The cdma2000 plea: We want overlay!
After months of press release wars, the cdma2000 lobby
used the CDMA Development Group's Los Angeles
congress last November to state their case against the
W-CDMA standard. Tony Chan reports from Los Angeles
The cdma2000 case in a nutshell: W-CDMA provides no
backwards compatibility. According to speakers at the CDG
event, the designers of W-CDMA have chosen several
technical parameters that make it non-backwards compatible
to today's cdmaOne networks, while adding no notable
performance improvement.
The W-CDMA camp, led by Ericsson, claims that the higher
chip rate provides higher spectrum efficiency, and offers a
performance improvements as much as 10% over the
cdma2000 proposal.
Cdma2000 advocates say, on the basis of claimed extensive
testing, that the claim is misleading and simply not true.
Qualcomm and other proponents of cdma2000 say that a
higher chip rate offers only the same or comparable
performance, and represents a concerted effort by the
European community to deprive existing cdmaOne users of a
smooth migration path to 3G.
The 4.096 Mbps chip rate chosen by W-CDMA is not, in any
way, compatible to the current generation of cdmaOne, but it
was never intended to be. The W-CDMA lobby states
explicitly that backwards compatibility to current generation
technology would only slow down the adoption of 3G
services. Even an Ericsson-proposed “compromise” chip rate
of 3.84 Mcps was rejected by Qualcomm as unsuitable.
On the other hand, the cdma2000 chip rate was specifically
designed to be three times the current cdmaOne chip rate,
which allows the two to work together on the same
spectrum.
The issue is accentuated in the US, where there is a need to
preserve investments though the overlay of networks.
Lucent' Technologies' manager for government and
international affairs, Francis O'Brien, who is representing
cdma2000 to the ITU, says the overlay requirement is crucial
to American operators.
“The fact is the US already has the PCS (1,900 MHz)
spectrum occupied. The cellular (800 MHz) service providers
also want to deploy 3G,” O'Brien said. “They need some
flexibility on how to deploy these systems, and so, we
(cdma2000 camp) say backwards compatibility, but the real
key for them is to be able to do an overlay.”
Several major American cdmaOne operators, including Sprint
PCS, Bell Atlantic, and Bell Mobility, have already pledged
support for cdma2000, and have told their suppliers (Nortel,
Motorola, and Lucent) to move forward in their development
of cdma2000-based 3G equipment.
The American cdmaOne concerns about W-CDMA would
seem to be valid, but should W-CDMA accommodate the
requirements of just one country? After all, the US should
surely live with the consequences of its own spectrum
planning. And with just 16 million active subscribers
world-wide, compared to some 170 million on 2G TDMA
platforms such as GSM, PDC and D-AMPS, the cdma2000
supporters can't argue from a position of market power.
Related stories:
CDMA vs. CDMA
|
