The CDMA and GSM technologies define the most basic functions of your phone. GSM (Global System for Mobile Communications) and CDMA (Code Division Multiple Access in the context of cellphones and mobile networks), they are both shorthand for different mobile phone technologies.
These technologies convert your data into radio waves that your cellphone sends and receives. GSM divides the frequency bands into multiple channels so that more than one user can place a call through a tower at the same time. Meanwhile, CDMA networks layer digitized calls over one another, and unpack them on the back end with sequence codes.
In the U.S. there are more CDMA users than GSM users, the two largest CDMA carriers have over 43% of the market share. The two largest GSM carriers barely break 37%; worldwide, CDMA accounts for around 13% of phones, with GSM and its successor, UMTS making up of the remainder.
CDMA carriers in the US:
Verizon, Sprint and whoever uses their networks (Virgin, Boost, Alltel)
GSM carriers in the US:
AT&T and T-Mobile
Both GSM and CDMA standards gives out information so that the phones are identified by carriers. GSM use a removable chip called a SIM card. If you are using an openline phone you can just remove the SIM card and transfer it to another openline phones with ease. The CDMA standard have RUIM (removable user ID module) these phones are locked to one network, and can only be switched to another with the approval of the both the old and new carriers.
In the US, phones are sold with contracts and discarded with after two years. However, in other countries phones are sold unlocked, and works with any and all local networks. If you are to choose between CDMA vs. GSM for travel GSM always wins.
Why are MVNO cheaper than their host providers?
There are cell phone service providers that have their own towers and there are those providers that use other carrier towers (called MVNO providers). If you noticed there are a lot of MVNO providers that charge cheaper prices for cell phone service than the provider that they are using. For example, Gizmo carrier have their own towers and another carrier Azmo uses Gizmo's towers to offer their customers cell phone service.
Gizmo charges $70/month for 600 minutes of calls, but Azmo offers unlimited calling for only $25/month. If you noticed this is what is happening with most of the MVNO providers today. The are selling their service for cheap while using the same towers that their host carriers uses.
How do they do it? Here is why.
The reason MVNO's are able to offer phone services at a low price is because they are operating on second tier bandwidth which means that they are second in line to subscribers that bought plans directly from a provider. This is why you may not have service in an area that gets AT&T service when on a resold AT&T band.
Gizmo charges $70/month for 600 minutes of calls, but Azmo offers unlimited calling for only $25/month. If you noticed this is what is happening with most of the MVNO providers today. The are selling their service for cheap while using the same towers that their host carriers uses.
How do they do it? Here is why.
The reason MVNO's are able to offer phone services at a low price is because they are operating on second tier bandwidth which means that they are second in line to subscribers that bought plans directly from a provider. This is why you may not have service in an area that gets AT&T service when on a resold AT&T band.
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