MIT16_36s09_lec15

MIT16_36s09_lec15 - MIT OpenCourseWare http/ocw.mit.edu...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
MIT OpenCourseWare http://ocw.mit.edu 16.36 Communication Systems Engineering Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
16.36: Communication Systems Engineering Lecture 15: Cyclic Codes and error detection Eytan Modiano
Background image of page 2
Cyclic Codes A cyclic code is a linear block code where if c is a codeword, so are all cyclic shifts of c E.g., {000,110,101,011} is a cyclic code Cyclic codes can be dealt with in the very same way as all other LBC s Generator and parity check matrix can be found A cyclic code can be completely described by a generator string G All codewords are multiples of the generator string In practice, cyclic codes are often used for error detection (CRC) Used for packet networks When an error is detected by the received, it requests retransmission
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Error detection techniques Used by the receiver to determine if a packet contains errors If a packet is found to contain errors the receiver requests the transmitter to re-send the packet Error detection techniques Parity check E.g., single bit Cyclic redundancy check (CRC)
Background image of page 4
Parity check codes k Data bits r Check bits Each parity check is a modulo 2 sum of some of the data bits Example: c 1 = x 1 + x 2 + x 3 c 2 = x 2 + x 3 + x 4 c 3 = x 1 + x 2 + x 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 15

MIT16_36s09_lec15 - MIT OpenCourseWare http/ocw.mit.edu...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online