Saturday, February 2, 2008

GSM Vs CDMA - Siblings at WAR

The mobility of people in personal and professional life is no longer an advantage, it has become a necessity. Technology that was seen on science fictions and bond movies are available at an affordable price. And not only is the technology available, it is present in so many forms and types that elimination of options and selecting the best fit has become a decision on which specialists are consulted.

Cell phones for example have come a long way from being seen as a non-usable invention to becoming an integral part of personal and professional life. Business on the move is the order of the day and a phone in today’s world does much more that “talk”. And the very reason that the cell phone application has grown far beyond the basic use of communication makes the decision of selecting a handheld device (Mobile), the service provider and the technology used very crucial.

When it comes time to selecting a cell phone or Smartphone, the major part of the evaluation we make focuses on the features and benefits of the handset. Does it provide access to the Internet and email? Does it contain an organizer that will sync with Outlook, so you can take your scheduler, contacts, and information on the road? And most importantly, does it look slick?
But if you are someone who conducts a lot of your business on the road or internationally, the most important decision you make regarding your service may not have anything at all to do with the features we usually consider important for handhelds. Your choice of carrier or service provider and the technology it uses for its network might make the difference between being productive or ending up out of area.

The options in technology

Most of us by now would have heard of the acronyms GSM and CDMA. And of course the endless stories of which one being the better of the two. As some of you might know that the mobile personal communication systems uses microwave frequencies above 800MHz for their transmission and reception purposes. They all are operating in some predefined or pre allocated frequency bands according to the international standards. For operating in these microwave frequencies they all need some access methods. And these methods are:

1. Frequency division multiple access (FDMA)
2. Time division multiple access (TDMA)
3. Code division multiple access (CDMA)

You can understand the meaning of FDMA, TDMA and CDMA eazily by just noting the word meaning for each letter. That is FDMA puts each call on a separate frequency and TDMA assigns each call a certain portion of time on a designated frequency for the above mentioned purpose. But CDMA gives a unique code to each call and spreads it over the available frequencies. All these are multiple access systems because more than one user can use the specified CELL ( not cell phone!) at a time.

GSM is a TDMA technology and the third option u see as CDMA itself. But before we enter into dissecting the two to see whose DNA is better than the other for a user let us learn more about both the technologies.

GSM – Global System for Mobile communication

GSM is the “branded” term referring to a particular use of TDMA (Time-Division Multiple Access) technology. GSM is the dominant technology used around the globe and is available in more than 100 countries. It is the standard for communication for most of Asia and Europe. GSM operates on four separate frequencies: You’ll find the 900MHz and 1,800MHz bands in Europe and Asia and the 850MHz and 1,900MHz (sometimes referred to as 1.9GHz) bands in North America and Latin America. GSM allows for eight simultaneous calls on the same radio frequency and uses “narrowband” TDMA, the technology that enables digital transmissions between a mobile phone and a base station. With TDMA the frequency band is divided into multiple channels which are then stacked together into a single stream, hence the term narrowband. This technology allows several callers to share the same channel at the same time.

CDMA – Code Division Multiple Access

CDMA, a proprietary standard designed by Qualcomm in the United States, has been the dominant network standard for North America and parts of Asia. CDMA takes an entirely different approach from GSM/TDMA. CDMA spreads data out over the channel after the channel is digitized. Multiple calls can then be overlaid on top of one another across the entire channel, with each assigned its own “sequence code” to keep the signal distinct. CDMA offers more efficient use of an analog transmission because it allows greater frequency reuse, as well as increasing battery life, improving the rate of dropped calls, and offering far greater security than GSM/TDMA. For this reason CDMA has strong support from experts who favor widespread development of CDMA networks across the globe. Currently, you will find CDMA mostly in the United States, Canada, and North and South Korea. As an interesting aside, CDMA was actually invented for the military during World War II for field communications.

The Comparison

Technically we can compare the two technologies on various parameters of performance and efficiency, but from a users perspective the technology part may well be transparent and we will go about comparing the two on the visible parameters as per use.

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 one of the 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. We will discuss the advantages of 3G in a different post.

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: All GSM phones use SIM. 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. In India both the leading players Reliance and Tata Indicom offer R-UIM based phones. 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.

One advantage with GSM service providers if offering services to other carriers if the same if not available in that area. So with a GSM you can always be on network as long as even a single GSM service provider has a network the area. The same does not apply to CDMA and CDMA service providers do not share network and provide service to competitor in their area.

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. You can check with your CDMA provider for your specific requirements.

According, CDMA networks support over 270 million subscribers worldwide, while 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.

The main GSM carriers in India are Airtel, BSNL, Hutch, Idea and the two leading players in CDMA are Reliance and Tata Indicom. In the United States the main GSM service providers are Cingular Wireless, recently merged with AT&T Wireless, and T-Mobile USA. Major CDMA carriers are Sprint PCS, Verizon and Virgin Mobile. There are also several smaller cellular companies on both networks.

The Best of both the worlds

If you travel often, it might be a worthwhile investment to purchase a dual-mode or tri-mode handset. Note that multiple band and multiple mode are different terms. Multiple-band phones offer the capability to switch between bands, while multiple-mode phones offer connectivity to networks based on different technologies. Although expensive, these handsets allow maximum flexibility for the international business traveler.

You can move the SIM (subscriber identity module) of a GSM-based phone to any other GSM-based phone, making GSM the optimal choice for international travelers who need connectivity.
You can find dual-mode and tri-mode phones, but before you buy, check to see which modes the phone actually connects. The term “tri-mode” can be deceptive. In most cases it will mean that a handset can support two digital technologies, such as CDMA and TDMA, as well as analog. In this case the handset is considered to be a true tri-mode phone.

However, there are manufacturers who advertise tri-mode phones that are actually dual-mode phones that connect to GSM and analog networks, only the GSM has multiple-band support for transport between the United States and Europe or Asia. These phones are, by the very loosest sense of the term, tri-mode, but they won’t fulfill your need to connect to CDMA and GSM networks if that’s what you need to do.


I hate to end the discussion with a open answer but reality remains that it would be irrational to vote one technology being better than the other. Both have their unique features and advantages to offer and as per your use you choose one of the two that best suits your requirement. But when you do so do remember to rate your use in terms of usage minutes, basic call rate offered, data / Internet requirements, Office application to be used and roaming requirements.

GSM or CDMA the struggle for supremacy continues and as the two technologies at war continue to surpass the other by offering better and more affordable features I see only one group to that would be benefitted and that would be “us” the users.

1 comment:

Linkon Khan said...

Hi I have read your post this is very helpful for me. This article have awesome topics that I want.
Now what about the 2G an 3G.
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