OFDM, COFDM: CIS-128

CIS-128

Br~21, Sh~23.5, Ch-128 in use, total 129 - 1 as gap/off/skiped

OFDM, COFDM

An example of CIS-128 signal is here

Author: SergUA6

Band Width ~3000-3100 Hz

Low Range 470-500 Hz

Baud Rate ~21 Hz

n-Ary (PSK/MPSK) Mixed mode QAM-16 and PSK

Count of Carriers 129 - 1

Step between carriers ~23.5 Hz

ACF ~476-477 ms

RX mode SSB

Sonograms:

pic.1 General view

pic.2 Clock frequency of manipulation (classical method of recieveing)

Diagrams:

pic.3 The signal's detalization in OFDM module

pic.4 Detalization of the signal if OFDM module

pic.5 Detalization of the signal if OFDM module

Pictures:

pic.6 ACF of the signal

pic.7 CCF of two adjacent fragments with duration 250 ms

CIS-128 - is an interesting enough signal, though quality of the record is not so high. Nevertheless, rather easily it is possible to receive all main parameters in module OFDM. It is shown on the pictures.

It is very interesting that there is divergence ACF with a real state of affairs. ACF shows that there is a periodicity in 10 symbols in the signal. The detailed analysis in module OFDM allows to find out that every fifth symbol is specia l(synchro), and it is logical to expect, that ACF will be with the same period, but it is not so. This moment is easily specified with usage of CCF function. As it is shown on rice 7.

It is well visible that every fifth symbol special (synchro), but special (synchro) symbols different, and alternate through one. It also shows ACF as in this case the repetition period is really equal to 10 symbols.

CCF allows to receive more fine and exact structure, where it is displayed both the general period of special (synchro) symbols, which is equal 5 symbols (steps), and the period of separately even and odd symbols, which is equal already to 10 steps.

One more feature of this record which is well visible in dynamics - is the intensive use of modulation QAM-16 in the first half of the signal, and episodical/rare in the second part of the signal.