Auto Electronics

Wireless technologies simplify wiring harness

Already extensively deployed in vehicles, wireless technology could simplify wiring harnesses, provide a weight saving and, perhaps most importantly, increase manufacturing flexibility in the future. Today's wireless systems include navigation and traffic information systems, wireless Internet, safety applications such as OnStar and tire pressure monitoring systems (TPMS), as well as remote controls and wireless headsets in entertainment systems. Wireless applications are poised to grow and evolve based on an increasing need for in-vehicle, vehicle-to-infrastructure[1] and vehicle-to-vehicle communications[2]. In-vehicle applications are within the implementation capabilities of a single carmaker and provide highly valued differentiation. Three promising in-vehicle communications technologies include Bluetooth, ZigBee and ultrawideband (UWB).

WIRELESS POSSIBILITIES

In “Strategic Analysis of North America In-Vehicle Wireless Technology Networks and Protocols” (http://www.frost.com/prod/servlet/report-homepage.pag?repid=F681-01-00-00-00), Sandeep Kar, Frost & Sullivan senior industry analyst for advanced automotive technologies, addressed the future of several wireless technologies. While briefly discussing UWB, ZigBee, and wireless universal serial bus, Kar covered Bluetooth, Wi-Fi, and WiMAX technologies and protocols in great detail.

Reducing wiring to improve fuel economy is one of the considerations for wireless technologies in vehicles. “That is one of the driving forces especially in today's world when gas is becoming more expensive by the day,” said Kar. “What people want to do is make the cars lighter and more fuel efficient.” Wireless technology is a way to eliminate the weight of copper in the wiring harness but more than one technology could be used.

“I'm not very bullish on ZigBee,” said Kar. “It has been around for a while but most of the automakers are more comfortable in dealing with Bluetooth and Wi-Fi.” While ZigBee might enable comfort and convenience applications based on wireless networking of multiple sensors and actuators, Kar thinks the existing local interconnect network (LIN) protocol reduces wiring complexity and provides a cheaper alternative.

However, beyond weight, vehicle wiring has difficulty in routing and limits flexibility. Consequently, several universities have investigated the use of wireless connectivity. Patrick Dessert, director of Oakland University's Product Development and Manufacturing (PDM) center, partnered with DaimlerChrysler, Arvin-Meritor, Eaton Corp., TRW, and Lear Corp. to evaluate the use of RF technology outside of its traditional role earlier this decade. The research applied RF nodes and a power line to control electrical vehicle features, including power doors, windows and mirrors.

“If you look at this technology piece by piece, you cannot justify the cost,” said Dessert. “However, when you look at it at a systemic level, the cost is justified through warranty reduction, intelligent diagnostics and added functionality.”

For a car dealer, inventorying vehicles with numerous option packages, which customers may or may not want, requires a significant monetary investment. A wireless approach would allow a dealer to install an item without disturbing the electrical architecture and provide customers exactly what they want. This reduces manufacturing complexity by requiring only a limited number of variations within a model, yet still provides flexibility by post assembly at the dealership with certainty that the systems will work properly.

In a 2005 paper titled, “Alternatives for Short-range Low-power Wireless Communications,” (http://csdl2.computer.org/comp/proceedings/snpd-sawn/2005/2294/00/22940320.pdf) university researchers evaluated Bluetooth, ZigBee and UWB wireless standards for potential use in a hybrid wireless automotive harness. Bluetooth was considered the leading choice for eliminating wires due to its excellent specification stability, large installed base, acceptable cost and data rate, and other criteria. Figure 1 shows one possible connectivity method for a hybrid wireless and wired architecture.

To date, except for tire pressure monitoring, wireless networks within the vehicle have been limited. “There is not enough payback for that and there is a very high risk,” said Joe Giachino, associate director and the director of external programs (industrial liaison) for the Michigan-NSF Engineering Research Center (ERC) in Wireless Integrated MicroSystems (WIMS) and a Ford Motor Company sensor expert for more than 20 years.

Giachino regards flexibility as the key benefit to implementing wireless networks. A tier one sup-plier could have the same system for a number of customers and auto manufacturers could easily add systems without having a wiring harness or harnesses designed for every possible system configuration.

However, technology advancements are still required for this to happen. “If you look at the work being done in non-automotive areas, particularly environmental monitoring and biomed, there is a big push toward low-power devices,” said Giachino. The University of Michigan is developing a low-power pressure sensor node with a built-in antennae as well as built-in battery and energy harvesting to power the wireless node. See Figure 2 for an example of this concept.

BLUETOOTH BECKONS

Driven by government regu-lations, Bluetooth has been im-plemented extensively for hands-free cell phone applications. This existing application and its ac-ceptance in automotive gives it momentum for future wireless applications. “They are looking at different applications using that technology because it is already there, it is already interoperable, and it is already installed in cars,” said Rafik Jallad, automotive business manager at CSR, a supplier of personal wireless technology that includes Bluetooth, GPS, FM receivers and Wi-Fi (IEEE 802.11). “There are several applications that people are looking at.”

By 2012, Frost & Sullivan's Kar forecasts that 25.9% of all light-duty vehicles manufactured in North America would have Bluetooth technology for interfacing. Figure 3 shows a variety of Bluetooth and/or Wi-Fi applications in vehicles.

Bluetooth technology has evolved from early v1 and v1.1 with limited data rate to v2.0 and now v2.1 in 2007. Table 1 shows historical and projected changes to the Bluetooth protocol. Even with an enhanced data rate (EDR) of 3.0 Mbit/s (Mbps), v2.0 is backward compatible with v1.1. “Most of the vehicles that are in production today are using 1.2 and most of the vehicles that are going to come out this year and next year will be using 2.0,” said Jallad.

With a higher data rate, streaming music becomes a practical application. Later this year, when Ford vehicles with Sync are available, an iPod with a Bluetooth dongle can stream music to the Sync. Bluetooth provides a wireless data link between an MP3 player or a cell phone with MP3 files to the Sync so music can be shared through the vehicle's stereo system. “That's becoming a must on most cars,” said Jallad.

As shown in Figure 4, there are two types of architectures for implementing Bluetooth. If a car manufacturer already has a host media system and wants to add Bluetooth, one alter-native is to have software running on the host and a specific ROM chip to provide the Bluetooth functionality. “But that requires software inte-gration and Bluetooth know-how,”noted Jallad.

The second arch-itecture has a chip that handles everything, the Bluetooth protocol stack, the profiles, and with the firmware in the chip, the rest of the system does not need to have any knowledge of the Bluetooth protocol. With less software integration this can mean reduced time to market. This provides an option for system designers to add Bluetooth when required and leave it off without affecting the system.

CSR's BlueCore4-ROM (http://www.csr.com/products/bc4range.htm) addresses the first case and its BlueCore5-Multimedia (http://www.csrsupport.com/document.php?did=2414) addresses the second. For differentiation, echo cancel-lation, audio enhancement, or back-boost algorithms can be implemen-ted on the DSP portion of the chip.

Another near-term Bluetooth application is non-audio cable replacement. With Bluetooth in the dashboard, rather than having a cable going from the stereo system to the amplifier or going from the stereo system to a box in the back of the car with a hard drive or DVD player, Bluetooth could replace the cable. “We have seen some car manufacturers who are seriously thinking about this,” stated Jallad. “Because the total cost of installing the cable and maintaining, it is outpaced by adding a Bluetooth chip.”

Tire pressure and general monitoring systems are additional possibilities for Bluetooth. Instead of plugging in a special cable at the dealer to obtain the diagnostic information, a Bluetooth link could provide the information without special wires or connectors. “There are people working on it,” added Jallad. “We have not seen any that are ready for production yet but that is one application that Bluetooth could enable in the future.”

Whether this will be used is another matter but Jallad said they have seen interest in Bluetooth for TPMS applications with potential customers currently working on prototypes.

Bluetooth v2.1 has specific features that could provide ad-vantages in automotive applications. One example is sniff subrating that reduces the power consumption when devices are in the sniff, or low-power, mode, especially on links with asymmetric data flows. This technology allows a remote device in a computer or potentially a remote control in the car. Today, a remote must wake up every several milliseconds to check for a connection. Sniff subrating allows the unit to sleep for a longer time at the remote device, reducing the power consumption.

“We are seeing applications with remote controls coming out on Bluetooth,” commented Jallad. With the remote control, a passenger in the back seat could access data from the multimedia unit in the front seat and choose a specific DVD or song. Like other features, this probably will be implemented by aftermarket suppliers before carmakers. Today, carmakers offer infrared (IR) technology but when Bluetooth is in the multimedia system, a single technology could perform these wireless functions. Bluetooth for wireless headsets for multimedia systems is a natural as well.

The key to where Bluetooth applications could appear in future vehicles is the profiles. “If you would go through the list of approved profiles (http://www.bluetooth.com/Bluetooth/Learn/Works/Profiles_Overview.htm) or profiles under development, you really would see the roadmap for Bluetooth,” said Delphi's Paul Dobosz, an engineering group manager in forward engineering of entertainment and communications with expertise in wireless com-munications technology. The pro-files provide commonality and avoid connectivity issues. Because they are developed by working groups, a profile has support from more than one company looking to implement that feature.

ULTRAWIDEBAND/BROADBAND

UWB and Bluetooth are similar technologies but UWB allows for higher bandwidth and higher data transfer rates required in applications such as streaming video. “That is where UWB comes into the picture,” according to Frost & Sullivan's Kar. “It can be used for several safety-critical applications like airbag activation systems, active suspension control, active braking and also wireless connectivity of control units within the vehicle.”

UWB seems to have the greatest potential to tie into other vehicle systems. The Frost & Sullivan report anticipates the incorporation of UWB-based electronic devices in light vehicles in North America in the 2011 to 2012 time frame.

With the adoption of UWB by the Bluetooth Special Interest Group, Kar sees more compatibility between wireless USB and Bluetooth. Wireless USB is an updated technology built on UWB that is expected to enhance multimedia and portable device connectivity within vehicles.

“Basically UWB or WiMedia is really an extension of Bluetooth,” said Delphi's Dobosz. Moving video around the vehicle without a coaxial cable or RBG lines to every monitor in the vehicle requires the per-formance of UWB. With UWB being a natural extension of Bluetooth, a seamless mating of the technologies will provide greater wireless oppor-tunities in the future.

UWB, as a stand-alone item, is possible today. Delphi has demonstrated UWB routing video programs to multiple monitors in the car where the only wired connection was power.

References

  1. January 2005, Auto Electronics, “Infotainment: Bringing Consumer Electronics Into the Vehicle,” http://autoelectronics.com/mag/electronics_into_vehicle/.

  2. November 2006, Auto Electronics, “Vehicle to Vehicle or Vehicle to Roadside Communications?” http://autoelectronics.com/telematics/navigation_systems/its-intelligent-transportation-system-changes-1106/.

ABOUT THE AUTHOR

Randy Frank is the president of Randy Frank & Associates Ltd., a technical marketing consulting firm based in Scottsdale, Ariz. He is an SAE and IEEE Fellow and has been involved in automotive electronics for more than 25 years. He can be reached at [email protected].

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