DATA TRANSMISSION
Data
transmission refers to the transfer of data such as digitized voice, digitized
image and video, computer-generated data, and so on. A data network is created
for the transmission and receipt of data. A data network is a system that allows
a data user in one area to access data processing functions or services in
another location.
Each keyed element is encoded into an analogous binary-coded
pattern within the keyboard when we enter data into the computer using the
keyboard. Standard coding techniques are available for this type of information
interchange. The most widely used codes for this function are the American
Standard Code for Information Interchange (ASCII) (7 bits) and the Extended
Binary Coded Decimal Interchange Codes (EBCDIC) (8 bits).
The flow of data in the form of bits between two or more
digital devices is known as data transmission. This data transfer takes happen
across a transmission medium of some sort (eg., twisted pair, coaxial cable,
fiber optic cable, etc). A station is a computer, terminal, phone, or other
communication device used in data transfer. Simplex, half-duplex, or
full-duplex channels or links connect two stations.
Types of Data transmission
As shown in the types of data transmission, digital data may be transmitted in several ways from one station to another.
SERIAL AND PARALLEL TRANSMISSION
Parallel transmission
We transfer a word or a byte at a time in parallel
transmission. As a result, all of the bits of data are sent via independent
communication channels at the same time. We need eight cables or lines to
convey eight bits. As a result, each bit has its line.
The figure represents this, with eight wires transmitting one byte (11001010) at a time.
All parallel wires must be identical for efficient
transmission of all 8 bits at the same time. As a result, parallel transmission
is only employed for a limited distance. This approach is used to transfer data
within a computer system, such as from the CPU registers to the memory or vice
versa, via the data bus. The data bus is simply a parallel data transfer
system. During a byte or word transmission, each clock pulse from one device to
another transmits all 'n' bits of one group, i.e., multiple bits are delivered
with a single clock pulse. As a result, the parallel transmission mechanism is
extremely fast.
Advantages of parallel transmission
• Data transmission is very fast.
• Simple maintenance, since any line/wire may be isolated for
testing or other purposes.
• There is less complexity.
Disadvantages
of parallel transmission
• The cost of
transmission is higher since each bit requires a separate cable connection
• For
long-distance communications, parallel transmission is not suitable.
Applications
• The data
bus is used to transmit data inside the computer system, such as from the CPU
to the memory and vice versa.
• Printers
employ parallel transmission also suitable for short-range communication.
Serial
Transmission
In serial transmission, data is sent one bit at a time, with each bit having a predetermined time interval. As a result, serial transmission only requires a single pair of cables or lines. The numerous pieces of data are transferred serially one after the other since there is only one communication channel. Only a single bit is transferred for each clock pulse. This can be seen in the figure, where 8-bit data (11001010) is sent. The LSB bit '0' will be sent first, followed by the following bits in a serial order. In the end, the MSB bit '1' will be sent.
On the transmitter side, the conversion devices transform
parallel data into serial data so that it may be broadcast over a single line.
On the receiving end, serial data is transformed to parallel data so that the
computer's internal circuitry can accept it. All of the bits are gathered,
measured, and stored in memory as bytes. Because just one data line is
required, serial transmission is ideal for long-distance communication. The
conversion between parallel and serial form in an asynchronous communication
design is normally performed by an integrated circuit called a Universal
Asynchronous Receiver-Transmitter (UART).
Advantages of serial transmission
• A single data line lowers the system's cost, and it's the
most preferred choice for long-distance communication.
Disadvantages of serial transmission
• The need for conversion devices at the sender and receiver
makes the system more complex.
• Since bits are communicated serially one after the other,
this approach is slower than parallel transmission.
• Only a single bit is transferred for each clock pulse.
Applications
• In most long-distance communications, serial transmission
is implemented.
Comparison
The table compares serial and
parallel transmission.
|
Factor |
Serial transmission |
Parallel transmission |
|
1) Number of bits transmitted at one clock pulse. |
One bit |
‘n’ bits |
|
2) No lines/wires are required to transmit ‘n’ bits. |
One wire |
‘n’ wires |
|
3) Speed of data transfer |
Slow |
Fast |
|
4) Cost of transmission |
Low as one line is required |
Higher as ‘n’ lines are required |
|
5) Application |
Long-distance communication between two computers |
Short distance communication like the computer to a printer |