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Technology Stocks : LAST MILE TECHNOLOGIES - Let's Discuss Them Here -- Ignore unavailable to you. Want to Upgrade?

To: ahhaha who wrote (3272)	3/31/1999 12:05:00 AM
From: ftth	Read Replies (1) \| Respond to of 12823

If anyone happens across more details of this Clearwire system, please post them. This system apparently uses the 1-watt x-mit 2400-2483.5MHz portion of the unlicensed ISM band and DSSS (direct sequence spread spectrum) with some proprietary protocol. Some potential issues would be: Not much usable bandwidth per cell (being spread spectrum by FCC mandate) or in the allocated spectrum for that matter (83.5 MHz). Maybe 1Mbps each way. There are POTENTIAL interference issues: both direct from the already crowded ISM band and IEEE802.11 wireless LANs(which is a good model for channel capacity), as well as microwave ovens [which have been known to interfere with ISM band equipment using the 2.4G portion of the band]) and indirect from the LO of the downconversion. Example of indirect:PCS (can) interfere(s) with MMDS (in the 2500-2700MHz band) because the LO at 2278 MHZ is about the same distance below the MMDS block as it is above the PCS block. It can literally squash the MMDS signals according to some accounts (but I believe these are analog systems (no FEC)). When you speak of Ka band I think you mean LMDS. LMDS (although it has its issues also) supports full reuse of all spectrum at every cell. Don't know the numbers for this system, or how it's partitioned, but for comparison 800 MHz cellular mobile service can reuse only 10-15% of the spectrum at each cell. Just some top of the head thoughts--don't know that any of these are serious issues. I like the idea and will be interested to see how it turns out in heavy-use deployment dh