From d579f553ca21c91769536435f3a772b2562fcfb3 Mon Sep 17 00:00:00 2001 From: drowe67 Date: Sun, 8 Apr 2018 02:17:07 +0000 Subject: [PATCH] updated specs git-svn-id: https://svn.code.sf.net/p/freetel/code@3452 01035d8c-6547-0410-b346-abe4f91aad63 --- codec2-dev/README_ofdm.txt | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/codec2-dev/README_ofdm.txt b/codec2-dev/README_ofdm.txt index e93079dc..1ae335a6 100644 --- a/codec2-dev/README_ofdm.txt +++ b/codec2-dev/README_ofdm.txt @@ -95,14 +95,22 @@ Text bits/s...: 25 Unique Word...: 10 bits Carriers......: 17 Symbol period.: 18ms -Cyclic Prefix.: 2ms +Cyclic Prefix.: 2ms (note 1) Pilot rate....: 1 in every 8 symbols Frame Period..: 160ms FEC...........: rate 1/2 (224,112) LDPC Operating point - AWGN........: Eb/No -0.5dB SNR(3000Hz): -2.5dB - HF Multipath: Eb/No 4.0dB SNR(3000Hz): 2.0dB -Frequency offset for acquisition: +/- 20 Hz + AWGN........: Eb/No -0.5dB SNR(3000Hz): -2.5dB (note 2) + HF Multipath: Eb/No 4.0dB SNR(3000Hz): 2.0dB (note 3) + +Freq offset.......: +/- 20 Hz (sync range) +Freq drift........: +/- 0.2 Hz/s (for 0.5 dB loss) +Sample clock error: 1000 ppm Notes: - 1/ HF Multipath is two path, 1Hz Doppler, 1ms delay + 1/ Modem can cope with 2ms of multipath + 2/ Ideal SNR(3000) = Eb/No + 10*log10(Rb/B) + = -1 + 10*log10(1400/3000) + = -4.3 dB, + So we have about 2dB overhead for synchronisation and implementation loss. + 3/ HF Multipath channel used for testing is two path, 1Hz Doppler, 1ms delay -- 2.25.1