GSM vs CDMA

There is a time when you start getting bored with your long time phone. And you feel like you've been holding it forever in your hands. And you decide to buy a new one. Buying a phone is a hard choice. Even more, it is a hard set of choices, a bunch of decisions wrapped into one. First, you have to think about your budget, then when your budget is ready you have to decide among many choices such as the operating systems, hardware, and feature lists. More importantly you've got to choose a network, with its distinct coverage areas, rate plans and customer service. Another quandary is the technology. GSM or CDMA? Physically there is no significant difference between GSM and CDMA even at the first glance they look similar. The major difference between the two technologies is how they turn voice data into radio waves and how the carrier connects to the phone. Other differences include the coverage area, the data transfer speeds, and the type of hardware used.

GSM (Global System for Mobile Communications)
GSM stands for Global System for Mobile Communications, is a standard set developed by the European Telecommunications Standards Institute (ETSI) to describe protocols for second generation (2G) digital cellular networks used by mobile phones. The GSM standard was developed as a replacement for first generation (1G) analog cellular networks, and originally described a digital, circuit switched network optimized for full duplex voice telephony. This was expanded over time to include data communications, first by circuit switched transport, then packet data transport via GPRS (General Packet Radio Services) and EDGE (Enhanced Data rates for GSM Evolution or EGPRS).

GSM is a digital technology that works by sending data packets based on time, or better known as the time slot. GSM itself is a derivative technology of Time Division Multiple Access (TDMA). TDMA is a technology to send data based unit consisting of time, it means a GSM data packet will be divided into multiple time slots. These time slots will be used by the GSM network users temporarily. The purpose and use of temporary time slots is, the time slots will be monopolized by users during their use, regardless, or when they're actively talking or even when they're being silent. GSM phones make use of a SIM card to identify the user's account. The use of the SIM card allows GSM network users to quickly move their phone number from one GSM phone to another by simply moving the SIM card. Currently, GSM networks operate on the 850MHz, 900MHz, 1800MHz, and 1900MHz frequency bands. Devices that support all four bands are called quad-band, with those that support three or two bands called tri-band and dual-band, respectively. GSM network is divided into three main systems: Swithing Systems (SS), Base Station System (BTS) and Operation and Support System (OSS).

CDMA (Code Division Multiple Access)
Code division multiple access (CDMA) is a channel access method used by various radio communication technologies. It should not be confused with the mobile phone standards called cdmaOne, CDMA2000 (the 3G evolution of cdmaOne) and WCDMA (the 3G standard used by GSM carriers), which are often referred to as simply CDMA, and use CDMA as an underlying channel access method.

CDMA describes a communication channel access principle that employs spread-spectrum technology and a special coding scheme (where each transmitter is assigned a code). CDMA also refers to digital cellular telephony systems that use this multiple access scheme, as pioneered by QUALCOMM, and W-CDMA by the International Telecommunication Union (ITU), which is used in GSM’s UMTS.

Here's the following considerations:

Coverage: The most important factor is getting service in the areas you will be using your phone. Upon viewing competitors' coverage maps you may discover that only GSM or CDMA carriers offer cellular service in your area. If so, there is no decision to be made, but most people will find that they do have a choice.

Data Transfer Speed: With the advent of cellular phones doing double and triple duty as streaming video devices, podcast receivers and email devices, speed is important to those who use the phone for more than making calls. CDMA has been traditionally faster than GSM, though both technologies continue to rapidly leapfrog along this path. Both boast "3G" standards, or 3rd generation technologies.

EVDO, also known as CDMA2000, is CDMA's answer to the need for speed with a downstream rate of about 2 megabits per second, though some reports suggest real world speeds are closer to 300-700 kilobits per second (kbps). This is comparable to basic DSL. As of fall 2005, EVDO is in the process of being deployed. It is not available everywhere and requires a phone that is CDMA2000 ready.

GSM's answer is EDGE (Enhanced Data Rates for GSM Evolution), which boasts data rates of up to 384 kbps with real world speeds reported closer to 70-140 kbps. With added technologies still in the works that include UMTS (Universal Mobile Telephone Standard) and HSDPA (High Speed Downlink Packet Access), speeds reportedly increase to about 275—380 kbps. This technology is also known as W-CDMA, but is incompatible with CDMA networks. An EDGE-ready phone is required.

In the case of EVDO, theoretical high traffic can degrade speed and performance, while the EDGE network is more susceptible to interference. Both require being within close range of a cell to get the best speeds, while performance decreases with distance.

Subscriber Identity Module (SIM) cards: In the United States only GSM phones use SIM cards. The removable SIM card allows phones to be instantly activated, interchanged, swapped out and upgraded, all without carrier intervention. The SIM itself is tied to the network, rather than the actual phone. Phones that are card-enabled can be used with any GSM carrier.

The CDMA equivalent, a R-UIM card, is only available in parts of Asia but remains on the horizon for the U.S. market. CDMA carriers in the U.S. require proprietary handsets that are linked to one carrier only and are not card-enabled. To upgrade a CDMA phone, the carrier must deactivate the old phone then activate the new one with the ESN (electronic serial number).

Roaming: For the most part, both networks have fairly concentrated coverage in major cities and along major highways. GSM carriers, however, have roaming contracts with other GSM carriers, allowing wider coverage of more rural areas, generally speaking, often without roaming charges to the customer. CDMA networks may not cover rural areas as well as GSM carriers, and though they may contract with other CDMA carries for roaming in more rural areas, the charge to the customer will generally be significantly higher.

International Roaming: If you need to make calls to other countries, a GSM carrier can offer international roaming, as GSM networks dominate the world market. If you travel to other countries you can even use your GSM cell phone abroad, providing it is a quad-band phone (850/900/1800/1900 MHz). By purchasing a SIM card with minutes and a local number in the country you are visiting, you can make calls against the card to save yourself international roaming charges from your carrier back home. CDMA phones that are not card-enabled do not have this capability, however there are several countries that use CDMA networks. Check with your CDMA provider for your specific requirements.

In the conclusion, Digital-based cellular phone system, whether it's GSM or CDMA has its advantages and disadvantages. For a populous areas, seems CDMA technology is way more superior to serve many connections simultaneously. This is due to the characteristics and CDMA network itself. A dense usage areas will have a higher possibility of connection, by using the CDMA network, although it could be any reduction in the coverage area and the sound quality when the networks load is too high. GSM technology is more suitable for less-populated areas, but need a constant coverage area. Moreover, urban areas have a lot of buildings. Geographical character like this is potentially reduce the signal so the coverage area is getting smaller.