Communications: electrical – Selective – Interrogation response
Reexamination Certificate
1998-02-23
2001-04-24
Zimmerman, Brian (Department: 2735)
Communications: electrical
Selective
Interrogation response
C340S870030, C340S870030, C340S870030, C340S870030, C342S463000
Reexamination Certificate
active
06222440
ABSTRACT:
MICROFICHE APPENDIX
A portion of this disclosure of this application contains microfiche appendix which includes one microfiche and 40 frames.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to identification, location, and telemetry systems, and more particularly, to a system for positively identifying and receiving telemetry from devices on assets and individuals using reduced power and reduced channel occupancy.
2. Description of the Related Art
Identification, location and tracking systems identify the presence, the absence, or movement of unique devices affixed to people and objects within a predefined area. These systems find increasing application in all areas of automation, accounting, manufacturing, and materials handling areas as well as medical facilities and other areas where real time location ant identification can be critical.
In a typical system, one or more objects or individuals are provided with transmitting devices, commonly known as “TAGs,” which can be tracked by an array of receivers in a given tracking area. Each TAG periodically traits a unique digital identification number which is sensed by one or more receivers. The receiver information is then forwarded to a data processing system for storage and tracking. A number of systems have been developed using various techniques, such as radio frequency (RF), and ultrasound for continuously tracking location.
Such systems typically employ radio frequency or ultrasonic based transmitters and sensors. RF systems can provide a high degree of accuracy while maintaining a comparably favorable ratio of range per watt of power. A system using RF tracking methods is disclosed in U.S. Pat. No. 5,119,104 to Heller, which is hereby incorporated by reference. The Heller patent discloses a system which addresses some of the issues associated with RF tracking systems. As disclosed, radio frequency transmissions can be susceptible to interference from multipath reflections, as well as signal attenuation through certain objects which tends to distort the accuracy of the location data. The Heller patent offers a method for incorporating a plurality of receivers and time-of-arrival data to more accurately identify target location.
The Heller patent also offers power conservation by including a motion detector with each TAG transmitter. By transmitting identification information when the target is in motion, but reducing transmissions when motionless, the system can conserve power during motionless periods. The receiving system simply uses the last recorded transmission to identify location. However, one power consumption issue of that system is that if the object is moving, the system of the Heller patent does require higher power consumption for more frequent transmissions.
SUMMARY OF THE INVENTION
The technique according to the invention provides for an abundance of devices present in the same area, with real time supervision for presence and for changes in sensory telemetry. The technique employs transmitters, which use the same carrier frequency, but having a unique identification. The system reduces transmitter power consumption by only transmitting a portion of that identification in any one burst. Thus, the transmitters use miniscule amounts of power but can be detected at long ranges. The system also provides for an antenna that receive signals at the transmit frequency and a signal processor that supervises the devices for presence and for telemetry. The system also provides for antennae that are located at similar points in space that can measure the signal strength of the incident signals in such a way as to determine their approximate sector or angle of reception of the incident signal. Hand-held antennae can be used as “finders”, and systems of antennas can be constructed as location grids.
A technique according to the invention provides for transmitting identification, location, and telemetry data while conserving power and increasing available bandwidth. According to the invention, each transmitter identification is split into multiple, smaller, timed transmission packets. The transmitter then transmits a portion of that identification (such as a single bit) periodically, such as once per second. The period of time between transmissions is precise, such that once the system identifies a transmitter, it can then accurately identify the transmitter based upon the next transmission packet's time of arrival. Because of the small bandwidth occupied by and the limited energy used in each single transmission bot the individual transmissions and resulting identifications are resistant to collisions from other transmitters, as well as from noise.
The receiver receives and accurately time-stamps each transmission. This information is then transmitted over a network by sending a map of the received transmission. The received transmission is then processed to identify the device that transmitted and any other data that may have been sent. In one embodiment, the packet is sent over a network that may accommodate other receivers, all feeding a signal processor used for device identification, storage, and/or forwarding of the further processed information.
A signal processor, (currently, a server over an RS-485 bus) receives such packets from all receivers, recognizes identifications from previously “unacquired” transmitters, and maintains information on previously acquired transmitters. From the start of receiving transmissions (or “symbols”) that are unexpected or unscheduled, the signal processor establishes an interval from the periodicity of the transmitted symbols. The signal processor attempts to lock onto a transmitter that was newly introduced into the field of the receiver based on the transmission interval. The signal processor does so by correlating the unexpected and unscheduled symbols and calculates a transmission period, or interval. It then predicts times to expect future symbols. As future symbols are received, their additional identification information is accumulated into the system, which both reinforces the algorithm's assurance that future receptions are from a given transmitter and more positively identifies that transmitter. Though the average delay between symbols may vary randomly somewhat or drift, the repeatability of symbols each second (i.e., jitter) is highly accurate. This repeatability allows the system to identify, and infer with an increasingly higher degree of certainty, the presence of a particular transmitter based on its transmission's time of arrival at the receiver.
When an unexpected symbol is first received, the system holds that uncorrelated symbol in a queue, and waits for the transmission of subsequent, associated symbols to establish an interval. Once that interval is established, the signal processor accumulates subsequent transmissions to establish the transmitter's identity. Partial identifications may be used to establish a probable identity. Once associated, approximately or exactly, the signal processor expects subsequent symbols at the predetermined interval. Lack of arrival of expected symbols is tolerated, but with locking lost after a certain number of “missed” symbols. As information packets reflecting subsequent receipts of symbols are detected, the information is added to the identification within the system. If no matching identification appears in the database, the new transmitter data is then added to the database. Once all data bits have been received, the identification of the transmitter is positively known. Successive transmissions of symbols received at known transmission periods allow for tee continuous supervision of the device without the device transmitting the entire identification on every transmission, unnecessarily using the energy and unnecessarily occupying channel space by continuously transmitting that complete identification code.
One advantage of the technique is that once an interval is acquired, the transmitter can be identified based primarily when it transmits, with the actual transmitted s
Akin Gump Strauss Hauer & Feld & LLP
Dalencourt Yves
Freshloc Technologies, Inc.
Zimmerman Brian
LandOfFree
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