Synchronous communication is direct communication where the
communicators are time synchronized. This means that all
parties involved in the communication are present at the
same time. This includes, but is not limited to, a telephone
conversation (not texting), a company board meeting, a chat
room event and instant messaging. Asynchronous communication
does not require that all parties involved in the
communication to be present at the same time. Some examples
are e-mail messages, discussion boards, blogging, and text
messaging over cell phones. In distance (specifically
online) education asynchronous communication is the major
(sometimes the only) method of communication. Usually, we
use different discussion boards in each class with each
having its own purpose.
A start bit and a stop bit are added to each data segment
for asynchronous communications. For synchronous
communication, both the start bit and stop bit ane
eliminated, so a faster transmission speed is achieved.
With INS-Net, the standard transmission speed of
asynchronous communication is 38.4 kbps, while that of
synchronous communication is 64 kbps or 128 kbps.
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• An asynchronous connection, in which each character
is sent at irregular intervals in time (for example a user
sending characters entered at the keyboard in real time).
So, for example, imagine that a single bit is transmitted
during a long period of silence... the receiver will not be
able to know if this is 00010000, 10000000 or 00000100...
To remedy this problem, each character is preceded by some
information indicating the start of character transmission
(the transmission start information is called a START bit)
and ends by sending end-of-transmission information (called
STOP bit, there may even be several STOP bits).
• In a synchronous connection, the transmitter and
receiver are paced by the same clock. The receiver
continuously receives (even when no bits are transmitted)
the information at the same rate the transmitter send it.
This is why the transmitter and receiver are paced at the
same speed. In addition, supplementary information is
inserted to guarantee that there are no errors during
transmission.
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| Synchronous Communication:
It is based on synchronization between the sender and the
receiver. Both must be synchronized before actual
communication takes place. The clock pulses are generally
used to provide synchronization.
Asynchronous Communication:
This communication doesn't need any synchronization between
the sender and the receiver. Sender may send the
information at anytime without waiting for the receiver to
be ready to receive the information. The the receiver may
receive it some other time later. ............................................................................ Both of these forms of communication are a means of transmitting data.
The difference is in the format that the data is transmitted.
Asynchronous
communications is the method of communications most widely used for PC
communication and is commonly used for e-mail applications, Internet
access, and asynchronous PC-to-PC communications. Through asynchronous
communications, data is transmitted one byte at a time with each byte
containing one start bit, eight data bits, and one stop bit, thus
yielding a total of ten bits. With asynchronous communications, there is
a high amount of overhead because every byte sent contains two extra
bits (the start and stop bits) and therefore a substantial loss of
performance.
Synchronous communications is the more efficient method
of communications. CQ's connectivity solutions communicate through the
synchronous method of communications.
Through synchronous
communications, data is transmitted as frames of large data blocks
rather than bulky individual bytes. One advantage of synchronous is that
control information is easily inserted at the beginning and end of each
block to ensure constant timing, or synchronization. Another advantage
of synchronous is that it is more efficient than asynchronous. For
example, a 56 Kbps dial-up synchronous line can carry 7000 bytes per
second (56000/8) compared to a 56 Kbps dial-up asynchronous line which
can only carry 5600 bytes per second (56000/10). When transmitting large
amounts of information, this translates into a significant increase in
speed and performance.
To see this work you can work out the efficiency rates and time that it takes to send each message
Asynchronous would be worked out as follows
To get the efficiency of it you
get assuming the message is being send over a 100mb line and 70 bytes to send and 300 characters
then it is
70*8 = 560 (the 8 is for the 8 bits to make up each byte)
the 70*2 (the start and stop bit) =140
= 700
then to
get 560*100/700= 80
that means that 80% efficient
To get the time
Asynchronous
300 *(1+7+1+1) =3000
take this and divide it by the size of the line in this case 100mb
so that is then
3000/100=30
that means that it would take 30 seconds to send
for
synchronous efficiency
Then
70*8= 560
then 4 bytes = 4*8 (the over head bits) = 32
560+32=592
560*100/592=94.5
then that's 94.5% efficient
and for the time then it is just
300+4*8=2342/100=23.42
that's then 23.42 seconds
this shows you which is faster and more efficient in each case
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