*** 2003 Software Defined Radio Conference
By John Latta
November 17-19
Orlando, Florida
The origins of the SDR date back 10 years with the US Department
of Defense. Under the JTRS (Joint Tactical Radio System) a
Software Communications Architecture (SCA) was developed which
has become the basis for military radio procurements. However the
potential of SDR goes well beyond the military. Early regulatory
efforts, including those by the FCC, recognized the potential of
this technology and now include regulation activities in Europe
and Japan.
With wireless filling out the anytime anywhere matrix this
technology is becoming all the more important. At the same time
the radio technology has become very complex. The standard for
GSM is 5,000 pages. The objective of SDR is to move the digital
and software controlled sections of the radio as close to the
antenna as possible. This has profound impacts on the
architecture of the radio and the processing rates of the
components. Some feel it requires fundamental rethinking of the
architecture of how processing is done to accomplish the radio.
Now some highlights.
University of Karlsruhe
Professor Friedrich Jondral gave an overview of SDR including
some of the latest work at the university. Some of the
interesting points included:
They did a spectrum utilization assessment at Lichtenau,
Germany in 2001. Those spectrum plots were shown and was
illustrated how little the spectrum bands are actually being
used. The measurements went from 50 – 1GHz. This shows the
potential for overlay uses of the spectrum if radios can
operate on a non-interfering basis.
Research at his institute examined the concept of Licensed
Users (LU) and Rental Users (RU). The assessment was done of
a LU based on FDMA/TDMA and the RU being HIPERLAN/2. The
intent was to show that these two very different
technologies could co-exist.
In the LU/RU problem, to keep the impact on the radios
small, there was no “out-of-band” coordination of the
spectrum use. Thus, the effectiveness of this technique was
very much dependent on interference detection and
minimization.
One of his graduate students, Arnd-Ragnar Rheimeier,
presented a concept for modular radios. He suggested that a
SDR means that the A/D and D/As are as close to the antenna
as possible and that the DSPs be done in software, when
flexibility is desirable.
It was suggested that significant work is underway in the
automobile industry with SDR. The realization has come that
all cars will have GPS and radio technology of some type –
even including satellite radio. Currently there are a number
of projects to integrate the radios for both into one.
Intel
Mike Chartier, the Intel Ombudsman for “Radio Free Intel”
reviewed the state of SDR regulatory actions. He made a number of
points that included:
If SDR is an inflection point in technology it must also be
met by an inflection point in the regulatory environment.
Key regulatory issues are spectrum management, device
certification and competitive issues. This latter point
asked the question if the radio interfaces should be Open.
Intel characterized the regulation in terms of generation.
2nd Generation SDR proceedings are already addressing
“overlays.” That is, the deployment of agile and smart
radios for innovative spectrum management techniques. One of
the most interesting suggestions is the consideration of an
Overlay in the existing TV bands. This is particularly
valuable spectrum because of its relative long wavelength
and excellent propagation characteristics compared to 2GHz
and 5 GHz. A 2nd FCC SDR proceeding is planned on cognitive
radios.
Xilinx
The CTO of Xilinx, Ivo Bolsens, looked at enabling the future of
SDR. Key points included.
SDR is at the union of computational and wireless complexity
in user devices. An example was given of a channelization
problem which has 1GHz 8 bit samples, over 16 channels which
in turn feeds 16 complex filters with 14 taps. This results
in a compute requirement of 30GMAC/s and memory bandwidth of
400 GB/s. Another example is a smart antenna with 12
elements and 12bit converters. The I/O requirement is 30
GB/s.
From Xilinx’s perspective FPGAs are the best way to address
these needs. One of the reasons is that FPGA have been in
close sync with the semiconductor fabrication technology,
especially the reduction in line width. This is, in part,
due to the regular nature of the gate arrays and the value
of high gate counts to fabricate essentially parallel and
random structures. He stated that last month Xilinx
announced a 1B transistor gate array.
A major issue is the cost cross over point between FPGA and
ASICs. In an interesting graph Ivo claimed that FPGAs have a
cost advantage over 90nm, 300mm based ASICs up to 200k to
300k units.
Xilinx is seeking to recast the role of the FPGA in this
market by creating a platform with their products. In order
to do this there must not only be the gate array but the
tools to accomplish the design. Ivo claimed that the
combination of:
Matlab
Simulab
Stateflow and Stateflow Coder and
Xilinx System Generator
makes the development of these complex circuits possible.
EU
Dr. Jorge Pereira, Scientific Officer, European Commission DG
XIII, Mobil & Personal Communications, provided a refreshing view
of the role of that the technology could play. It is expected
that SDR will eventually lead to “full spectrum sharing.” Given
the long term leases of spectrum, which has been gained from
auctions, it could be 10 – 20 years before the full scope of
available spectrum can be used in a shared environment. There is
another twist, those holding spectrum, which is not being used,
may be forced to lease it. In the near term, actions are being
taken by the FCC, German RegTP and UK RA to consider options for
Dynamic Spectrum Allocation.
At the center of Jorge’s views was a broad vision for 4G or the
next generation of radio technology. It includes:
Multimode terminals
Adaptive Array Antennas
Optical backbone
Reconfigurable Radio networks including the antennas and
Remoting of base stations including ad hoc base stations.
A central theme of Dr. Jorge Pereira’s comments is that
Reconfigurability is critical to these networks. These should be
self-organizing reconfigurable networks. The importance of this
extends to seamless security, scalability and distributed
control. An open architecture is intended to allow 3rd parties to
contribute to and improve the provisioning of personalized
services.
Vanu
Dr. John Chapin, CTO of Vanu gave what he described as a
software-centered view of SDR. He sees the industry in transition
from hardware to software. History has shown when such
transitions happen the challenge of implementation moves from
hardware which becomes progressively easier to implement and with
a rise in the software challenge and its complexity. In SDR this
is particularly forbidding.
He cited the SDR hardware challenges which include:
Need for high-speed processors;
Need for low power processors;
Ability to convert formats across broad frequency spectrums;
Need for improved wideband linear power amplifiers
Very High-Q tunable filters and
Antennas which operate for multiple bands.
Consistent with the view that software will rise in complexity as
it overtakes hardware he provided the following challenges:
Processing the increasing waveform complexity;
Managing the high computational load;
Achieving interoperability with legacy radios and
Meeting time to market objectives.
The following factors only serve to multiply the cost of software
development: need to support multiple waveforms and field
upgradeability.
All the more difficult is that many of these radios are both
mission critical and life critical. To meet these goals implies
costs which are X those without such requirements.
His overall message was one of caution, from a company that is
doing just what he described.
Papers
Here is a sample of papers presented at the conference.
FPGA Tradeoffs for Software Radio Applications
Company: Pentek
Interesting assessment of the trades and likely uses
for FPGA’s compared to ASICs in SDR implementation.
The Use of Ontologies for Self-Awareness of Communications
Nodes
Company: Northeastern University
An important topic is to be aware of how nodes operate.
This is called the ontology of communication. This
paper examines how this can be done.
Field Trials of an All-Software GSM Basestation
Company: Vanu
This is an example of how SDR can be done and it used
HP ProLiant servers to accomplish the task.
Compact Multi-Band Handset Antennas for SDR Application
Company: SK-Telecom
This is not a SDR hardware example but the
implementation of an antenna that could be used in a
SDR handset. The antenna was designed to support both
CDMA and GPS.
Open-Source Experimental B3G Networks Based on Software-
Radio Technology
Company: Institut Eurecom
Considerable momentum is building behind the use of
Linux and the open source model for SDR. This paper
examines a radio architecture based on the open source
model.
Biometrically Enhanced Software Defined Radios
Company: MIT Lincoln Laboratory
Why not include security and the authentication
function in the radio. This paper suggests that
biometrics can be used in SDR.
Wave Comments
One can only take a long range view of SDR. It is at its
earliest stages. The technical challenges are very
formidable and the regulatory issues daunting. The prospect
for realizing anytime anywhere any bandwidth any mobility is
significant.
Speculating on the future is easy, what is difficult, is the
present. It was very clear that SDR is enormously complex.
The scope of this was evident when it was suggested in a
talk that SDR is the end of standards. That is, the radio
implementation will be so complex that standards will not be
possible. We regard this as a reflection of the immaturity
of the technology and not a fatal statement on the futility
of standards.
What will the wireless landscape look like when that time
comes? Will there still be value in emulating today's motley
assortment of wireless standards, or will there be enough
convergence around UWB, 802.11n, and 3G such that one or two
radios can do it all? In this case a highly reconfigurable
radio would be less valuable in a consumer application?
We strongly doubt that the PC will ever move to the
requirements of the date flow machine which is at the heart
of SDR, especially at the front end of the radio. However,
even at SDR we saw examples, from Vanu, that PCs can have a
major role. Thus, it remains to be seen what role an
attached computation device will have in SDR. This is an
important question that remains to be addressed.
Wave Issue 0345 01/09/04 Article 2-01