Abstract:
A remote telemetry system utilizing dual communication pathways comprising low-cost remote communications devices operating on existing wire-based communications systems, wireless communications systems, and/or a combination thereof, to provide real-time reading and control of the remote telemetry units. A central controller directs the operation of the remote telemetry units and receives data from the remote telemetry units. The central controller is configured to utilize a conventional broadcast communications channel to transmit commands to individual remote telemetry units, each of which is assigned a unique identification code. Signals broadcast from the central controller are received at receivers associated with each remote telemetry unit, which performs a directed operation if a unique identification code included in the broadcast signal matches the identification code assigned to the remote telemetry unit. Each remote telemetry unit is provided with access to a conventional shared two-way communication pathway for return communication to the central controller. The shared two-way communication pathway is inactive unless specifically activated by a remote telemetry unit upon receipt of a signal from the central controller. In this manner, a large number of remote telemetry units may be provided with regulated access to a single shared two-way communications channel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   None. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable. 
   BACKGROUND OF THE INVENTION 
   Remote telemetry is a technique by which telemetry data collected at a remote location is collected in a central repository (e.g., a host computer) for analysis and archival purposes. The telemetry data might be any physical measurement, such as a liquid level, weight, pH, chlorine concentration, temperature, pressure, proximity, etc., and is sensed by a Remote Telemetry Unit (RTU). It is common for a number of RTUs to be in relatively close proximity to one another (e.g., on a factory floor); even though they might be quite a distance from the central host (e.g., in another city). 
   In many potential applications of remote telemetry, there are barriers that must be overcome to make the application feasible. One barrier present in many situations is the need to establish two-way communications between each RTU and the central host in a manner that is inexpensive and/or power efficient. Examples of such two-way links commonly include dedicated telephone lines, cellular telephone links, wireless data networks, shared media data networks, and other wireless technologies. Each of these two-way links has drawbacks. A high financial cost is associated with dedicated telephone lines due to regulations limiting the routing of the phone lines, as well as regulations controlling the cost to the consumer. Similar high costs are associated with cellular telephone networks and data networks, which must pay either a monthly fee or per packet of information transferred. In the case of wireless technologies, there must be a wireless receiver active at all times as to receive signals transmitted either from the RTUs or from the host computer. 
   U.S. Pat. No. 6,014,089 to Tracy et al. for “Method For Transmitting Data Using Digital Control Channel Of A Wireless Network,” herein incorporated by reference, discloses an apparatus and method for transmitting data to and from a data collection device using the short message service functionality of the control channel of a personal communications system transmission protocol. The &#39;089 patent discloses a method wherein a request for data from a remote device is transmitted to a data collection device using the short message service portion of a digital personal communications system control channel protocol. The requests are received at the data collection device, interpreted, and the requested data compiled therein. The compiled data is then transmitted back to the remote device from the data collection device on the same short message service portion of the digital personal communications system control channel as was used to transmit the request for data. 
   U.S. Pat. No. 5,892,758 to Argyroudis for “Concentrated Subscriber Wireless Remote Telemetry System” and U.S. Pat. No. 5,748,104 to Argyoudis for “Wireless Remote Telemetry System”, both herein incorporated by reference, each disclose variations on a wireless remote telemetry system utilizing low-cost remote communications devices operating on an existing wireless communications system in order to provide real-time reading and control of the remote devices. In these systems, remote metering devices collect and forward data to an associated wireless remote telemetry device which in turn, relays data over existing wireless communications systems, such as cellular base stations, using a shared random access channel to a central controller. The central controller of these systems, in turn, regulates the operation of the wireless remote metering units by transmitting messages over a corresponding paging channel. The shared random access channel and the associated paging channel are separate logical partitions of a single physical mechanism for delivering data. Specifically, these patents disclose using a PCS communications link having a common frequency band and utilizing CDMA code to establish a link. Furthermore, to effectively utilize this system, each of the remote telemetry units is required to have a unique address on the two-way communications link, such that the central controller can communicate individually with each remote unit over this link. 
   BRIEF SUMMARY OF THE INVENTION 
   Briefly stated, the present invention is a novel and improved remote telemetry system which uses low-cost remote communications devices operating on existing wire-based communications systems, wireless communications systems, and/or a combination thereof in order to provide real-time reading and control of remote telemetry units. 
   A central controller for directing the operation of the remote telemetry units and for receiving data from the remote telemetry units is configured to utilize a conventional broadcast communications channel, such as a cellular paging system, to transmit commands to individual remote telemetry units, each of which is assigned a unique identification code. This unique identification code does not need to be known to the broadcast communications channel mentioned above, or to the two-way communications channel mentioned below. It is known to the central controller and the remote telemetry units only. 
   Signals broadcast from the central controller are received at a low-cost receiver associated with each remote telemetry unit, which performs a directed operation if a unique identification code included in the broadcast signal matches the identification code assigned to the remote telemetry unit. 
   Each remote telemetry unit further includes access to a conventional shared two-way communication channel, for example, each remote telemetry unit may be provided with one of several cellular radiotelephones assigned to the same telephone number, or may be associated one of several line extensions on the same wire-based telephone line. Each shared two-way communications channel will be inactive unless specifically activated by a remote telemetry unit upon receipt of a signal from the central controller. 
   By broadcasting only a single unique identification code at a time, the central controller regulates access to the shared two-way communications channel, such that no conflicts arise. In this manner, a large number of remote telemetry units may be provided with regulated access to a single shared two-way communications channel. Furthermore, by utilizing a conventional broadcast communications channel to transmit commands from the central controller to the remote telemetry units, the costs associated with dedicated lines may be eliminated or reduced and power consumption minimized. 
   The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the accompanying drawings which form part of the specification: 
       FIG. 1  is a system diagram of the present invention, illustrating two separate communication pathways between a number of central controllers and a number of remote telemetry units; 
       FIG. 2  is a system diagram of the present invention illustrating a broadcast communication pathway between the central controller and the remote telemetry units; 
       FIG. 3  is a system diagram, similar to  FIG. 2 , further illustrating each of the remote telemetry units connected to a telephone line extension to establish a shared two-way communication pathway to the central controller; 
       FIG. 4  is a system diagram, similar to  FIG. 2 , further illustrating a cellular telephone shared two-way communications pathway connecting the remote telemetry units to the central controller; 
       FIG. 5  is a system diagram, similar to  FIG. 2 , further illustrating a radio-based shared two-way communications pathway connecting the remote telemetry units to the central controller; and 
       FIG. 6  is a system diagram, similar to  FIG. 2 , further illustrating a party-line shared two-way communications pathway connecting the remote telemetry units to a plurality of controllers. 
   

   Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. 
   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The following detailed description illustrates the invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention. 
   Turning to the drawings, and to  FIGS. 1 and 2  in particular, the broad concept of the present invention is shown generally by the communications network  10  interconnecting a number of remote telemetry units  12   a - 12   n , comprising one or more sets, and one or more central controllers  14 - 14   n . The following general description is set forth in the context of a single central controller  14 , and will be expanded to cover multiple central controllers  14 - 14   n  below. 
   The communications network  10  comprises two separate and distinct communication pathways  10 A and  10 B. The first communication pathway  10 A, is a broadcast communications pathway, utilized by the central controller  14  through a transmitter  15  to transmit control messages to the remote telemetry units  12   a - 12   n . Each remote telemetry unit  12   a - 12   n  in a set is assigned a unique identification code, and each control message transmitted from the central controller  14  over the broadcast communications pathway  10 A may include the unique identification code of the intended recipient remote telemetry unit  12   a - 12   n , or may be intended as a general instruction for each of the remote telemetry units  12   a - 12   n  in the set. Remote telemetry units  12   a - 12   n  each incorporate a receiver  16  configured to receive the control messages transmitted by the central controller  14  over the broadcast communications pathway  10 A. Preferably, the receivers  16  are low cost to manufacture, and are optimized for low power consumption. The broadcast communications pathway  10 A is utilized only by the central controller  14  to transmit control messages to the remote telemetry units  12   a - 12   n.    
   The second communication pathway  10 B, which interconnects each of the remote telemetry units  12   a - 12   n  of a set and the central controllers  14 - 14   n  is a shared two-way communications pathway, and is utilized only by the remote telemetry units  12   a - 12   n  in the set to transmit report messages to the central controller  14  or to establish a communications link thereto. Since the two-way communications pathway  10 B is shared among each of the remote telemetry units  12   a - 12   n  of the set, to avoid cross-talk and communications conflicts, only one remote telemetry unit in each set may transmit a report message or establish a communications link to the central controller  14  at any given time. Accordingly, while each of the remote telemetry units  12   a - 12   n  includes a transceiver  18  configured to access the shared two-way communications pathway  10 B, each transceiver  18  is inactive, or turned off, until specifically activated by the associated remote telemetry unit  12   a - 12   n  upon receipt of a control message over the broadcast communications pathway  10 A from the central controller  14 . 
   When an individual remote telemetry unit  12   a - 12   n  of the present invention receives a broadcast message from the central controller  14  over the communications pathway  10 A, it interprets the message to obtain the unique identification contained therein. If the unique identification contained in the message corresponds to the unique identification code associated with the individual remote telemetry unit  12   a - 12   n , the remainder of the control message is interpreted to identify the operational instructions transmitted from the central controller. The operational instructions may direct the individual remote telemetry unit to perform one or more actions, for example, shut down, to update a measurement, to erase stored data, or to transmit a current and/or stored data to the central controller over the shared two-way communications pathway  10 B. 
   In the event a remote telemetry unit receives an instruction to transmit data to the central controller  14  over the shared two-way communications pathway  10 B, the remote telemetry unit activates the transceiver  18 , establishes a connection to the central controller  14  over the shared two-way communications pathway  10 B, and transmits the requested information. No unique identification of the remote telemetry units  12   a - 12   n  is present on the shared two-way communications pathway  10 B, hence all communications over communications pathway  10 B to the central controller  14  must be initiated by a remote telemetry unit  12   a - 12   n . Upon completion of the data exchange, the remote telemetry unit closes the connection to the central controller  14 , and again deactivates the associated transceiver  18 , thereby freeing the shared two-way communications pathway  10 B for use by another remote telemetry unit  12   a - 12   n.    
   As is indicated in  FIG. 1 , the communication pathways  10 A and  10 B may be shared by a number of central controllers  14 - 14   n . In such cases, the messages transmitted from an individual central controller  14 - 14   n  over the broadcast communications pathway  10 A includes an identification for both the intended recipient remote telemetry unit  12   a - 12   n  and the central controller  14 - 14   n  initiating the communication. In this manner, the remote telemetry unit  12   a - 12   h  can direct a return message over the shared two-way communications pathway  10 B to the identified central controller  14 - 14   n . Those of ordinary skill in the art will recognize that for networks utilizing multiple central controllers  14 - 14   n , the central controllers must coordinate transmissions over the broadcast network  10 A to maintain media access control. 
   In a first alternate embodiment, a conventional wireless pager system serves the function of the broadcast communications pathway  10 A from the central controller  14  to each of the remote telemetry units  12   a - 12   n . Each receiver  16  at the remote telemetry units is a wireless pager, capable of receiving messages broadcast over a conventional cellular pager system. Each of the wireless pagers is assigned to the same cellular pager number within the conventional cellular system, such that when the central controller  14  is required to communicate with any remote telemetry unit, it calls the single cellular pager number, and transmits a unique identification code together with one or more operating instructions as the pager message. Each of the remote telemetry units receives the broadcast cellular pager message on its associated wireless pager, and compares the unique identification code in the broadcast message with its own unique identification code. The remote telemetry unit  12   a - 12   n  for which the message is intended will identify a match between its unique identification code and the unique identification code broadcast on the cellular paging message, and will subsequently carry out the one or more operating instructions contained within the remained of the cellular broadcast message. None of the other remote telemetry units  12   a - 12   n  will perform any action. 
   In a second alternate embodiment illustrated in  FIG. 3 , the transceiver  18  of each of the remote telemetry units  12   a - 12   n  within a set is a conventional telephone unit (i.e. a conventional modem) linked to the shared two-way communications pathway  10 B such as a line extension  20  associated with a multiplexer  22  assigned to a single subscriber telephone line  24  in a conventional telephone network  26 , in much the same manner as multiple telephone units are connected to a single residential subscriber telephone line. Here, all of a set of remote telemetry units are associated with a single telephone number. The central controller  14 , in turn, is linked to a second subscriber telephone line  28 , and connected to the conventional telephone network  26 . Each remote telemetry unit  12   a - 12   n  will only activate its associated conventional telephone unit, (i.e., go “off-hook”) upon receiving a request for communication from the central controller  14  over the broadcast communications pathway  10 A, or only after first determining that the telephone line is not currently in use by another remote telemetry unit. Since no two remote telemetry units will ever utilize the shared two-way communications pathway  10 B simultaneously, conflicts over usage of the single telephone line will not arise. 
   In a third alternate embodiment, illustrated in  FIG. 4 , the transceiver  18  of each of the remote telemetry units  12   a - 12   n  within a set is a conventional cellular radiotelephone, with a conventional cellular telephone network  30  forming the shared two-way communications pathway  10 B. The conventional cellular telephone network  30  may be either a digital or analog cellular system, and may include one or more wire-based telephone connections. Each of the transceivers  18  may be associated with a unique cellular telephone identification number, or, to reduce the costs associated with maintaining large numbers of cellular telephone numbers, each of the transceivers  18  may be associated with the same cellular telephone identification number. During periods of non-use, each of the transceivers  18  is powered down, such that it is not visible to the conventional cellular telephone system. Only after receiving a command from the central controller  14  over the broadcast communications pathway  10 A will a single remote telemetry unit within a set activate its associated transceiver  18  and establish a connection to the central controller  14  over the conventional cellular telephone system. Since no two transceivers  18  associated with a set of remote telemetry units  12   a - 12   n  will be activated at the same time, the conventional cellular telephone system cannot distinguish between multiple cellular telephones having a common cellular identification number and a single cellular telephone which is turning on and off as it is moved from one physical location to another. Therefore, the costs associated with maintaining a single cellular telephone identification number in the conventional cellular telephone system will be greatly reduced from the cost of having to maintain a unique cellular telephone identification number in the conventional cellular telephone system for each of the remote telemetry units  12   a - 12   n.    
   In a fourth alternate embodiment, illustrated in  FIG. 5 , both communications pathways  10 A and  10 B are broadcast radio channels. Communications pathway  10 A, intended primarily for broadcasting messages from the central controller  14  to the individual remote telemetry units  12   a - 12   n  is optimized for low-power reception at the receiver  16  of each of the remote telemetry units  12   a - 12   n , using conventional analog or digital radio communications techniques. For example, a high-powered radio transmitter  15  may be associated with the central controller  14 , which transmits messages at a low data rate. Corresponding low-power receivers  16  may be associated with each of the remote telemetry units  12   a - 12   n  to receive and interpret the messages sent by the central controller  14  over communications pathway  10 A. The second communication pathway  10 B, is optimized as a broadcast shared two-way communications pathway. The transceivers  18  associated with each of the remote telemetry units  12   a - 12   n  are maintained in an inactive or powered down state when not in use, to significantly reduce power consumption, and thereby either extend battery life or reduce operating costs, by each of the remote telemetry units  12   a - 12   n . When activated, a transceiver  18  will transmit requested data to a receiver in the broadcast shared two-way communications pathway  10 B, which will relay the message to the central controller  14 , either directly or through a number of repeater sub-stations (not shown). Those of ordinary skill in the art will recognize that any conventional broadcast technology may be utilized by the shared two-way communications pathway  10 B, for example, radio using frequency modulation, radio using amplitude modulation, microwave or infrared transmission systems, and that any conventional encoding or encryption techniques may be employed. 
   In a fifth alternate embodiment, shown in  FIG. 6 , both communications pathways  10 A and  10 B utilize a conventional telephone system  26 . The transceiver  18  of each of the remote telemetry units  12   a - 12   n  within a set is a conventional telephone unit (i.e. a conventional modem) linked to the shared two-way communications pathway  10 B. Each of the telephone units is assigned a single shared telephone number on a single subscriber telephone line  24 , in much the same manner as a “party-line” residential subscriber telephone line. Each central controller  14   a - 14   n  is linked to a second subscriber telephone line  28   a - 28   n , and connected to the conventional telephone network  26 . To communicate with the remote telemetry units  12   a - 12   n , a central controller  14  initiates a call to the single shared telephone number via the telephone network  26 , causing each of the transceivers  18  to answer, or go “off-hook”. Once each of the transceivers  18  associated with the remote telemetry units  12   a - 12   n  is “off-hook”, the central controller  14  transmits a recipient identification code to all of the “off-hook” transceivers using standard DTMF codes. Only the remote telemetry unit having a unique identification code matching the recipient identification code will continue to remain “off-hook”. The transceivers associated with each of the other remote telemetry units will return to an inactive or “on-hook” state, thereby permitting the remaining “off-hook” transceiver and the central controller  14  to establish a conventional modem connection over the open communications channel for the exchange of information. 
   As will be readily recognized, the alternate methods of the present invention for communicating between one or more central controllers  14 - 14   n  and a number of remote telemetry units  12   a - 12   n  may be utilized exclusively or in combination, for example, the central controllers may communicate messages to the remote telemetry units  12   a - 12   n  using a high-powered radio broadcast communications pathway  10 A, and in turn, the remote telemetry units may communicate with the central controller over a conventional telephone line communications pathway  10 B. In each embodiment, inexpensive resources (the broadcast communications channel  10 A) and expensive resources (the shared two-way communications channel  10 B) are utilized in combination to achieve a high degree of efficiency. 
   In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.