RF and baseband SOC in 65 nm CMOS for Intelligent Transport Systems based on the Catena IEEE802.11x platform Mats Carlsson Catena

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Wireless communication is finding its way into our daily life in numerous applications where most of us take it for granted to access information wherever we go. As an example, internet access over WiFi is getting more and more widespread in homes, businesses and hot spots. To increase capacity and to address new applications, the underlying WiFi standards are evolving into new versions of the IEEE802.11x family, where IEEE802.11p is one of the latest amendments to the standard to add wireless access in vehicular environments (WAVE). One important topic which has been investigated and studied in the ongoing research for Intelligent Transport Systems (ITS) is wireless communication between cars and between cars and road infrastructure. The WAVE standard as well as government frequency allocation is playing an important role in making wireless communication in cars widespread, which will increase road safety as well as reducing emissions from cars stuck in traffic jams.

Even though the benefits of wireless access in vehicles are obvious, it will take several years for such emerging market to really take off with large penetration. This was seen in the early days of Bluetooth, where early adopters and manufacturers were often too optimistic about market share and production volumes. Nevertheless, when Bluetooth evolved into its present widespread position, the importance of being an early adopter could not be underestimated for long term success. Catena is therefore member of National research programs, e.g. the Strategic Platform for Intelligent Traffic Systems (SPITS), as well as active with software and hardware development for wireless communication in ITS applications. Check this video at You Tube(www.youtube.com/watch?v=gzxmkZerrsQ) to learn more about SPITS and to get an idea on what can be achieved by connecting your car to the outside world for better safety, traffic incident management, and more energy-efficient driving.

In 2008, the European Commission allocated the frequency band 5.85 - 5.925 GHz for ITS applications, with the intention to ensure compatibility with the USA allowing the same RF interface and antenna system to be used in the two markets. In 2010, the amendment to the 802.11 standard was approved and published, resulting in WAVE or IEEE 802.11p. WAVE is a derivative of the IEEE 802.11a standard, where the main differences are that rapid changes in the physical layer properties and short duration communication should be supported. Short duration communication typically exists in safety applications, e.g. when warning a driver about nearby and fast approaching cars, which makes it obvious that long delays could become devastating and can hence not be tolerated. The communication must also be efficient in non-safety applications, e.g. when a service provider updates digital maps when passing by a roadside unit or when driving through a road toll station at high speed. In addition, the complex radio environment from fast moving vehicles and reflections from building and other objects in the urban environment imposes additional challenges in the implementation of the physical layer.

Catena has for many years successfully brought products to the market for both consumer and automotive applications. We are working with both startups as well as with large semiconductor companies. With our experience from WiFi and WiMAX, we have a very good basis for our Car-ITS developments, where we are starting from the silicon proven platform as can be seen in Figure 1 below. The WiFi/WiMAX platform supports quadruple frequency bands in a 2x2 MIMO configuration and integrates both the RF Frontends as well as the Catena Baseband processor on a silicon proven SOC in 65 nm CMOS.

Figure 1. The block diagram of the silicon proven Catena Transceiver SOC platform for WiFi and WiMAX

To be able to develop an optimized system for a complex application like ITS, it is important to concurrently optimize both hardware and embedded software. At Catena, we are therefore developing a complete system for IEEE 802.11p including hardware in 65 nm LPe from GLOBALFOUNDRIES as well as embedded software for our software programmable baseband processor. The high level block diagram of the system can be seen in Figure 2 below.

Figure 2. Catena 802.11p system

The RF Frontend for 802.11p is derived from our existing and silicon proven WiMAX and WiFi platform as was shown in Figure 1, which reduces risk and time to market. The new device was taped out in October 2011 and is using direct conversion for both the transmitter and receiver, which eliminates expensive and external filters. Support for digitally controlled AGC provides fast gain adaptation, low noise, and high dynamic range. The analog baseband filter is calibrated with an internal tuning loop and the filter supports modulation bandwidths up to 20 MHz. An internal crystal oscillator is implemented to allow the use of a low cost crystal and if an external baseband processor is used, a clock output buffer delivers the system reference frequency. Two fractional-N synthesizers are used to support simultaneous 2x2 MIMO and dual channel operation. An auxiliary ADC is implemented for calibration purposes and to serve various external functions like power and temperature measurements. Control of the chip is done via a four-wire SPI interface or a five wire JTAG interface. External pins are available to support fast RX-TX switching and RX gain control.

The Catena software programmable baseband processor is currently implemented in FPGA, which allows us to optimize software algorithms for Doppler shift and Multipath signal handling. The Catena baseband processor handles also the lower layer MAC functions such as modulation, demodulation, filtering, I/Q correction and gain control. The upper layer MAC and application specific software is to be implemented on an embedded core, e.g. from ARM.

Even though the RF Frontend and Baseband processor are integrated together onto an SOC in our existing WiFi/WiMAX system, we have kept the RF Frontend and Baseband separated in the Car-ITS development platform. This offers great flexibility and possibilities for system and performance optimization prior to a product tape out, explains Peter Johansson, Project Manager for the WiFi and Car-ITS programs at Catena. With the Car-ITS optimized RF Frontend, a field trial system is scheduled to be built in Q1 2012 continues Peter Johansson. A picture of the existing Catena Car-ITS development platform can be seen in Figure 3 below.

Figure 3. Catena Car-ITS development platform.

When the field trials of our Car-ITS system are finalized, the complete system will be integrated onto an SOC in a state of the art sub micron CMOS technology. Currently 65 nm CMOS from GLOBALFOUNDRIES is used for the RF Frontend and hence it would make sense to stay in this technology also for the SOC. However, since we already have IP available in 40 nm CMOS (targeting FM Broadcast and GPS SOCs) and since we see a market push for smaller geometries, we are considering going directly with 40 nm CMOS also for our Car-ITS SOC.

The development of platforms for WiFi, first addressing the IEEE 802.11abgn standards and now the 802.11p standard, makes it easy for Catena to address specific customer requirements and to quickly go to volume production with advanced RF SOCs. The RF Frontend developed at Catena is optimized for interfacing with either our own Baseband processor or alternatively with a third party Baseband processor. With the experience at Catena from automotive applications, it was fairly straightforward to make our WiFi solution automotive graded. Even though we are already engaged with several customers on product development of our WiFi solutions, our platform thinking makes it easy to support also other customers with either an RF Frontend only or alternatively a complete SOC in 40 or 65 nm CMOS. If you have any further inquires on our WiFi solutions, don´t hesitate to contact us.

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About the Author

Mats Carlsson
Catena

Mats Carlsson received the M.Sc. degree in electrical engineering from the Royal Institute of Technology, Stockholm, Sweden, in 1989. From 1989 to 2001, he withheld different design and managing positions at Ericsson, Stockholm, Sweden, e.g. as RF IC Research and Development Manager of radio chipsets and modules for GSM mobile handsets. Since Catena Wireless Electronics, Stockholm, was founded in 2001, he has been Operations Manager and is actively involved in the development of Systems on Chip for various applications.