Mar 11, 2003 07:47 PM
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(Updated Mar 11, 2003 07:48 PM)
Before we go on this .please note that in the current marketing war between telecom co's, consumer is the end beneficiary . Here let us limit the discussion about technology only and not specific to any Brand/Company . All Brand/Company names are for illustration only . Comparison between GSM-based cellular Service and Limited Mobililty GSM and CDMA: The Basics GSM: The Global System for Mobile Communications(GSM) divides the users by frequency channels and time slots. The available spectrum(4.4 MHz – 6.2 MHz in India) is first split 200 kHz channels, which are then chopped sequentially into time slices. Users of the channel take turns in their allotted time slots in a round robin fashion; thus only one person is using the channel but he uses it for very short bursts(about 577 micro seconds). Further to optimize the frequency usage and cover the large areas, the total available channels(22 for 4.4 MHz) are split into 7 reusable groups. To avoid interference at the boundaries of cells, no adjacent cell shares the same frequency channels. CDMA: Code Division Multiple Access(CDMA) on the other hand, lets everyone transmit at the same time. CDMA works by assigning unique codes to all speech bits and the encrypted signals are dispersed over a wide frequency spectrum(1.25 MHz). The signals are picked out by the receiver’s equipment that is tuned/programmed to identify that code. In contrast to GSM, same frequency channels are used in each cell In India, Limited mobility for Basic Operators(BSOs) was recommended by TRAI in Jan'01 and subsequently adopted by the government as a cheaper alternative to fixed line to increase the Tele-density. This is typically done through Wireless in Local Loop(WLL) systems where only the last mile is wireless(instead of Copper wires) and the terminal is either fixed or has extremely limited mobility .The approval of WLL in the Indian context envisaged mobility within a Short Distance Coverage Area(SDCA), and each DSCA can be as large as 25kms radius. WLL or ‘Wireless in Local Loop ‘ mobile service is a restricted service. It will work only within the Short Distance code Area(SDCA), which is typically city limits. For instance, a subscriber to WLL mobile in New Delhi cannot use your same phone & phone number in Gurgaon, Faridabad, Ghaziabad or NOIDA, which fall in different SDCA This service is offered by Tata Indicom, Garuda from MTNL, Reliance et al. On the other hand, GSM(provided by AirTel, Hutch, Idea, Spice, Escotel etc) is a ‘Complete Mobile service’, gives you unlimited freedom to stay in touch wherever you go – within your city, across the country or around the globe- on a single number CDMA(or Code division multiple access) is a mobile standard that is used in a limited part of the world. In India, WLL mobile services are being brought with CDMA mobile standard, and hence some operators are referring to it as “CDMA mobile”. A correct way of refer to this mobile service would be “Limited mobile or WLL mobile ” using CDMA standard. Speaking from statistics in 2001, 78% of the world’s mobile users went on GSM as compared to only 22% on CDMA standard. It is estimated that GSM is more popular than CDMA . Even the countries where CDMA originated are now moving to CDMA In case of CDMA you are stuck with one WLL mobile operator, because the WLL handset is programmed and ‘locked’ to work with the service provider who sells it to you. It does not have a SIM card. It is expensive and time-consuming to re-program the handset in case you want to change your service provider. On the other hand, GSM mobile services are based on SIM card that gives you the flexibility and the freedom to move from one operator to the other. In the unfortunate event of your handset being stolen/lost/damaged you can’t be reconnected almost immediately. You would have to go though the hassles of procuring a new handset, getting it re-programmed. The same process would have to be repeated when you want to change/upgrade your handset. So with CDMA you can forget the convenience of “Card Dalo, say Hello.” Also in case you like your friends phone model, you just can’t go & buy a new handset & fbe ready to flash around your new gizmo – all in a matter of 10 minutes as in GSM . In CDMA before you get ready to flash, you will be at your operators mercy . So forget a-new-model a month mantra in CDMA . Voice clarity & reach would go up as CDMA catches up . In current form it is acceptable in the areas where it is up . Remenber in Initial days of GSM voice clarity & coverage was an issue too, which got resolved over time . On CDMA SMSing is possible, but the legality of this is still an issue . And in today’s Mobile culture SMSing is crucial.You can send SMS from CDMA to CDMA, but not from CDMA to GSM & vice versa in all cases . It really is dependent on the two operators in question On CDMA, mobility outside of SDCA is still an issue and is not hassle free and seamless. Also, CDMA isrelatively newer technology in India and we do not know it’s flaws as of now while GSM has already undergone those teething troubles way back in 1995-96. Following parameters may help to make an informed choice: Importance of following in your usage pattern – 1. Mobility( i.e between different circles) 2. SMSing 3. Frequency of Handset change( or the need to change handset) 4. Your expenses on mobile Incase you are heavy user on first three parameters, then go for GSM and wait for CDMA to grow up . If last point governs your mobile life, and you can compromise on first three then go for CDMA, but read the fine print of the operator’s offer .Do not let slick marketing gimmick mislead you . Following table may further help you Parameter GSM-Service CDMA-Based Limited Mobility Mobility GSM-Service - Within each circle; nation-wide roaming CDMA-Based Limited Mobility - Limited to SDCA only Pre-Paid GSM-Service Allowed CDMA-Based Limited Mobility -Not Allowed Roaming GSM-Service Allowed CDMA-Based Limited Mobility -Not Allowed Handset Cost( Grey & refurbished included) GSM-Service - Available from Rs. 2, 500 onwards CDMA-Based Limited Mobility -Available from Rs. 5, 000 onwards Spectrum GSM-Service 4.4 Mhz going up to 8.8 Mhz based on need CDMA-Based Limited Mobility -5 MHz, alloted in slots of 1.25 MHz based on roll out
