Nice link provided by the Rocket thread.....
CDMA Leads GSM in Migration to 3G
Although GSM (global system for mobile communication) has assured consumers and organizations of a trans-global roaming facility and mobile voice and data communication services, developers think that its rival, CDMA (code division multiple access) could offer an edge in its evolutionary migration path towards wideband 3G (third generation) capabilities.
The migration paths for CDMA and GSM, both internationally recognized standards for mobile cellular wireless communication, will eventually converge on equivalent versions supporting 3G services for hybrid data types comprising voice, video and graphics. CDMA is expected to dovetail into wideband CDMA (WCDMA) while a similar evolution for GSM is destined for UMTS (universal mobile telecommunications service).
But technology developers do not see either WCDMA or UMTS being commercially deployed for at least a year, possibly two. The reason for this has to do with settling standards, interoperability and backward compatibility issues rather than technology or end-user pricing.
Given normally to the practice of risk-hedging, vendors have spread their products across the two competing standards and, as a consequence, do not expect to find gaping holes in their revenue profiles if a standards shake-out occurs.
Upgrade Paths by Nortel
What looks like an inevitable evolution for vendors is, however, a nightmare for service providers who have invested heavily in current and previous generation equipment as well as in developing services and marketing them to subscribers.
Technology developer Nortel Networks, for instance, perceives the migration to 3G differently for the two "families."
With CDMA's current implementations, IS95A and IS95B, using channel width of 1.25MHz, the path offers modular scale-up in terms of speed of data transfer. The first step is a module upgrade to 1xRTT CDMA allowing speeds of 144 kbps. The company has also announced the success of packet data and voice call trials on a live 800MHz CDMA network by Telstra in Australia.
Intermediary upgrade for the GSM stream is a 2.5G GPRS (general packet radio services) system capable of handling a maximum of 107 kbps, according to Mark Whitton, Nortel Networks director Product Managment CDMA Access 3G Wireless and Carrier Solutions.
The CDMA route has two further product upgrades from 1xRTT - one path to high speed data-only capable 1xEv or HDR (high data rate) of 600 kbps capacity and the other to wideband both voice and data capable 3xRTT with 800 kbps. Both upgrades can sustain busy traffic rates of up to 2 Mbps.
The voice/data upgrade 3xRTT is further differentiated into two flavors - one of them a multi-carrier 3x1.25MHz three-split channel and another a direct spread 5MHz single tube.
The best intermediate upgrade landing for GSM - ahead of a full-steam quantum jump to 3G UMTS/WCDMA - is an EDGE system offering 384 kbps speeds at maximum, Whitton said.
GSM Fights Back
This summer, AT&T Wireless Services and Nortel Networks are to conduct non-commercial trials of GPRS core networks that are part of the 3G TDMA-EDGE architecture in the US.
The CDMA progression is a logical one while GSM has no migration path to CDMA but to GPRS, according to Herman Pon, chief technology officer for Nortel Networks.
The predominance of current generation GSM in Europe and many parts of Asia and elsewhere would make a decision difficult for service providers although vendors such as Nortel offer bridges between GSM and CDMA IS95 at the physical interface to the protocol layer (though not for voice). The data side bridges are facilitated by IP (Internet Protocol) that is at the core of networking.
In the current reckoning - judging by spread of acceptance - GSM has won. But lacking the incremental migration path would be a disadvantage, according to Pon.
Pre-standardized versions of WCDMA are being tested in field trials in France and Canada but no trials of UMTS are scheduled up to the second quarter of next year, according to Whitton, due to a great deal of work still needing to be done to arrive at standards specs for UTMS.
While its future looks bright, current CDMA implementations have not made a dent in the global market, with the exception of US. Potentially large markets like China have been cautious.
The delay in a decision by China Unicom on the deployment of CDMA was due to upgrades becoming available in the market and not because of second thoughts on CDMA itself, Pon said. In a recent announcement, however, Unicom had expressed preference for 1xRTT. It would be a great advantage for China to deploy both systems as that would give the local equipment manufacturer-exporters essential exposure to the functioning of both, Pon observed.
Emerging requirements for higher data rate services - spurred by the convergence of voice, video and text that IP has enabled - and the need to enhance spectrum efficiency for multiple access, are driving the move towards 3G systems.
by T M Shankar
(August 2000 Issue, Nikkei Electronics Asia)
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