TITLE OF THE INVENTION

POSITIONAL LINKING OF ANALOG TWO-WAY RADIOS

TECHNICAL FIELD

The present invention relates to systems, apparatus, and methods for tracking and transmitting location information over radio frequencies. More particularly, it relates to systems, apparatus, and methods for the transmission of location information, such as digital Global Position Satellite (GPS) information, over existing "voice grade" two-way radio networks.

BACKGROUND

Transportable devices which detect and transmit locational information have been developed. For example, U.S. Patent 6,459,371 to Pike, the disclosure of which is incorporated herein, discloses a locating device consisting of a microphone attachment for a portable radio. A location circuit in the microphone can determine location information. When an alarm state is reported by pressing an alarm button on the microphone, the device may be capable of using the radio to transmit the location information. Similarly, U.S. Patent Application Publication Number U.S. 2003/0160725 to Baxter, the disclosure of which is incorporated by reference, discloses a GPS unit located in the handset of a radio. However, each of these references lacks information on the actual manner by which the digital data of the location information is placed in a format capable of transmission over an analog radio frequency. Other systems use digital communications. Such systems may not be readily integrated into pre-existing communications networks, such as police, fire or security dispatch control networks using traditional analog radios.

U.S. Patent 6,784,853 to Evans, the disclosure of which is incorporated by reference herein, discloses a personal surveillance system that may be worn by an individual. In addition to a GPS unit, the personal surveillance system includes the components necessary for creating video and audio data files regarding the surroundings of a user. Upon an alarm or other command, such information, including the GPS information may be transmitted using WAP, Bluetooth or another wireless digital transmission protocol. Such a system is not readily integrated into

pre-existing communications networks using traditional analog radios.

U.S. Patents 6,912,397 and 6,941,147 to Liou, the disclosure of each of which is incorporated by reference, disclose systems for the transmission of GPS data over a radio frequency. However, such systems may require the use of multiple units attached to a two-way radio. Further, these systems require a relatively high baud rate for transmission of a standard GPS format data string. This limits the functionality of the system and can restrict usage. Similarly, U.S. Patent 5,884,199 to Maki, the disclosure of which is incorporated by reference, discloses a handheld microphone incorporating a GPS receiver, but requires the GPS receiver to be at the top of the microphone and does not address the encoding of locational information for transmission over a voice-grade analog radio frequency.

Thus, systems and methods that provide alternate, easier to use, more efficient, and less expensive ways of incorporating locational information determination and transmission capabilities into pre-existing communications networks using traditional analog radio frequencies would be an improvement in the art.

SUMMARY

The present invention provides apparatus, systems and methods for determining locational information and transmitting that information over analog radio frequencies. A locational link unit (or "LL") attaches to a standard analog communication two-way radio. The LL receives locational information, processes the information to create coordinate data regarding the unit's location, compresses the coordinate data into a structured data packet and encodes the structured data packet by conversion to an analog format "tone set" that can be sent over an audio analog radio channel as part of a transmission from the radio. A second unit, the dynamic data link unit (or "DDL") may communicatively attach to a central dispatch radio via an audio output connection. The DDL decodes the analog tone set received from a LL over the audio channel into a structured data packet, and extracts digital data from the structured data packet. The digital data may then be converted into a format compatible with electronic mapping/location software and forwarded to a

computer operating such mapping/location software.

DESCRIPTION OF THE DRAWINGS

It will be appreciated by those of ordinary skill in the art that the elements depicted in the various drawings are for exemplary purposes only. The nature of the present invention, including the best mode, as well as other embodiments of the present invention, may be more clearly understood by reference to the following detailed description of the invention, to the appended claims, and to the several drawings. FIG. 1 is a schematic of set of components for one illustrative embodiment of a positional link unit, in accordance with the principles of the present invention.

FIG. 2 is a depiction of one embodiment of a corded expansion unit for a two-way radio for housing a positional link unit in accordance with the embodiment of FIG. 1.

FIG. 3 is a schematic of set of components for one illustrative embodiment of a dynamic data link, in accordance with the principles of the present invention.

FIG.4 is a schematic of a process for encoding digital locational data for transmission over an analog radio frequency in accordance with the principles of the present invention.

DETAILED DESCRIPTION

The present invention relates to apparatus, systems and methods related to the transmission of location information, such as digital Global Position

Satellite (GPS) information over existing "voice grade" two-way radio networks. It will be appreciated by those skilled in the art that the embodiments herein described, while illustrating certain embodiments, are not intended to so limit the invention or the scope of the appended claims. Those skilled in the art will also understand that various combinations or modifications of the embodiments presented herein can be made without departing from the scope of the invention. All such alternate

embodiments are within the scope of the present invention. Similarly, while the drawings depict illustrative embodiments of devices and components in accordance with the present invention and illustrate the principles upon which the depicted device or component is based, they are only illustrative and any modification of the invented features presented herein are to be considered within the scope of this invention.

FIG. 1 depicts a schematic for a locational link unit (LL) 10, which in combination with a dynamic data link (DDL) 20 (FIG. 3) may form a system that permits the transmission of digitally obtained locational information, such as Global Position Satellite (GPS) information, over existing "voice grade" two-way radio networks. As depicted, the circuitry for a LL 10 may include a locational receiver 112, a data packet controller 110, a Frequency Shift Keyed (FSK) encoder or bit- slicer 108, a microcontroller for an audio path controller 106 (which may be located on the same microcontroller as the data packet controller 110, or these may be separate microcontrollers). It will be appreciated that where the individual functions of these components may be performed by a single microcontroller executing a suitable software program, such embodiment may be used within the scope of the present invention.

The circuitry for the LL 10 may be mounted within a handheld, push- to-talk (PTT) microphone 15 that attaches to a targeted two-way radio R (as depicted in FIG. 2). In such embodiments, the LL 10 may further include a push to talk button 104, a microphone 100 and a speaker 102). Where the LL 10 is mounted in a handheld, push-to-talk (PTT) microphone 15, attachment to the targeted radio may be made through the radio's standard accessory port. In other embodiments, the LL 10 may be a unit that attaches to the targeted radio R through the standard accessory or another port, or a dongle or an in-line enclosure, but does not provide an additional microphone or speaker, instead utilizing those already present in the radio R.

The targeted radio R may be any standard two-way analog radio for broadcasting voice transmissions. Radios intended for police, military, fire or security work, such as the Motorola radios offered under the model numbers

Motorola MTS-2000, MTS-2500, and MTS-3000 are presently preferred target radios R. Significantly, in some embodiments, no alteration of the target radio R is made other than connection thereto, by a data or expansion port. These radios and similar models exhibit parameters or characteristics similar to the following, allowing for use the LL 10 circuitry: a transmitted audio bandwidth from about 620

Hz to about 2550 Hz; a squelch break of about 1 second duration; an audio input amplitude of about ±2.25 V; and a detectable audio output amplitude of about ±0.6V.

It will of course be appreciated that these values are illustrative only and radios R having other characteristic values may be used, provided suitable modifications are made to the LL 10.

FIG. 2 depicts the LL 10 as mounted within a handheld, push-to-talk (PTT) microphone 15 that attaches to a targeted two-way radio R by a cable with an attachment fitting 16 inserted into a data or expansion port. For such an embodiment, the power to operate the circuitry of the microphone 15, including the LL 10, may be supplied by the battery of the targeted radio R. In such embodiments, the locational receiver 112 component (depicted as a box) may be mounted in the attachment fitting 16 or dongle 14. This may improve reception by the locational receiver 112, as it is less subject to motion in such fitting than in the handheld portion of microphone 15. The attachment fitting 16 makes electrically communicative attachment to the radio R, allowing the radio's power source to power the components of the microphone 15, including LL 10.

Of course, it will be appreciated that a communicative attachment to a target radio R may be made in any suitable manner. For example, the LL 10 may be mounted within a wireless handheld, push-to-talk (PTT) microphone, which makes a communicative connection to a targeted radio using a wireless protocol, such as

BLUETOOTH, WAP, ZIGBEE, or other suitable protocol. Any necessary additional components for making such a connection may be included, for example, the circuitry to support wireless communication may be present in the microphone body, and, where a targeted radio R lacks wireless capability, a wireless communication component may be inserted into a data or expansion port on the targeted radio.

In one embodiment, locational receiver 112 may be a GPS receiver

that interacts with a global positioning system (GPS). GPS is a satellite-based navigational and location system which aids in determining the location of individuals, objects, or landmarks nearly anywhere on Earth. GPS was developed by the United States Defense Department as part of a satellite navigation system and includes up to twenty-four satellites. Four satellites are spaced around each of six circular orbits, which are inclined at an angle of fifty-five degrees relative to the Earth's equator and are spaced around the Earth at approximately sixty degree intervals. The satellites move relative to time on Earth below them. As such, four or more satellites will theoretically have line of sight access to most points on the Earth's surface at any one time. If an object has line of sight access with at least three satellites at one time, GPS can be used to ascertain the position of the object anywhere on Earth. Accordingly, where locational receiver 112 is a GPS receiver that interacts with the GPS satellites to determine the location of the LL 10, the location receiver 112 includes the hardware and/or software capable of converting signals from the GPS satellites into location information.

In one alternative embodiment, locational receiver 112 may be a receiver that interacts with a global navigation satellite system (GLONASS) instead of GPS. GLONASS, developed by the Soviet Union and maintained by the Russian Republic, is a satellite system consisting of twenty-four satellites spaced around three orbits positioned at approximately 120 degree intervals around the Earth. As with GPS, GLONASS is also capable of locating nearly any object on Earth in which at least three satellites are able to establish a line of sight relationship.

Although GPS or GLONASS systems are generally reliable locating systems, both GPS and GLONASS often cannot provide a location of an object or individual within buildings, natural canyons, or urban canyons. The locational receiver 112 may also include an alternate positioning system to facilitate determination of the location of personal surveillance system such as an inertial navigational unit (INU), an e-GPS unit, or other suitable locating system. For example, an e-GPS unit that wirelessly interacts with multiple cellular towers to ascertain its location by triangulation and the length of time required to receive a signal from each of the multiple cellular towers may be used. On suitable e-GPS

interface may be that commercially available from Cell-Guide of Revovot,

Israel.

Where an alternate positioning system forms part of the locational receiver 112, (or a separate alternate positioning system is included in the LL 10), such an alternate positioning system may allow for tracking of the unit where GPS or e-GPS information is not available, through "dead reckoning." For example, an inertial navigational unit (INU) 113 or motion sensing components, such as accelerometers, magnetometers, or gyros may be included in the LL 10. Where present, it is preferred that multiple units be included (where required) to allow for tracking of motion along all three directional axes (x, y, and z). Data on motion detected by such components may be supplied to the microcontroller (for data packet controller 110). When the locational receiver 112 is unable to obtain positional information from an outside source (such as GPS satellite signal information), the microcontroller uses the data on motion detected by motion sensing components and supplied to it since the last detected outside positional information to calculate an approximate position for the LL 10. The locational information for the calculated approximate position may then be utilized in the same manner as locational information detected from an outside source.

An indicator may be present on the LL 10, such as an LED 17 (FTG. 2) visible on the microphone 15 to inform a user of the status of the locational information. When the locational receiver is able to obtain locational information from an outside source, such as GPS satellite information, the indicator may be actuated to alert the user. Thus the LED may be lit when there is a GPS "lock." Alternatively, the indicator may alert the user that outside locational information is not available and a "dead reckoning system" or a last known reading is being utilized.

In use, the locational information determined by the locational receiver 112 is converted from a digital data format to an analog tone set format than can be sent and decoded over the analog radio channels used for voice communication. Details of the conversion and transmission will be discussed further herein. It will be appreciated that locational information may be transmitted by the

LL 10 every time the push to talk button 104 is keyed, at automatic time intervals, only when the locational information ahs changed since a prior transmission, at preset time intervals (which may alter when the LL 10 is stationary), or if the push to talk button has not been keyed within a certain time period. The LL 10 may also store a last "good" set of locational data, in the event the user enters an area where reception of locational information (such as GPS satellite data) is obscured.

The LL 10 may also be assigned and retain a unique identification key ID, which is transmitted as an ID data packet. Transmission of the packet can allow an agency using multiple LLs 10 to keep individual track of the personnel carrying each LL 10.

Conversion of the locational information obtained by the locational receiver is performed by the packet controller 110, and the Frequency Shift Keyed (FSK) encoder or bit-slicer 108, in accordance with the following principles. A targeted radio R typically possesses fairly narrow passbands (audio bandwidth) because its primary purpose is to support voice grade communication with a bandwidth of approximately 3 kHz (3,000 hertz). Consequently, suitable tone sets must be selected to operate within this limited bandwidth. Operation beyond the audio bandwidth would result in selective clipping so as to make the signal un- useable. Bandwidth calculations for FSK systems either require selection of the highest desired data rate or the highest available transmission bandwidth. Since a targeted radio's bandwidth is relatively low, at approximately about 2.6 kHz, this establishes the maximum data rate. The lower frequency may be approximately about 55% of the highest frequency resulting in a value of 1.4 kHz. The subsequent data rate is the result of the high frequency less the low frequency, divided by the acceptable sampling rate as follows: high frequency - low frequency . ,

— - — — - = maximum data rate

75%

With a typical target radio R, this typically results in a useable data rate of about 1.6 kHz or about 1600 baud with an upper end rate of about 2200 baud.

An industry standard GPS packet (such as NMEA-0183, TSIP, TADP,

etc.) are typically ASCII format text strings, which include "format

"information, such as commas and other punctuation. Transmission of such a file using a tone set modem requires the transmission of a data payload tone-set, that can be as long as about 80 bytes and as short as about 45 bytes. Prior attempts to transmit data over audio band radio channels, such as that disclosed in U.S. Patents

6,912,397 and 6,941,147 to Liou, require a relatively high baud rate for transmission of a standard GPS format data string, which falls outside this usable data range. Such systems thus can result in the misreading of transmitted information and the inclusion of longer tone sets over the channel. Thus, such systems have limited functionality and restricted usage. Transmission of such a data packet requires data transmission times of from about 0.4 seconds to about 0.225 seconds.

In one aspect of the present invention, the conversion of the locational information obtained by the locational receiver performed by the packet controller 110, and the Frequency Shift Keyed (FSK) encoder or bit-slicer 108 includes a data compression aspect. First, the standard GPS ASCII format data string may be trimmed to remove the "format" information to appear as a string of numbers. This shortens the data string, reducing its size. Next, the string of numbers may be converted from a binary-encoded ASCII file to a hexadecimal encoded format. This further reduces the size of the data string. In practice, it has been found that data compression using such a protocol allows a locational information and unique ID (identification) data packet containing both GPS and ID data to be trimmed down to approximately about 26 bytes, producing a tone set data packet transmission time of about 0.13 seconds at about 1600 baud. This is possible as the LL 10 reduces redundant or unnecessary information in the locational data stream coming from the locational receiver 112, then formats the locational data into a unique packet and finishes by calculating CRC (Cyclic Redundancy Check) checksum of each data field in the packet to result in a transmission time of less than about 0.25 or ¹ A of a second. The resulting data packet may be inserted into the radio's R voice traffic either preceding a voice transmission or following the voice transmission at the release of the push-to-talk button 104. The microcontroller for an audio path controller 106 ultimately controls the push-to-talk

button 104 so that the radio's transmission has been completed before the push-to-talk button 104 is released.

In another aspect of the present invention, a four-level frequency shift keying arrangement is implemented to enhance or improve the data transmission speed through the narrow bandwidth of the voice grade channel. This process is graphically depicted at 300 in FIG.4, which illustrates an exemplary four level (4L) frequency shift keying system.

In the depicted illustrative embodiment, the digital bit stream is split into a series of bit-pairs. Each bit-pair may then be coded as one of four voltage levels and passed through a low-pass filter section. In one embodiment, the optimum channel shape for passing of bandwidth limited digital data is that of a

Raised Cosine. Filtering can be provided at the transmitter for the purpose of transmission bandwidth reduction and at the receiver for the limitation of noise bandwidth to the data detector. This filtering optimally should have an overall Raised Cosine response. The raised cosine is normally split equally in the transmitter and receiver as two Root-Raised Cosine low pass filters.

The over-the-air signal may consist of 4-level symbols (tones), the raw data passing between the modem and the μC is in binary form. Translation between binary data and the 4-level symbols is done by converting two binary bits into a single symbol, graphically depicted at 310 in FIG.4. One suitable symbol-to- data bit pattern is depicted in Table I, below.

Table I

In such an embodiment, 8 bits or 1 byte equals 4 symbols. In lieu of doubling the raw data rate, a state machine can add data correction information such as FEC (Forward Error Correction) to the data packet such that data errors can be corrected on-the-fly on the receiving end of the transmission. The data rate with

error correction can achieve a net data increase of approximately 50% over a two tone pair FSK (Frequency Shift Keying) arrangement within the same given bandwidth. Utilization of such a process can support bidirectional data transmission over the analog voice channel or to further reduce transmission times by increasing the data payload which can be sent in a given time

FIG. 3 depicts a schematic for a dynamic data link (DDL) 20, which can receive and process transmissions from one or more LLs 10, in order to form a system in accordance with the present invention. The DDL 20 is communicatively attached to a supplied dispatch radio DR and detects, decodes, buffers and sends the received locational information in an appropriate data format to communication port

220. Additional interface circuitry, networking cables to a computer or computer network running mapping software or mapping software utilities, or other devices that may use the locational data may be connected though the communication port 220. Communication port 220 may be configured as a serial communication port, a USB port, or other suitable port, as known to those of skill in the art.

The DDL 20 may be attached to the central communication or dispatch radio/receiver DR at an audio output port thereof. The DDL 20 circuitry may contain an automatic gain control (AGC), a FSK (Frequency Shift Keyed) bit sheer 208 and a data decoder 210, which may be combined in a single microcontroller or may be controlled by separate communications microcontrollers.

In use, the DDL 20 decodes locational data packets transmitted by a LL 10, which are received by the dispatch radio DR to which the DDL 20 is operatively connected.

In practice, it has been found that the signal-to-noise ratio of the DDL

20 decoding hardware/software should be kept quite high due to the narrow passband of the analog two-way radios. Consequently, an audio AGC (Automatic Gain

Control) and a narrow bandpass filter may be placed ahead of the FSK bit slicer 208 and data decoder 210 to help achieve accurate reception by eliminating pulse-width jitter. In one illustrative embodiment, the FSK 208/decoder 210 circuitry may exhibit the following characteristics: a minimum upper/lower band separation of about 40% (2.5 : 1 ; a tracking range (±δf) of about 750 Hz; an un-corrected error rate at 1600bps of about 2.IxIO ⁵ ; and a typical GPS & ID packet transmission period of

about 200 ms.

To decode the transmitted data packet, the DDL 20 decodes the received data packets from the transmitted format to an industry standard GPS format. Where the packet has been converted from a binary or ASCII format to a hexadecimal format prior to transmission, the DDL 20 will perform an opposite conversion following receiving the packet. Where the packet has been trimmed to remove formatting data, the DDL 20 will follow a protocol to place a received number or character string in the appropriate format by restoring formatting data to the packet. As part of decoding a received data packet, the DDL 20 may perform a mathematical CRC (Cyclic Redundancy Check) analysis of the entire received data packet. For example, if an error exists in a decoded GPS data packet, then each GPS data field is compared against its corresponding CRC value to determine which data field may have been corrupted. The DDL 20 will then attempt to correct the error from the checksum while comparing against previously transmitted data fields. If the data is corrupt and the DDL 20 cannot repair it, then the DDL 20 will not forward the GPS data packet to the communication port 220, but rather will issue a unique error code. If the data is correct and accurate, then the DDL 20 will re-format the data into the desired industry standard GPS packet (such as NMEA-0183, TSIP, TAIP, etc.) and send the data onto communication port 220.

The data format for the locational data packet delivered through the communications port 220 may be determined by the needs of the user of the system. For example, where the user is a police department, a number of LLs 10 may be provided to police officers for use with target radios R transported by them. A DDL 20 may be in communicative operation with a dispatch radio DR located at the police dispatch. As locational data and unique ID data packets are received by the dispatch radio DR, the DDL decodes the information therein and forwards it to the communications port 220 in a format compatible with the electronic mapping software used by the department. The computer or computer network running the electronic mapping software then can process the locational information. For example, where locational information is GPS location information and is

accompanied by unique ID information, the electronic mapping software may

"map" the location of the LL 10. A display generated by the electronic mapping software may then include this information. For example, where the electronic mapping software is configured to create an out put of a display of a map on a computer controlled video screen, the GPS data (and unique ID information) may be incorporated into the displayed map.

As additional transmissions occur, the displayed map may be updated to reflect the most recent information. Such a map may aid the dispatch in assigning duties to officers, by accurately allowing "real-time" location of the officers to be tracked. When officers are needed at a location, currently available officers can be assigned based on their proximity to that location.

In some embodiments, the LL 10 may include a video display 18 (FIG. 2) on the microphone 15, such as an LCD or LED screen. A computer system, such as a computer or computer network running electronic mapping software may automatically track the locations of the various LLs 10 transmitting information to the DDL 20. The computer may automatically assemble "real-time" lists of unique identifiers for the LLsIO and their locations. The computer may then utilize the DDL 20 through communications port 220 to encode a "list" for each LL 10 of the LLs 10 in closest proximity to it. Such information may then be transmitted from the dispatch radio to the LLs 10. Each LL 10 may then decode the information and utilize the video display 18 to display the list. Each user of a radio R, within the system may be provided a listing of the nearest other police officers, security agents, etc. using a radio R with an LL 10. This can allow the user to directly call the nearest available personnel for assistance when needed. Other information may similarly be conveyed to LL 10 to be displayed to the user on display 18, using the radio channel tone set modem methods and systems disclosed herein.

Using a system of the present invention, may allow for "bread crumbing" or the calculated reconstruction of the movements of LL 10 units. A computer system in communication with DDL 20, through communications port 220 may receive and store individual locational data packets from one or more LL units

10. The unique ID of each unit and the transmission or reception time of each data

packet may be stored in a memory associated with the data packet. By executing an appropriate command, the computer may reconstruct the movements of one or more LL 10 units over time from these individual data packets, using each data packet as an individual data point. Reports could be constructed for any desired time period, such as certain hours, days or weeks.

These reconstructed tracking reports can be utilized for a variety of purposes. For example, such reports may be used to identify potential improvements in routing patrols for police officers, or security agents based on recorded movements. Route improvement based on this hard data could save expenses by reducing fuel costs without comprising coverage, or could be used to ensure adequate police presence in areas over the course of a typically shift.

While this invention has been described in certain illustrative embodiments, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.