FUNDAMENTALS OF COMMUNICATION AND NETWORKING
Communication
Serial transmission sends data bits one after another over a single
channel or wire (e.g. USB)
Parallel transmission sends data simultaneously over multiple channels
(e.g. older computers)
While parallel transmission can be faster for short distances due to
simultaneous data transfer, serial transmission offers significant
advantages in terms of reduced interference, longer transmission
distances, simpler cabling, and higher data integrity.
Synchronous data transmission involves sending data in a continuous
stream, synchronised by a clock signal shared between the sender and
receiver (e.g. ethernet).
Asynchronous data transmission sends data in discrete packets, each with
its own start and stop bits, without relying on a shared clock signal (e.g.
serial communication protocols).
Start and stop bits indicates the beginning and end of a data packet,
ensuring the receiver is ready or allowing the receiver to process the
data.
Comparison: Synchronous uses a shared clock signal and is faster and
more complex however is faster due to continuous flow, more efficient at
error handling. Asynchronous is slower and less efficient at error handling
however is simpler and uses start and stop bits, no shared clock.
A symbol is a particular pattern of bits represented by a signal. For
example, a symbol of four bits might be 1101
A communication system’s Baud rate is the number of signal changes in
the medium per second. 1 Baud (or 1Bd) is equal to 1 symbol change per
second.
Bit rate is the number of bits transmitted per second (bps). It equals the
Baud rate multiplied by the number of bits per signal. Bit rate is higher
than Baud rate if more than one bit is sent per signal.
Bit rate = Baud rate × № of bits per signal
Difference between baud and bit rate is that baud refers to the number of
signal changes whereas bit refers to the number of bits transmitted per
second.
Bandwidth (Hz) relates to the range of frequencies that a communication
medium is capable of transmitting. There is a direct relationship between
bandwidth and bit rate. Higher bandwidth results in a higher bit rate.
Bit rate is the number of bits transmitted per second, while bandwidth is
the maximum rate at which data can be transferred. The higher the
bandwidth, the higher the potential bit rate, meaning more data can be
transmitted per second.
Latency in a communication medium, often measured in milliseconds, is
the difference in time between an action being initiated and its effect
being noticed. Latency usually increases with distance.
, A protocol is a set of rules relating to communication between devices.
International organisations decide upon and publish protocols which allow
devices made by different manufacturers in opposite ends of the world to
communicate seamlessly.
In serial data transmission, data is sent one bit at a time over one
communication line (this is usually a metal wire but could also be an
optical fibre or a wireless channel). Serial data transmission is frequently
used for transmitting data over medium to long distances
(computationally speaking), such as from wired peripherals like mice and
keyboards to your computer.
Parallel data transmission uses numerous parallel communication lines to
send multiple bits between components in a computer simultaneously.
The more lines that a parallel communication medium uses, the more data
can be transferred simultaneously. Each of the communication lines that
forms part of a parallel communication medium will have slightly different
electrical properties, meaning that the time taken for one bit to be
transferred will differ slightly from line to line. This means that bits sent
together may not be received together, a problem referred to as skew.
www.pmt.education Skew is worst over long distances and, in extreme
cases, can lead to bits from different pulses overlapping, causing
corruption of data. Furthermore, parallel communication mediums are
more expensive than their serial counterparts because of their use of
multiple lines. For these reasons, parallel data transmission is most often
used over short distances, such as between parts of the processor and
within RAM. Another issue, referred to as crosstalk, can occur with parallel
data transmission. When communication lines are tightly packed, signals
from one line can “leak” into another, another cause of data corruption.
The advantages of serial over parallel:
1. Serial data transmission doesn’t suffer from skew or crosstalk
making it a more reliable communication method, especially over
long distances.
2. Serial communication mediums, which use just one line, are cheaper
to install than parallel mediums which use more than one line.
When data is transmitted using synchronous transmission, a clock signal
(which is shared by both the sender and the receiver) is used to time
when signals are sent. Synchronous data transmission is used within the
busses of a computer’s processor in the fetch-execute cycle. The signals,
which are sent at regular intervals, will be received in the same order that
they were sent. This makes synchronous data transmission suitable for
transmitting information in real-time systems.
Communication
Serial transmission sends data bits one after another over a single
channel or wire (e.g. USB)
Parallel transmission sends data simultaneously over multiple channels
(e.g. older computers)
While parallel transmission can be faster for short distances due to
simultaneous data transfer, serial transmission offers significant
advantages in terms of reduced interference, longer transmission
distances, simpler cabling, and higher data integrity.
Synchronous data transmission involves sending data in a continuous
stream, synchronised by a clock signal shared between the sender and
receiver (e.g. ethernet).
Asynchronous data transmission sends data in discrete packets, each with
its own start and stop bits, without relying on a shared clock signal (e.g.
serial communication protocols).
Start and stop bits indicates the beginning and end of a data packet,
ensuring the receiver is ready or allowing the receiver to process the
data.
Comparison: Synchronous uses a shared clock signal and is faster and
more complex however is faster due to continuous flow, more efficient at
error handling. Asynchronous is slower and less efficient at error handling
however is simpler and uses start and stop bits, no shared clock.
A symbol is a particular pattern of bits represented by a signal. For
example, a symbol of four bits might be 1101
A communication system’s Baud rate is the number of signal changes in
the medium per second. 1 Baud (or 1Bd) is equal to 1 symbol change per
second.
Bit rate is the number of bits transmitted per second (bps). It equals the
Baud rate multiplied by the number of bits per signal. Bit rate is higher
than Baud rate if more than one bit is sent per signal.
Bit rate = Baud rate × № of bits per signal
Difference between baud and bit rate is that baud refers to the number of
signal changes whereas bit refers to the number of bits transmitted per
second.
Bandwidth (Hz) relates to the range of frequencies that a communication
medium is capable of transmitting. There is a direct relationship between
bandwidth and bit rate. Higher bandwidth results in a higher bit rate.
Bit rate is the number of bits transmitted per second, while bandwidth is
the maximum rate at which data can be transferred. The higher the
bandwidth, the higher the potential bit rate, meaning more data can be
transmitted per second.
Latency in a communication medium, often measured in milliseconds, is
the difference in time between an action being initiated and its effect
being noticed. Latency usually increases with distance.
, A protocol is a set of rules relating to communication between devices.
International organisations decide upon and publish protocols which allow
devices made by different manufacturers in opposite ends of the world to
communicate seamlessly.
In serial data transmission, data is sent one bit at a time over one
communication line (this is usually a metal wire but could also be an
optical fibre or a wireless channel). Serial data transmission is frequently
used for transmitting data over medium to long distances
(computationally speaking), such as from wired peripherals like mice and
keyboards to your computer.
Parallel data transmission uses numerous parallel communication lines to
send multiple bits between components in a computer simultaneously.
The more lines that a parallel communication medium uses, the more data
can be transferred simultaneously. Each of the communication lines that
forms part of a parallel communication medium will have slightly different
electrical properties, meaning that the time taken for one bit to be
transferred will differ slightly from line to line. This means that bits sent
together may not be received together, a problem referred to as skew.
www.pmt.education Skew is worst over long distances and, in extreme
cases, can lead to bits from different pulses overlapping, causing
corruption of data. Furthermore, parallel communication mediums are
more expensive than their serial counterparts because of their use of
multiple lines. For these reasons, parallel data transmission is most often
used over short distances, such as between parts of the processor and
within RAM. Another issue, referred to as crosstalk, can occur with parallel
data transmission. When communication lines are tightly packed, signals
from one line can “leak” into another, another cause of data corruption.
The advantages of serial over parallel:
1. Serial data transmission doesn’t suffer from skew or crosstalk
making it a more reliable communication method, especially over
long distances.
2. Serial communication mediums, which use just one line, are cheaper
to install than parallel mediums which use more than one line.
When data is transmitted using synchronous transmission, a clock signal
(which is shared by both the sender and the receiver) is used to time
when signals are sent. Synchronous data transmission is used within the
busses of a computer’s processor in the fetch-execute cycle. The signals,
which are sent at regular intervals, will be received in the same order that
they were sent. This makes synchronous data transmission suitable for
transmitting information in real-time systems.
