Cdma technology or “code division” is essentially coding of calls giving them a unique id whereas Gsm technology follows “time division” whereby multiple calls are assigned time slots.
Cdma was pioneered by chipmaker Qualcomm and quickly adopted by American operators like Verizon as it happened to be the ` hot ‘ new technology of the time whereas Gsm was started by European consortium of mobile operators and was adopted by most countries other than the US.
As mentioned earlier, US is dominated by Cdma (80%) whereas worldover it was Gsm standard. Now Gsm is a more flexible technology in that user data is stored on the sim cards whereas Cdma operators didnt follow the sim based method of storing of user data and had other means of verifying user data. In effect, a gsm network subscriber could switch mobile operators and handsets easily whereas cdma network subscriber was “wedded” to the operator since its a non – sim based technology.
In india reliance communications (rcom) and tata teleservices ( ttml in maharashtra) offer cdma based networks whereas Bharti airtel, Idea, Vodafone offer gsm based networks.
This lack of flexibility to switch has led to cdma users in india getting stuck and unable to uptrade to higher end cdma handsets as the two operators and handset makers seem to be completely ignoring them instead handset makers have flooded the market with gsm compliant handsets.
So much so Htc Desire had launched a dual sim ( cdma+gsm) handset which obviously way overpriced but still off the self now having been sold out. I have tried in vain to search for decent cdma based smartphone in the 10000 rs range other than Samsung offering of duos but there is nothing. I am sure it is the case with many other cdma users happy with network but wanting to uptrade. Handset makers out there looking for a money making oppurtunity have one in this premiumisation play.