Advantages of CDMA are:
- It can accommodate more users per MHz of bandwidth than any other technology.
- It has no built-in limit to the number of concurrent users.
- CDMA is able to produce a reasonable call with lower signal (cell phone reception) levels.
- Its variable rate voice coders reduce the rate being transmitted when speaker is not talking, which allows the channel to be packed more efficiently.
- Has a well-defined path to higher data rates
- Increased cellular communications security.
- Extended reach - beneficial to rural users situated far from cells.
Disadvantages of CDMA include:
- Most technologies are patented and must be licensed from Qualcomm and due to its proprietary nature, all of CDMA's flaws are not known to the engineering community.
- Breathing of base stations, where coverage area shrinks under load. As the number of subscribers using a particular site goes up, the range of that site goes down.
- Manufacturers are often hesitant to release CDMA devices due to the smaller market, so features are sometimes late in coming to CDMA devices.
Advantages of GSM:
- Talktime is generally higher in GSM phones due to the pulse nature of transmission.
- The availability of Subscriber Identity Modules allows users to switch networks and handsets at will.
- GSM covers virtually all parts of the world so international roaming is not a problem.
- GSM's maturity means engineers cut their teeth on the technology, creating an unconscious preference.
Disadvantages of GSM:
- In GSM multiple users share the same bandwidth
- GSM has a fixed maximum cell site range of 35 km, which is imposed by technical limitations.
- Pulse nature of TDMA transmission used in 2G interferes with some electronics, especially certain audio amplifiers. 3G uses W-CDMA now (Dont know if the same applies to CDMA)
Which technology is the best for me?
When asking yourself which technology to choose between CDMA vs. GSM, first ask yourself the following questions:
1. Is international roaming important to me?
If you travel a lot to foreign countries, you might want to opt for a GSM phone for a better coverage.
2. Am I going to transfer a lot of data using the phone?
If you intend to use the phone for mobile web browsing, watching television or downloading MP3s, you might be better off with a CDMA phone. Currently, it offers the best data transfer speed with its EVDO technology and is the clear winner for now.
3. Do I plan to change phone often?
If you do, a GSM phone is best for you since you can swap the SIM card to a new device without having to re-enter your personal data.