Principles of Signal Theory

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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
And adding the numbers up.

= 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
    Address          Address


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
has been received.
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)