EBU • UER - Technical Review

No. 291 (July 2002)

Software defined radio

The title of this book may be grossly misleading for radio broadcast enthusiasts. The word "radio", as used here, does not mean the sound radio we are all so familiar with – it refers to all radio-frequency devices, networks and services, including any communications and broadcasting systems. In the book, "Software defined radio" – or SDR, for short – is defined as a reconfigurable, downloadable, software-controlled, multimode, multiband, terminal that could potentially adapt itself automatically to differing regional and "vertical" (proprietary) standards, interfaces and APIs (Application Programming Interfaces).

It is not a surprise to learn that the beginnings of SDR were to be found in the military community during the late 1980s, particularly in the USA. It was developed in order to overcome a multitude of different communications standards which receiving terminals would automatically have to decode and interpret.

The book gives numerous examples of how software radio may become an essential component of future 3G and 4G mobile communications systems. First of all, SDR could provide the potential for the handset to support multiple-air interface standards. Furthermore, SDR could support advanced roaming capabilities and the selection of the most favourable network to meet the user's preferences. It will be capable of optimizing radio transmission characteristics according to the service and traffic demands. It will facilitate over-the-air downloads of application software, as and when required.

However, there are a number of issues that require investigation, such as increased complexity and cost ... user control of the reconfigurability ... reliability and continuity of services ... and the effective and usable presentation of complex system trade-offs.

The SDR concept is potentially very attractive for broadcasters. Consider, for example, a broadcaster that is offering its subscribers a new version of a video codec, available as a downloadable software module. Software download may allow rapid and transparent improvements to the standard multimedia platforms. However, while in the mobile communication world every customer will be able to choose which features he (she) wishes to add to the terminal according to his (her) own needs and budget, in the broadcasting world the service operator will decide which features are to be implemented for all the users.

By the same token, reconfigurability will allow mobile operators to achieve increased control of their network capacity resources, in order to make more efficient use of them. For example, there may be congestion in a certain cell of a network, leading eventually to a collapse of the system. This can happen on the occasion of large public events, and at business and commercial centres, airports, etc. The operator may wish to increase the local capacity by dynamically reducing the bit-rate per user. One possibility would be to establish different prices for different levels of QoS (Quality of Service). In digital broadcasting, such as DAB and DVB, multiplex reconfiguration (e.g. altering the bit-rates of the programmes) is already a standard feature in order to maximize the number of programmes, while not going below a certain quality threshold. Such a reconfiguration must be followed automatically by a similar change in the receiver.

It can be concluded that the introduction of software radio technology will revolutionize the wireless communication market, altering the current business structure (new value chain, new services and applications, new business models). Similar changes, albeit not so profound, may be expected to occur also in broadcasting.

In the mobile telecom world, the first step in SDR standardization has already been taken by adopting MExE (Mobile Execution Environment). MExE is essentially a security framework to download and execute software directly on a mobile terminal. This system is designed to support SDR capabilities in a standardized manner in future 3G terminals.

Although mainly devoting its pages to wireless communication, the book gives an example of a successful implementation of SDR technology in DAB – by RadioScape in 1999. The company has actively pioneered SDR techniques in its own products, such as its RST 3000 and RST 5000 receivers for DAB, and also in the development of solutions at the heart of third-party products – Psion's Wavefinder (a PC-based DAB receiver) and the Texas Instruments DRE200 and DRE3xy digital radio baseband chips. At the core of these developments is the Communication Virtual Machine (CVM), a flexible development process that combines both design flow and runtime environments.

Furthermore, the RadioScape-led VIADAB project – Versatile Information Architecture for DAB – has defined an open-specification API for digital radio receivers in a PC environment. This interface allows the decoding of DAB data services, regardless of the make of the DAB PC card. The goal of VIADAB is to provide a set of middleware definitions and reference implementations. All functionality is provided in the form of plug-in data decoders which can quickly and easily be replaced with a new version, automatically over the air and with minimal disruption.

Those readers who would like to learn more about SDR should consult the findings of recent EU-funded IST 2000 research projects – such as CAST (Configurable Radio with Advanced Software Technology), MOBIVAS (Downloadable Mobile Value Added Services through Software Radio and Switching Integrated Platforms), SODERA (Reconfigurable Radio for Software Defined Radio for 3G Mobile terminals) and, in particular, TRUST (Transparently Reconfigurable Ubiquitous Terminal). There is also an SDR Forum <www.sdrforum.org> with more than 100 members representing all sectors of the telecommunications industry.

In conclusion, this interesting book is highly relevant for broadcasters. SDR approaches will bring new opportunities to digital radio and television. The book is comprehensive and representative, easy to read, and gives a lot of real-life information. It shows that SDR is not limited to the mobile and telecom communities but is increasingly being taken up by broadcasters. But at the same time, the book recognizes that the advent of a true software-reconfigurable "universal handset" still lies some way off in the future.

Software Defined Radio; Origins, Drivers and International Perspectives
Edited by Walter Tuttlebee
Hardbound volume of 329 pages
Ref: ISBN 0-470-84464-7. Price £55.00.
John Wiley & Sons, UK, 2002.
http://www.wileyeurope.com/cda/product/0,,0470844647,00.html

Franc Kozamernik