Abstract:
A collaborative speed measurement device detection system provides early warning and increased reliability by sharing the responses of multiple detectors through a broadcast radio network. A vehicle with one detector (e.g., radar, laser detector) broadcasts a detection event to any other detectors in its vicinity. The receiving detectors generate a warning signal in response to the broadcast. The receivers can combine the results of multiple detections to generate a reliability estimate. The location of the detection events may be broadcast and used in generating alarms in the receiver as well.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to warning devices that give notice of the use of speed detectors, for example by law enforcement agencies, such as radar detectors. More particularly, the invention relates to such systems that employ multiple receivers to increase reliability and lead time of warnings. 
     2. Background 
     Many operators of motor vehicles utilize radar detectors to alert them to the fact that their speed is being monitored by law enforcement agencies. However, conventional radar detectors often generate “false alarms.” They are also prone to respond too late, giving the vehicle operator insufficient time to adjust speed. 
     False alarms are annoying to the operators of motor vehicles. In fact, various automotive publications publish results of “false alarm” tests. Thus, anything that can be accomplished by the manufacturer to reduce the number of false alarms without reducing detection of police radar is commercially valuable 
     In addition to police radar signals, there are many different sources of microwave signals in the frequency bands allocated to police radar by the U.S. Federal Communications Commission (FCC). For example, motion-detecting burglar alarms and automatic door openers also operate in the frequency bands allocated to police radar. Thus, a need exists for a radar detector that can distinguish between signals generated by a police radar transmitter and those generated by other devices that utilize microwave signals within the same frequency bands. 
     As is known in the art, speed detection systems may be used to determine the speed of moving objects, such as ground based or airborne motor vehicles for example. It is often desirable for the operator of the moving vehicle to know when the speed of the vehicle is being measured. For example, it may be desirable for an operator of a moving automobile to know when the speed of the automobile is being detected by a speed detection system. 
     As is also known, such speed detection systems may utilize either radar or laser devices in their operation. A speed detection system that utilizes radar may generally be referred to as a so-called radar gun. Radar guns typically include a microwave signal source that emits a signal having a frequency in either the X, K or Ka frequency regions of the electromagnetic spectrum. Furthermore, radar guns may emit signals in either a continuous or a pulsed mode. 
     A laser speed detection system or so-called laser gun, on the other hand, includes a laser, which is a device that converts input power into a very narrow, intense beam of coherent energy at a single optical frequency, generally, but not necessarily, within the visible to infrared frequency region of the electromagnetic spectrum. Like radar guns, laser guns may also operate either continuously or in a pulsed mode. Laser guns generally operate in a pulsed mode due to input power requirements, cooling problems, and other considerations of the laser. The pulse width of the output of a pulsed laser is typically on the order of nanoseconds or picoseconds. 
     As is also known, there exists two particular classes of detecting systems generally referred to as radar detectors and laser detectors. A radar detector is a device used to detect the presence of a radar gun. A laser detector, on the other hand, is a device used to detect the presence of a laser gun. Typically, devices which detect the presence of radar guns are unable to detect the presence of laser guns. Similarly, devices capable of detecting the presence of laser guns are unable to detect the presence of radar guns. 
     Radar detectors typically detect signals having frequencies in the X-band, K-band and Ka-band frequency ranges. Such radar detectors often include a fixed frequency oscillator which generates a signal in the X-band frequency range. The so-called third harmonic of some X-band signals, however, fall generally within the Ka-band frequency range. Thus, one problem with conventional radar detectors which detect signals in the Ka-band frequency range is that such radar detectors may provide an alarm in response to the third harmonic signal of the fixed frequency oscillator of a nearby radar detector rather than in response to a signal emitted from a radar gun. This is generally referred to as a “false alarm” or simply “falsing.” 
     Laser detectors also have problems with sounding false alarm signals in response to light signals emitted from sources other than laser guns. Laser detectors may also pose an additional problem in that they may be expensive, and may require accurate or pre-determined alignment or positioning of the laser detector within the path of a laser beam in order to function properly. Such systems are thus impractical for use by personnel on moving airborne and ground-based vehicles. 
     It would, therefore, be desirable to provide a detection device which detects the presence of both laser and radar speed detection systems and which is able to distinguish between signals provided from speed detection systems and signals provided from other detection devices such as other radar detectors. The other problem with all types of detectors is the extremely short notification provided by them. A driver has little time to adjust his/her speed after the warning is given before a speed estimate is generated by the scanning device used by the law enforcer. Thus, there exists a need in the art to provide more advanced warning of the use of laser, radar, and other scanning devices. 
     SUMMARY OF THE INVENTION 
     The invention provides a mechanism whereby detectors of speed detection devices, such as laser and radar speed detectors, communicate with each other so that each detector can use information available from other detectors to provide early warning and reliable detection. Each detector may be equipped with a radio transmitter and receiver. Upon detection of probe signal, a data signal is generated and received by all detectors in the vicinity. Recipients of the signal may generate a warning or use the information to generate a reliability metric to determine whether a warning should be generated. 
     The invention will be described in connection with certain preferred embodiments, with reference to the following illustrative figures so that it may be more fully understood. With reference to the figures, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a figurative illustration of a number of vehicles with collaborative detectors according to an embodiment of the invention. 
     FIG. 2 is a block diagram of a node of a collaborative detector according to an embodiment of the invention. 
     FIG. 3 is a flowchart illustrating a method for controlling a collaborative radar detector according to a first embodiment of the invention. 
     FIG. 4 is a flowchart illustrating a method for controlling a collaborative radar detector according to a second embodiment of the invention. 
     FIG. 5 is a flowchart illustrating a method for controlling a collaborative radar detector according to a third embodiment of the invention. 
     FIG. 6 is a flowchart illustrating a method for controlling a collaborative radar detector according to a fourth embodiment of the invention. 
     FIGS. 7A-7C are flowcharts illustrating a method for controlling a collaborative radar detector according to a fifth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a speed detector  100  illuminates several vehicles  115  and  130  with a radio or laser scan to determine their speed. The illuminated vehicles  115  and  130  are equipped with detectors, such as a radar or laser detector (not shown in the figure), with the added capability of transmitting broadcast signals to other vehicles such as  105  and  125  as illustrated by the communication links  110  and  135 . Vehicle  125  further rebroadcasts the signal, as indicated by link  140 , to another vehicle  145 , which is further up the road. Not all vehicles on the road need have detectors with an ability to transmit and receive broadcast signals. Such vehicles  120  simply do not respond in any way. 
     Data transmitted by the illuminated vehicles may include the following information: 
     1. location given by global positioning system (GPS) subsystem of the vehicle when the illumination event was detected; 
     2. speed of the illuminated vehicle given by the GPS when the illumination event was detected; 
     3. heading of the illuminated vehicle given by the GPS when the illumination event was detected; and 
     4. reliability estimate based on the detector&#39;s ability to generate such. 
     Referring now to FIG. 2, a collaborative speed measurement detector system  200  includes a controller  205 , which may exchange data with a GPS subsystem  230 , a radio transceiver  210 , a speed measurement detector  220 , and a user interface  215 . 
     In a simple embodiment, the collaborative speed measurement detector system  200  may consist solely of the detector  220 , controller  205 , and a rudimentary user interface  215 . Referring now also to FIG. 3, in such a simple embodiment, a signal indicating detection of an illumination event (the detection of radar or laser from a detector as indicated at  100  in FIG. 1) is generated by the transceiver  210  which is then picked up by the transceivers  210  of nearby collaborative speed measurement detector systems  200 , but not forwarded in step S 10 , at which point an idle loop is exited and an alarm generated in step S 20 . Alternatively, the idle loop of step S 10  may be exited by a local detection event with the same effect. In a simple embodiment, the signal may not be repeated and only broadcast by the collaborative speed measurement detector system  200  that actually detected the illumination. In this simple embodiment, the collaborative speed measurement detector system  200  generates the warning signal through the user interface  215  if it receives a broadcast signal from another collaborative speed measurement detector system  200  or if it detects an illumination event through the detector  220  or if it receives a signal from another collaborative speed measurement detector system  200 . 
     Referring now also to FIG. 4, in a refinement of the above system, the controller  205  is programmed to generate different signals in the user interface depending on the type of alarm condition; direct detection of illumination or detection by another collaborative speed measurement detector system  200 . In step S 30 , an idle loop waits for either receipt of signal from another collaborative speed measurement detector system  200  or a local illumination event. When the loop S 30  is exited, in step S 40  the type of illumination event, remote (a signal was received from another collaborative speed measurement detector system  200 ) or local (an illumination event was detected by the collaborative speed measurement detector system  200  itself) is determined. Here, it is contemplated that a local illumination event would correspond to a more urgent condition than a remote one, for two reasons. One reason is that a remote illumination event has a higher probability of being irrelevant, potentially being from a different road or from traffic in an opposing direction. The other is that the distance to the detector is probably further away than when a local illumination event is detected and therefore warrants less immediate response. If the type of event is a local detection, a local alarm is generated in step S 50 , otherwise a remote alarm is generated in step S 60 . The remote and local alarms could simply be different audio signals, or colored lights (e.g., local=red and remote=yellow). Many alternative alarm signals are possible such as machine speech, graphical icons on a display, etc. 
     Referring now also to FIG. 5, in a further refinement of the previous embodiment, the heading and speed of the vehicle carrying the collaborative speed measurement detector system  200  that detected the illumination event are transmitted and used by other collaborative speed measurement detector systems  200 . Also, collaborative speed measurement detector systems  200  rebroadcast the illumination event detection signal to extend the range of the devices, particularly in the vicinity of obstacles such as bridges, or buildings. 
     As in the previous embodiment, in step S 100 , an idle loop waits for either receipt of signal from another collaborative speed measurement detector system  200  or a local illumination event. In step S 110 , the distance to the transmitting collaborative speed measurement detector system  200  is compared to an upper limit. If the distance is over the limit, the signal is not rebroadcast. If it is under the limit, the signal is rebroadcast in step S 105 . In step S 125 , the heading of the vehicle whose collaborative speed measurement detector system  200  received the illumination event signal is compared with the headings, potentially combined with distance information, indicate that the transmitter is headed in a direction opposite that of the receiver, determined in step S 135 , then no alarm level is calculated or generated in step S 130 . Otherwise, an alarm is generated in step S 130 . 
     Before generating an alarm, an alarm level may be generated, the level corresponding to a reliability/urgency estimate for the alarm condition. In the embodiment of FIG. 5, the heading and distance from the illumination event may be used to estimate the degree of reliability and urgency of the event. For example, if there is a high probability, but less than 100% certainty, that a vehicle in opposing traffic generated the illumination event signal, then the alarm level could be set to a low value. If the illumination event occurred a great distance away, then the alarm level could also be set to a low value. If the illumination event were local, the alarm level would be set to a high value. Different outputs could correspond to the different alarm levels. 
     Referring now also to FIG. 6, a map of illumination events is updated each time an illumination event signal is received (local or remote). As in the previous embodiment a loop S 205  is exited when an illumination event occurs and the signal is rebroadcast (S 215 ) if (S 210 ) the location of the illumination event is closer than some predefined limit. In step S 220 , the data corresponding to the illumination event is used in updating a map of illumination events in the vicinity of the collaborative speed measurement detector system  200 . The map may be a database with records specifying each event. The records may each contain a field indicating the time of the event, its location, a vehicle heading upon detection of the event, and a reliability estimate based on other criteria employed by prior art laser and radar detectors. In step S 225 , the database is filtered and a probability of intercepting the area of illumination is calculated for each entry in the database. In step S 230 , the heading of the local vehicle is compared with those of the illuminated vehicles in the map database and the probability of intercepting the illumination area adjusted accordingly. In this case, instead of determining if the vehicle transmitting the illumination event signal is different from that of the receiving vehicle, the vehicle headings are used to adjust a probability that the local vehicle will intercept the illuminated area, the probability being adjusted downwardly the more the vehicle headings appear to be opposite in general direction and upwardly, the more the headings appear to be generally the same. In step S 235 , the worst-case alarm level is calculated and the corresponding alarm level generated. 
     Note that the heading information may be time-integrated heading. Alternatively, the heading information may be one of the two possible directions of the route determined by the GPS system  230  to be the one on which the vehicle is travelling. The illumination event signal may contain a route indicator as well as a direction indicator. This may be compared with a route and direction predicted for the receiving vehicle. The prediction may be based on current location and direction as in map-matching software used for GPS navigation systems or it may be based on a route plan indicated by the user in a vehicle navigation system. 
     Referring now to FIG. 7A, a first process continually updates the map described with respect to the embodiment of FIG.  6 . The loop through step S 305  is exited upon reception of a signal indicating an illumination event. In the present embodiment, it is assumed the signal can be either an illumination event signal or an idle signal simply indicating other vehicles that are “connected” to the local collaborative speed measurement detector system  200 . The reason for the idle signal will become clear from the discussion of FIG.  7 C. If (S 310 ) the distance to the event is not too great, the signal is rebroadcast in step S 315 . The map is updated with the data in the illumination event signal as discussed above with respect to the embodiment of FIG.  6 . Referring now also to FIG. 7B, simultaneously, an idle loop through a test S 305  is exited upon detection of a local illumination event. When a local illumination event is detected, an alarm is immediately generated in step S 340 . Referring now also to FIG. 7C, another simultaneous process continuously updates the alarm level of the map database entries as the vehicle carrying the collaborative speed measurement detector system  200  (the local vehicle) moves. 
     In the process of FIG. 7C, a path projection of the local vehicle and probabilities of each illumination location in the map database being intercepted along the path projection are calculated in step S 325  and the map database updated. The headings of the sending collaborative speed measurement: detector systems  200  are compared with the local heading in step S 330 . Again, alternatively, the illumination event signal may indicate the route and travel direction and the local GPS may provide corresponding information permitting the system to determine with greater certainty whether the sender and receiver are on the same route. 
     In step S 335 , a reliability adjustment calculation may be made for each illumination event based on the number of illumination events for a given location normalized by the density of traffic. The latter may be indicated by the idle signals from other collaborative speed measurement detector systems  200 . Thus, where the number of other collaborative speed measurement detector systems  200  in a vehicle&#39;s vicinity is high, but the number of illumination event signals received is low, the illumination event can be discounted as a false-positive. In step S 340  an alarm level is calculated for each entry in the map database and an alarm signal generated as appropriate (which may include not alarm signal being generated). 
     It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.