Friday, 24 February 2012

Data Transmission

 In our class today, we learn about Data Transmission. Data transmission is defined as data travel over a network in various characteristics: form, amount of data: type, direction and timing. There are 6 of data transmission that we have learnt in today’s class. They are Analogue vs. Digital, Bandwidth, Serials vs. Parallel, Transmission timing, Transmission directions and lastly, Circuit switched, Packet‐switched and Broadcast connections. Firstly, I will tell about Analogue vs Digital.

Analogue transmission is actually using signals that are exact replicas of a sound wave or image. Signals of varying frequency or amplitude are added to carrier waves with a given frequency of electromagnetic current to produce a continuous electric wave. The examples of analogue are standard phones, fax machines, and modems. On the other hand, Digital transmission uses the signals that are converted into a binary code that has two elements in it. This format is ideal to an electronic communication because the string of 1s and 0s can be transmitted by a series of "on/off" signals represented by pulses of electricity or light.
 Secondly, we learn about Bandwidth. 
Bandwidth is the amount of data that can be transmitted in a fixed amount of time. For digital devices, the bandwidth is usually measured in bits per second (bps), Megabits per second (Mbps) etc. normally, medium that with higher bandwidth can deliver data faster. After that, we are introduced to another type of data transmission which is Serial vs. Parallel Transmission. 
The serial transmission will send a data one bit at a time, one after another a long a single path. Then the parallel transmission sends data at least one byte at a time, each bit in the byte taking separate path.
  Then, the other data transmission is Transmission Timing.
 This transmission consists of three which are Synchronous transmission, Asynchronous transmission and Isochronous transmission. Synchronous transmission is where the data is organised into blocks or groups and transferred at regular specified interval. Asynchronous transmission is the process where transmitted data is encoded with starts and stop bits, specifying the beginning and end of each character. Isochronous transmission is where the data is sent at the same time as other related data to support certain types of real time applications for example streaming voice, video and music.

 Directions of data transmission divide to two, simple and half duplex.  One way of communications, and the data travel in single direction only i.e. door bell. It is relatively uncommon in computer communications.
Circuit switched data used dedicated path from sender to receiver.
Packet‐Switched Data sent as individual packets, which are assembled at the recipient’s destination.

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