CDMA or GSM after battery pull ?
This should explain why your device (Storm) prompts you for CDMA or GSM after a battery pull. The information will help you make an informed decision on how you want to proceed. I compiled this from several different sources in the hopes of answering your questions.
CDMA (Code Division Multiple Access) and GSM (Global System for Mobile Communications).
CDMA Wireless Service vs. GSM Wireless Service
CDMA offers improved coverage, improved voice quality, reduced dropped calls, far more security, and higher data speeds compared to GSM and TDMA.
CDMA was originally developed by the military during World War II, for field communications to create a more secure communications system, that was resistant to interference by the enemy. Users are separated using randomly generated codes(data) that are never transmitted over the air. The signals from other users appear like noise, providing a security mask, and encryption makes it impossible to identify the individual user. CDMA technology makes it virtually impossible to hack into data or voice conversations.Every GSM carrier in the world today is upgrading their network to CDMA technology.
CDMA takes an entirely different approach from GSM/TDMA. CDMA spreads data out over the channel after the channel is digitized. Multiple calls can then be overlaid on top of one another across the entire channel, with each assigned its own ?sequence code? to keep the signal distinct. CDMA offers more efficient use of an analog transmission because it allows greater frequency reuse, as well as increasing battery life, improving the rate of dropped calls, and offering far greater security than GSM/TDMA. For this reason CDMA has strong support from experts who favor widespread development of CDMA networks across the globe. Currently, you will find CDMA mostly in the United States, Canada, and North and South Korea.
CDMA and GSM are Radio technologies, and a mobile Phone is just an Antenna to recieve these Radio Signals. Since both the technologies work on different frequency range and has different modulation shemes therfore the mobile phones for both are different ( excluding the Storm).
Apart from this 3G tehchnology which is combination of both GSM and CDMA (WCDMA) is compatible with both GSM and CDMA. So a 3G mobile can serve for both GSM and CDMA radio signals.
SIM (Subcriber Idendity Module) is consists of Credential for network authorization. Since Both GSM and CDMA technologies has different Authorization functions and parameters hence both SIMs are different.
Note: In CDMA technology SIM is often called as RUIM (Removable User Idendity Module)
CDMA uses Different Frequencies than GSM. CDMA also does not require a SIM card.
Now some companies do provide SIM cards for CDMA connections also, such as Reliance communications and TATA Indicomm in India.
CDMA can hold more calls per channel on their towers, while GSM drops alot of calls. That is why people are always complaining about T-Mobile and At&t dropped calls. GSM is used internationally while CDMA is mostly used in the domestic United States. CDMA carriers are Verizon, Alltel, Sprint, Cricket....while GSM carriers here in the U.S. are T-Mobile and At&t.
GSM (Global System for Mobile Communications).
GSM is the "branded" term referring to a particular use of TDMA (Time-Division Multiple Access) technology. GSM is the dominant technology used around the globe and is available in more than 100 countries. It is the standard for communication for most of Asia and Europe.
Where international useage is important, GSM really does win hands down. GSM networks are used in more than 74% of the markets across the globe, and so users of tri-band or quad-band GSM handsets can travel to Europe, India, and most of Asia and still use their cell phones. CDMA offers no multiband capability and is rare outside of the United States so it is not
really much use for international travellers. You can also move the SIM of a GSM-based phone to any other GSM-based phone, or use a different SIM in your own phone, making GSM the optimal choice for international travelers who need connectivity.