What's New In 5G [telecom]

I heard the old cell phones ("3G") will no longer work effective January 1st.

Would anyone know how to identify if an old phone is 3G?

Would anyone know if they in fact will be no longer usable, and if so, are carriers doing anything about it (like offering a free decent upgrade)?

Thanks!

***** Moderator's Note *****

I hope not: I got my phone as a gift from my sister-in-law, who upgraded. I /think/ it's "4G," but up here in the North Carolina hills we're lucky to get 0G!

Bill Horne Moderator

It depends on the phone. Usually you can look up the model number and find out what sort of radio module it has in it -- anything that doesn't support "LTE" is toast. That includes all "CDMA" technologies (LTE is also Code-Division Multiple-Access but isn't "CDMA" brand CDMA) and all "classic GSM". (The carriers that supported IS-135 "TDMA" sunsetted it in favor of GSM when they rolled out "3G", so there is no longer any IS-135 service anywhere.)

It's a bit sad for many time geeks like me; IS-95/IS-2000 CDMA has a nice feature that it transmits a GPS-synchronized timecode (accurate to within a few microseconds), which could be used to derive a network timing standard without needing a rooftop antenna (or a subscription); when CDMA sunsets, those of us who have CDMA timecode receivers will lose our precision timing source. (I have a work-owned GPS receiver at home, but because of ISP delays it can't provide nearly as good a timebase as the CDMA receiver at the office.)

-GAWollman

To article , The Moderator appended:

See, that was the great thing about IS-95/IS-2000: if you didn't get the time synchronization within 15 microseconds, it just wouldn't work. (Well, it would appear to work, but calls would be dropped at every handoff, which would make customers angry.) That's also why you could build a timecode receiver to use the signal without a subscription. (GSM has a time feature, but it's "wall clock time at the MTSO", not a rigorously derived timebase.) There's nothing else in telephony that depends *as a business requirement* on that level of clock synchronization.

I have at times suspected Qualcomm engineers of designing IS-95 intentionally as a way of tricking telcos into investing in a high-quality time distribution infrastructure for the country. But it's all going away now.

-GAWollman

No. LTE is OFDMA downlink; SC-FDMA uplink. In some sense it is the dual of CDMA - CDMA transmits info in very short elements or bursts - OFDM (and OFDMA) transmits in very long bursts. In each case, the signal format allows a receiver to eliminate (or at least substantially reduce) the effects of echos or ghosts of radio signals (multipath).

Both OFDM and CDMA have been around for about 60-70 years. IIRC, CDMA was first developed to provide protection against jamming and OFDM was developed to protect against multipath on HF radio circuits.

See

Chuck