***Software Defined Radios (SDR) in Secondary Markets***

***J. Mitola III***

## 31 May 2000

Mr. Chairman, Members of the Commission, distinguished panelists, ladies
and gentlemen.

Thank you for the opportunity to address the question of how
software-defined radio may contribute to secondary markets.

As many of you know software-defined radio is an emerging technology. It
has its roots in digital radios, radios that use software in digital
signal processing chips to implement air interfaces within a single
radio band, within a spectrum allocation.

SDR technology extends digital radio by the inclusion of wideband
antennas, wideband RF front-ends, and wideband analog-to-digital
converters, so that one radio device may access multiple RF bands under
software control. With multiple air interface personalities, one radio
may operate on multiple bands in multiple modes, although not all at the
same time. A single channel radio uses only one of its personalities at
once. A dual channel radio can operate on two different bands with two
different air interfaces at once, and so on. Commercial operators are
actually sponsoring the development of this technology because it offers
the potential of "future proofing" the infrastructure against changes in
air interface standards. For example, the third generation of wireless
(3G) will be based on wideband code division multiple access (W-CDMA).
But the 3G standard defines an enormous number of combinations of data
rate, Quality of Service, tariff, and availability. Data rates, for
example, range from a few kilobits per second to 2 million bits per
second for a single user. The W-CDMA air interface could be implemented
in single-function silicon in a handset. More likely, however, that
silicon will include some kind of programmable analog to digital
conversion function so that the handset can operate on second and/or
first generation networks while 3G is rolling out. The first- and
second-generation modes would be based on software personalities. This
is the direction in which the gobal wireless industry is moving. So we
have a wideband, 20 MHz-capable hardware device that is also operating
as the front-end for a 200 kHz RF carrier for its software GSM mode and
for a 25 or 30 kHz RF carrier for IS-136, AMPS, Nordic Mobile, or other
first generation standard. These narrowband modes are being implemented
almost entirely in software.

That same SDR technology could be unleashed for secondary markets.

Let me use an analogy. About 25 years ago, my wife, Lynne' and I bought
our first home, a townhouse. On our first Thanksgiving there, we
neighbors got together for a game of touch football in our back yards.
There were no fences, so we had plenty of room to play. The next year,
however, we couldn't play because everybody had a fence -- some for
dogs, some for kids, some to protect their flowers from us football
players. Next Thanksgiving we all commiserated about the good old days
when we could play football in the back yards.

Using secondary spectrum is a lot like playing football in the back
yard. In the past, the only way to guarantee that the football players
would not crash through the Petunias was to build physical fences,
physical limits on the hardware transmission devices. With
software-defined radio, however, we are beginning to tear down the
fences. For example, within a year or two, an SDR handset could access
not just first through third generation cellular and PCS, but all the
other spectrum from 400 to 960 MHz in a low band and from 2 to 5 GHz in
a high band. This is a football player who can jump over the existing
fences in stride.

As we progress towards a proliferation of ever-more-affordable and
smarter SDR technology, we will be approaching the backyards in my
current neighborhood. We live on a golf course, and there are no fences
in the back yards. There are, however discrete little white stakes that
show the golfers where their balls are out of bounds. Occasionally, a
Divot is taken out of my back yard. But my neighbor and I can throw a
football around when the mood strikes.

In order to have an orderly system with few physical fences, you have to
have good rules and effective enforcement measures. In the past, though,
the radios were not smart enough to obey the complex rule sets needed to
switch from, say, a cellular band to what is normally a police band in
order to get to a spare Digital AMPS channel during peak loading of the
cellular radio network. I recently wrote a paper called "Cognitive Radio
for Flexible Mobile Multimedia Communications" in which I describe a
spectrum rental protocol by which spectrum "owners" like the police
could rent unused spectrum for periods as brief as a few seconds to
secondary users such as cellular operators. Within a few years, the
radio technology will be capable of accessing the spectrum in this way
and of automatically obeying the intricate rule sets needed to assure
equitable access of primary users. I call this the spectrum rental
protocol because in this vision of the future, those to whom the
spectrum is allocated would have the free-market incentive to generate a
revenue stream by charging secondary users for that spectrum. This
creates financial incentives for primary users to invest in the SDR
technology required to offer spectrum for well-orchestrated secondary
use -- i.e. for rent. I think it will take a combination of SDR
technology, SDR based rules of etiquette that are algorithmic and that
admit few abuses, and financial incentives to take the next big step in
secondary uses of spectrum.

Let me conclude by emphasizing the fact that we need good rules, and it
will take some well-instrumented scientific experiments to develop them.
I know how I feel when I see physical proof that somebody's Doberman
visited my unfenced back yard conducting business in an unauthorized
way. Now if that Doberman had had a smart electronic collar with a GPS
motion sensor, he would have been persuaded not to stop for ***that***
long in my back yard. Some secondary users of spectrum might
inadvertently fall into similarly undesirable behavior unless the
regulators have smart electronic collars on the SDRs. I believe,
however, that well-heeled SDR technology can be developed. It can help
us both create the economic incentives and enforce and rules needed for
both good football games and good neighbors. Oh, as always, these are my
personal views and not those of the US DoD nor The MITRE Corporation.

Thank you very much.

Joe Mitola