GSM  -> GSM Vs CDMA

By Ed Sutherland

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.

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.

• 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.

• 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.

• 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.