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Technology Stocks : Wi-LAN Inc. (T.WIN) -- Ignore unavailable to you. Want to Upgrade?

To: P2V who wrote (573)	9/10/1999 4:58:00 AM
From: axial	Read Replies (1) \| Respond to of 16863

Mardy - Won't have time to research CSMA/CD tonight; if it's the same tech that I've read about, it works by assigning timing intervals to different devices. Will have to read more, because it seems to me that we're running into such a proliferation of standards (WAP, Bluetooth,WECA, etc.) that it's going to be a transmission/reception jungle out there. The interesting thing about Wi-LAN is that it's fairly easy to make projections based on their existing contracts with Telia and Tele2 UK, that should have them bringing in about 75-100 million over the next 2 years (my projections). Everything I've read indicates that this projection is fairly safe. It's the market beyond that's fuzzy; some of that fuzzy vision derives from my own lack of knowledge about what a buyer of Wi-LAN's technology wants to see. But a good part of it comes from wireless technology itself - there are so many emerging technologies, companies, standards, alliances etc., and it's changing extremely quickly. I'll do some research on the weekend, maybe we can scare up a sensible answer to your question. An interesting link for the meantime, data.com

To: P2V who wrote (573)	9/10/1999 12:03:00 PM
From: Artifex	Read Replies (1) \| Respond to of 16863

CSMA/CD is an acronym for Carrier Sense Multiple Access/Collision Detection, and it is in fact a means of avoiding collisions on a LAN, but its operation is a bit more complicated. The first point of complication is "Carrier Sense". Strictly speaking, this isn't as simple as "listening before talking", but is rather a detection of another station's intelligence already occupying the communications channel. For a wired network such as Ethernet, the distinction is not terribly important, but in a heterogeneous wireless environment, it could be. Stations using different modulation schemes are unable to demodulate each others' carriers, and so each could assume that the channel is clear, when in fact they are interfering with each other. Even stations with the same modulation at the fringe of each others' reception range may interfere fatally with each others' communication with other stations. Most wireless systems use some form of a channel assessment algorithm based on a number of factors, usually including carrier detection and received RF level. A station typically will not transmit if its receiver detects a high RF level, whether or not it can demodulate the signal. The second part of the complication is Collision Detection. On an Ethernet, each station listens to the channel as it transmits, and if it detects another stations signal at the same time as its own, both stations signal a collision and stop transmitting, allowing the medium to recover more quickly from a collision. RF systems aren't able to listen to the transmit channel at the same time as they are transmitting, and are therefore unable to detect collisions with other stations. Section 9 of 802.11 specifies extensive collision avoidance mechanisms also designed to avoid the "hidden station" and "exposed station" problems associated with simple "listen before talk" protocols. As a last aside, 802.11a is a proposal to extend 802.11 for higher-speed operation in the 5GHz ISM band by adding OFDM operation to the PHY, and 802.11b is a similar proposal for the 2.4GHz band.