New Horizons for Chip Design


The Road Less Traveled: How Mesh Networks Might Enable Autonomous Driving Beyond Cities

So far, connected autonomous vehicles have been tested in urban settings. That may be part of a larger business model that suggests on-demand driverless vehicles may soon dominate urban areas. It may also reflect a much harsher reality: While there’s plentiful internet within urban centers, there’s less so everywhere else.

What happens when you take a connected autonomous vehicle on the open road?

Even when using one of the largest cellular networks, there are still pockets of dead internet connectivity outside of any urban center. How would such gaps affect connected automated vehicles? Would the connected vehicle stop in the middle of the road when the signal drops, like some shopping carts when taken from their parking lots? Would there be lines of stalled vehicles on the side of the road where all known connectivity ends?

Probably not.

Over the next decade the current 4G LTE cellular networks will be transitioning over to 5G. Among its many virtues, 5G will offer speeds of 10Gbps – much faster than the current 4G cellular we have today. That means we can have concurrent video streams and exchange a lot of non-video data quickly. But a lot of the specifics about 5G have yet to be standardized. That hasn’t stopped some experimentation.

Already Verizon has teamed with Samsung to test 5G router capabilities (but not wireless) in home routers and wireless access points across six U.S. cities in California, Georgia, New Jersey, Massachusetts, Michigan, and Texas. Additionally, 5G is being tested in Washington D.C.

That still doesn’t address the issue of cellular gaps, so autonomous vehicle makers have been looking elsewhere. In fact, the bandwidths allocated in the U.S. for 5G are all in the high frequency range, which have shorter range and will require many more antennas to equal the 4G coverage of today. If anything, 5G will make it much harder for connected autonomous vehicles to operate outside urban areas crammed full of antennas.

One promising option is the new communications protocol 802.11p. Distinct from conventional Wi-Fi (802.11g), the new protocol is designed for automotive use, specifically wireless access in vehicular environments (WAVE). Among the changes, 802.11p does not authenticate the user and uses a default Basic Server Set Identifier (BSSID) and allows for direct communications among similarly equipped devices.

Another option, one based on 802.11p, is Dedicated Short-Range Communications (DSRC) which is described as “a two-way short-to-medium-range wireless communications capability that permits very high data transmission critical in communications-based active safety applications,” according to the U.S. Department of Transportation’s Intelligent Transportation Systems Joint Program Office. More simply, DSRC is an open-source protocol for wireless communication that uses 75 MHz of spectrum in the 5.9 GHz band in the U.S. and 30 MHz of spectrum in the 5.9 GHz band in Europe. DSRC has already been used for electronic toll collection around the world.

However, just designing new communications protocols still doesn’t address the fundamental remote internet access problem. For that, engineers are also looking at additional methods for extending networks out on the open road. For example, using a mesh network.

Traditional networks require using a small number of wired nodes and from there you can make wireless connections. Mesh networks distribute the internet access across a variety of devices, routers, and bridges, creating an ad hoc grid interoperability. Here, only one device must access the internet; the other devices then connect and share that connection. This wireless ad hoc network already has practical uses in privacy – internet traffic cannot be directly traced to a specific device on a mesh network, for example. It also carries with it the possibility of solving the road less traveled problem.

The wide-scale use of a mesh network with DSRC might assume the nearest connected vehicle was always at least .6 miles away. This may provide connectivity along long stretches of barren highway. Additionally, infrastructure enhancements, such as connected road signs embedded into the open road could also provide continuous connectivity to motorists traveling beyond urban centers.