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Top message: why no cdma by disland
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CDMA vs. GSM... BROUGHT IT!
There are many models of Treo smartphone, from the old Handspring 180 to the newest Palm Treo 700p, but within these models there are two important distinct types of handset: GSM and CDMA.
For instance, a Treo 600 could be a CDMA or GSM handset, and the difference is very important!
The digest for lazy readers: GSM and CDMA are two types of mobile phone network. GSM is used all over the world, CDMA is largely restricted to the USA and North America. CDMA is often faster for data but using data blocks voice calls. GSM data is often slower but doesn't block voice calls. Tri and quad band GSM phones (like the Treo) can be used all over the world, CDMA phones can't. GSM phones use SIM cards, CDMA phones don't.
Why You Should Know The Difference
CDMA or GSM refers to the type of network technology the phone uses. Some carriers use CDMA and some use GSM. Your choice of carrier and the technology it uses for its network might make the difference between being productive and connected or ending up with no signal.
The Terms Explained
Really want to know? Prepare yourself now...
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.
GSM operates on four separate frequencies: You’ll find the 900MHz and 1,800MHz bands in Europe and Asia and the 850MHz and 1,900MHz (sometimes referred to as 1.9GHz) bands in North America and Latin America. GSM allows for eight simultaneous calls on the same radio frequency and uses “narrowband” TDMA, the technology that enables digital transmissions between a mobile phone and a base station. With TDMA the frequency band is divided into multiple channels which are then stacked together into a single stream, hence the term narrowband. This technology allows several callers to share the same channel at the same time.
CDMA (Code Division Multiple Access).
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. (As an interesting aside, CDMA was actually invented for the military during World War II for field communications.) (Can you spell propaganda?)
CDMA (Code Division Multiple Access) vs. GSM (Global System for Mobile Communications).
Both GSM and CDMA have good coverage all across the United States, however it is still important to choose the right network...
Data transfer methods
GSM’s high-speed wireless data technology, GPRS (General Packet Radio Service), usually offers a slower data bandwidth for wireless data connection than CDMA’s high-speed technology (1xRTT, short for single carrier radio transmission technology), which has the capability of providing ISDN (Integrated Services Digital Network)-like speeds of as much as 144Kbps (kilobits per second). However, 1xRTT requires a dedicated connection to the network for use, whereas GPRS sends in packets, which means that data calls made on a GSM handset don’t block out voice calls like they do on CDMA phones. Note: The new GSM EDGE technology means that GSM speeds have caught up with CDMA, but EDGE coverage and availability remains patchy.
GSM phones use SIM cards
The most obvious distinction between GSM and CDMA is the SIM (subscriber identity module) card, the onboard memory device in a GSM phone that identifies a user and stores their information. You can swap GSM SIM cards between phones which enables you to move all of your contact and calendar information over to a new handset with no hassle.
CDMA operators answer this flexibility with their own service that stores user data on the operator’s database. This service makes it possible to swap handsets with little trouble and also provides the ability to recover contact data even if their phone is lost or stolen. These services are usually available for GSM phones too, so it's not really an advantage of CDMA, more of a disadvantage is that they don't have SIM cards.
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.
Note: common 850MHz/1,900MHz GSM phones in the United States are not compatible with international standards. If you live in the United States and need to have cell phone access when you travel overseas you will need a tri-band or quad-band GSM phone with 900MHz and 1,800MHz bands. These types of phones will let you use your phone while in the United States and overseas without having to change handsets. You will, however, need to obtain a SIM card that works overseas.
CDMA phones tend to have better battery use. CDMA networks have more capacity and are generally better for data. CDMA also has more widespread coverage in the United States, especially when you count analog roaming, and offers more stateside high-speed data networks. Some people claim CDMA has better call clarity, others say GSM does. CDMA is often cheaper, especially for unlimited data plans.
If you like in the US and never travel oversees then CDMA appears to have many advantages over GSM, but if you live outside the US or travel oversees a lot then GSM is the only way to go!
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