LTE for automotive applications

Guest post by Charles Sturman and Carl Fenger, u-blox.

The 4G-enabled car is the next hot “consumer device”

LTE for automotive - figure 1
Fig. 1: LTE is enabling a new generation of high-speed video-rich in-vehicle applications and services
At the 2014 CES, the world’s largest consumer electronics trade show held annually in Las Vegas, there was a clear emphasis on intelligent, broadband connected cars.

All the major automotive suppliers were showcasing cars with sophisticated navigation and infotainment. To a large extent, the key technology enabling these innovations is 4G LTE.

LTE possesses the speed, low latency and IP-connectivity (voice, video and data are all transmitted over IP), to enable a whole new generation of high-quality in-vehicle applications supporting attractive video-rich communication, navigation, information, entertainment and location-based services for driver and passengers.

The speed and guaranteed quality of service of LTE as compared to previous generation cellular standards improves vehicle instrumentation systems dramatically: not only in the types and sophistication of services available, but also the quality of the services. Perhaps the most visible innovation is seamless, high definition, low-latency, multi-channel video streaming, just like that experienced at home on a large HD television.

For the automobile industry where profit margins on vehicles are low – typically much less than 10% of the retail price of the car, LTE provides a clear and compelling way for automakers to add new services and revenue models to their new LTE-equipped models.

Bandwidth Evolution

“Edholm’s law” was originally postulated in 2004 by the then CTO of Nortel, Phil Edholm. The law states that connectivity speeds in wide area wireless (“cellular”, e.g. LTE, UMTS), short range wireless (“nomadic” such as Wi-Fi) and fixed-line (“wireline”, e.g. copper, fiber) are on a converging trajectory. The law, which so far has held true, claims that the lines will converge at a point in the future where the speed of cellular communications will be equivalent to short range communications, and for all practical purposes completely replace fixed-line connections (“the end of wireline”).

LTE for automotive - figure 2
Fig. 2: LTE is significantly closing the gap on both wired and local area wireless technology. Edholm’s Law of Bandwidth, Steve Cherry – IEEE Spectrum, July 2004

Looking at the state of commercially deployed connectivity today, we already see speeds in the range of 1-10 Gbps for office Ethernet, 100 Mbps – 1 Gbps for residential cable services, 300 – 600 Mbps for Wi-Fi (802.11a,b,g,n) and 1 Gbps for Wi-Fi (802.11ac).

On the cellular side, we already have LTE at 150 Mbps (cat. 4). With “LTE-Advanced” being deployed over the next few years, we will see this speed going up to a peak of 500 Mbps uplink and 1 Gbps downlink.

Guaranteed Quality
of service (latency)
single HDTV
multiple HDTV channels
ADSL/Cable comparable internet
(rel. 10)
1 Gb/s500 Mb/sYesYesYesYes
(cat. 6)
300 Mb/s100 Mb/sYesYesYesYes
(cat. 4)
150 Mb/s50 Mb/sYesYesYesYes
UMTS/HSPA+42 Mb/s11.5 Mb/sNo, best-effortYesNoNo
UMTS/HSPA7.2 Mb/s5.76 Mb/sNo, best-effortNoNoNo
CDMA2000 1xRTT153 Kb/s153 Kb/sNo, best-effortNoNoNo
CDMA2000 EVDO3.1 MB/s1.8 MB/sNo, best-effortNoNoNo
EDGE384 Kb/s384 Kb/sNo, best-effortNoNoNo
GSM/GPRS171 Kb/s171 Kb/sNo, best-effortNoNoNo
Fig. 3: LTE bandwidth compared with previous cellular generations

By comparison, the bandwidth required to stream a single 1080p HD movie is “only” 10 – 20 Mbps. With support for multiple streaming HD video channels, currently the internet’s highest bandwidth user, virtually any service is available over the internet today via LTE!

New vehicle applications enabled by LTE

Let’s now consider some real examples of the new applications that LTE will make possible over the next few years.

Infotainment / Mobile hotspot

LTE for automotive - figure 4
Fig. 4: Google Earth based navigation streamed over 4G LTE in the 2015 Audi A3
In March 2014, Audi announced that the 2015 model Audi A3 will come equipped with 4G LTE. The Audi Connect 4G service provides Google Earth (Figure 4) and Street View maps for navigation and supports Google search queries and Internet / social media browsing via speech recognition and audio read out.

In addition, online music / video streaming, collision assistance and an integral 4G / Wi-Fi router supporting up to eight other passenger devices turns this car into a mobile internet hotspot!

Interactive TV and Movies
The enhanced performance of 4G LTE networks enables HD movie streaming without buffering or waiting, as well as support for multiple simultaneous users (everyone gets to watch their own on-demand movie!).

Many cars, especially premium models, now offer TV screens for passenger use on long journeys, and also for driver use when the vehicle is stationary. It is easy to see how adoption of in-car TV might mirror the evolution of in-car audio – albeit more rapidly – from FM radio in the 1960s to the currently popular on-demand music streaming services such as Pandora and Spotify.

Live events and broadcast content
Certain premium events such as the World Cup or Superbowl attract hundreds of millions of simultaneous viewers. To handle such high-demand live content, LTE’s Enhanced Multimedia Broadcast Multicast Services (E-MBMS) provides a low-latency, spectrum efficient way for the same content to be received by all users (broadcast) or a selected number of subscribers on the LTE network. It does this by implementing point-to-multipoint transmission (multicast) where a single live video stream is transmitted through the network core, multiplied and distributed to viewers or subscribers as required at the edge of the network.

LTE for automotive - figure 5
Fig. 5: Verizon LTE Multicast Superbowl 2014 Demonstration
In January this year, Verizon USA showcased an LTE Multicast system in Bryant Park, New York for the 2014 Superbowl. The system combined live in-the-park camera feeds with broadcast TV and additional real-time data such as advertising.

With the increasing trend of “watching TV” on the internet, multicasting enables cellular operators to offer new video services to their users and allows TV broadcasters to reach more of their audience without excessively loading the LTE network with millions of point-to-point video streams.

Other broadcast content such as local news bulletins, location-relevant information services as well as off-peak pre-downloading of movies can also take advantage of LTE’s Multimedia Broadcast Multicast Services.

Manufacturer-branded Mobile Devices

In addition to providing high-quality LTE-enabled services, some automotive manufacturers are going one step further by introducing their own branded mobile devices such as tablets for use in their car models.

LTE for automotive - figure 6
Fig. 6: Audio in-car tablet: 10.2 inch Android Tablet
Audi announced its intention to develop an Audi-branded tablet at CES in January 2014. It was described as a “full-blown Android tablet” which will dock into the back of the front headrests for use by passengers in the rear.

The company stated that the tablet, which will be in production in four to five years’ time, will reside in the car and enable deeper integration with the car than is possible with third party mobile devices. The tablet will be manufactured to meet robust automotive environmental (temperature, vibration, lifecycle) specifications.

Passengers can use the tablet to control the radio, media and navigation systems, and also to call up data on the car’s operating status. Since the device is based on the Google Android operating system, it will also have access to all of the apps, movies and music available through the Google Play app store. An interesting feature is that a film which has been partially watched on a particular journey can be resumed back at home in the living room.

Augmented Reality and Head-Up-Displays

LTE for automotive - figure 7
Fig. 7: In-car Augmented Reality
Increasingly, status and safety information is being presented to the driver as an overlay on his forward view via the windscreen, similar to aircraft instrumentation. The ability to view information such as speed, navigation and vehicle proximity without having to look away contributes to a safer and more efficient driving experience.

LTE takes this development to a new level by leveraging the information content and power of the internet. For example, upcoming traffic hazards may be monitored by cameras and road-sensors in real-time, and then combined with data from surrounding vehicles. The ‘fused’ data is processed in the cloud and then relayed to all cars. Thanks to the low transmission latency of LTE, this is possible in real-time with respect to the relative velocities of surrounding vehicles.

These “smart cars” are then able to modify on-screen lane guidance displays accordingly and even change navigation choices automatically in advance of detected hazards. The driver may be presented with a red box around the car ahead together with green arrows indicating which lane to move into before taking the desired exit indicated by virtual markers in the distance, all without taking his eyes off the road.

Other aiding information may also be displayed such as proximity (and price) of fuel stations, services, parking or bridge toll options and real time updates overlaid on the road ahead as illustrated in Figure 7.

The need for legacy fall-back

As these types of services become standard equipment in vehicles and LTE networks grow to provide 100% coverage, we will see the phasing out of 2G and 3G legacy technologies. However, for quite some time it will be necessary to provide 2G and 3G fallback support in the car (“LTE Multimode”) to ensure that connectivity is always possible and not just where there is good LTE coverage, which today is in or near urban areas.

Although LTE is preferable to enable most of the use cases described in this example, good coverage with HSPA+ (the very latest incarnation of 3G) does provide up to 42 Mbps downlink albeit with a much longer latency. It is important to realise that the peak data rates are only peak figures in ideal conditions and that bandwidth is shared amongst multiple users sharing the same cell. This is another area where LTE wins out due to LTE’s OFDMA modulation scheme which makes it possible to share bandwidth amongst a significantly larger number of people than is possible with 3G.
In the case where LTE is not available, HSPA+ is still capable of delivering acceptable service to a reasonable number of users. Adaptive video / audio encoding technology, such as that already seen on the internet (e.g. YouTube) is able to down-scale performance in real time as bandwidth availability changes. Combined with local data caching, this can deliver a high quality experience while occasionally switching between LTE and HSPA+ as network conditions demand.

Audio communication is another key requirement and any LTE enabled infotainment system will integrate hands-free voice calling, enabling the driver to safely make and receive traditional telephone calls. Furthermore, some new applications such as concierge services will use voice interaction, as this is the safest and most natural and comfortable method of interaction while driving. With global high quality telephony coverage with 2G / 3G services, these network connections will remain in the car for some time to come.

Finally, the roll-out of emergency calling systems, such as the European eCall system, demands that cellular coverage be available everywhere in the EU. Since GSM is well established across Europe (and the world), and eCall uses very low bandwidth, this is also a reason to keep 2G connectivity within the car – at least until LTE has become all-pervasive.

LTE Automotive Requirements

There are several factors particular to the automotive applications which need consideration when integrating LTE within the car environment and these are outlined below.

Radio spectrum and antennae
There has been much publicity around the complex geographic mix of radio bands utilised for LTE service. Today there are more than 40 LTE bands defined and in many regions it is necessary to support at least 5 or 6 bands simultaneously. Because a car may well roam from one region to another, from North to South America or East to West Europe for example, it is likely that cars will need to support as many as 10 LTE bands.

In addition to this, LTE already utilises 2 antennae for MIMO (multiple-input and multiple-output, which is the use of multiple antennas at both the transmitter and receiver to improve performance) and further evolution will likely expand this to 4 antennae. Given the difficulty of routing so many antennae cables from one end of the car to the other, it may well be that the cellular modem becomes split between a digital part inside the car and a form of remote radio head placed with the antennae in an external assembly such as the shark’s fin present on many cars today. A further complication is that the shark’s fin already contains a number of antennae to support GNSS, FM and Digital radio, etc so careful system design and RF co-existence modelling is going to become important.

Environmental requirements
Due to the long service lifetime of a typical automobile and the harsh conditions typically endured (heat, cold, vibration), all in-car components are subject to stringent quality and performance criteria. These are generally specified by the US-based Automotive Electronics Council (AEC).

For cellular modems, AEC-Q100 is the key requirement which defines tests for parameters such as electrical, lifetime and stress reliability. The main topic is reliability over an extended operating temperature range and this depends on where the device will reside in the car, for example, an in-cabin application, may require Grade 3 (-40 to +85°C). For an in-dash application, this may be Grade 2 (-40 to +105°C), or for a densely populated space in full view of the sun this may need to be Grade 1 (-40 to +125°C).

Since consumer electronic products, such as smartphones are usually specified to only the Grade 4 equivalent level, this presents a problem and is one reason why automotive manufactures do not typically use standard mobile phone components within automotive systems.

System architecture
Another consideration is how LTE and legacy technologies are integrated within the car. There are effectively three overlapping requirements. In practice each of these may be specified and designed by different design teams, supplied by different component vendors, and installed based on customer preference:

  • Safety / security systems (e.g. eCall): Typically 2G based, they include global positioning (GPS) technology. Increasingly today this is a standard feature.
  • Navigation: Typically 2G based but moving to 3G, this includes high performance multi-GNSS positioning technology. This is a standard feature in higher-end models.
  • Infotainment: Typically 3G based and rapidly moving to LTE, this may use positioning information from the navigation system or include its own built-in positioning system. This is usually a high-end option.

In theory, it would be ideal for these systems to be integrated and able to share resources, and in time that will likely become the default situation. For the next 5 to 10 years, however, we expect supply chain and marketing pressures to keep these systems functionally separate. Due to this, design flexibility and system-level compatibility (layout, interfaces and software APIs) are a key requirement for the modem components.

u-blox’ approach to in-car LTE

LTE for automotive - figure 8
Fig. 8: u-blox TOBY-L200 Automotive grade LTE Multimode module
u-blox has developed a range of both cellular modules and satellite positioning components that provide plug and play compatibility and a range of options from 2G to 3G to 4G LTE multimode (which includes both 2G and 3G HSPA+). TOBY-L2 modules a are qualified according to ISO16750 qualification for systems installed in vehicles.

The LTE multimode modules TOBY-L200 and TOBY-L210 are available to cover the radio spectrums deployed in America and Europe respectively, offering performance at LTE Release 9, Cat. 4 (150Mbps downlink / 50Mbps uplink). The devices support both circuit switched speech and Voice over LTE together with fall-back for both data and voice traffic to 2G / 3G. This enables support for all potential system architectures from fully integrated to functionally independent, as discussed above.

For more information about u-blox’ LTE modem modules for automotive applications, visit

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