# Principles of Signal Theory by nyut545e2

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```									Principles of Signal Theory

BTEC National
Signal Theory
• Data is represented in
digital format based
on binary (base 2)
principles
• Digital signals are
discrete.
Data
• The smallest element of data is the ‘bit’ or
‘binary digit.’
• This can be represented by a ‘0’ or a ‘1’.
• When bits are grouped together they can
be more useful units of data. For example
8 bits form a byte
Converting Denary to Binary
• To convert denary to binary you must
firstly know the ‘base 2’ rules. (This is
similar to the units, tens, hundreds you
were taught at primary school)

128 64    32    16   8    4     2    1
Converting Denary to Binary
128 64 32      16   8    4    2    1
0    0  1       0   1    1    1    1 = 47

We work this out by looking at the headings

= 32 + 8 + 4 + 2 + 1 = 47. Therefore 47 is
represented as 00101111 (byte format)
Concept of a packet
• In networking, data must be formed in a
suitable ‘package’ to be able to be
transported across the network.
• The actual format of the package is
different for different types of network.
However the term ‘data packet’ is always
used to describe the package
Concept of a packet
• A data packet should minimally contain the
source and destination address, data and
error control.

Source          Destination
Data              Error Control

The source address is sent so the recipient knows who has sent the data.
The destination address is used to find the right recipient. Data is the ‘actual
message’. Error control is sent to help identify problems with the data once it
Asynchronous versus synchronous
transmission
• Asynchronous transmission means that
device 2 (the receiver) must acknowledge
receipt of the data before device 1 (the
sender) will send more.
• In synchronous transmission both devices
(sender and receiver) will synchronise with
each other before the data is sent.
Bandwidth
• This is generally defined as the quantity of data that can
be sent through data transmission over a specified
period of time.
• Bandwidth is usually quoted in (from slow to fast)
– Bits per second (bps)
– Kilo bits per second (kbps)
– Mega bits per second (mbps)
– Giga bits per second (gbps)

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