NRZ/NRZI

["Woolner, John" <JohnWoolne@auslig.gov.au>]

Greetings Apostolos,

Quoting from a old paper I have here on PCM modulation schemes.


     NRZ-C     Non-return-to-zero-change
   also   NRZ-L           "      level
   also NRZ (ambiguous)

A ONE bit is represented by one signal level, a ZERO bit is
represented by a different signal level.


     NRZ-M     Non-return-to-zero-mark
   also   NRZ-I   Non-return-to-zero-index (NOT INVERT!)

A ONE bit is represented by a change in signal level, a ZERO bit is
represented by no change in signal level.

     NRZ-S     Non-return-to-zero-space

A ONE bit is represented by no change in signal level, a ZERO bit is
represented by a change in signal level.

All three modulation schemes exhibit the same bandwidth
characteristics DC to half the bit rate.  However NRZ-C requires you
to know which signal level represents a ONE and which signal level
represents a ZERO.  With NRZ-M and NRZ-S it is only necessary to know
that a ONE is represented by a change (or vice-versa).

Regards


 ----------------------------------------------------------------------------
John Woolner                          Email: JohnWoolner@auslig.gov.au
vk1zaao    PG44ms                    Packet:  vk1zao@vk1bbs.act.aus.oc
Canberra, ACT, Australia              Amprnet:    vk1zao@vk1zao.ampr.org
Phone +61-6-254-3140 (h)       Snail:   PO Box 118
Phone +61-6-201-4122 (w)           Kippax  2615
                              AUSTRALIA
 ----------------------------------------------------------------------------