Types of Error

Types of Errors o    Whenever   an   EM   signal   flows   from   one   point   to   the   other,   it   is   subject   to unpredictable interference from heat, magnetism and other forms of electricity o    This interference can change the shape or timing of the signal o    If  the  signal  is  carrying  encoded  binary  data,  such  changes  can  alter  the  meaning  of the data Types of Errors ™   Single Bit & Burst o    In a burst error multiple bits are changed o    For  Example,  a  0.01  second  burst  of  impulse  noise  on  a  TX  with  a  data  rate  of 1200 bps might change all or some of 12 bits of information o    In a single-bit error, a 0 is changed to a 1 or a 1 to a 0

o    The  term single  bit  error  means  that  only one  bit  of  a  given  data  unit  (such  as  a byte, character, or a packet) is changed from 1 to 0 or from 0 to 1 o    Figure shows the effect of a single bit error on a data unit o    ASCII  character  000000010  (ASCII  STX)  is  sent  but  00001010  (ASCII  LF)  is received o    Single bit errors are the least likely type of error in serial data TX o    To see Why? Imagine a sender sends data at 1Mbps o    This means that each bit lasts only 1/1,000,000 seconds or 1 microsecond o    For  single  bit  error  to  occur,  the  noise  must  have  a  duration  of  1  microsecond which is very rare, noise lasts much longer than that o    However, single bit error can occur if we are sending data using parallel TX o    For Example, if 8 wires are used to send all of the eight bits of a byte at the same time and one of the wires is noise, one bit can be corrupted in each byte