Let's Show Them What We Can Do
By Matt Desch
Processor power is not a problem. Voice coding is well served. New markets beckon for fixed access applications. We no longer need to tell ourselves that CDMA works, says Matt Desch, Nortels President, Wireless Networks. Its time to discuss the advantages of CDMA and to look to its future.
CDMAS: In your presentation at the CDMA World Congress, when you talked about the speed with which CDMA has been taken up compared with the time it took GSM to get established, you mentioned processing power as a reason CDMA may not have been viable 10 years ago.
Matt Desch: CDMA is a fairly complicated technology;
the algorithms that are required in processing a CDMA call are quite
complicated. One of the fundamentals of CDMA is that every mobile has
to be kept at the same relative power level coming in to a base station,
so you have to be able to be very fast and very precise in terms of
making power adjustments in each mobile. That requires a lot of computing
power both in the base station as well as in the mobiles. The power
control technology has to be very precise. It has to be controlled very
quickly in real time and so it is fairly processor intensive technology
- much more so say than IS-54, IS-136 TDMA or even GSM in terms of the
raw processing speed expected in a chip in a handset mobile. And 100
MIPs worth of power in a mobile might not have been cost-effective 10
CDMAS: Are you surprised that technology met your needs so fast?
Matt Desch: No its called Moores law. Basically it says that every 18 months or so, the computer chip can operate at twice the capacity in half the space of previous generations. What that means is you that can almost forecast from now until the year 2000 what kind of computing power youll be able to put into a chip in a cellular phone or a PCS phone, how many instructions per second and how fast those istructions will be able to operate. Its pretty mind-boggling: what today we can do on our fastest computer on a desk we can probably do on a cellular phone in two or three years. And if we can do that, then think of the kind of applications that you can have. We thought that you couldnt go any faster than 100 MHz , then 250 and then we get to 400 and now... I thought wed be gated by storage and by bus technology but were seeing very fast buses, were seeing terabyte storage. I think in five years well be amazed at how far weve come.
CDMAS: Fixed access is seen as an application that while second to network deployment may actually catch up in the next ten years to twenty years especially in developing countries.
Matt Desch: It wont take ten to twenty years.
I think itll probably take three to five at most for it to really
catch up. There are a couple of things keeping it back in developed
countries. One is cheap spectrum. If youve got to pay an awful
lot of money for the spectrum its going to make the business case
a little more difficult to achieve. And the other thing is the ability
to really drive the costs down to a very, very low level, say, $400-$500
per subscriber, which is really linked to technology and volume and
CDMAS: You remarked at the CDMA Congress that there was a feeling that everyone was relieved that CDMA had established itself and that was all very well but next year you would have to take on more issues in terms of differentiation.
Matt Desch: In the first world congress I felt that
everyone was saying since that there really werent many live applications:
"Dont worry this is going to work its a great technology."
CDMAS: Is that what you think the talking point would be or should be at the next world congress - and also differentiation?
Matt Desch: Absolutely. Differentiation in terms of
services in terms of what we can do. I think we have to talk
a lot more about data and data applications. I think we have to talk
more about how operators using CDMA can differentiate themselves from
those using GSM or TDMA. I think we have to consider applications of
this technology where its being used in new and unique ways. I
think we have to stress innovation, which which has always been a hallmark
of CDMA. We have to start demonstrating, talking about what are truly
the advantages of CDMA and what CDMA can do.
Matt Desch: Well, it varies by manufacturer so its hard to make a completely general statement but CDMA is able to achieve greater coverage than other technologies right now. CDMA is capable of using fewer base stations than you would use in another technology at the same frequency. But there are differences too between manufacturers of CDMA systems. For example, Nortel has something called a receiver noise figure - its very important in terms of deciding what your link budget is which lets you know how many cell sites you require for the same amount of coverage. Our receiver noise figure is under four decibels for 1900 Mhz and under 5 db for 800 Mhz which is better than our competition. That allows us to use fewer base stations when we engineer systems. So its not only variable by technology but by manufacturers.
CDMAS: Are you happy with whats available in the area of voice coding?
Matt Desch: There are three voice coders in CDMA right
now: the standard 8 kbit per second voice coder, the 13 kbit per second
voice coder and the enhanced variable rate 8 kbit/s vocoder. No-one
ever really used the original standard 8kbit/s vocoder . Some of the
early networks did but everyone seems to be pretty much in agreement
that that vocoder isnt good enough for the kind of capability
that CDMA is able to offer. All the networks in the 30 cities that we
have up and running in the US and the others around the world
are primarily the 13 kbit/s vocoder which everyone agrees is
the best-sounding vocoder bar none. The new 8kbit enhanced variable
rate - EVRC - vocoder is quite good: its certainly better than
the original one and its almost as good as the 13 kbit vocoder.
It has the advantage of course of providing additional capacity to systems.
CDMAS: Are you all ready for the next generation whatever that might be?
Matt Desch: Youd think thats where all the action is based
on the press releases. In fact multimedia PCS, as I like to
call third generation, is still four or five years away from
true implementation. The real fight thats on right now
in the industry is over whos going to own the IPR, whos
going to define the standards...