Yeah I did read that from the site. In ways sounds a lot like Amtor and Pactor.
At 07:38 PM 2/18/06, you wrote: How does PSK-arq work in theory? >PSK63 is a BPSK mode with twice the speed, and twice the ><http://pskmail.wikispaces.com/bandwidth>bandwidth of PSK31. To cater for >the 3 dB loss with respect to PSK31, PSK63 needs double the power to >realise the same S/R ratio. >Like PSK31, PSK63 uses a varicode scheme with symbols of 3 bits (space) to >10 bits (the DEL character). In average, in normal english upper/lowercase >text there is 6.5 bits per character, which is a lot better than ASCII >(8N1, 10 bits), and even better than (upper case only) Baudot with 8 bits. > >PSKmail puts protocol overhead on top of PSK63. Depending on block size, >protocol overhead is 100% (8-character blocks with 8 extra bytes), down to >12% (64-character blocks with 8 extra bytes). By the way, the max. >throughput of 6.3 cps was measured at 64-character blocks). As a frame >normally contains 8 blocks, turnaround loss is much less important then >the number of repeats. > >PSK_arq cuts the text into blocks of 8 64 characters, depending on band >conditions. Small blocks when there is a lot of QRM or QRN, large blocks >when the signal is steady and the channel is clear. > >The blocks are numbered and they all get a sequence number from 0 to 63. >They also get a <http://www.eagleairaust.com.au/code/crc16.htm>CRC16 >number so the receiver can see if the block has been received ok. > >The transmitter sends 8 blocks in a frame. The receiver checks every block >against its CRC checksum and tells the transmitter with a short status >block which text blocks were damaged. These will be prepended to the next >frame, so the receiver gets another chance. > >This goes on until the text has been received 100%. This is better than >FEC. With FEC everything is send 2x, with PSK_arq only the parts that are >damaged have to be repeated.... > >The protocol was proposed by Paul Schmidt, K9PS. It is documented in ><http://sharon.esrac.ele.tue.nl/pub/linux/ham/pskmail/ARQ2.pdf>http://sharon.esrac.ele.tue.nl/pub/linux/ham/pskmail/ARQ2.pdf > > > >Because of the adaptive frame lenght used (typically 8 blocks of 32 >characters), PSK_arq seems uninteresting for keyboard-to-keyboard >operation, but on-air tests show that PSK31 speed can be easily reached >with reasonable channel quality. And of course at 0% error!! Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
