This Small Business Innovation Research Phase I project is focused on wireless Time Difference Of Arrival (TDOA) positioning technology for indoor or cluttered outdoor environments. Indoor TDOA technologies have had little commercial success to date primarily because of multipath - signal reflections off of surfaces that smear the arrival time of the over-the-air signals, making it difficult to determine the arrival time of the location beacon from the Line-Of-Sight or shortest distance path. The best way to combat multipath is to use very wideband beacon signals. The wide signal bandwidth increases the resolution in the time-domain, allowing the receiver to distinguish between paths. A key challenge with using such wide signal bandwidths is that it can?t be done with commercially-available highly-integrated low-cost components. Another constraint is regulatory restrictions that limit the transmit power of such signals. The focus of this research is to develop a way to overcome these practical limitations by defining a special type of narrowband location beacon that gives the same performance as very wideband signals but that can be implemented using affordable, off-the-shelf radio components.
A great number of applications could benefit from high-resolution indoor location technology, including: Indoor floor map positioning and route guidance for smartphones, indoor location-based advertising, indoor E911, location-based security, medical staff and asset monitoring and Search and rescue. However, existing solutions such as nearest Access Point or Received Signal Strength triangulation are neither accurate enough nor cost-effective due to the high density required to achieve this accuracy. There are TDOA solutions based on Ultra WideBand that have better accuracy but these networks have limited range due to FCC power limitations and limited market success to date. WiFi has already revolutionized wireless mobility and the solution presented here will leverage WiFi as a go-to-market strategy. If successful, the solution will not be limited by regulatory power restrictions and will, because it is based on WiFi, be affordable.
Our Small Business Innovation Research Phase II project was focused on high-accuracy wireless positioning technology for indoor environments. Fueled in part by the ubiquity of the smartphone, a large and growing number of applications could benefit from this technology, including: Indoor route guidance Mobile retail - find products, receive targeted ads, use proximity-sorted shopping lists Staff and asset tracking for healthcare and manufacturing industries Indoor E911 Indoor search and rescue Location-based security Exhibit tracking commentary Route guidance for the blind Wireless robotics Existing state-of-the-art positioning systems such as WiFi received signal strength (RSS) techniques are not accurate enough (typically ten meters or 33 feet at 90% confidence) for many of these applications. Attempts to further improve the accuracy have had little commercial success to date primarily because of multipath - signal reflections that smear the arrival time of the over-the-air signals, making it difficult to determine the arrival time from the line-of-sight (LOS) or shortest distance path. The best way to combat multipath is to use ultra-wideband (UWB) location beacon signals with bandwidths in excess of 500 MHz; the wide signal bandwidth increases the resolution in the time-domain, allowing the receiver to distinguish the LOS from other paths. The challenges with using conventional UWB signals are high manufacturing costs, too much DC power consumption and regulatory issues limiting its range and operating frequencies. Diani’s core innovation, referred to herein as Multi-Channel Wideband (MCW) signaling technology, is an important innovation because it can be used to get today’s wireless standards such as IEEE 802.11/WiFi to effectively transmit and receive ultra-wideband (UWB) signals for time-of-arrival-based positioning. We believe MCW is the only way to reliably deliver sub-meter positioning accuracy for cellular or WiFi devices such as smartphones, tablet or notebook computers indoors. We believe we have successfully fulfilled all of the technical objectives identified in our Phase I proposal and can summarize our accomplishments thus far as follows: Developed a software simulator to test the MCW wireless transmit, receive and time-of-arrival estimation algorithms Developed a hardware platform to transmit and receive WiFi-based MCW signals, and demonstrated that we could achieve 2.7 nanosecond TOA accuracy in 90% of 52 measurements made in three indoor environments – a walled indoor basement, and two large walled indoor office spaces. The results from these measurements were consistent with those obtained from the software simulator. Since light travels about one foot per nanosecond, this suggests that we could develop a MCW-based time-of-arrival location system that could deliver sub-meter accuracy. Identified all the low-level VLSI changes required to support the technology in a WiFi chipset. Came up with a way to deploy an initial go-to-market release of the technology in WiFi networking equipment that requires only software changes on the network side, and neither hardware nor software changes on the mobile device side. The business solution we are proposing will leverage WiFi in our go-to-market strategy. The goal is to propose a way to make straightforward modifications to a WiFi chipset in order to achieve an indoor location accuracy of 3 feet or better with 90% confidence, yielding an order-of-magnitude accuracy improvement at no additional cost, since WiFi is already a standard feature in most mobile devices such as smartphones and laptops.
