Article : GSM CDMA

GSM CDMA

The ultimate outcome of the battle for dominance between these two competing cellular data transmission technologies may lie more in their history than their respective merits. To understand the current prevalence of GSM, one needs a foundation in the forces that converged to push one technology ahead of the other.
One of the most contentious battles being waged in the wireless infrastructure industry is the debate over the efficient use and allocation of finite airwaves. For several years, the world's two main methods -- Code-Division Multiple Access (CDMA) and Global System for Mobile communications (GSM) -- have divided the wireless world into opposing camps. Ultimately, the emergence of a victorious technology may owe more to historical forces than the latest wireless innovation, or the merits of one standard over the other.
CDMA's World War II Foundations
CDMA, put into an historical context, is a recently patented technology that only became commercially available in the mid-1990s, but had its roots in pre-World War II America. In  
 1940, hollywood actress turned inventor, Hedy Lamarr, and co-inventor George Antheil, with World War II looming, co-patented a way for torpedoes to be controlled by sending signals over multiple radio frequencies using random patterns. Despite arduous efforts by the inventors to advance the technology from experiment to implementation, the U.S. Navy discarded their work as architecturally unfeasible. The idea, which was known as frequency-hopping, and later as frequency-hopping spread-spectrum technology (FHSS), remained dormant until 1957 when engineers at the Sylvania Electronic Systems Division, in Buffalo, New York took up the idea, and after the Lamarr-Antheil patent expired, used it to secure communications for the U.S. during the 1962 Cuban Missile Crisis. After becoming an integral part of government security technology, the U.S. military, in the mid-80s, declassified what has now become CDMA technology, a technique based on spread-spectrum technology.
What interested the military soon caught the eye of a nascent wireless industry. CDMA, incorporating spread-spectrum, works by digitizing multiple conversations, attaching a code known only to the sender and receiver, and then dicing the signals into bits and reassembling them. The military loved CDMA because coded signals with trillions of possible combinations resulted in extremely secure transmissions.
Qualcomm, which patented CDMA, and other telecommunications companies, were attracted to the technology because it enabled many simultaneous conversations, rather than the limited stop-and-go transmissions of analog and the previous digital option.
CDMA was not field tested for commercial use until 1991, and was launched commercially in Hong Kong in 1995. CDMA technology is currently used by major cellular carriers in the United States and is the backbone of Sprint's Personal Communications System (PCS). Along with Sprint, major users of CDMA technology are Verizon and GTE.
Advantages of CDMA include:
•   Increased cellular communications security.
•   Simultaneous conversations.
•   Increased efficiency, meaning that the carrier can serve more subscribers.
•   Smaller phones.
•   Low power requirements and little cell-to-cell coordination needed by operators.
•   Extended reach - beneficial to rural users situated far from cells.
Disadvantages of CDMA include:
•   Due to its proprietary nature, all of CDMA's flaws are not known to the engineering community.
•   CDMA is relatively new, and the network is not as mature as GSM.
•   CDMA cannot offer international roaming, a large GSM advantage.
 
The Euro-Asian Alternative: GSM
Analysts consider Qualcomm's major competitive disadvantage to be its lack of access to the European market now controlled by Global System for Mobile communications (GSM). The wireless world is now divided into GSM (much of Western Europe) and CDMA (North America and parts of Asia).
Bad timing may have prevented the evolution of one, single global wireless standard. Just two years before CDMA's 1995 introduction in Hong Kong, European carriers and manufacturers chose to support the first available digital technology - Time Division Multiple Access (TDMA). GSM uses TDMA as its core technology. Therefore, since the majority of wireless users are in Europe and Asia, GSM has taken the worldwide lead as the technology of choice.
Mobile Handset manufacturers ultimately split into two camps, as Motorola, Lucent, and Nextel chose CDMA, and Nokia and Ericsson eventually pushed these companies out and became the dominant GSM players.
Advantages of GSM:
•   GSM is already used worldwide with over 450 million subscribers.
•   International roaming permits subscribers to use one phone throughout Western Europe. CDMA will work in Asia, but not France, Germany, the U.K. and other popular European destinations.
•   GSM is mature, having started in the mid-80s. This maturity means a more stable network with robust features. CDMA is still building its network.
•   GSM's maturity means engineers cut their teeth on the technology, creating an unconscious preference.
•   The availability of Subscriber Identity Modules, which are smart cards that provide secure data encryption give GSM m-commerce advantages.
In brief, GSM is a "more elegant way to upgrade to 3G," says Strategis Group senior wireless analyst Adam Guy.
 Disadvantages of GSM:
•   Lack of access to burgeoning American market.
Conclusion
Today, the battle between CDMA and GSM is muddled. Where at one point Europe clearly favored GSM and North America, CDMA, the distinct advantage of one over the other has blurred as major carriers like AT&T Wireless begin to support GSM, and recent trials even showed compatibility between the two technologies.
GSM still holds the upper hand however. There's the numerical advantage for one thing: 456 million GSM users versus CDMA's 82 million.
Other factors potentially tipping the scales in the GSM direction include :
AT&T Wireless' move to overlay GSM atop its TDMA network means the European technology (GSM) gains instant access to North America's number two network.
Qualcomm's recently announced that Wideband-CDMA (WCDMA) won't be ready in Europe until 2005. This comes amidst reports that GSM's successor, General Packet Radio Services (GPRS) remains on target for deployment in 2001-2002.
For all of the historical and technological reasons outlined above, it appears that GSM, or some combination of GSM and CDMA, will become the long sought after grail for a global wireless standard. A universalization of wireless technologies can only stand to benefit the compatibility and development costs and demands on all wireless commerce participants.

In cellular service there are two main competing network technologies: Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA). Cellular carriers including Sprint PCS, Cingular Wireless, Verizon and T-Mobile use one or the other. Understanding the difference between GSM and CDMA will allow you to choose a carrier that uses the preferable network technology for your needs.
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The GSM Association is an international organization founded in 1987, dedicated to providing, developing, and overseeing the worldwide wireless standard of GSM. CDMA, a proprietary standard designed by Qualcomm in the United States, has been the dominant network standard for North America and parts of Asia. However, GSM networks continue to make inroads in the United States, as CDMA networks make progress in other parts of the world. There are camps on both sides that firmly believe either GSM or CDMA architecture is superior to the other. That said, to the non-invested consumer who simply wants bottom line information to make a choice, the following considerations may be helpful.
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. The old phone becomes useless.
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 GSM cells 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.
According CDG.org, CDMA networks support over 270 million subscribers worldwide, while GSM.org tallies up their score at over 1 billion. As CDMA phones become R-UIM enabled and roaming contracts between networks improve, integration of the standards might eventually make differences all but transparent to the consumer.