Parallel vs Serial Data Transmission

Parallel and serial data transmission are most widely used data transfer techniques. Parallel transfer have been the preferred way for transfer data. But with serial data transmission we can achieve high speed and with some other advantages.

In parallel transmission n bits are transfered simultaneously, hence we have to process each bit separately and line up them in an order at the receiver. Hence we have to convert parallel to serial form. This is known as overhead in parallel transmission.

Signal skewing is the another problem with parallel data transmission. In the parallel communication, n bits leave at a time, but may not be received at the receiver at the same time, some may reach late than others. To overcome this problem, receiving end has to synchronize with the transmitter and must wait until all the bits are received. The greater the skew the greater the delay, if delay is increased that effects the speed.

Another problem associated with parallel transmission is crosstalk. When n wires lie parallel to each, the signal in some particular wire may get attenuated or disturbed due the induction, cross coupling etc. As a result error grows significantly, hence extra processing is necessary at the receiver.

Serial communication is full duplex where as parallel communication is half duplex. Which means that, in serial communication we can transmit and receive signal simultaneously, where as in parallel communication we can either transmit or receive the signal. Hence serial data transfer is superior to parallel data transfer.

Practically in computers we can achieve 150MBPS data transfer using serial transmission where as with parallel we can go up to 133MBPS only.

The advantage we get using parallel data transfer is reliability. Serial data transfer is less reliable than parallel data transfer.


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Anonymous said...

serial is not better than parallel. never will be. of course that's what the industry would have us all think. parallel access to a bus is direct, and serially there is no such thing. i'm almost sure the underlying agenda behind pushing serial interfaces is making 'everyday' access to system's buses complicated, thus effectively keeping the 'tinkerer' off the internals of a system and the system itself a 'proprietary' secret. there's also the matter of control and dependence (tying people "irrevocably" to an operating system and of course to drivers). -- sickening.

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