Random interval inventory system

Abstract

A method for accounting for individual ones of a plurality of items based upon random times that occur as a function of a first specified time interval, and a random interval inventory system that operates in accordance with the method. The method includes a first step of transmitting information signals based upon random times from individual ones of a plurality of tags ( 5 a 1 - 5 xx ) to at least one of at least one master transceiver and at least one transceiver ( 4 a - 4 n ). The individual tags ( 5 a 1 - 5 xx ) are affixed to respective individual ones of a plurality of items. The information signals transmitted from each tag ( 5 a 1 - 5 xx ) correspond at least to the respective item to which the tag ( 5 a 1 - 5 xx ) is affixed. The random times occur as a function of a first specified time interval. For a case wherein the information signals are transmitted to the at least one remote transceiver, each at least one remote transceiver ( 4 a - 4 n ) receives information signals from at least one of the tags ( 4 a - 4 n ), and in response to receiving each information signal, relays the signal to the master transceiver ( 3 ). In response to the master transceiver ( 3 ) receiving an information signal, a next step includes supplying the signal to an associated confirmation device ( 2 ). Within the confirmation device ( 2 ), in response to receiving an information signal from the master transceiver ( 3 ), a next step includes confirming that the item corresponding to the information signal is accounted for.

What is claimed is:  
     
         1 . A method for accounting for individual ones of a plurality of items, comprising the steps of: 
 transmitting information signals at random times from individual ones of a plurality of tags to at least one master transceiver, the individual ones of the plurality of tags being affixed to respective individual ones of a plurality of items, the information signals transmitted from the individual tags corresponding at least to the respective items to which the tags are affixed;    in response to the at least one master transceiver receiving an information signal, supplying the information signal to an associated confirmation device; and    within the confirmation device, in response to receiving an information signal from the master transceiver, confirming that the item corresponding to the information signal is accounted for.    
     
     
         2 . A method as set forth in  claim 1 , wherein the random times occur as a function of a first specified time interval.  
     
     
         3 . A method as set forth in  claim 2 , wherein the random times also occur as a function of a rate at which specified events are detected by at least one sensor.  
     
     
         4 . A method as set forth in  claim 1 , wherein the step of transmitting is performed to transmit the information signals from individual ones of a plurality of tags to at least one of the at least one master transceiver and at least one remote transceiver.  
     
     
         5 . A method as set forth in  claim 4 , wherein for a case in which the information signals are transmitted to the at least one remote transceiver, the remote transceiver receives information signals from at least one of the plurality of tags and, in response to receiving each of the information signals, relays the signal to the master transceiver.  
     
     
         6 . A method as set forth in  claim 4 , wherein the remote transceiver receives information signals from the at least one of the plurality of tags depending upon, at least in part, a position of the remote transceiver relative to that of the at least one of the plurality of tags.  
     
     
         7 . A method as set forth in  claim 4 , wherein whether the individual ones of the plurality of tags transmit information signals to the master transceiver or to the remote transceiver depends upon, at least in part, positions of the individual ones of the plurality of tags relative to positions of the master transceiver and the remote transceiver.  
     
     
         8 . A method as set forth in  claim 1 , wherein individual ones of the random times occur randomly during respective individual ones of sequentially occurring time intervals.  
     
     
         9 . A method as set forth in  claim 1 , further comprising the step of: 
 detecting an occurrence of a specified event affecting any of the plurality of items, wherein in response thereto, the tag affixed to an affected one of the plurality of items transmits information signals based upon random times occurring as a function of a second specified time interval.    
     
     
         10 . A method as set forth in  claim 9 , wherein at least a first one and a second one of the information signals are transmitted such that they are temporally separated as a function of the second specified time interval, thereby indicating the detection of the specified event occurring to the affected item; 
 and wherein the step of confirming further comprises the step of: 
 determining that the first one and the second one of the information signals have been received and are temporally separated as a function of the second specified time interval, and recognizing thereafter the detection of the specified event occurring to the affected item.  
   
     
     
         11 . A method as set forth in  claim 10 , wherein the specified event is at least one of movement and a predetermined temperature.  
     
     
         12 . A method as set forth in  claim 10 , wherein individual ones of the random times occur randomly during respective individual ones of sequentially occurring time intervals.  
     
     
         13 . A method as set forth in  claim 4 , further comprising the step of: 
 within at least one of the master transceiver, the at least one remote transceiver, and the confirmation device, in response to receiving an information signal originally transmitted from an individual one of the tags, measuring a signal strength of the received information signal to obtain a measured signal strength of the received information signal; and    based upon a difference between the measured signal strength of the received information signal and a reference signal strength, determining at least one of a displacement and a location of an item to which the tag is affixed.    
     
     
         14 . A method as set forth in  claim 1 , wherein the step of transmitting is performed using a Direct Sequence Spread Spectrum (DSSS) technique.  
     
     
         15 . A method as set forth in  claim 5 , wherein the step of transmitting is performed using a Direct Sequence Spread Spectrum (DSSS) technique.  
     
     
         16 . A method as set forth in  claim 1 , wherein each individual one of the plurality of tags transmits information signals independently from other ones of the plurality of tags, thereby limiting a probability that the master transceiver will receive more than one information signal simultaneously.  
     
     
         17 . A method as set forth in  claim 1 , wherein a probability that an individual one of the plurality of tags will transmit an information signal during a period of time when none of the other ones of the plurality of tags are transmitting information signals is represented by Ptx, where:  
       
         
           
             
               
                 Ptx 
                 = 
                 
                   
                     [ 
                     
                       1 
                       - 
                       
                         ton 
                         
                           toff 
                           = 
                           ton 
                         
                       
                     
                     ] 
                   
                   n 
                 
               
               ; 
             
           
           
           
               
           
         
       
       and where: ton represents a duration of an information signal transmission; toff represents an average time interval between chronological information signal transmissions of interest; and n represents the number of the other ones of the plurality of tags.  
     
     
         18 . A method as set forth in  claim 1 , where a probability that an individual one of the plurality of tags will transmit an information signal during a period of time that none of the other ones of the plurality of tags are transmitting information signals is represented by Pm, where:  
       
         
           
             
               Pm 
               = 
               
                 1 
                 - 
                 
                   
                     [ 
                     
                       1 
                       - 
                       
                         
                           [ 
                           
                             1 
                             - 
                             
                               ton 
                               
                                 toff 
                                 + 
                                 ton 
                               
                             
                           
                           ] 
                         
                         n 
                       
                     
                     ] 
                   
                   m 
                 
               
             
           
           
           
               
           
         
       
       and where: m represents a number of transmissions attempted during the time period; ton represents a duration of an information signal transmission; toff represents an average time interval between chronological information signal transmissions of interest; and n represents the number of the other ones of the plurality of tags.  
     
     
         19 . A method as set forth in  claim 1 , wherein in response to a user operating a user-interface associated with one of the tags to indicate a personal distress alarm (PDA), the tag transmits information signals based upon random times occurring as a function of a second specified time interval, thereby indicating the personal distress alarm.  
     
     
         20 . A method as set forth in  claim 1 , further comprising the steps of: 
 at individual ones of the plurality of tags, in response to transmitting a first one of the information signals, switching to a receive mode of operation for a predetermined time interval; and in response to an expiration of the predetermined time interval, switching to a transmit mode of operation by which a second one of the information signals is transmitted.    
     
     
         21 . A method as set forth in  claim 20 , wherein in response to the at least one master transceiver receiving a first information signal from any one of the plurality of tags, the master transceiver performs the steps of: 
 determining a frequency of the received first information signal to obtain a measured first information signal frequency; and    transmitting a response signal to the tag from which the first information signal was received such that the tag receives the response signal during the predetermined time interval, wherein the response signal is transmitted on a frequency that is offset from the measured first information signal frequency by a predetermined amount.    
     
     
         22 . A method as set forth in  claim 21 , wherein in response to receiving the response signal, the tag error checks the response signal, whereafter the tag transmits a signal to the master transceiver indicating whether or not an error has been detected in the response signal.  
     
     
         23 . A method for inventorying a plurality of items, individual ones of the plurality of items having respective individual ones of a plurality of tags affixed thereto, the individual tags transmitting information signals at random times to at least one remote transceiver, the information signals transmitted from the individual tags corresponding to the respective ones of the plurality of items to which the tags are affixed, comprising the steps of: 
 at the at least one remote transceiver, setting a timer to run in response to receiving a first information signal received from an individual one of the tags;    storing information which indicates an alarm status and which identifies the item corresponding to the first received information signal in response to one of: (1) the timer reaching a first predetermined time value before a second information signal is received and (2) the timer not reaching a second predetermined time value before the second information signal is received; and    communicating the stored information to a master transceiver in response to the remote transceiver receiving an interrogation command from the master receiver.    
     
     
         24 . A method for inventorying a plurality of items, individual ones of the plurality of items having respective individual ones of a plurality of tags associated therewith, the individual tags transmitting information signals at random times in a predefined manner to at least one remote transceiver, the information signals transmitted from the individual tags corresponding to respective ones of the plurality of items with which the tags are associated, comprising the steps of: 
 monitoring for at least one change in status effecting individual ones of the tags indicated by the at least one remote transceiver receiving information signals transmitted from the individual tags in a manner other than the predefined manner; and    notifying a master transceiver of the at least one change in status effecting the individual tags in response to the remote transceiver receiving an interrogation command from the master transceiver.    
     
     
         25 . A random interval inventory system, for accounting for individual ones of a plurality of items, comprising: 
 at least one master transceiver having an output, said master transceiver for receiving information signals and for providing said information signals to said output;    a security station, having an input coupled to said master transceiver output, said security station for confirming that an item corresponding to an information signal received at said input is accounted for; and    a plurality of transmit-only tags, individual ones of said plurality of transmit-only tags being affixed to respective individual ones of a plurality of items, said individual ones of said plurality of transmit-only tags for transmitting information signals, based upon first random times to said at least one master transceiver, said information signals transmitted from said individual ones of said plurality of transmit-only tags correspond at least to said respective individual ones of said plurality of items to which said transmit-only tags are affixed.    
     
     
         26 . A random interval inventory system as set forth in  claim 25 , wherein said random times occur as a function of a first specified time interval.  
     
     
         27 . A random interval inventory system as set forth in  claim 26 , further comprising at least one sensing means, wherein said random times also occur as a function of a rate at which specified events are detected by said at least one sensor.  
     
     
         28 . A random interval inventory system as set forth in  claim 25 , further comprising: 
 at least one remote transceiving means, wherein said individual ones of said plurality of transmit-only tags transmit said information signals to at least one of said at least one transceiver and said at least one remote transceiving means.    
     
     
         29 . A random interval inventory system as set forth in  claim 28 , wherein for a case in which said information signals are transmitted to said remote transceiving means, said remote transceiving means receives said information signals from at least one of said plurality of transmit-only tags, and in response thereto, relays said received information signals to said master transceiver.  
     
     
         30 . A random interval inventory system as set forth in  claim 28 , wherein said at least one of said master transceiver and said at least one remote transceiver comprise at least one of a Direct Sequence Spread Spectrum (DSSS) transmitter and at a DSSS receiver.  
     
     
         31 . A random interval inventory system as set forth in  claim 25 , wherein individual ones of said plurality of transmit-only tags comprise at least one DSSS transmitter.  
     
     
         32 . A random interval inventory system as set forth in  claim 25 , wherein each of said plurality of transmit-only tags further comprises: 
 at least one sensing means, said sensing means for detecting an occurrence of a specified event affecting said one of said plurality of items to which said transmit-only tags is affixed, and for outputting a detection signal in response thereto; and    transmitting means responsive to an output of said sensing means for transmitting information signals at a greater temporal rate, thereby indicating the detection of the occurrence of the specified event;    and wherein said security station is also for determining that information signals applied to said security station input were originally transmitted at said second random times, and for confirming thereafter the occurrence of the specified event affecting said one of said plurality of items.    
     
     
         33 . A random interval inventory system as set forth in  claim 29 , further comprising at least one power line, wherein said remote transceiving means relays said received information signals to said master transceiver via said at least one power line.  
     
     
         34 . A random interval inventory system as set forth in  claim 25 , further comprising: 
 user-interface means coupled to at least one of said plurality of transmit-only tags, said user-interface means being operable for indicating a personal distress alarm (PDA), wherein in response to a user operating said user-interface means, said at least one transmit-only tag transmits information signals at random times occurring as a function of a second specified time interval, thereby indicating a PDA.    
     
     
         35 . A transmit-only tag, said transmit-only tag being associated with an object of interest, said transmit-only tag for transmitting information signals to a receiving station at random times that occur as a function of at least one of a first average time interval and a second average time interval.  
     
     
         36 . A transmit-only tag as set forth in  claim 35 , wherein said transmit-only tags transmit, in response to an occurrence of a specified event, said information signals to said receiving station at said random times that occur as a function of said second average time interval.  
     
     
         37 . A receive/transmit (RX/TX) tag, comprising: 
 a controller;    a receiver portion; and    a transmitter portion, wherein said controller controls said transmitter portion to transmit signals at random times occurring as a function of a specified time interval, said controller turns off said transmitter portion after a first one of said signals is transmitted, said controller thereafter turns on said receiver portion for a predetermined time period, and thereafter turns on said transmitter portion again for transmitting a second one of said signals.    
     
     
         38 . A random interval inventory system, comprising: 
 a receive/transmit (RX/TX) tag comprising means for transmitting signals at random times occurring as a function of a specified time interval, said RX/TX tag further comprising a receiver and a controller, said controller turns off said means for transmitting signals after a first one of said signals is transmitted, said controller thereafter turns on said receiver for a predetermined time period, and thereafter turns on said means for transmitting signals for transmitting a second one of said signals; and    at least one transceiver, said at least one transceiver for receiving said first one of said signals from said RX/TX tag, and for transmitting, in response thereto, a response signal to said RX/TX tag such that the response signal is received by said RX/TX tag within the predetermined time period.    
     
     
         39 . A Random interval inventory system as set forth in  claim 38 , wherein said at least one transceiver comprises an On-Off Key (OOK) transmitter, and wherein said receiver of said RX/TX tag is an OOK receiver.  
     
     
         40 . A Random interval inventory system as set forth in  claim 38 , wherein said at least one transceiver comprises: 
 means for measuring a frequency of said first one of said signals from said RX/TX tag to obtain a measured frequency, wherein said response signal is transmitted on a frequency that is offset from the measured frequency by a predetermined amount sufficient to optimize the performance of the RX/TX tag.    
     
     
         41 . A random interval inventory system, for accounting for individual ones of a plurality of items, comprising: 
 a plurality of tags, individual ones of said plurality of tags for transmitting information signals in a predefined manner based upon random times, said information signals transmitted from said individual ones of said plurality of tags corresponding to respective ones of said plurality of items;    at least one remote transceiver, said at least one remote transceiver for monitoring at least one change in status effecting individual ones of the items indicated by the at least one transceiver receiving information signals transmitted from individual ones of the tags in a manner other than the predefined manner;    at least one master transceiver for providing an interrogation command to said at least one remote transceiver, wherein said at least one remote transceiver responds to an interrogation command received from said master receiver by notifying said master transceiver of a monitored at least one change in status effecting individual ones of the items.