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To: apochromat
I think FH is a CD

Nope, not quite.

The key is this: Look at the IF filter bandwidth.

A DSSS (direct sequence spread spectrum) system (which CDMA is) literally occupies a bandwwidth as wide as the 'chipping' code - as wide as 1.2 MHz or so for CDMA as used in cellular systems ...

Whereas a FH system has *only* has an IF BW as wide as the data or modulation rate expected ... and the LO is 'frequency hopped' to keep track of the transmitted 'hopped' data ...

There are other differences too, such as a FH system *still* requires a S/N ratio of some 10 to 15 dB or more whereas a CDMA system can have Eb/No (Energy per bit to noise ratio) of just over one ... equivalently a unity S/N ratio ...

All non-coherent 'codes' during recovery (mixing with the original chipping code again, a demodulation process if you will) still results in noise whereas the *desired* signal, when the recovered bit stream is low-pass filtered, will result in the original bit stream ...

61 posted on 10/07/2002 10:42:11 PM PDT by _Jim
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From the FCC's 7th report to congress:
Two-way SMS was introduced in the United States in May 2000 when VoiceStream began to offer the service.458

As of year-end 2001, the six nationwide mobile telephone carriers, as well as handheld providers and some smaller mobile telephone carriers, were offering SMS.459

At the end of 2001, AT&T Wireless became the first carrier to offer cross-carrier network SMS capabilities.460

A short time later, most of the nationwide carriers announced similar plans.461 Mobile telephone carriers that offer crosscarrier SMS have reported increased traffic since implementing this capability on their networks.

AT&T Wireless stated that it has experienced 29 percent SMS growth from November 2001 through the end of March 2002, while Verizon has reported SMS traffic up to 4 million messages per day.

This isn't *quite* correct -

- I know for a fact that it has been possible to send messages between various phones, PDAs and 2-way wireless pagers for sometime now - IF they had internet e-mail addressability through their various carriers ... we were doing 2-way e-mail messaging via Skytel's 2-way pagers in '98!

71 posted on 10/07/2002 11:05:14 PM PDT by _Jim
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