[NCLUG] Data Through Cellular Technology?

[John L. Bass]

	Actually, Verizon's 3G CDMA network is at 800MHz.  So it has an 
	advantage over the 1900MHz SprintPCS CDMA system.

In the local market that is true - they are deployed at 1.9Ghz in other
markets. Likewise, they did not deploy CDPD in the Colorado market, just
AT&T at this time.

	> Additionally, 800mhz CPDP has much less problems with phase noise
	> caused by multipath - the higher data rate 1.9Ghz systems are much
	> more sensitive to multipath (as are 802.11 systems).

	CDMA systems /depend/ on multipath.  Their rake receivers listen to 
	multiple tower and multiple paths at the same time, making the signal 
	/more/ reliable instead of less.

	http://denbeste.nu/cdmafaq/index.shtml

That's as much hype as fact. The rake filters only handle long multipath as found
off mountains and far away buildings - multipath that is over about 1,000ft. In
building and local area multipath still is a serious problem that the rake filter
can not deal with. Local multipath generally has much higher signal levels since you
are closer to the reflector and there is less attenuation as a function of distance
from the reflector.

Humans tend to compensate better, by moving the phone inside the standing wave
patterns until the multipath is well phased and additive. Datacomm applications
typically suffer worse, because of less feedback and fewer degrees of freedom in
locating the laptop.

John