CDMA

Overheard - Difference between CDMA and GSM

“The two biggest differences between the CDMA and GSM standards are international compatibility and how the networks handle activating phones.” Adama D. Brown, Brighthand FAQ: What’s the difference between CDMA and GSM?

Outside the U.S. and Canada, most GSM phones will still work, while almost all CDMA phones simply can’t be used overseas.

CDMA phones are activated remotely, by the carrier, using the phone’s serial number, known as the ESN. Since each carrier has a database of all the ESNs that are approved for its network, this lets most CDMA carriers refuse to activate phones not originally intended for their network.

GSM phones are activated differently. Each account is associated with what’s called a SIM card, or Subscriber Identity Module. This card, about the size of a fingertip and the thickness of a piece of paperboard, carries an encrypted version of all the information needed to identify your wireless account to the network. You slip it into the appropriate slot on a GSM phone (usually under the battery) and that phone is ready to use.

Overheard: White space, the Dixie Chicks and wireless microphones

As part of an ongoing effort to bar internet devices from the country’s television white spaces, Goosoft-battling government lobbyists have rolled out two pillars of the American heartland: God and Dolly Parton. Cade Metz, Anti-white-space lobby enlists God, Dolly Parton

What do Dolly Parton, Neil Diamond, the Dixie Chicks, Clay Aiken,  Pastor Joel Osteen and Guns N’ Roses have in common? They all use wireless microphones and they’ve all joined together to ask the FCC to delay a vote on a proposal that would open up unused white space in the wireless spectrum.

The white spaces are empty “buffer” channels scattered throughout the 54- to 698-MHz region of the RF spectrum that were set up when TV was in its infancy to prevent interference. Now that we’re all moving to digital TV and analog is dead, the white space below 700 MHz could be up for grabs. Because the space is currently being used for wireless microphone transmission, the League of American Theatres & Producers and others don’t want the FCC to make the space freely available.  They want to keep the status quo because they’re worried about interference issues — despite a lot of testing on the FCC’s part that says it shouldn’t be a problem.

Google seems to be leading the charge to make the unused white space available for a new generation of wireless devices, pretty much saying that current wireless microphones have to use FDMA technology, but if the white space spectrum was opened up, wireless mic vendors could make new microphones that use CDMA-based technologies and that would take care of the problem — as long as nobody minds going out and getting new sound systems.

The FCC will have the final word. As of today, you need a license to operate a wireless mic unless it operates in the 49 MHz, AM/FM | broadcast, 902-928 MHz or 2.4 GHz band.

UPDATE: The FCC voted unanimously yesterday (Election Day) to allow conditional unlicensed use of the “white space” television spectrum.

The FCC says that to prevent white space devices from interfering with each other, the devices should use spectrum sensing (scan for unused channels) and geo-location (a technology that cross-references your location with a database of licensed spectrum users in your area.)

What does this decision mean for those of us who don’t use wireless microphones?

Well, the waves in white space can travel through walls.  What it means for us is that someday soon you’ll be able to get broadband Internet in every part of the county and when our kids are talking to our grandchildren, they’ll say things like “When I was your age,  people had to go outside to the driveway to talk on their cell phone.”   I can’t wait.