All about CDMA & GSM

[chandramauli 0]

Which technology is better CDMA or GSM?

[Arun 795]

CDMA rulez !

[misquitas 0]

Hi there,

Found an interesting article which may be of interest to the RIM users. Would be interesting to hear views on this issue.

Melvyn

------------------------

http://www.techno-preneur.net/timeis/techn...3/hotfight.html

THE HOT FIGHT :: GSM Vs. CDMA

In past few years India has seen a large growth in its Telecom and Internet Infrastructure. The fixed line and Cellular Subscribers base has shown a steep rise. The cellular market in India has grown at the rate of 80-85 Per cent, and achieved a subscriber base of 10.4 million by end -2002. According to Cellular Operators Association of India (COAI), the industry has grown from Rs. 3,285 crore in FY 2000-2001 to Rs. 4,700 crore in FY 2001-2002. But with shot of CDMA arrow from Reliance, Is it that the fast growing cellular industry has started slowing down ? Today this is the billion-dollar question.

Working of GSM based Cellular

A large geographic area is subdivided into relatively small areas called cells. Each cell has a base station which transmits to and received from all mobile phones within the area of the cell. A base station is an antenna, similar to a microwave antenna. Each base station is connected to a mobile switching office by either a conventional terrestrial line or microwave relay. Each base station sends and receives signals from mobile phones located in their cell. Each adjoining transmitter uses a different frequency, but transmitters in nonadjacent cells use the same frequencies.

The mobile station is the subscriber end of network and consists of the GSM device (cell phone) and the Subscriber Identity Module (SIM). Each mobile device has a globally unique International Mobile Equipment Identity (IMEI) and each SIM has an International Mobile Subscriber Identity (IMSI), which is used to identify and authorize the subscriber for various services.

As a mobile user passes from one cell to another it must be assigned another voice channel very quickly so that the cell is not interrupted as the frequencies, change. The process of reallocating a different voice channel as a user moves between cells is called the "hand-off".

The mobile switching office is similar in operation to a conventional switching office in that it handles the switching of cells between mobil subscribers and calls to and from the public network. The principal functions of a mobile switching, routing and overall control, Interface with the conventional public network, Directory management, control of subscriber location and hand-off, Signaling control etc.

How does CDMA work?

CDMA works on the principle called interference averaging. Signals are spread uniformly over the entire available bandwidth. Different calls are assigned different codes. Together, they appear as noise-like interference to each other. During the receiving stage, when a particular call is decoded, this noise becomes supressed. In other words, the interference is one of the limiting factors, its averaging results in increased capacity.

CDMA makes full use of the processing power of the modern computers CDMA allows a channel to carry multiple con-versations at the same time by assigning each conversation at different code. A code is a pattern of bits. The receiver looks for that bit pattern. So even if there are ten conversation in a particular channel at the particular instant of time, no calls interferes with another. As long as the receiving device has the right code, it can pick up its conversation but from all the others. Since CDMA spreads multiple conversations across a wide segment of spectrum, it is known as a Spread Spectrum Technology.

The Spread Spectrum uses two types of modulation schemes

Frequency Hopping Modulation : Frequency hopping rapidly switch among several predetermined frequencies. For this work, the transmission and receiver must be in nearly perfect synchronization. Bandwidth can increase by simultaneously transmitting on several frequencies.

Data sequencing modulation

It works by breaking the original data into parts (called chips), which are then transmitted on separate frequencies. The receiver can then isolate the chip and reassemble the data while ignoring the decory information.

The chipping code used in transmission is known only to the sending and receiving stations, making it difficult for intruder to intercept and decipher wireless data encoded in this manner.

Thus it provides following benefits:

CDMA reduce background noise and cross talk, ensuring better voice quality, which is further enhanced by the microprocessor inside the phones.

CDMA provides capacity for voice and data communications, allowing more subscribers to connect at any given time and makes it capable for multimedia task.

CDMA provides better spectral efficiency and consumes very little power leading to enhanced battery life and longer talk time.

Due to its design, it is more secure against eavesdropping.

CDMA phones due to their low-power requirements can do with smaller-sized batteries, which decreases the overall weight of a CDMA phone.

Calling capacity is superior due to better spectral efficiency

Difference between TDM and CDMA

GSM is based on Time Division Multiplexing and is very different form of Direct Sequence spread spectrum used by CDMA. To understand the difference between GSM and CDMA consider a large gathering in a hall with GSM people are allowed to talk one by one; each have a time slot for communication one after the other. CDMA gives more out of this. It allows each couple to talk at the same time but in different language because in this code is divided, not the time, hence neither creating problem of cross talk nor the background noise. This helps in extracting the desired signal while rejecting everything else treated as noise.

Viewing the technical aspects, the differences between the two standards: TDM users take turns sharing the frequency in a round-robin fashion with each one periodically getting the entire bandwidth for a little burst.

Thus, each user get a times lot on which to send and receive data. On the other hand spread spectrum uses the same frequency for several users simultaneously with minimal interference and use noise like carrier weaves that provides larger bandwidth.

The Road Ahead

Involvement of India's foremost Corporate families and large scale advertising created a lot of confusion regarding selection of standard among users. So we point some consideration which may prove out to be useful for making the right choice before selecting a standard.

GSM is mature, having started in the mid-80s. This maturity means a more stable network with robust features. GSM is already used worldwide. CDMA is still building its network.

GSM supports International roaming which permits subscribers to stay in touch wherever you go within your city, across the country or around the globe-on a single number. CDMA will work only within the Short Distance code Area (SDCA), which is typically city limits.

The availability of Subscriber Identity Modules (SIM), which are smart cards that provide secure data encryption give GSM m-commerce advantages.

GSM Voice clarity is less superior to CDMA.

GSM Talk time is lower than that of CDMA.

With a GSM service, you can upgrade your handset anytime you wish. You can be within reach wherever you go. You can conveniently change your tariff plan. You can easily switch from one service provider to the other (BSNL, Airtel, Hutch, Idea). With CDMA, none of the above can happen.

Due to different standards, GSM handsets cannot be used for CDMA. CDMA supporting handsets are different, and more expansive than GSM handsets.

Never before has the country seen such heavy action in the telephony arena.

CDMA technology is relatively new compared to GSM.

GSM Mobiles offer international roaming and a SIM Card for mobile commerce.

But CDMA offers more talk time and better voice quality, even though the handset costs more and there is no SIM Card with a regulation that denies the roaming facility to CDMA phones in India, which technology will emerge stronger? We will have to wait and see.

(Writer: Manish Maheshwari and Ravi Mohan Sharma)

[sunil_jok 2]

hey,

this is quite a good find.

very informative.

great work misquitas

[Greens 21]

What do you prefer? CDMA or GSM?

NEERAJ SAXENA

TIMES NEWS NETWORK[ WEDNESDAY, APRIL 21, 2004 11:10:29 AM ]

NEW DELHI: GSM operators are not the only ones who are worried about the rapid strides made by CDMA mobile players, Reliance Infocomm and Tata Indicom in the Indian cellular market?

The GSM suppliers ? both handset and equipment - who incidentally also have their other foot firmly placed in the CDMA pie, are beginning to lose some sleep over what was earlier termed as ?niche? and ?miniscule? data carriage market by the operators.

Apart from the strong success of the two CDMA operators whose networks are based on code division multiple access (CDMA), the miserable showing of the four global standard for mobile (GSM) based networks that had launched general packet radio service (GPRS) service for data connectivity last year, has the vendors worried.

GSA now believes that even though India will primarily remain a voice traffic-led market in next two-three years, the data traffic component will grow by 25-30 per cent, an optimism that it trying to make GSM operators feel as well.

The CDMA challenge:

CDMA players had launched their services with CDMA 2000 1X-based networks which can give hi-speed, always-on connectivity to the Internet and other data services.

GSM operators, on the other hand, have had to migrate from the frustrating experience of WAP (wireless application protocol) to GPRS which has not significantly improved the subscriber?s experience of surfing the Net on/from mobile.

The top brass of Global mobile Suppliers Association (GSA) - an organisation comprising Nokia, Siemens, Ericsson, Alcatel and Lucent Technologies - met on Tuesday in the capital to persuade the operators to adopt EDGE (Enhanced Data rates for GSM Evolution) and leave GPRS behind as a dream gone sour.

Only Airtel, Hutch, BPL Mobile and Idea Cellular had launched GPRS, but the data transfer speeds of GPRS have been abysmal. The field trials gave a speed of around 54 kbps, but the actual speeds have not exceeded 14-18 kbps, a major reason why GPRS growth has been so slow.

As against the total GSM cellular base of 2.61 crore, the country has between 80,000-1 lakh GPRS users only. In comparison, the two CDMA operators have about 90 lakh connections. All these sets are data compliant. Though no figures are available as to how many use these for data services, the figure is believed to be respectable as a percentage ratio for CDMA.

Bharti Cellular is close to commercially launching its EDGE service in Delhi and Mumbai by end ay or early June, sources said. The company was the first to conduct field trials in November with its equipment supplier Ericsson.

Idea too held EDGE field trials in February this year with its vendor Nokia. Hutch and BPL are yet to hold the trials. The two companies would eventually migrate to EDGE, but perhaps after seeing the response to Bharti?s service.

EDGE holds the promise of delivering data speeds of around 170-180 kbps (as against the theoretical speed of around 380 kbps) which, if achieved, promises the launch of many data applications. The scalable cost of migrating from GPRS to EDGE is not too high and mainly comprises software upgrades in case of a modern network such as Bharti and Hutch, claimed chairman of GSA India chapter Rakesh Malik.

Will GSM maintain its headstart?

At the GSM Evolution Forum held in New Delhi, GSA president Alan Hadden predicted that GSM growth will far outstrip CDMA as was happening globally. He felt India could have as many as 100 million GSM subscribers by 2007-2008, up from nine million in December 2002.

According to GSA, there are over 1 billion GSM subscribers worldwide as against 200 million CDMA customers. The revenue of top 25 global operators from data averages 18 per cent and 22 of these operators run GSM networks. Overall, there are 76 operators in 50 countries that have committed to deploy EDGE.

Almost every country has a GSM based network and even those US operators which operated on now-defunct TDMA technology were migrating gradually to GSM, not CDMA, pointed out Hadden at the GSM Evolution Forum.

The Forum is a global GSA programme to assist the operators for evolution to third generation (3G) technologies.

?People are using their phones for much more than voice. Fifteen networks have commercially launched EDGE as it can run 3G like services in the existing spectrum for the operators without needing a 3G license. Even the migration to a full-fledged 3G level of Wideband CDMA (WCDMA) will be smooth with EDGE,? said Hadden.

?Besides, the automatic roaming provided by GSM networks in almost 200 countries is a power that CDMA doesn?t give you. We know for sure that almost 20-25 per cent of the revenue for some GSM operators comes from roaming customers,? he added.

But CDMA is no pushover with Korea and Philippines as the shining jewels in its crown. The first CDMA 2000 1X was commercially deployed in October 2000.

Already, 81 operators have launched 77 CDMA 2000 1X networks whereas nine have launched services based on 1xEV-DO platform across Asia, the Americas and Europe. At least 16 new 1X and six 1xEV-DO networks are scheduled to be deployed in 2004, according to CDMA Development Group. EV-DO and EV-DV are the next level of evolution on the CDMA 2000 1X platform, capable of delivering services comparable to 3G WCDMA.

Where are the models?

What will matter a lot in this war will be the availability of EDGE compliant handsets at affordable rates. While the two CDMA operators have been giving out handsets that can give hi-speed data transfer, same has not been the case with GSM. Even now, GPRS handsets have not become commonplace and GPRS feature is found only in mid and high-end segment handsets.

Edge handsets have just begun trickling in to the market. Nokia has launched 6220 and 3200 in India so far, while its? 7600 is a WCDMA phone. On the anvil is 7610, an enhanced GPRS phone. Siemens and others are close to launching a couple of EDGE sets this summer.

In contrast, there are more than 524 CDMA handsets available in the market with colour displays, cameras and global positioning system (GPS) capabilities. Most of these can work on CDMA 2000 1X, delivering speeds almost like EDGE.

End sum game:

When EDGE is deployed by the networks, subscribers can expect the delivery of advanced mobile services such as easy downloading of video and music clips, full multimedia messaging, besides high-speed Internet and e-mail access, provided their handset supports all this.

But the real cruncher will be the migration at a later stage to 3G technologies such as WCDMA, EV-DO or EV-DA as and when the government decides what to do with the 3G licences. WCDMA for example promises delivery of a phenomenal 2 megabytes per second (mbps), equivalent to what a leased line in many middle level corporates gives. More importantly, WCDMA will spawn a whole new range of full motion audio-video applications, including video telephony.

GSM lobby may continue to remain gung ho over the future of their technologies over that boosted by the American firms Qualcomm and Motorola, but Indian market could well throw an interesting scenario that industry experts will do well to watch.

In the coming months, Reliance plans to offer its CDMA subscribers much more than what GSM players intend to deliver through their EDGE for their subscribers. Who succeeds in this battle for mobile customer?s eyeballs is most difficult to predict.

A Korea and Japan may not be waiting to happen in India, but India will probably be more like the Chinese market with both standards co-existing. For now, GSM rules!

[chandramauli 0]

Thank You Greens

[Chirag 5]

hi,

can u tell me wats cdma

how it works and how is it better for a country like india.

Hey Dude, maybe this topic shall help u! Post more queries abt the same here!

[Utsav 0]

Hi there, I believe here is an authentic sourcr for those who want it in a more lucid manner!

http://electronics.howstuffworks.com/cell-phone.htm

You can also download the edited version in form of this zip file attached herewith.

GSMvsCDMA.zip

Edited July 24, 2004 by turbasu

[chandramauli 0]

Hi ..

is there a way to convert a GSM phone to a CDMA one. .. ( i wont mind if r-world aint there) as long as the number remains the same !!! ??

[Mahidhar 3]

i think static or code already mentioned that both the phones use completely different components or technology ... cant convert from one to another - what is common is probably only the keypad ... check that post out

[Ashokjp 15]

Ya you can use the cover and other such parts

Nothing else can be done..

[inderpalsingh 0]

i am not able to understand CDMA , GSM & 3G. any body expain in detail

[chandramauli 0]

see these links

1) http://infotech.indiatimes.com/articleshow...123,curpg-5.cms

2) http://infotech.indiatimes.com/articleshow...123,curpg-6.cms

3) http://infotech.indiatimes.com/articleshow...123,curpg-9.cms

i dont know wheather they will prove to be useful.... but it shall give u an idea.

Edited February 4, 2005 by chandramauli

[inderpalsingh 0]

I found the below mentioned article from the net regarding GSM,CDMA's differences, comparison technology evrythin about them.

I made lot of efferts in searching this article & hence I all request you all to communicate/post your reactions.

GSM vs. CDMA:

Implications for the development of Wireless Communications

India is on the threshold of major telecom investments. Licenses were recently granted for the fourth cellular operators in all circles. The cellular operator has the option of deploying one of the multiple technology platforms available. Besides the cellular operators, the basic telephony sector is also heating up with WiLL (Wireless in Local Loop) being the talk of the town. Amidst all this excitement there are some voices of concern too. Given the scale of investments, everyone wants to be on the safer side, the same holding when it comes to deciding about the mobile transmission technology to be implemented. Of the many possible alternatives the two most likely probable are GSM and CDMA. When mobile telephony was introduced in India, CDMA was an emerging technology, and as such GSM was the only choice. The situation is different now and hence there is a need for evaluating the deployment alternatives. This paper tries to do a comparative evaluation of the two technologies and then suggest recommendations concerning possible deployments.

CDMA

Developed by Qualcomm for the US Military, Code Division Multiple Access is a system that enables many users to share the same frequency band at the same time (called frequency spread). Each signal is encoded differently so that it can be understood by a receiver with the same code. CDMA is often compared to an airport transit lounge, where many people are speaking in different languages. Each listener only understands one language, and therefore concentrates on his or her own conversation, ignoring the rest. But a roomful of people all talking at once soon becomes very loud. Everyone ends up trying to shout above the background noise, which just makes the problem worse. To prevent CDMA codes are chosen so that they cancel each other out.

GSM

Short for Group Speciale Mobile, GSM uses narrowband TDMA, which allows eight simultaneous calls on the same radio frequency. As of the end of 1997, GSM service was available in more than 100 countries and has become the de facto standard in Europe and Asia.

The Technologies Behind

GSM CDMA

Type of Multiplexing TDMA & FDMA Spread Spectrum

Modulation Used GMSK QPSK/BPSK

Carrier Bandwidth Available 800, 1800, 1900 MHz 800, 1800, 1900 MHz

Per user bandwidth 200KHz, 13 Kbps for voice, 9.6 Kbps for data 1.25 MHz

Frequency Reuse 3,5,7 None

Handoff Hard Soft

Countries Employed In Europe, Asia US, South Korea

Which is better?

While it may not be possible to conclusively state which is superior, these competing technologies can be compared on some select parameters.

Cost to roll out Network

The cost parameter used in evaluating a cellular technology is data rate/per subscriber per rupee. On this parameter, CDMA scores over the GSM. CDMA based technology is also cheaper in terms of capital expenditure, measured on the scale of cost of line equipment per subscriber. A CDMA line costs $ 180 vis-à-vis $250 for a GSM line. The cost of cell sites is also reduced. The advantage in variable costs are:

• Smaller cell-to-cell operation overhead

• Increased efficiency (in terms of telephone traffic, or Erlang capacity)

Scalability

CDMA can support more subscribers in a given cell area for a given bandwidth. In addition, the capacity of the system is not as rigid as in GSM. While, GSM cannot add more than a fixed number of subscribers in a cell, in a CDMA network the system can add on users, though with a deterioration in service. It is also easier to extend range of reception and service area in a CDMA based network.

Quality of Service

CDMA is widely believed to offer superior voice quality. Since CDMA works on a single frequency, transition from one cell sites leads to softer handoffs in comparison to a hard one in GSM.

Cellular Communications Security

The principle of operation of CDMA makes it a very secure communication technology. Even GSM has not been found wanting in security aspect of mobile fraud.

Power requirement

The power requirements in CDMA are lower than in GSM. This results in longer battery life & low radiation risk for the user.

Hotspots

In GSM, high mobile density areas lead to creation of Hotspots, where it is not possible to add more subscribers. This happens in areas like Stock exchanges & financial districts. The CDMA based network can delay this.

Initial & Handset costs

Though running costs of CDMA based networks may not be high, they have high initial costs. If an operator is going for a second network, this may turn out to be costly as marginal increase in subscribers would not be very large. Handsets for CDMA are most expensive as compared to those for GSM.

Roaming

The biggest advantage with the GSM is its widespread deployment in Europe and Asia. This is self evident from the diagram below. CDMA currently has merely 82 million users vs. the 456 million of GSM. The user of a GSM network can thus expect easy international roaming. (See Figure)

Value Added Services

Value added services like SMS, gaming and internet access have become a major source of revenue of network operators. They also help in attracting customers. Both GSM and CDMA score almost equally on this front.

There are a few factors that do not favour deploying a CDMA network. CDMA being a patented technology, all CDMA equipment & handsets require a royalty to be paid Qualcomm. Moreover, CDMA being of a new, proprietary nature not all its flaws are known

The Indian Scene

The critical factors on which decision to adopt a technology in India will depend can be examined as below:

Penetration of Telecom Network

It is imperative for India to improve the penetration of telecom services which at present is at abysmal levels compared to rest of the world. CDMA based WLL is a step in the right direction. With operators such as BSNL saying that WLL will be cheaper than landlines, it is hoped that the penetration in India would improve. Any cellular technology, likewise, should be amenable to the above objective.

Investments

In India, the cellular service providers have set up extensive GSM based networks. An estimated Rs. 21,000 crores have been sunk in building this network (entirely GSM based). A new technology such as CDMA needs to be examined for any potential destructive innovation.

Roaming

One of the major concerns of cellular operators planning to roll out a CDMA network is whether the mobile device will enable roaming facility in other parts of the country. If there is no large scale adoption of CDMA among the operators, a consumer can be stuck with a service which does not offer roaming service. With GSM already have been set as the standard all over India, this is quite a possibility. At the same time, it needs to be borne in mind that the number of subscribers going in for roaming is rather low and most of the calls being made are inter SDCA calls. There are even fewer people who opt for International roaming. An Indian consumer would not care much for premium services such as roaming as long as he gets mobility within his circle.

3G

India had an advantage over the rest of the world in that it did not have any legacy networks and was directly able to leap frog into an advanced technology like GSM. In a similar vein, while implementing any new technology, we need to consider its upgradability to 3G. 3G promises to become a major revenue driver for operators, though not in the near future. Unfortunately, at this point of time it is not clear which of the two - CDMA 2000 1X and WCDMA - CDMAone’s and GSM’s migration path to 3G respectively are going to be adopted worldwide. CDMA 2000 1X is believed to have a straighter path to 3G with fewer stages.

Recommendation

In recommending the deployment strategy for a telecom operator, the following need to be kept in mind. Firstly, Indian customer is price sensitive who would not mind a cheaper option even if it comes with a lower quality level. Second, given the low penetration levels in India, any technology which promises to increase it radically should be seriously considered. Thirdly, the telecom operator would have to make a huge investment while setting up its network; hence it is imperative that it gets the customers to make it economically viable to operate. Hence a technology which can support more customers at the same time would be beneficial to the operator. Given these considerations we suggest the following recommendations.

The Basic Services Telecom Operator

What to deploy

CDMA based Limited WiLL telephony.

Why

The current policy framework of Indian telephony is such that in case a Basic Service operator provides limited mobility then there are no spectrum costs to be paid to the government. There is therefore a possibility of providing mobile telephony services at prices equal to that of landline services. Hence Basic Service operators should take advantage of this policy and provide cheap limited CDMA based WiLL services to the customers. CDMA technology is stressed it alone can address the huge user base which would result once WiLL services are introduced.

The Fourth Cellular Mobile Services Operator

What to deploy

CDMA based cellular mobile services.

Why

The rational is quite simple. CDMA supports more user than GSM, given the same resources. This means that a mobile services operator using CDMA would be able to support more customers than an operator using GSM. In cellular mobile services industry a major portion of the costs to customers originates from the huge fixed costs borne by the operator. This cost reduces as the number of users increases, implying that more users means lesser call rates, which results in still more users. This obviously is a cycle which only a CDMA operator can support given its excess capacity as compared to a GSM one.

Given these recommendations, it is possible to create a telecom infrastructure in India which not only helps in the underlying goal of increasing telephony penetration but also suits an increasingly market dominated environment.

At the same time, we may point out that having a stand-alone CDMA network with the rest of the country having GSM based networks is fraught with technological and financial risks.

References

1. WirelessAdvisor.com Forums- TDMA or CDMA,800 or 1900 – which is best?

retrieved August 11, 2002 from http://www.wirelessadvisor.com/waforums/

messageview.cfm? catid=16&threadid=3561

2. War of the Standards GSM vs CDMA - M-CommerceTimes.htm

Retrieved August 12, 2002 from http://www.mcommercetimes.com/Technology/ 95

3. Wireless Communications – GSM vs CDMA

Retrieved August 12, 2002 from Wireless www.telecom.globalsources.com/ MAGAZINE/WC/0206/GSMVS.HTM

4. The Shosteck Group (june 2001) GSM OR CDMA :The Commercial and Technology Challenges for TDMA Operators 38 pages CDMA development group

5. Cellular Operators Association of India

Retrieved August 12, 2002 from http://www.coai.com/telephny.htm

Edited March 11, 2005 by inderpalsingh

[vb86 0]

3g=3rd generation.

We have 3g in both gsm and cdma. As far as i know there i no seperate technology known as 3g.

[AmanJ 1]

3g=3rd generation.

We have 3g in both gsm and cdma. As far as i know there i no seperate technology known as 3g.

u r right buddy.

but as far as technology gos both cdma and gsm camps claim their technology to be better than others

[deepu 0]

GSM Vs CDMA

------------------

courtesy -- bsnl.in

Cellular is one of the fastest growing and most demanding telecommunications applications.And the continuous advancement in this technology has provided many options to a consumer.

Today, the two alternatives that face the mobile world is - GSM and CDMA technology.First of all, Let’s comprehend the meaning and functionality aspects of these technologies.

Global Service for Mobile Communications (GSM)

----------------------------------------------------------

During the 80s, when the cellular system was introduced, each nation had its own system.As a result, a couple of problems arose.Firstly,the equipment was limited to operate only within the boundaries of a country and secondly,the market for mobile equipment was also limited.In order to overcome these problems, the conference of European Posts and Telecommunications (CEPT) formed the Group Special Mobile (GSM) to create a common European mobile telephone standard.

The GSM later came to be known as Global Service for Mobile communications (GSM).At the end of 1997, GSM was made available in more than 100 countries.Today it has become the global standard in Europe and Asia.GSM operates in 900-MHz – 1800MHz. If one has to connect to the specific service provider in different countries, GSM-users simply need to switch Subscriber Identification Module (SIM) cards.As per GSM technology, a mobile unit logs on to the network after being switched on.The mobile unit tries to contact a nearby BTS, which then transmits all the frequencies of the neighbouring BTS’ to the mobile unit, which identifies the frequency on which the reception is the best and passes on the information to the BTS.

The BTS then transmits the information to the BSC which has the deciding power as to which BTS should the mobile unit be assigned.

Code Division Multiple Access (CDMA)

----------------------------------------------

Developed by Qualcomm for the US Military, Code Division Multiple Access is a system that enables many users to share the same frequency band at the same time.

CDMA is a spread spectrum technology whereby multiple users share the same time and frequency allocation in a given band.Each speech signal is modulated (spread) across an entire band.The respective receiver demodulates and interprets the signal using relevant code that is embedded in the signal.The final signal contains only the relevant conversation.

The CDMA based mobile technology was introduced in India to provide WLL services as the GSM was the choice for full mobility.CDMA based WLL operators were given license of operation as fixed line operators.As CDMA can very well connect large geographical area, WLL operators were given the rights to provide "limited mobility" whereby a WLL operator could allow network coverage to the boundary of a Short Distance Charging Area (SDCA).

Differences

--------------

While TDMA and FDMA are the types of multiplexing in GSM, CDMA works on spread spectrum.However the bandwidth available is same for both the technologies, which is 800, 1800 and 1900 MHz.

While GSM cannot add more than a fixed number of subscribers in a cell, the capacity of the system is not rigid in CDMA.The biggest advantage with GSM is its widespread network in Europe and Asia, whereas CDMA is predominant in US and South Korea.The user of GSM is enabled an easy international roaming.As far as SMS, gaming and internet is concerned, both GSM and CDMA score an equal point.

GSM has already set a standard in India.Being a patented technology,all CDMA equipments and handsets require a royalty to be paid.

The Choice: is determined by the service used by those whom you call most frequently.When mobile telephony was introduced in India, CDMA was an emerging technology.Hence GSM was the only choice.But today’s scenario calls for an evaluation of the alternatives.

[anujit 0]

Which is the best technology really depends on where you are and what your needs are.

[inderpalsingh 0]

Through out the world it can be seen that GSM mobile system of communication is very widelly used & in terms of the handsets there are many options and the variety is very wide. They are available in every price range and also the cost is quite competitive.Ringtones, Wallpapers, Games etc are available in large numbers.

Were as in CDMA there is a very limited variety, the handset costs are comparitively high and option for ringtones,wall papers,games is very limited.

why :'(

[rakesh5295 0]

Regarding ringtons wallpapers etc it available for cdma also. now regarding handsets and availablilty of ringtones its just very less countries have accepted cdma so mobile manufacturer r not much into it though u can see in so less time relaince has a good collection and same were the days when gsm had come into india. now even 6610 of gsm is availble with tata and relaince so time is chaning now.

[Chirag 5]

Through out the world it can be seen that GSM mobile system of communication is very widelly used & in terms of the handsets there are many options and the variety is very wide. They are available in every price range and also the cost is quite competitive.Ringtones, Wallpapers, Games etc are available in large numbers.

  Were as in CDMA there is a very limited variety, the handset costs are comparitively high and option for ringtones,wall papers,games is very limited.

    why :'(

27151[/snapback]

Maybe u cud find out when the two technologies actually came into existence or were invented. And u'd know why this difference!

[deepu 0]

If you compare the voice clarity of CDMA vs GSM... I will always say that CDMA is much better...

[inderpalsingh 0]

I find the below mentioned article from the net regarding GSM,CDMA's differences, comparison technology evrythin about them.

I made lot of efferts in searching this article & hence I all request you all to communicate/post your reactions.

GSM vs. CDMA:

Implications for the development of Wireless Communications

India is on the threshold of major telecom investments. Licenses were recently granted for the fourth cellular operators in all circles. The cellular operator has the option of deploying one of the multiple technology platforms available. Besides the cellular operators, the basic telephony sector is also heating up with WiLL (Wireless in Local Loop) being the talk of the town. Amidst all this excitement there are some voices of concern too. Given the scale of investments, everyone wants to be on the safer side, the same holding when it comes to deciding about the mobile transmission technology to be implemented. Of the many possible alternatives the two most likely probable are GSM and CDMA. When mobile telephony was introduced in India, CDMA was an emerging technology, and as such GSM was the only choice. The situation is different now and hence there is a need for evaluating the deployment alternatives. This paper tries to do a comparative evaluation of the two technologies and then suggest recommendations concerning possible deployments.

CDMA

Developed by Qualcomm for the US Military, Code Division Multiple Access is a system that enables many users to share the same frequency band at the same time (called frequency spread). Each signal is encoded differently so that it can be understood by a receiver with the same code. CDMA is often compared to an airport transit lounge, where many people are speaking in different languages. Each listener only understands one language, and therefore concentrates on his or her own conversation, ignoring the rest. But a roomful of people all talking at once soon becomes very loud. Everyone ends up trying to shout above the background noise, which just makes the problem worse. To prevent CDMA codes are chosen so that they cancel each other out.

GSM

Short for Group Speciale Mobile, GSM uses narrowband TDMA, which allows eight simultaneous calls on the same radio frequency. As of the end of 1997, GSM service was available in more than 100 countries and has become the de facto standard in Europe and Asia.

The Technologies Behind

GSM CDMA

Type of Multiplexing TDMA & FDMA Spread Spectrum

Modulation Used GMSK QPSK/BPSK

Carrier Bandwidth Available 800, 1800, 1900 MHz 800, 1800, 1900 MHz

Per user bandwidth 200KHz, 13 Kbps for voice, 9.6 Kbps for data 1.25 MHz

Frequency Reuse 3,5,7 None

Handoff Hard Soft

Countries Employed In Europe, Asia US, South Korea

Which is better?

While it may not be possible to conclusively state which is superior, these competing technologies can be compared on some select parameters.

Cost to roll out Network

The cost parameter used in evaluating a cellular technology is data rate/per subscriber per rupee. On this parameter, CDMA scores over the GSM. CDMA based technology is also cheaper in terms of capital expenditure, measured on the scale of cost of line equipment per subscriber. A CDMA line costs $ 180 vis-à-vis $250 for a GSM line. The cost of cell sites is also reduced. The advantage in variable costs are:

• Smaller cell-to-cell operation overhead

• Increased efficiency (in terms of telephone traffic, or Erlang capacity)

Scalability

CDMA can support more subscribers in a given cell area for a given bandwidth. In addition, the capacity of the system is not as rigid as in GSM. While, GSM cannot add more than a fixed number of subscribers in a cell, in a CDMA network the system can add on users, though with a deterioration in service. It is also easier to extend range of reception and service area in a CDMA based network.

Quality of Service

CDMA is widely believed to offer superior voice quality. Since CDMA works on a single frequency, transition from one cell sites leads to softer handoffs in comparison to a hard one in GSM.

Cellular Communications Security

The principle of operation of CDMA makes it a very secure communication technology. Even GSM has not been found wanting in security aspect of mobile fraud.

Power requirement

The power requirements in CDMA are lower than in GSM. This results in longer battery life & low radiation risk for the user.

Hotspots

In GSM, high mobile density areas lead to creation of Hotspots, where it is not possible to add more subscribers. This happens in areas like Stock exchanges & financial districts. The CDMA based network can delay this.

Initial & Handset costs

Though running costs of CDMA based networks may not be high, they have high initial costs. If an operator is going for a second network, this may turn out to be costly as marginal increase in subscribers would not be very large. Handsets for CDMA are most expensive as compared to those for GSM.

Roaming

The biggest advantage with the GSM is its widespread deployment in Europe and Asia. This is self evident from the diagram below. CDMA currently has merely 82 million users vs. the 456 million of GSM. The user of a GSM network can thus expect easy international roaming. (See Figure)

Value Added Services

Value added services like SMS, gaming and internet access have become a major source of revenue of network operators. They also help in attracting customers. Both GSM and CDMA score almost equally on this front.

There are a few factors that do not favour deploying a CDMA network. CDMA being a patented technology, all CDMA equipment & handsets require a royalty to be paid Qualcomm. Moreover, CDMA being of a new, proprietary nature not all its flaws are known

The Indian Scene

The critical factors on which decision to adopt a technology in India will depend can be examined as below:

Penetration of Telecom Network

It is imperative for India to improve the penetration of telecom services which at present is at abysmal levels compared to rest of the world. CDMA based WLL is a step in the right direction. With operators such as BSNL saying that WLL will be cheaper than landlines, it is hoped that the penetration in India would improve. Any cellular technology, likewise, should be amenable to the above objective.

Investments

In India, the cellular service providers have set up extensive GSM based networks. An estimated Rs. 21,000 crores have been sunk in building this network (entirely GSM based). A new technology such as CDMA needs to be examined for any potential destructive innovation.

Roaming

One of the major concerns of cellular operators planning to roll out a CDMA network is whether the mobile device will enable roaming facility in other parts of the country. If there is no large scale adoption of CDMA among the operators, a consumer can be stuck with a service which does not offer roaming service. With GSM already have been set as the standard all over India, this is quite a possibility. At the same time, it needs to be borne in mind that the number of subscribers going in for roaming is rather low and most of the calls being made are inter SDCA calls. There are even fewer people who opt for International roaming. An Indian consumer would not care much for premium services such as roaming as long as he gets mobility within his circle.

3G

India had an advantage over the rest of the world in that it did not have any legacy networks and was directly able to leap frog into an advanced technology like GSM. In a similar vein, while implementing any new technology, we need to consider its upgradability to 3G. 3G promises to become a major revenue driver for operators, though not in the near future. Unfortunately, at this point of time it is not clear which of the two - CDMA 2000 1X and WCDMA - CDMAone’s and GSM’s migration path to 3G respectively are going to be adopted worldwide. CDMA 2000 1X is believed to have a straighter path to 3G with fewer stages.

Recommendation

In recommending the deployment strategy for a telecom operator, the following need to be kept in mind. Firstly, Indian customer is price sensitive who would not mind a cheaper option even if it comes with a lower quality level. Second, given the low penetration levels in India, any technology which promises to increase it radically should be seriously considered. Thirdly, the telecom operator would have to make a huge investment while setting up its network; hence it is imperative that it gets the customers to make it economically viable to operate. Hence a technology which can support more customers at the same time would be beneficial to the operator. Given these considerations we suggest the following recommendations.

The Basic Services Telecom Operator

What to deploy

CDMA based Limited WiLL telephony.

Why

The current policy framework of Indian telephony is such that in case a Basic Service operator provides limited mobility then there are no spectrum costs to be paid to the government. There is therefore a possibility of providing mobile telephony services at prices equal to that of landline services. Hence Basic Service operators should take advantage of this policy and provide cheap limited CDMA based WiLL services to the customers. CDMA technology is stressed it alone can address the huge user base which would result once WiLL services are introduced.

The Fourth Cellular Mobile Services Operator

What to deploy

CDMA based cellular mobile services.

Why

The rational is quite simple. CDMA supports more user than GSM, given the same resources. This means that a mobile services operator using CDMA would be able to support more customers than an operator using GSM. In cellular mobile services industry a major portion of the costs to customers originates from the huge fixed costs borne by the operator. This cost reduces as the number of users increases, implying that more users means lesser call rates, which results in still more users. This obviously is a cycle which only a CDMA operator can support given its excess capacity as compared to a GSM one.

Given these recommendations, it is possible to create a telecom infrastructure in India which not only helps in the underlying goal of increasing telephony penetration but also suits an increasingly market dominated environment.

At the same time, we may point out that having a stand-alone CDMA network with the rest of the country having GSM based networks is fraught with technological and financial risks.

References

1. WirelessAdvisor.com Forums- TDMA or CDMA,800 or 1900 – which is best?

retrieved August 11, 2002 from http://www.wirelessadvisor.com/waforums/

messageview.cfm? catid=16&threadid=3561

2. War of the Standards GSM vs CDMA - M-CommerceTimes.htm

Retrieved August 12, 2002 from http://www.mcommercetimes.com/Technology/ 95

3. Wireless Communications – GSM vs CDMA

Retrieved August 12, 2002 from Wireless www.telecom.globalsources.com/ MAGAZINE/WC/0206/GSMVS.HTM

4. The Shosteck Group (june 2001) GSM OR CDMA :The Commercial and Technology Challenges for TDMA Operators 38 pages CDMA development group

5. Cellular Operators Association of India

Retrieved August 12, 2002 from http://www.coai.com/telephny.htm

[@ksh@T 20]

dear friends in my study of telecom market i came to know something about he issue of spectrum which is HOT these days...Actually spectrum is the only thing which acts as a life line for CELLs. You might be aware that TATA had offered 1500cr for spectrum...Does ne1 knows why?

the answer is that all the GSM operators have "Stuffed the govt. and TRAI and all The DoT officers" to go agaonst the CDMA operators so that the spectrum is available of 1900MHz to GSM Operators so that they can offer great services....BUT after this step of TATA all the GSM operators are giving a thought....Ans Y?

Simple they wont be able to expand asap. as CDMA expands more fast than GSM and if CDMA operators get a major chunk in spectrum then GSM would fail in india as its in AmericaS. This is the only reason why The good CDMA handsets are not introduced in india. as they have been optimized for global Frequencies....SO ne comments by others....This is just to share the hidden Facts... int it!

Akshat Jain

[Puneet 0]

the answer is that all the GSM operators have "Stuffed the govt. and TRAI and all The DoT officers" to go agaonst the CDMA operators so that the spectrum is available of 1900MHz to GSM Operators so that they can offer great services....

If I read the TRAI recommendations right, GSM operators would be getting the IMT-2000 spectrum only by December 2006, when the defence would vacate it. One and a half years is a too long a period in telecom, so GSM operators certainly do not have an edge over CDMA here. However, CDMA operators are getting additional spectrum in the lower range, which would still enable them to offer enahanced data services. That's why GSM operators were crying foul, as this would give backdoor entry to Reliance in 3G services, while GSM would have to wait till defence vacates the spectrum.

GSM would fail in india as its in AmericaS.

GSM never failed in America. In the initial days of mobile technology, two seperate streams were developed, one led by european companies which favoured GSM and second led by American companies which favoured TDMA/CDMA. Till recently, there were no GSM networks in America as it was never launched there. However, all recent networks (led by T-Mobile) in America use GSM.

This is the only reason why The good CDMA handsets are not introduced in india. as they have been optimized for global Frequencies....

32976[/snapback]

There is a basic difference in CDMA and GSM handsets. GSM handsets require only a SIM card to network enable them whereas CDMA handsets require operator programming to do so. So there is a wide open market for GSM handsets, as one can change his/her handset as his/her clothes, however, changing CDMA handset would require operator intervention everytime which is a cumbersome process. And this drastically reduces the market size.

As CDMA handsets have to be programmed by the operator, the handset needs to be compatible with their network and this further restricts the model availability.

Also, CDMA is a patented technology and most of the handsets use chipsets developed by Qualcomm which holds the patent over CDMA, thus increasing the costs of the handset. To get over this, CDMA handsets have traditionally been subsidzed by operators (in US market).

CDMA has been operating on Global frequencies in India till now.

There are plenty of factors which affect the model availability in any market, and these are just a few of them.