Subject: [NEXTEL-1] Vanu Bose, President Vanu, Inc - A Software Driven Approach to SDR Design

From: Marcelrf <[email-masked]>
Date: Thu, 11 Mar 2004 19:40:07 -0500

.Jan. 2004

A Software Driven Approach to SDR Design

Vanu Bose, President Vanu, Inc

It’s been nearly ten years since the SpectrumWare SDR project’s unique
software-first
approach showed that a hardware-independent, object-oriented methodology
was the
right decision. How’d we get there, and where to next?

Software radio architectures have traditionally taken a
hardware-oriented approach, driven by the signal processing capabilities
of the underlying processing platform. SDR systems have typically been
designed around a combination of processing technologies such as DSPs,
FPGAs and other specialized reconfigurable processing devices. The other
aspects of the system architecture, such as the RF, analog-to-digital
conversion and the system I/O, are then designed around the capabilities
and limitations of the processing devices.

Unfortunately, the software architecture itself is often an
afterthought, and consists of several different development and
operating environments to accommodate the processing elements in the
system. This approach results in a complex software development and
operating environment, which significantly increases cost, development
time, portability and software flexibility. As the underlying processing
devices continue to improve,more of the system complexity gets moved
into software, increasing the penalty associated with a poor software
architecture.

A better approach is to focus on the software architecture first, using
a distributed computing, open operating system, and an object-oriented
methodology.  In this way, COTS hardware can easily be introduced and
spiraled via technology refresh. This software-driven SDR design
approach has nicely evolved over the past decade. Its evolution can be
traced by following the path from a university research project called
SpectrumWare to the first commercial deployment of an SDR-based cellular
network using industry-standard servers.

SpeakEasy

The SpectrumWare project applied a
software-oriented wireless communications
approach with distributed signal
processing. The research direction of the
SpectrumWare project was heavily influenced
by two software radio efforts: the
military SpeakEasy project and the commercial
products of the Steinbrecher
Corporation.

According to Upmal and Lackey in
“SPEAKeasy, the Military Software
Radio” IEEE Communications Magazine
(NY: IEEE Press) 1995, the SpeakEasy project was started in 1991 and was
the first large-scale software radio. SpeakEasy was motivated in large
part by the communications interoperability problems that resulted from
different branches of the military services having dissimilar
(non-interoperable) radio systems. This lack of communications
interoperability can be directly linked to casualties in several
conflicts. SpeakEasy had a very aggressive goal of implementing ten
different radio waveforms in software on a single platform. The
designers chose the fastest DSP available at the time, the Texas
Instruments TMS320C40 processor, which ran at 40 MHz. Since this was not
enough processing power to implement all of the waveform processing, the
system boards were designed to each support four ’C40s as well as some
FPGAs.

In 1994, Phase I was successfully demonstrated; however it involved
several hundred processors and filled the back of a truck. Moore’s Law
provides a doubling in speed every eighteen months, and since it had
taken three years to build the system and write all of the software, two
doublings had taken place. This seemed to indicate that the number of
processors could be reduced by a factor of four.  However, SpeakEasy
could not take advantage of these newer faster processors, and the
reason was the software.

The software was tied to ’C40 assembly
language, plus all of the specialized
glue code to get four C40s to work
together with the code for the particular chosen FGPA. The observation
was that it had taken three years to write software for a platform that
Moore’s Law made obsolete in eighteen months. Furthermore, a software
radio pushes most of the complexity of the radio into software, so the
software development could easily become the largest, most expensive
part of the system. These observations led to software portability being
a key goal of Vanu Bose, President Vanu, Inc.

More:
http://www.cotsjournalonline.com/pdfs/2004/01/cots01_softerside2.pdf
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