OT correction/elucidation to the prior post:
To be more specific, the figure of merit is the average throughput (kilobits/sec, e.g.) experienced by each user within the coverage area. The issue when comparing different systems is the distinction between quoted 'burst rates' and the actual amount of time needed to transmit the number of bits required to represent a web page, for instance. I mentioned two factors which scale the throughput, and in my haste to express in the vernacular, misspoke slightly (and you all know my penchant for precision <ggg>). The greater the bandwidth, the greater the throughput. The greater the *fraction of time* (not time itself) that that bandwidth is available to a given user, the greater the throughput for that user.
The key distinction between HDR/3G and Ricochet is the cellular vs microcellular coverage. Cellular typically has 1 to 1.25 mile radius cells, and Ricochet's 'microcellular' approach has about a 1/4 mile radius (4-6 transmitters per square mile). So imagine covering an area with a larger number of smaller cells. All non-adjacent cells can use the same modulation patterns, etc. without interference. What this means is that for a given amount of spectrum available to the system (MCOM's Ricochet, in this case), more users can be actively receiving 128k downloads continuously over a specific coverage area. (And, there are no 'per minute' charges, and the bandwidth is not being 'stolen' from voice channels/users.)
FWIW, MCOM uses frequency-hopped spread spectrum. This also has better interference rejection for the types of expected interference. Their systems have been operated in the field for 15 years, and this rollout commences an upgrade to a higher data rate. The data rate is to be software upgradeable for the users at a later time. (Trying to get more specifics, still.)
Try this post for Metricom's technology overview:
metricom.com
and this one
Message 14115069
then try this post:http://www.siliconinvestor.com/readmsg.aspx?msgid=14094237
and this one too:
Message 14098507
and an accurate, discursive whitepaper comparing 3G to Ricochet:
geocities.com
Enjoy!~ |
