The Amateur Radio Relay League (ARRL) is requesting comments on HF radio digital protocol. See http://www.arrl.org/news/stories/2007/02/22/102/?nc=1. A major component is going to be DSP so this DSP group is a good place for discussion. I know just enough about RF communications and DSP to be very dangerous so I personally see this as a learning opportunity. I have a paper from Agilent (referenced at http://www.k5rud.us/over50/wiki/index.php/Modulation%20Techniques) that discusses the basics of modulation, although it does not go into OFDM. A table on page 17 leaves me bewildered. As I (mis?)understand it the theoretical limits on bit rate FSK/BPSK start at 1 bps/Hz and increase for more complex modulation techniques, e.g. 8PSK, nQAM. Practical results, page 18, are somewhat less (pi/4 DQPSK at 1.6 bps) but still respectable. The only commercially available HF modem I am familiar with, I am sure there are others, uses a protocol called Pactor III. It uses the 3k Hz bandwidth to achieve some 3k bps with a lot of "black magic" under good conditions. Once the SNR gets bad the rate slows. [Personally I do not think they are taking advantage of good FEC.] Why are better results not obtained? Given a blank white board, where would you start? -- Rud K5RUD ARES AEC Montgomery County, TX http://over50.k5rud.us/wiki/ ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =----
RFC on HF Protocol
Started by ●February 23, 2007
Reply by ●February 23, 20072007-02-23
Rud Merriam wrote:> The Amateur Radio Relay League (ARRL) is requesting comments on HF radio > digital protocol. See http://www.arrl.org/news/stories/2007/02/22/102/?nc=1. > > A major component is going to be DSP so this DSP group is a good place for > discussion. I know just enough about RF communications and DSP to be very > dangerous so I personally see this as a learning opportunity. > > I have a paper from Agilent (referenced at > http://www.k5rud.us/over50/wiki/index.php/Modulation%20Techniques) that > discusses the basics of modulation, although it does not go into OFDM. A > table on page 17 leaves me bewildered. As I (mis?)understand it the > theoretical limits on bit rate FSK/BPSK start at 1 bps/Hz and increase for > more complex modulation techniques, e.g. 8PSK, nQAM. Practical results, page > 18, are somewhat less (pi/4 DQPSK at 1.6 bps) but still respectable.In what way does this confuse you? The basic truth is that the theoretical limit is one symbol / second /Hz, and reality doesn't live up to theory. So a simple scheme that gives one bit per symbol will have low spectral efficiency, and a scheme that gives many bits per symbol will have high spectral efficiency.> > The only commercially available HF modem I am familiar with, I am sure there > are others, uses a protocol called Pactor III. It uses the 3k Hz bandwidth > to achieve some 3k bps with a lot of "black magic" under good conditions. > Once the SNR gets bad the rate slows. [Personally I do not think they are > taking advantage of good FEC.] Why are better results not obtained?I don't know, because I haven't followed the digital modes for HF. HF throws some curve balls that you don't get with microwave transmission, and amateur radio modes are spotty, ranging from the stupidly simple to the sublime, depending on who was motivated to do the work at the time. Attaining one (corrected) bps/Hz in real-world conditions isn't too bad, all things considered.> > Given a blank white board, where would you start? >By looking for a dry erase marker that actually marks :-). I'm not sure just exactly what you need to know -- the basics of modulation theory, why HF is a difficult medium, what modulation modes work well at HF (or higher), why dry erase markers are always dry -- what? -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ "Applied Control Theory for Embedded Systems" came out in April. See details at http://www.wescottdesign.com/actfes/actfes.html
Reply by ●February 23, 20072007-02-23
Hi Tim, Yes, HF radio is nasty stuff in many ways. Actually, I was just hoping to get a discussion going on how to best approach the problem given the SOTA. What are good answers for the RFC questions? Also, I know why dry markers are always dry. For some reason people never throw them out. When I find one I dispose of it. Most people put it back in the tray. -- Rud K5RUD ARES AEC Montgomery County, TX http://over50.k5rud.us/wiki/ "Tim Wescott" <tim@seemywebsite.com> wrote in message news:9Iudnfc3hIEj4ELYnZ2dnUVZ_ternZ2d@web-ster.com...> Rud Merriam wrote: >> The Amateur Radio Relay League (ARRL) is requesting comments on HF radio >> digital protocol. See >> http://www.arrl.org/news/stories/2007/02/22/102/?nc=1. >> >> A major component is going to be DSP so this DSP group is a good place >> for discussion. I know just enough about RF communications and DSP to be >> very dangerous so I personally see this as a learning opportunity. >> >> I have a paper from Agilent (referenced at >> http://www.k5rud.us/over50/wiki/index.php/Modulation%20Techniques) that >> discusses the basics of modulation, although it does not go into OFDM. A >> table on page 17 leaves me bewildered. As I (mis?)understand it the >> theoretical limits on bit rate FSK/BPSK start at 1 bps/Hz and increase >> for more complex modulation techniques, e.g. 8PSK, nQAM. Practical >> results, page 18, are somewhat less (pi/4 DQPSK at 1.6 bps) but still >> respectable. > > In what way does this confuse you? The basic truth is that the > theoretical limit is one symbol / second /Hz, and reality doesn't live up > to theory. So a simple scheme that gives one bit per symbol will have low > spectral efficiency, and a scheme that gives many bits per symbol will > have high spectral efficiency. >> >> The only commercially available HF modem I am familiar with, I am sure >> there are others, uses a protocol called Pactor III. It uses the 3k Hz >> bandwidth to achieve some 3k bps with a lot of "black magic" under good >> conditions. Once the SNR gets bad the rate slows. [Personally I do not >> think they are taking advantage of good FEC.] Why are better results not >> obtained? > > I don't know, because I haven't followed the digital modes for HF. HF > throws some curve balls that you don't get with microwave transmission, > and amateur radio modes are spotty, ranging from the stupidly simple to > the sublime, depending on who was motivated to do the work at the time. > > Attaining one (corrected) bps/Hz in real-world conditions isn't too bad, > all things considered. >> >> Given a blank white board, where would you start? >> > By looking for a dry erase marker that actually marks :-). > > I'm not sure just exactly what you need to know -- the basics of > modulation theory, why HF is a difficult medium, what modulation modes > work well at HF (or higher), why dry erase markers are always dry -- what? > > -- > > Tim Wescott > Wescott Design Services > http://www.wescottdesign.com > > Posting from Google? See http://cfaj.freeshell.org/google/ > > "Applied Control Theory for Embedded Systems" came out in April. > See details at http://www.wescottdesign.com/actfes/actfes.html >----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =----
Reply by ●February 24, 20072007-02-24
Rud Merriam wrote:> The Amateur Radio Relay League (ARRL) is requesting comments on HF radio > digital protocol. See http://www.arrl.org/news/stories/2007/02/22/102/?nc=1. >[...]> Given a blank white board, where would you start? >The first question to answer is what is this protocol intended for. I.e. what is the concept of the communication system. All other stuff is the minor technical details. Those details depend on the answer to the first question. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Reply by ●February 24, 20072007-02-24
Vladimir Vassilevsky wrote:> > > Rud Merriam wrote: >> The Amateur Radio Relay League (ARRL) is requesting comments on HF >> radio digital protocol. See >> http://www.arrl.org/news/stories/2007/02/22/102/?nc=1. >> > > [...] > > >> Given a blank white board, where would you start? >> > > The first question to answer is what is this protocol intended for. I.e. > what is the concept of the communication system. > > All other stuff is the minor technical details. Those details depend on > the answer to the first question.I think a sufficient answer to that question is (with a little added imagination) given in the first sentence at the URL provided: "The ARRL is seeking comments from amateurs concerning development of an open-source (non-proprietary) data communications protocol suitable for use by radio amateurs over high-frequency (HF) fading paths." Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by ●February 24, 20072007-02-24
Jerry Avins wrote:>>> The Amateur Radio Relay League (ARRL) is requesting comments on HF >>> radio digital protocol. See >>> Given a blank white board, where would you start? >>> >> >> The first question to answer is what is this protocol intended for. >> I.e. what is the concept of the communication system. >> All other stuff is the minor technical details. Those details depend >> on the answer to the first question. > > > I think a sufficient answer to that question is (with a little added > imagination) given in the first sentence at the URL provided: > > "The ARRL is seeking comments from amateurs concerning development of an > open-source (non-proprietary) data communications protocol suitable for > use by radio amateurs over high-frequency (HF) fading paths."This is a meaningless sentence. The 2..3 receivers with diversity antennas is all that you may need. VLV
Reply by ●February 24, 20072007-02-24
On Feb 24, 12:26 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com> wrote:> Jerry Avins wrote: > >>> The Amateur Radio Relay League (ARRL) is requesting comments on HF > >>> radio digital protocol. See > >>> Given a blank white board, where would you start? > > >> The first question to answer is what is this protocol intended for. > >> I.e. what is the concept of the communication system. > >> All other stuff is the minor technical details. Those details depend > >> on the answer to the first question. > > > I think a sufficient answer to that question is (with a little added > > imagination) given in the first sentence at the URL provided: > > > "The ARRL is seeking comments from amateurs concerning development of an > > open-source (non-proprietary) data communications protocol suitable for > > use by radio amateurs over high-frequency (HF) fading paths." > > This is a meaningless sentence. > The 2..3 receivers with diversity antennas is all that you may need. > > VLVThat proposal triples the cost. We're talking about hams, not military or corporate people. John
Reply by ●February 24, 20072007-02-24
Yup. Ham == cheap <g> -- Rud K5RUD ARES AEC Montgomery County, TX http://over50.k5rud.us/wiki/ <sampson164@gmail.com> wrote in message news:1172355503.951641.6830@p10g2000cwp.googlegroups.com...> On Feb 24, 12:26 pm, Vladimir Vassilevsky <antispam_bo...@hotmail.com> > wrote: >> Jerry Avins wrote: >> >>> The Amateur Radio Relay League (ARRL) is requesting comments on HF >> >>> radio digital protocol. See >> >>> Given a blank white board, where would you start? >> >> >> The first question to answer is what is this protocol intended for. >> >> I.e. what is the concept of the communication system. >> >> All other stuff is the minor technical details. Those details depend >> >> on the answer to the first question. >> >> > I think a sufficient answer to that question is (with a little added >> > imagination) given in the first sentence at the URL provided: >> >> > "The ARRL is seeking comments from amateurs concerning development of >> > an >> > open-source (non-proprietary) data communications protocol suitable for >> > use by radio amateurs over high-frequency (HF) fading paths." >> >> This is a meaningless sentence. >> The 2..3 receivers with diversity antennas is all that you may need. >> >> VLV > > > That proposal triples the cost. We're talking about hams, not military > or corporate people. > > John > >----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =----
Reply by ●February 25, 20072007-02-25
Vladimir Vassilevsky wrote:> > > Jerry Avins wrote: > > >>>> The Amateur Radio Relay League (ARRL) is requesting comments on HF >>>> radio digital protocol. See Given a blank white board, where would >>>> you start? >>>> >>> >>> The first question to answer is what is this protocol intended for. >>> I.e. what is the concept of the communication system. >>> All other stuff is the minor technical details. Those details depend >>> on the answer to the first question. >> >> >> >> I think a sufficient answer to that question is (with a little added >> imagination) given in the first sentence at the URL provided: >> >> "The ARRL is seeking comments from amateurs concerning development of >> an open-source (non-proprietary) data communications protocol suitable >> for use by radio amateurs over high-frequency (HF) fading paths." > > > This is a meaningless sentence. > The 2..3 receivers with diversity antennas is all that you may need. > > VLV > >If you can't take vague requirements and expand them into something useful without pissing people off, how do you stay in business? As it stands the sentence is quite meaningful, if you think about it. It means that you have to understand the population you're proposing to design for, and do what they want and expect. This means that you need a box that will connect to a transceiver that's connected to an antenna, and have the system work well. You can put some requirements on turn-around time, but probably nothing tighter than AMTOR. You must have a system that will go into a box that costs less than $500, and preferably less than $200 -- remember that the average radio amateur will spend a man day to save $1, and be proud of it. Something that would just plug into a sound card would be better yet, from this perspective. The system has to be plug and play for the folks who passed their tests by memorizing all possible answers to the questions, yet should also provide enough flexibility that experts can get significantly better performance. It also has to comply with all applicable FCC regulations, some of which are quite sensible and some of which are absurd. If the system were robust to having someone naively (or maliciously) transmit a carrier smack in the middle of the signal that would be good, but not essential. There's more, but you should be getting the idea. I suspect that if you really wanted to make a project out of this you'd need to take that "data sheet" definition from the ARRL and turn it into a number of criteria such as I've outlined, agree on them, the work on turning _those_ into numbers, if they're not obvious as they stand. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ "Applied Control Theory for Embedded Systems" came out in April. See details at http://www.wescottdesign.com/actfes/actfes.html
Reply by ●February 25, 20072007-02-25
