I think you're on to something here.
One quick thought that occurs to me is that for some of the gain, I see no reason forward error correction couldn't be used within the IP payload, at least for a few dB of gain (has this been tried?) Of course, the FEC probably won't help the header information very much, but doesn't IP broadcast use a small set of broadcast IP addresses? Thus, it might be possible for payload-based FEC to know a-priori what will be in the header and basically correct for it. Then there's simply the matter of the reduced bandwidth due to the FEC, but it might be possible for that to look just like good old Ethernet shared-bandwidth-based conjestion (but I'm no IP guy so I could be talkin' out my arse here).
-TD
From: Steve Schear <[EMAIL PROTECTED]>
To: "Tyler Durden" <[EMAIL PROTECTED]>
CC: [EMAIL PROTECTED]
Subject: Re: Idea: Sidestepping low-power broadcast regulations with infrared
Date: Mon, 17 Mar 2003 14:45:15 -0800
Another possibility occurred to me. It might be possible to use the 802.11-like devices for this purpose. The problem for this application with Wi-Fi is its focus on high data rate and therefore low process gain. But there is no inherent reason why almost the same circuits (perhaps even the off-the-shelf PC cards themselves) couldn't be re-purposed for used at lower effective data rates and higher process gain for much greater range and interference immunity while still operating within the FCC Part 15 guidelines.
As I recall most of the notebook cards have a max output of about 80 mW. Each of the 5 channels in the 2.4 GHz band can support up to 11 mbps. If you assume that you will use this for stereo broadcasting then only 128 kbps offers a pretty good quality .mp3 This is a data rate ratio of 85 :1 or about 18 dB. For every 6 dB of link margin improvement a signal's range is doubled. 18 dB should, all other things being equivalent, extend the device range by 8 times. (If data rates were lowered to those now common for PCS and used for that sort of purpose, link margins would expand by another 9-12 dB.)
steve
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