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| Re: Canarsie CBTC (98173) | |||
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Re: Canarsie CBTC |
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Posted by Stephen Bauman on Mon Jun 13 14:37:48 2005, in response to Re: Canarsie CBTC, posted by RonInBayside on Mon Jun 13 12:10:40 2005. Other posts have mentioned that Siemen's scheme for NYC has features like frequency-hopping, which would reduce the potential for interference. This would imply that at least one aspect of Siemen's approach is superior to other schemes. This would tend to contradict your conclusion.5. IEEE 802.11 Layers The IEEE 802.11 standard places specifications on the parameters of both the physical (PHY) and medium access control (MAC) layers of the network. The PHY layer, which actually handles the transmission of data between nodes, can use either direct sequence spread spectrum, frequency-hopping spread spectrum, or infrared (IR) pulse position modulation.... All the 802.11 CBTC implementations, in use or under construction, are using FHSS (frequency-hopping spread spectrum) and not the more common DSSS (direct sequence spread spectrum) flavor. The DSSS flavor is used for most wi-fi networks and is probably why the CBTC receivers/transmiters are $100 and not $10. So, a Palm Pilot cannot be programmed to hold the doors for you on the platform. |
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