From b571f63d985e8698d21939e02d579936e7f02478 Mon Sep 17 00:00:00 2001 From: Joe Taylor Date: Tue, 24 Sep 2024 09:59:14 -0400 Subject: [PATCH] Add the file describing bit packing for SuperFox message types. --- lib/superfox/superfox_qpc_2.txt | 65 +++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 lib/superfox/superfox_qpc_2.txt diff --git a/lib/superfox/superfox_qpc_2.txt b/lib/superfox/superfox_qpc_2.txt new file mode 100644 index 000000000..48a43b841 --- /dev/null +++ b/lib/superfox/superfox_qpc_2.txt @@ -0,0 +1,65 @@ + Bit packing of SuperFox QPC Messages +----------------------------------------------------------------------------- +The IV3NWV Q-ary Polar Code has parameters (n,k) = (127,50). The last +three 7-bit information symbols convey a 21-bit CRC based on the first +47 symbols. Thus, each Super Fox transmission carries a payload of +47*7=329 bits. On a modern x86 processor the decoder executes in +deterministic time around 5 ms per decode, and always produces a +result. The CRC test rejects all but around 1 in two million false +decodes. + +Bit fields are labeled with tags as defined in the QEX article "The +FT4 and FT8 Communication Protocols" by Franke, Somerville, and Taylor +in QEX for July/August 2020, available on the WSJT web site here: +https://wsjt.sourceforge.io/FT4_FT8_QEX.pdf. As one example, the tag +'c28' denotes a standard callsign, which requires 28 bits. + +============================================================================= +i3 = 0: Standard message: FoxCall, up to 9 HoundCalls, up to 4 signal +reports, "MoreCQs" flag, a digital signature, and a 3-bit message type. +----------------------------------------------------------------------------- + F H1 H2 H3 H4 H5 H6 H7 H8 H9 R6 R7 R8 R9 U Q D M Type +c28 c28 c28 c28 c28 c28 c28 c28 c28 c28 r5 r5 r5 r5 u5 q1 d20 i3=0 Std Msg + 280 300 305 326 329 +============================================================================= +i3 = 1: If Fox uses a compound callsign we have space for only 8 Hound calls. +Otherwise like type i3=0. +----------------------------------------------------------------------------- + FC H1 H2 H2 H4 H5 H6 H7 H8 R5 R6 R7 R8 U Q D M +c58 c28 c28 c28 c28 c28 c28 c28 c28 r5 r5 r5 r5 u3 q1 d20 i3=1 + 58 282 302 305 326 329 +============================================================================= +i3 = 2: A free text message with up to 26 characters can be transmitted along +with messages to as many as 4 Hounds conveying either reports or RR73s. +----------------------------------------------------------------------------- + F H1 H2 H3 H4 R1 R2 R3 R4 T T U Q D M Type +c28 c28 c28 c28 c28 r5 r5 r5 r5 t71 t71 u3 q1 d20 i3=2 FT+4H + 140 160 302 305 326 329 +============================================================================= +i3 = 3: Message "CQ FoxCall Grid " +----------------------------------------------------------------------------- + FC G T T U Q D M Type +c58 g15 t71 t71 u90 q1 d20 i3=3 CQ FT + 58 73 144 215 305 326 329 +============================================================================= + +D Digital signature (20 bits) +F Fox call (28 bits) +FC Compound Fox call (58 bits) +G Grid locator (15 bits) +H Hound call (28 bits) +M Message type (3 bits) +Q MoreCQs flag +R Report, (5 bits: -18 to +12 dB, or RR73) +T Free text, up to 26 characters total +U Unused bits + +Unused callsign slots are set to 2, the numerical value for CQ. +Unused report slots are set to 0 (-20 dB). "CQ FoxCall" will be +displayed along with other messages if the "q1" bit is 1. + +The SuperFox decoder displays its results with a separate line for each Hound. +Thus, the old-style message "K1ABC RR73; W9XYZ -14" becomes + +K1ABC VP8PJ RR73 +W9XYZ VP8PJ -14