Editor's notes:
1. SEO tags: GPS, Internet of Things, IoT, M2M, GLONASS, Galileo, QZSS, Beidou/Compass, Wi-Fi, MEMS, cellular, CANbus, automotive, 4G, LTE, ,
2. Extension Media channels/sites: M2M, Transportation, Automotive, 4G/LTE, Mil/Aero, CompactPCI/ATCA, Smartphone, Medical
3. Mandatory Pull Quote: "It might seem intuitive that the world has positioning abundantly well served. The fact is it does not."
CONVERGENCE OF M2M AND POSITIONING
By: Georgia Frousiakis, Director of Engineering GNSS, Telit Wireless Solutions
Deck:GPS has got you covered, unless you're inside, underground, or out of satellite range. Next-gen cognitive augmentation solutionsovercome satellite-only line-of-sight limitations.
In a not so distant future,a conversation around the water cooler might go something like this: “Do you remember when we used to say GPS as short for positioning?” GPS will, of course, continue in the role of key ingredient, or certainly one of the top technology elements in positioning solutions.Positioning is however quickly moving to become the result of a long recipe of technology ingredients coming together in a cognitivearchitecture.
One of the key drivers of this accelerated shift is machine-to-machine communications (M2M). Device makers were quick to realize that as they connected machines to each other, to servers, and to the Internet-of-Things (IoT), the very next thing they requiredwas the knowledge of where these machines are located. This need was even more pronounced inmobile devices such as cars, buses and construction equipment.
With the proliferation of connected devices, needing to know a position became an imperative. It became instantly inacceptable that a position fix was contingent on line of sight to a large area of sky. Devices and machines need to know where they are, and to communicate that position whether they are underground, inside a building, under a bridge or in a container inside a ship.
The Quick Rise of Positioning
GPS was conceived during the “Space Race” between the Soviet Union and the United States, primarily for use by Armed Forces to overcome limitations from its military-use-only predecessor. GPS gave us all our first true experience with positioning when it went live in 1993.It has since served the military and civilian worlds for decades as a source of latitude-longitude coordinates used by devices ranging from tactical weapon targeting systems to today’s smartphones.
However, over the last decade other satellite-based positioning system initiatives from governments in other parts of the world have risen to add to GPS. Thus, Global Satellite Navigation Systems (GNSS), a generic term created for satellite navigation systems that provide autonomous geo-positioning with global coverage (see Table 1), was introduced. Projects inRussia, China and Europe have managed to gain and sustain momentum. The Russian GLONASS system, originally completed in 1996 was brought back to an operational state in 2011 as the Russian economy recovered.China’s Beidou/Compass system became operational in 2011 for local use and is slatedforcomplete global coverage by 2020.The EU network Galileo began sending test signals from its third satellite at the beginning of December 2012. India (GAGAN) and Japan (QZSS) have also announced satellite-based systems and are currently in different stages of development and planning.
GPS / GLONASS / Galileo / Beidou/Compass / QZSSSystem / USA / Russia / EU / China / Japan
Type / Global / Global / Global / Global / Regional
Date Deployed / 1993 / 1996/2011 / Future (ex. 2015) / Future (ex. 2018) / Future (ex. 2020)
Frequency / L1=1575.42MHz / L1=1602MHz / E1=1575.42MHz / B1=1589.74MHz / L1=1575.42MHz
Number of Satellites / 24-32 / ~ 30 / 22-30 / 30-35 / 4
Table 1: Key Global Satellite Navigation Systems (GNSS) technologies.
Satellites Alone Fall Short of the Solution
With this large number of constellations, standards, and, foremost, features, it might seem intuitive to assume that the world has positioning abundantly well served. The fact is it does not. Not by relying solely on satellite-based location anyway. It is a fact that with every new generation of satellite location receiver chipset, the number of supported constellations will increase.It will eventually get to the point where all commercial satellite-positioningsystems will be supported by all chipsets.
There is however a fundamental weakness in satellite-based location systems. They all rely in some shape and form on the ability to receive and resolve some very low-intensity radio transmissions from these satellites. To mitigate some of this, the GPS hardwareis being upgradedwith new Block 4 and 5 satellites flown into orbit to integrate the constellation and boost transmission power.Still, there are circumstances such as obtaining fixes deep inside buildings, tunnels, urban canyons, and underground where the solution requires augmentation.
Going Beyond Satellites
With the multi-trillion dollar consumer electronics industry, and others less rich but equally influential like machine-to-machine (M2M) clamoring for solutions, solutionshave been forthcoming. Generically referred to as Assisted GPS, the process of enhancing a device’s ability to obtain a position fix anywhere entails usinga mosaic of different types and sources of data. These includedownloading ephemerides data (part of the GPS broadcast data)off a server or from the satellites themselves while they are visible and storing them; triangulating signals from cellular communication towers;using Wi-Fi hot-spots in range of the position seeking device; “dead-reckoning” algorithms taking advantage of miniature high-resolution 3-axis accelerometers, 3-axis gyro and micro solid state altimeters for both asset as well as pedestrian tracking, and other exciting new developments in technology.
The answer is clearly not abandoning satellite-based positioning, but augmenting it to address the specific set of circumstances when reception of signals from enough satellites is impossible. Below we discuss some augmentation solutions available that are gaining momentum as positioning takes its place in fundamental electronics.
Autonomous Assisted GPS
Autonomous assisted GPS is a scheme to mitigate the satellite-only weakness in positioning. ItcapturesGPS broadcast ephemerides(a kind of moving map of where satellites are likely to be over time) when the device is under open sky and stores this information in itsinternal database. The receiver works to maintain this information as fresh as possible, so that when the time comes, it can use it to predict future ephemerides (See Figure 1). With the internal database continuously updated with new ephemerides, thepredicted ephemerides are then updated as well and the expiration time of theprediction—the time after when the prediction is deemed too unreliable to be used—is also moved forward. Under the current technology, if the ephemerides database is not updated, the predicted ephemerides can be usedfor up to about five days in the future before they will expire.
Autonomous assisted GPS is a robust enhancement since it relies on the device “seeing” GPS satellites for a few hours every five daysor so. That turns out to be a reasonably acceptable assumption to make for most M2M applications.But, the expiration time of the predicted ephemerides does depend on the last timethat the broadcast ephemerides were updated.
Figure 1: Position error probability according to age of ephemerides data (1-5 days)
Cellular Service Based Positioning
These are cloud-based positioning services that provide a cellular-connected M2M device position based on observed cellular Cell-IDs. They are able to provide city-block accurate positioning information only, but they can do it entirely independently of the ability to see, or even have a satellite receiver. The information from this type of service can optionally provide real-time GNSS assistance data to accelerate satellite-based fixes, including server-based ephemeris prediction data valid for up to 31 days.
The way Cell-ID positioning works is by cross-referencing the current identification of the cell towers that the device can “see”, with a global database of the world’s more than40 million cell-IDs. With that cross-reference, the service can interpolate the most likely position of the device (see Figure 2). This type of service can provide a position for every use-case including indoors/underground, outdoors, and boundary situations. For devices with satellite receiver capability and a good view of the sky, it can provide an approximate position while the receiver determinesa more accurate fix.
Figure 2: Position fix interpolated by obtaining position and geometry of cellular cells in range of a device.
Wi-Fi Based Positioning
Similarly to the cellular-based, this service can providea position based on observed Wi-Fi hot-spots. These access-points can be looked up in databases containing currently nearly half a billion hot-spot locations, and can produce a position fix autonomously or assist the satellite receiver with an initial position fix.
Dead-reckoning
Dead reckoning (DR) takes inputs such as yaw and distance from several types of motion-related sensors, and does the “math” to determine where you are now by taking your last absolute fixand projecting where you moved. This last known position is typically obtained from the satellite receiver. This is common practice in today’s M2M Telematics solutions where motion information is readily available on the car’s CANbus (seeTable 2). In-vehicle dead-reckoning systems have a good supply of sensor data such as individual wheel speed coming from ABS breaking systems or speed data from the odometer plus compass data.
DR Configuration / Yaw Rate Sensor / Distance Sensor / Other SensorsClassic / MEMS Gyro
(1 or 3 axis) / Discrete Odometer / Discrete Reverse Signal
CAN Bus / CAN Gyro / CAN Odometer / CAN Reverse Signal
Differential Wheel Pulses (DWP) / CAN DWP
(ABS) / CAN Odometer / CAN Reverse Signal
Mixed / MEMS Gyro
(1 or 3 axis) / CAN Odometer / CAN Reverse Signal
Table 2: DR-based continuous navigation during satellite obscuration by use of sensors
The Cognitive Positioning Future
At Telit we are currently working on helping this transition from GPS to positioning happen by researching the neural-network-like architectures that bring all these sources of data together into a cognitive system. The result is that when these new positioning solutions arrive, they will promote the final transition from our industry’s humble GPS beginnings to a hybrid-positioning module. In the future, this positioning module will be an electronic component which will unequivocally and reliably deliver data accurate enough to let you know that you are standing at the east elevator lobby on the 42nd floor at 30 Rockefeller Center. At Telit, we are working to combine all of the components discussed in this article into a cognitive solution based upon GPS, AGPS, DR, Wi-Fi, cellular ID, and more.
Georgia Frousiakis, Director of Engineering GNSS, Telit Wireless Solutions
Georgia Frousiakis received her BSEE from California State University in Fullerton, California. She then worked in various design, system, and engineering capacities before becoming GPS worldwide customer applications manager at Rockwell in Anaheim and Newport Beach, California. After Rockwell, she held GPS applications and technical marketing management positions at IBM and RF Micro Devices. She is recognized on the global stage as a leader in the design and application of GPS functionality. She is presently the Director of Engineering GNSS at Telit Wireless Solutions in Foothill Ranch, California.