SAN JOSE, Calif. -- When you think about positioning, the first thing that comes to mind is GPS. The Defense Department Global Positioning System uses a constellation of 24 satellites, each containing a highly accurate atomic clock. Your location is determined by measuring the speed of light delay triangulating from three or more of those satellites.
But GPS has some limitations that keep it from being a reliable solution for tracking objects. First, GPS requires an unobstructed view of the sky so that the satellite signals can reach the GPS receiver. Secondly, propagation interference caused by a variety of factors that include reflections off buildings and landscape features, such as mountains, make calculating the distance to the satellite uncertain. Add that to the fact that the computing in a GPS device takes place in the device, and you have limitations due to battery life.
PoLTE has another idea. This is a Richardson, Texas-based software company whose location technologies seamlessly track the internet of things and mobile devices indoors and outdoors via its cloud-based, virtualized location platform.
Reuniting Split-Up Frequencies for Fun and Profit
With the advent of LTE (Long-Term Evolution, a standard for high-speed wireless communication for mobile devices and data terminals, also known as 4G), the timing signals in cellular radios have become very exact. This is because LTE uses OFDM (orthogonal frequency division multiplexing), in which the content of a cellular signal is divided into several separate signals at slightly different frequencies.
When the signal reaches its destination, those separate divisions of the main signal are recombined into a single signal that you can understand--perhaps even appearing as your voice.
Those separate frequency-divided signals have to have such exact timing, because they need to be understandable when they’re recombined. PoLTE takes advantage of that exact timing to determine the distance from a given cellular antenna, in much the same way that a GPS receiver using the timing from those satellites.
But there are important differences, as PoLTE CEO Ed Chao explained to me in a meeting at the NetEvents Global Press and Analyst Summit here on May 24. Chao said that LTE signals aren’t subject to some of the problems of GPS signals, such as diffraction delays caused by changes in air density, as GPS signals travel long distances through the atmosphere.
He said that while they are subject to the same issues of multipath distortion, which is caused when radio signals bounce off things like buildings or mountains, PoLTE’s software is able to sort out the original signal and filter out the other signals. This is possible because it’s possible to determine the angle of arrival of the signal and to use that to tell which signals came from slightly different angles and are thus caused by reflections.
Filtering Out Long-Path Signals
The reason it’s important to filter out the multipath signals is because of their longer path, they have different arrival times, and therefore would give inaccurate location information. LTE signals have some characteristics that make them better for determining location than GPS. Perhaps most important is that they have good building penetration. GPS signals are stopped by any sort of substantial roof, for example, and while some of those signals may filter in through windows, they lose location accuracy.
But there’s more to PoLTE’s technology than just a new way to determine location. The other part that makes it useful for logistics operations is its extremely low power consumption. What the radio receivers using the PoLTE software do is collect samples of the LTE timing information and transfer those to a cloud service where the actual location is determined. Because it’s not required that the PoLTE device know its location, it’s not necessary to process the location information on the device itself. Instead, the identity of the device and its location data is sent to the cloud service, which does the heavy lifting by crunching the location data and timing to determine where the device actually is.
The device reports its data using the LTE carrier that it’s using for location. However, PoLTE can use signals from any LTE transmitter to help in determining location, not just the service that it’s using to report its location. Because it only receives LTE data and reports samples, power usage is very low.
Low Power Always a Good Thing in Logistics
Low-power usage is important to logistics users, because it means that the sensor can stay operational on whatever it’s being used to track for the duration of its trip without needing its batteries replaced. To a shipper or to the company that’s having the item shipped, this continuous ability to find the actual location at any time can be critical for on-time deliveries.
But there’s actually a lot more that PoLTE is doing with its technology than simply logistics. For example, use cases are already in the works for tracking material through a factory during the production process. This makes it possible to know actual inventory in real time without stopping the flow of products so that they can be counted. It also dramatically eases the complications of just-in-time manufacturing, because it removes the uncertainty of parts availability on site exactly at the time they’re needed.
PoLTE does not make the sensors or the radios it uses for its software. Those are built through agreements with Riot Micro and Sequans, which are companies already building small, lower-power communications devices (think of those Amazon ordering buttons). Chao said that existing products should be able to work with PoLTE using little more than a firmware upgrade.
This is a significant advance in useful products in the IoT world. It’s significant enough that PoLTE won a technology innovation award at this year’s summit. I think it will have an important impact on how logistics tracking is performed.