Mesh Networks Reduce Parking Pain
On most people’s list of least-desirable experiences, hunting for a parking space probably falls somewhere between paying taxes and having a root canal. That may soon change, however. Several companies will begin to offer wireless technology that will bring parking into the age of the Internet – and in the process, reduce traffic congestion and give cities a revenue boost.
Companies like ParkingCarma, Streetline Networks, and VehicleSense, mostly located in the Boston and San Francisco Bay areas, have developed small wireless sensors that can tell if a parking space is occupied or not. Glued to the street, or buried an inch or two below the pavement to escape being scraped off by snowplows, these ultra-low-power devices – the companies say their batteries will last a half-dozen or more years – contain magnetometers that detect when a car arrives or leaves.
There’s “powerful consumer pain” in the hunt for parking places, says Rick Warner, CEO of ParkingCarma. That’s clear to anyone who’s ever looked for a spot downtown. It takes eight minutes, on average, to find a parking place in the central areas of U.S. cities.
This fall, San Francisco will implement the largest mesh network for monitoring parking to date. Around 6,000 wireless sensors from Streetline Networks will be fixed alongside as many parking spots, monitoring both parking availability and the volume and speed of passing traffic. The city hopes that displaying information from the sensors on Web maps, smart phones, and signs on the street will reduce the traffic and pollution caused by circling cars.
When sensor networks have been deployed roadside, it’s usually been to monitor traffic, not parking. Some parking garages have signs that tell drivers where the available spaces are, but such systems generally rely on manual car counting, not sensors.
A mesh network differs from a typical wireless network in that there’s no central transmitter: every node can transmit to every other node.
Placed on city streets, Streetline’s parking sensor is part of a mesh network.
In San Francisco, clusters of plastic-encased, networked sensors are embedded in the surface of the street. To relay information, the Streetline sensors use Dust Networks’ SmartMesh system. Dust Networks CEO Joy Weiss says that SmartMesh and Streetline’s technology combined gives the nodes an average lifespan of 5 to 10 years on only two AA batteries.
Dust Networks uses several techniques to combine efficiency and reliability. The first is redundant routing: if a signal doesn’t go through the first time, the sending node tries other nearby nodes, or tries the same node after a period of time. A technique called channel hopping circumvents interference by assuming that changing channels every few seconds is more efficient than trying to find a good or bad channel. To save power, Weiss adds, the nodes go to sleep in between transmissions.
The sensors in Streetline’s monitoring system don’t have any wires, which makes installation cheaper and easier than tearing up roads to put down cables. Every four to six blocks is a wired receiver – usually on a lamppost – that relays the sensor data to a central server.
Jim Reich, VP of engineering at Streetline, says the system can suggest transit alternatives at the same time that it displays parking availability, and that it will eventually be able to predict whether parking spots will be available in a particular location by the time you get there.
Source: Kristina Grifantini, Technology Review