above mentioned waves retains their own propagating properties and on the bases of those properties their coverage areas defined for reading in details, refer to the same unit of computer network book as mentioned for above, on the broad prospective and application three kind of propagations are used:

-          Ground propagation

-          Sky Propagation

-          Line of sight propagation

 

Below displayed image contains all the three ways.

 

 

There are three different kinds of antennas are used on the basis of what kind of propagation is used:

 

Omnidirectional antenna

 

Dish Antenna

 

 

Horn antenna

 

 

 

Now as we are using wireless communication mediums so we have various kinds of different wireless devices & few of them are mentioned below:

-          Cellular phones and pagers

-          Global positioning system revicever devices

-          Cordless computer peripherals

-          Cordless telephone sets

-          Satellite television or DTH’s etc

 

Why the use of wireless communication required, few points are as follows:

-          To cover the areas where the cabling is not possible like mountain regions

-          To avoid structures/ obstacles

-          To provide a backup communication links in case of normal network failure

-          To link portable or temporary workstations

-          For providing remote connections etc

 

 

Various kind of wireless networks that we use or already used in past are:

-          Wireless LAN

-          Global system for mobile communication

-          Personal communcation system : uses radio band signals only

-          D-Amps- obsolute version of GSM

-          Wi-Fi

-          Fixed wireless data

-          WLL phone network  etc.

 

This is it for the first post for mobile computing. In next post will post the basics about the mobile computing and related contents….. till then happy reading……..