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On Fri, 30 Jan 2009, Dave Berkeley wrote: > That is very interesting. Good to hear from someone with real experience of > this. I suppose that the system comes into its own when there is no > alternative. Developing world countries often have sparse infrastructure. Indeed - and ever better, no regulation, so he who can pump out the most power wins... I worked for Orthogon (Now Motorola), for a while and their point to point kit was widely deployed in developing countries with very good results - 300Mb/sec over 10 miles? > note: the VoIP bandwidth depends very much on the codec used. But that is in > the hands of the user. Bandwidth isn't the issue, and ironically it can be worse with some of the more compressed codecs because the packet size may be smaller. (and they sometimes sound worse with packet loss) The real thing at issue is the number of packets per second and the full-duplex nature of VoIP vs. the half duplex nature of Wi-Fi. Using G711 it's 50 packets per second each way, and the data part of those packets is 160 bytes (do the sums: 50 * 160 = 8000 bytes per second or 64,000 bits per second both ways) So a Wi-Fi access point has to do a turn-around 50 times a second to keep up with a single VoIP channel. When I was working with the wi-fi networks, myself and the others did a lot of testing and benchmarking of Wi-Fi (and 5.8GHz) kit - now addmittedly, this was some 5 years back and using '802.11b' grade equipment, but what we found was that when the packet size got to below about 130 bytes, then the access points gave up because the link tun-around time was longer than the packet transmission time. Wi-Fi really is optimised to stream data, so big back to back 1500 byte packets in one direction and small ACK packets in the other. Mix just one file copy with VoIP and you'll find your average AP will struggle and VoIP quality will suffer. I have used VoIP over Wi-Fi - I have a purpose designed Wi-Fi VoIP phone (it's a Starcom and is rubbish - don't waste your money!) and my Nokia E90 supports it and I use it at home - occasionally, and I have a couple of friends who use it over their point to point links they're using to bridge buildings together (or in one case because he's a mile away from where ADSL would work in Wales) and it's fine when nothing else is usin the link, but as soon as something does, it's snap, crackle and pop time )-: Gordon -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html