Tracking Indoor Positioning Solutions
June 16, 2009 By: Janice PartykaLast month I covered indoor location technology provider Skyhook and their relationship with Qualcomm. This month I’m on the track of WirelessWERX, TruePosition, and Andrew Corporation, and have some good news for Long Term Evolution (LTE), fourth-generation mobile broadband.
TruePosition and Andrew Corporation both offer an Uplink Time Difference of Arrival (U-TDOA) solution for location that works in both indoor and outdoor environments. A legal battle over patents prevents Andrew from selling part of the solution in certain situations.
U-TDOA is a network-based solution that depends on receivers (called Location Measurement Units or LMUs) installed at the wireless network operator’s base transceiver stations. U-TDOA determines a mobile phone's location by comparing the times at which a cell signal reaches multiple LMUs. Accuracy depends on the network layout and deployment density of LMUs to base stations. U-TDOA does not do well in rural areas, where base stations are sometimes far apart or arranged in a line — often along highways — making triangulation difficult. In those cases U-TDOA needs to be used in concert with other location technologies.
The advantage of U-TDOA is that it works with any handset and requires no modification, chipsets, or software in the handset. TruePosition’s self-reported accuracy is “usually within 50 meters.” U-TDOA will not meet the open-sky accuracy of Assisted GPS (A-GPS), but will locate a handset in areas that GPS has limitations , such asindoors and in corridors with tall buildings.
GSM carriers, who mostly have used U-TDOA technology, are now joining the ranks of CDMA carriers by migrating to A-GPS. The future of U-TDOA is in working as a hybrid solution in combination with A-GPS, Angle of Arrival (AOA), and Enhanced Cell Identity (E-CID). The TruePosition U-TDOA location platform is used by AT&T Mobility and T-Mobile for their E-911 solutions.
Switching gears, WirelessWERX, an emerging location technology company, addresses a subset of indoor location with an adjunct solution called SiteWERX. It is targeted at indoor location environments in large or tall buildings, such as arenas, large office buildings, and dormitories. Unlike other indoor solutions, SiteWERX can identify the room, floor, and building in which a handset is located.
A handset’s x,y coordinates (two-dimensional location) is the same for hotel room 102 as for 2202, a full 21 stories higher. Calls like this can be an emergency responder’s nightmare. To find the exact location, including altitude, SiteWERX communicates with Bluetooth location nodes installed within buildings, such as in a dorm room. Each device covers about 1,000 square feet and requires a 12-volt power connection. The retail cost of a node is about $50 plus the cost of installation (ADT is their partner). The trickiest part is that PSAP equipment must be modified to handle the location sent by the WirelessWERX service. A special application must be downloaded to the handset, which is evoked when 911 is dialed. WirelessWERX is trying to make headway in the market and currently has a pilot underway at an apartment building catering to students at the University of Denver.
Long Term Evolution (LTE), a fourth-generation mobile broadband standard, got a lift this month when the Association of Public-Safety Communications Officials (APCO) International and the National Emergency Number Association (NENA) endorsed LTE as the technological standard to be used in the development of a nationwide interoperable broadband network in the 700-MHz band assigned to public safety. The joint press release praised LTE as “a standard capable of supporting public safety needs for voice, video, and data communications with high bandwidth and low latency, which can significantly improve first-responder access to mission-critical communications using bandwidth-hungry applications. Further, LTE’s all-IP architecture, spectral efficiency, and bandwidth flexibility will improve overall network economics.”
We’ve got mail. Brian Varano of TruePosition weighed in on last month’s column: “If Qualcomm and Skyhook developed a real indoor solution, they would not be so tentative about using it for emergency services. I agree with them; the A-GPS and WPS combination is fine for commercial location-based services, but it doesn’t meet the necessary requirements for mission critical situations — like E-911.”
Next month I’ll continue discussing indoor location solutions with a look at Polaris, a provider of wireless signature technology. Until then, go inside, shut the door, and see if we can find you.
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