Software-defined radio opens up new chances for the automobile industry
There was one thing in particular that 18-year-old George Frost missed when driving back in the year 1922 — listening to the radio. So he simply fitted a receiver into the door of his new Ford Model T, and thus invented the car radio. More than 80 years later, the car radio presents the automobile industry with much greater challenges: today, engineers have to provide a solution so that car radios are not only able to receive conventional analog signals, but digital radio too. Digital radio means better sound quality, a wider choice of stations, and services like weather and traffic information.
The multiple broadcasting standards for digital radio worldwide are a major challenge here — from Digital Radio Mondiale (DRM) or DRM+ through Digital Audio Broadcasting (DAB) or DAB+ to Terrestrial Digital Multimedia Broadcasting (T-DMB) and HD Radio. It does not look as though there could be any agreement on a single standard in the near future, because different countries have their own preferences: in the USA, HD Radio is standard, while Europe generally opts for DAB/DAB+/T-DMB, India listens to DRM, and Brazil cannot decide whether to go for DRM or HD Radio.
Fig 1: Around the world, listeners - and radio designers - are confronted with a confusing multitude of radio standards.
For the automobile industry as a global operator, that means producing a specific digital radio solution for each market, a degree of variety that costs time and money. Engineers are faced with evaluating, testing, and integrating different types of hardware so that drivers in different countries can simply do what George Frost wanted to do — listen to the radio in their car.
Software is more flexible than hardware
One solution can be seen in software-defined radio (SDR) together with multistandard processors plus flexible hardware accelerators. SDR is a radio system in which, in its pure form, typical components such as mixers, filters, modulators/demodulators, or detectors are replaced by software. The idea is not new, but since the software effort that goes into it is extremely high, to date the system was more relevant at an academic level.
The increasing performance of today's processor technology has changed that. Even though the SDR ideal — the entire radio processing by software being done by an all-purpose processor — still lies some way ahead of us, more and more aspects of signal processing can be handled efficiently in software. That helps OEMs to save hardware costs and get their vehicles to market faster.
The practical side of this can be seen in the following example: India is a budding market that is extremely interesting for automobile producers. The digital radio standard in place there is DRM (Digital Radio Mondiale), and by the end of 2012 the majority of Indians should be able to listen to the radio by this standard. Actually, in future, India's entire fleet of vehicles would have to be fitted with a dedicated chip tailored to support this standard. The solution must be found, evaluated, and integrated — a lot of work, work that has already been undertaken for other markets and other standards.
The economical approach
SDR is more attractive in this respect — instead of having to develop a separate solution for each standard, OEMs can integrate a chip with hardware supporting a number of standards. With the right software, they can activate it for a particular market. One example of such a chip is the SAF356x digital radio coprocessor from NXP, supporting the generally optional standards HD Radio plus DAB, DAB+, and T-DMB. The different standards are activated by software. The advantage for the OEMs is that they only have to run the integration process for the hardware once, no matter whether the radio is then put into the car of an American, an Indian, or a European.
The example also shows that SDR technology is not a matter of playing the radio just with an all-purpose processor and software. Such a system would not be economical at all. Instead the focus is on designing the chips so that each function is executed precisely by the function block that is best suited for it both technically and economically, regardless of whether they are based on hardware or software. This radio system consequently consists of at least two hardware modules: one for the FM/AM radio function, which always has to be created as the core system, so to speak, and a second one by which different digital standards are implemented through SDR. The latter can be used to match the market and then programmed to the appropriate standard.
Transitions and support
Nevertheless, there are two important aspects to bear in mind in modular solutions of this kind: interaction of the technologies and customer support. Firstly, the radio experience of today's George Frost should not be interrupted when a station changes its broadcasting from analog to digital reception (or vice versa). This is why the radio systems should support functions like seamless DAB-FM blending — i.e., roaming between standards — or time shift functions so that a radio program continues at the point where it was interrupted by the user, e.g., upon receiving a call.
Fig2: A flexible approach with seamless digital/analog blending is essential for the acceptance of digital radio solutions.
The second aspect is customer support. With radio systems to date, the question of support was relatively clear, because it came from the chip manufacturer. The increase in software components could complicate the situation somewhat, because the code might come from different suppliers. For this reason, it is best to make sure the radio system provider can render complete support — or their competence might wane as the software share grows.
A further advantage of SDR technology besides its economical attraction is the subject of flexibility. The more open the hardware platform that OEMs integrate, in other words the more standard components it uses and the more potential functionality the software can implement, the easier a system can be matched to future developments and trends — like the wealth of possibilities emerging under the buzzword "vehicle-to-X," for example. Here in particular it is better not to commit yourself to any hardware before it is certain whether a function is really going to make its way on the market.
Vehicle-to-X enables vehicles to communicate with each other ("vehicle-to-vehicle") by the IEEE 802.11p transmission standard or to connect to intelligent stationary facilities in their surroundings ("vehicle-to-infrastructure"). In this way, cars can literally see around corners and recognize backups or danger spots before they would normally become visible. Drivers could be alerted in advance of other vehicles that they cannot see because a truck is blocking their vision or the road is twisting. Warnings about breakdown trucks, ambulances, or traffic lights could also be given so that drivers adapt their speed and manner of driving in good time.
SDR is an essential component in current demonstrations of the possibilities of vehicle-to-X. The V2X platform used by NXP for its recent practical presentation in Eindhoven in Holland is based on SDR technology, among other things. The platform is targeted at the special requirements of the automobile industry, including a multistandard wireless receiver architecture that can be flexibly programmed and on which even mobile TV and satellite radio reception have been demonstrated. That means whatever V2X functionality is later called for on the market, this open platform will enable it to be integrated in automobiles through SDR, and without substantial hardware changes.
Increasingly digital, increasingly innovative
As long as we have Moore's Law and signal processors continue to become more powerful, the significance of SDR will grow. Instead of silicon, tomorrow's innovations will appear to the drivers of vehicles through software code. One thing is certain: the new possibilities opening up for designers are set to take us much further than what George Frost wanted almost 90 years ago — just to listen to the radio while he was driving.
About the Author: Sebastian Schreuder is product marketing manager at NXP Semiconductors.
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