What's the Difference Between GSM and CDMA Cell Phones?

Stands for SIM : A subscriber identity module or subscriber identification module (SIM) is an integrated circuit chip that is intended to securely store the international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephony devices (such as mobile phones and computers). It is also possible to store contacts on many SIM cards. SIM cards are always used on GSM phones; for CDMA phones, they are only needed for newer LTE-capable handsets. SIM cards can also be used in satellite phones.

The SIM circuit is part of the function of a Universal Integrated Circuit Card (UICC) physical smart card, which is usually made of PVC with embedded contacts and semiconductors. "SIM cards" are designed to be transferable between different mobile devices. The first UICC smart cards were the size of credit and bank cards; the development of physically smaller mobile devices has prompted the development of smaller SIM cards, where the size of the plastic carrier is reduced while keeping electrical contacts the same.

A SIM card contains its unique serial number (ICCID), international mobile subscriber identity (IMSI) number, security authentication and ciphering information, temporary information related to the local network, a list of the services the user has access to, and two passwords: a personal identification number (PIN) for ordinary use, and a personal unblocking code (PUK) for PIN unlocking.

What is CDMA?

CDMA stands for Code Division Multiple Access. CDMA does not specifically refer to one kind of technology or one network, but for a system of networks that have evolved over time. Each successive version of this network has sought to provide better, faster network access with a larger amount of coverage.

One of the notable things about CDMA technology is that it is the primary type of technology used for cell phones and smartphones in the United States. Cell phone providers that use CDMA technology include Verizon,Sprint, and US Cellular.

This means that for the most part, in the United States CMDA networks have seen more growth, and are likely to provide a much better user experience in terms of the amount of coverage a cell phone is able to receive within the United States. In addition, data might be more accessible, and users may be less likely to experience issues such as dropped calls, depending on the cell phone and the network provider they are using. One of the downsides is that using a CDMA network makes it much more difficult to switch out phones between networks.

What is GSM?

GSM stands for Global System for Mobile Communication, and unless you live in the United States or Russia, this is probably the technology your phone network uses, given it’s the standard system for most of the world. GSM networks use TDMA, which stands for Time Division Multiple Access. TDMA works by assigning time slots to multiple conversation streams, alternating them in sequence and switching between each conversation at very short intervals. During that interval, the phones can transmit their information. In order for the network to know which users are connected to the network, each phone uses a subscriber identification module card, or SIM card.

SIM cards are one of the key features of a GSM network. They house your service subscription, network identification, and address book information. The identification is used to assign time slots to the phone conversation, and moreover, it tells the network what services you have access to, while storing your address book and relative contact information. Said cards can even to pass the information between phones, if a carrier allows it.

Notable Difference Between CDMA and GSM Technologies

What, Which, and Who

GSM and CDMA both serve as shorthand for different mobile phone technologies. GSM stands for Global System for Mobile Communications; it's the world's most prolific mobile standard (a standard being a set of rules and suggestions about how a mobile network should work). CDMA stands for Code Division Multiple Access—in the context of cellphones and mobile networks, people tend to use it interchangeably to refer to two different mobile standards: CDMAOne or CDMA 2000.

What's the core difference? It all has to do with the way your data is converted into the radio waves that your cellphone broadcasts and receives. To keep from lulling you to sleep with the deep dive, I'll just scratch the surface and say that 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; CDMA networks layer digitized calls over one another, and unpack them on the back end with sequence codes.

CDMA was a late response to GSM, and in 1995 this more complex and modern channel access promised better security, fewer dropped calls, and more efficient infrastructure. But that was 1995, when car phones were still regularly spotted on city streets.

America is unique in that it's home to more CDMA users than GSM users, with the two largest CDMA carriers accounting for over 43% of the market. 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.

Of course, none of this tells us anything at all about what it means to use networks on either standard. Standards being basically a set of guidelines that participating companies abide by, most of the differences between CDMA and GSM are small details that you'll never have to concern yourself with: frequency bands, audio codecs, the physical specifications of the network infrastructure, the way a user is linked to a phone, and so on.

• answered 8 years ago
• B Butts