Abstract:
A transceiver includes a two-way communication component capable of powering down to conserve energy and capable of powering up in response to an electronic signal, the two-way communication component including a transmitter and a first receiver; and a second receiver that is configured to screen a radio frequency broadcast and provide the electronic signal to the two-way communication component in order to power up the two-way wireless communication component. The second receiver is configured to screen the radio frequency broadcast for first criteria, and screen the radio frequency broadcast for second criteria. The electric current may be an order of magnitude larger when screening for the first criteria than the second criteria. Screening also may be performed for third criteria, namely, specific data. The second receiver is adapted to draw substantially less current while awaiting receipt of and listening for a radio frequency broadcast than the two-way wireless communication component.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is entitled to the benefit of, and claims priority to, provisional U.S. Patent Application Ser. No. 60/687,415 filed Jun. 3, 2005 and titled “CLASS-BASED SOFT HAND-OFF IN WIRELESS COMMUNICATIONS,” and provisional U.S. Patent Application Ser. No. 60/691,884 filed Jun. 17, 2005 and titled “REMOTE SENSOR INTERFACE (RSI) STEPPED WAKE-UP SEQUENCE,” the entirety of each of which is incorporated herein by reference. 
     
    
     INCORPORATION BY REFERENCE  
       [0002]     The present application hereby incorporates by reference: U.S. Pat. No. 6,753,775 B2 (titled “Smart Container Monitoring System”); U.S. Pat. No. 6,745,027 B2 (titled “Class Switched Networks for Tracking Articles”); U.S. Pat. No. 6,665,585 B2 (titled “Method and Apparatus for Container Management”); U.S. Pat. No. 5,458,042 (titled “Container for Packaging an Object Provided with a Radio Frequency Transmission Device and Removable Element for Such a Container”); International Patent Application Publication No. WO 03/032501 A2, which international patent application designated the United States and was published in English (titled “Network Formation in Asset-Tracking System Based on Asset Class”); International Patent Application Publication No. WO 03/098851 A1, which international patent application designated the United States and was published in English (titled “LPRF Device Wake Up Using Wireless Tag”); U.S. Patent Application Publication No. 2005/0093703 A1 (titled “Systems and Methods Having LPRF Device Wake Up Using Wireless Tag”); U.S. Patent Application Publication No. 2005/0093702 A1 (titled “Manufacture of LPRF Device Wake Up Using Wireless Tag”); U.S. Patent Application Publication No. 2004/0082296 A1 (titled “Network Formation in Asset-Tracking System Based on Asset Class”); U.S. Patent Application Publication No. 2004/0183673 A1 (titled “Portable Detachable Self-Contained Tracking Unit for Two-Way Satellite Communication with a Central Server”); U.S. Patent Application Publication No. 2004/0021572 A1 (“Electronic baggage tracking and identification”); and U.S. patent application Ser. No. 11/306,765 (titled “Keyhole Communication Device for Tracking and Monitoring Shipping Container and Contents Thereof”).  
       COPYRIGHT STATEMENT  
       [0003]     All of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the patent files and records of government agencies of countries wherein this patent document has been filed, but otherwise reserves all copyright rights whatsoever.  
       BACKGROUND  
       [0004]     RSIs are utilized for remotely collecting data in the field and communicating the collected data to one or more centralized locations. For example, RSIs are utilized in tracking and/or monitoring assets that are stored and/or transported in association with wireless transceivers, such as radio frequency identification tags (RFIDs). In such implementations, such as those described in U.S. Patent Application Publication No. 2005/0093702 A1, an RSI has sometimes been previously referred to as a “wireless reader tag” or “WRT.” The data regarding the tracked and/or monitored assets is communicated by an RSI to one or more central servers for processing. Such data is useful, for instance, in supply chain management. Such data further is useful, for instance, in homeland security, especially when the assets being tracked and/or monitored are being imported into the United States from foreign countries.  
         [0005]     Of course, the RSIs of the present invention are preferably capable of wireless communications with external devices. For example, the RSI preferably communicates with other RSIs in forming one or more wireless networks. Furthermore, the RSI preferably communicates with a gateway that itself serves as a bridge to other networks, such as the Internet, a cellular network, or a Satellite network.  
         [0006]     In order to reduce power consumption by the RSIs, attempts have been made to utilize a “wake-up receiver” to determine, according to predetermined criteria, when a higher power radio should be turned on for two-way wireless communications with the gateway. Such a wake-up sequence was described in the aforementioned U.S. Patent Application Publication No. 2005/0093702 A1. In that reference or other references, the wake-up receiver may have been referred to as a “WT Component,” or on occasion, as a “tag turn-on circuit” or “TTOC.” In addition, the signal received by the wake-up receiver for waking up the RSI is transmitted by a wake-up transmitter. The wake-up transmitter occasionally has been referred to as a “tag turn-on” or “TTO” in this previous reference or another reference, and the wake-up transmitter is capable of sending signals to other RSIs and/or gateways that may include wake-up receivers, TTOCs, or the like, for wake-up of the other RSIs and/or gateways. Unfortunately, the wake-up sequence performed in the aforementioned reference does provide a sufficient amount of reduction in the power consumption of the RSI or RSI-equivalent. Further, the previous wake-up sequence does not provide the opportunity for different functions to be triggered at different power levels.  
         [0007]     The present invention relates in particular to a stepped wake-up sequence of an RSI in activating circuits thereof in response to a wake-up signal that is received from a gateway or another RSI. The stepped wake-up sequence provides extended duration of the life of the battery power supply of the RSI, especially in a noisy radio frequency (RF) environment. This wake-up sequence and the preferred circuit diagrams for performing this wake-up sequence is deemed to be an improvement over the general wake-up sequence performed by the “WT Component” described in detail, for example, in incorporated International Patent Application Publication No. WO 03/098851 A1.  
       SUMMARY OF THE PRESENT INVENTION  
       [0008]     In addition to the aforementioned aspects and features of the present invention, it should be noted that the present invention further includes the various possible combinations of such aspects and features.  
         [0009]     The present invention includes many aspects and features.  
         [0010]     In a first aspect of the invention, a wireless transceiver includes: a two-way wireless communication component capable of powering down to conserve energy and capable of powering up in response to an electronic signal, the two-way wireless communication component including a transmitter and a first receiver; and a second receiver that is configured to screen a radio frequency broadcast and provide the electronic signal to the two-way wireless communication component in order to power up the two-way wireless communication component. In particular, the second receiver is configured to: screen the radio frequency broadcast for first criteria, wherein the wireless transceiver draws a first electric current when screening the radio frequency broadcast for the first criteria, and screen the radio frequency broadcast for second criteria, wherein the wireless transceiver draws a second electric current when screening the radio frequency broadcast for the second criteria, the second electric current being an order of magnitude larger than the first electric current. Furthermore, the second receiver is adapted to draw substantially less current while awaiting receipt of and listening for a radio frequency broadcast than the current that the two-way wireless communication component would draw while awaiting receipt of and listening for a radio frequency broadcast.  
         [0011]     In a feature of this aspect, the electronic signal is provided only if the first criteria and the second criteria are both met.  
         [0012]     In a feature of this aspect, the second receiver draws on the order of magnitude of tens of microamps of electric current when screening the radio frequency broadcast for the second criteria, and the second receiver draws on the order of magnitude of hundreds of microamps of electric current when screening the radio frequency broadcast for the second criteria.  
         [0013]     In a feature of this aspect, the second receiver further is configured to screen the radio frequency broadcast for third criteria, and the wireless transceiver draws on the order of magnitude of a milliamp of electric current when screening the radio frequency broadcast for the third criteria. Moreover, the screening for the third criteria is performed only if the first criteria and the second criteria are met. Additionally, the electronic signal may be provided only if the third criteria is met.  
         [0014]     In a feature of this aspect, the first criteria is a particular frequency and wherein the second criteria is a particular modulation type.  
         [0015]     In yet another feature of this aspect, the third criteria is specific data to be identified in the radio frequency broadcast.  
         [0016]     In another aspect of the invention, a wireless transceiver includes: a two-way wireless communication device capable of powering down to conserve energy and capable of powering up in response to an electronic signal, the two-way wireless communication device including a transmitter and a first receiver; and a second receiver that is configured to screen a radio frequency broadcast and provide the electronic signal to the two-way wireless communication device in order to power up the two-way wireless communication device. Furthermore, the second receiver is configured to: screen the radio frequency broadcast for first criteria; screen the radio frequency broadcast for second criteria if the first criteria is met; and screen the radio frequency broadcast for third criteria if the second criteria is met. Moreover, the second receiver is adapted to draw substantially less current while awaiting receipt of and listening for a radio frequency broadcast than the current that the two-way wireless communication device would draw while awaiting receipt of and listening for a radio frequency broadcast.  
         [0017]     In a feature of this aspect, the electronic signal is provided only if the first criteria, the second criteria, and the third criteria are met. The first criteria may be a particular frequency, the second criteria may be a particular modulation type, and the third criteria may be specific data identified in the radio frequency broadcast.  
         [0018]     In another aspect of the invention, a wireless transceiver includes both a two-way wireless communication device having a transmitter and a first receiver and a second receiver, and a method of operating a wireless transceiver includes: powering down the two-way wireless communication device to conserve energy; and in response to receiving an electronic signal at the two-way wireless communication device, powering up the two-way wireless communication device. Furthermore, the second receiver provides the electronic signal to the two-way wireless communication device upon certain criteria being met. In particular, the second receiver screens a radio frequency broadcast for first criteria while drawing an electric current that only is on the order of magnitude of tens of microamps; and, if the first criteria is met, screens the radio frequency broadcast for second criteria while drawing an increased electric current that only is on the order of magnitude of hundreds of microamps. Furthermore, the second receiver is adapted to draw substantially less current than the two-way wireless communication device while awaiting receipt of and listening for a radio frequency broadcast.  
         [0019]     In accordance with this aspect, the first criteria may be a particular frequency, and the second criteria may be a particular modulation type. The third criteria may be specific data that is identified in the radio frequency broadcast.  
         [0020]     In yet another aspect of the invention, a wireless transceiver includes both a two-way wireless communication device having a transmitter and a first receiver and a second receiver, and a method of operating a wireless transceiver includes: powering down the two-way wireless communication device to conserve energy; and in response to receiving an electronic signal at the two-way wireless communication device, powering up the two-way wireless communication device. Furthermore, the second receiver provides the electronic signal to the two-way wireless communication device upon certain criteria being met. In particular, the second receiver screens a radio frequency broadcast for first criteria; and, if the first criteria is met, screens the radio frequency broadcast for second criteria; and, if the second criteria is met, screens the radio frequency broadcast for third criteria. If the third criteria is met, then the second receiver provides the electronic signal to the two-way wireless communication device. Furthermore, the second receiver is adapted to draw substantially less current than the two-way wireless communication device while awaiting receipt of and listening for a radio frequency broadcast.  
         [0021]     In accordance with a feature this aspect, the first criteria may be a particular frequency, and the second criteria may be a particular modulation type.  
         [0022]     In another feature of this aspect, the third criteria may be specific data that is identified in the radio frequency broadcast such as, for example, a common designation of an ad hoc network. The common designation may be a class-based designation.  
         [0023]     In another aspect of the invention, an asset-tracking system includes a wireless transceiver in accordance with any of the foregoing aspects as well as one or more sensor devices that are disposed externally to and in proximity of the wireless transceiver. The asset-tracking system may be used to read the one or more sensor devices and the asset-tracking system may utilize class-based, ad hoc hierarchical networks.  
         [0024]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]     One or more embodiments of the present invention will be described in detail with reference to the accompanying drawings which are briefly described below, and wherein the same elements are referred to with the same reference numerals, and wherein:  
         [0026]      FIG. 1  is a block diagram of an exemplary wireless communication system in accordance with the preferred embodiments of the present invention;  
         [0027]      FIG. 2  is a diagram illustrating wireless communication between one of the gateways and one of the remote sensor interfaces of  FIG. 1 ;  
         [0028]      FIG. 3  is a block diagram of a first exemplary implementation of a wake-up transmitter for use in the gateway of  FIG. 2 ;  
         [0029]      FIG. 4  is a block diagram of a first exemplary implementation of a wake-up receiver for use in the remote sensor interface of  FIG. 2 ;  
         [0030]      FIG. 5  is a graphical representation of a stepped wake-up sequence, performed by the wake-up receiver of  FIG. 4 , in accordance with a preferred embodiment of the present invention;  
         [0031]      FIG. 6  is a block diagram of a second exemplary wake-up transmitter, for use in the gateway of  FIG. 2 ;  
         [0032]      FIG. 7  is a block diagram of a second exemplary wake-up receiver for use in the remote sensor interface of  FIG. 2 ; and  
         [0033]      FIG. 8  is a graphical representation of an alternative stepped wake-up sequence, performed by the wake-up receiver of  FIG. 7 , in accordance with another preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0034]     As a preliminary matter, it will readily be understood by one having ordinary skill in the relevant art (“Ordinary Artisan”) that the present invention has broad utility and application. Furthermore, any embodiment discussed and identified as being “preferred” is considered to be part of a best mode contemplated for carrying out the present invention. Other embodiments also may be discussed for additional illustrative purposes in providing a full and enabling disclosure of the present invention. Moreover, many embodiments, such as adaptations, variations, modifications, and equivalent arrangements, will be implicitly disclosed by the embodiments described herein and fall within the scope of the present invention.  
         [0035]     Accordingly, while the present invention is described herein in detail in relation to one or more embodiments, it is to be understood that this disclosure is illustrative and exemplary of the present invention, and is made merely for the purposes of providing a full and enabling disclosure of the present invention. The detailed disclosure herein of one or more embodiments is not intended, nor is to be construed, to limit the scope of patent protection afforded the present invention, which scope is to be defined by the claims and the equivalents thereof. It is not intended that the scope of patent protection afforded the present invention be defined by reading into any claim a limitation found herein that does not explicitly appear in the claim itself.  
         [0036]     Thus, for example, any sequence(s) and/or temporal order of steps of various processes or methods that are described herein are illustrative and not restrictive. Accordingly, it should be understood that, although steps of various processes or methods may be shown and described as being in a sequence or temporal order, the steps of any such processes or methods are not limited to being carried out in any particular sequence or order, absent an indication otherwise. Indeed, the steps in such processes or methods generally may be carried out in various different sequences and orders while still falling within the scope of the present invention. Accordingly, it is intended that the scope of patent protection afforded the present invention is to be defined by the appended claims rather than the description set forth herein.  
         [0037]     Additionally, it is important to note that each term used herein refers to that which the Ordinary Artisan would understand such term to mean based on the contextual use of such term herein. To the extent that the meaning of a term used herein—as understood by the Ordinary Artisan based on the contextual use of such term—differs in any way from any particular dictionary definition of such term, it is intended that the meaning of the term as understood by the Ordinary Artisan should prevail.  
         [0038]     Furthermore, it is important to note that, as used herein, “a” and “an” each generally denotes “at least one,” but does not exclude a plurality unless the contextual use dictates otherwise. Thus, reference to “a picnic basket having an apple” describes “a picnic basket having at least one apple” as well as “a picnic basket having apples.” In contrast, reference to “a picnic basket having a single apple” describes “a picnic basket having only one apple.” 
         [0039]     When used herein to join a list of items, “or” denotes “at least one of the items,” but does not exclude a plurality of items of the list. Thus, reference to “a picnic basket having cheese or crackers” describes “a picnic basket having cheese without crackers”, “a picnic basket having crackers without cheese”, and “a picnic basket having both cheese and crackers.” Finally, when used herein to join a list of items, “and” denotes “all of the items of the list.” Thus, reference to “a picnic basket having cheese and crackers” describes “a picnic basket having cheese, wherein the picnic basket further has crackers,” as well as describes “a picnic basket having crackers, wherein the picnic basket further has cheese.” 
         [0040]     Referring now to the drawings, the preferred embodiments of the present invention are next described. The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0041]      FIG. 1  is a block diagram of an exemplary wireless communication system in accordance with the preferred embodiments of the present invention. As shown, the system  10  includes one or more gateways  11 , each of which communicates wirelessly with one or more remote sensor interface (“RSI”)  12  following wake-up of the RSI  12  by the gateway  11 . As will be evident to the Ordinary Artisan, the gateway  11  may be any central radio unit, the design and implementation of which will likewise be apparent to the Ordinary Artisan, that is capable of initiating and carrying out wireless communication with RSIs  12 . Indeed, it will likewise be evident that the specific communication devices and methods described and illustrated herein may be used for wireless communication between other types of radio devices. The gateway  11  serves as a fixed-area or mobile interface between RSIs  12  and other networks, such as the Internet, a cellular network, or a Satellite network. Though not shown, one or more central servers, used for functions such as tracking and storing monitored data and the like, may be linked to the gateways  11  via the network.  
         [0042]     Optionally, the gateway may consist of the Wide Area Network (WAN) interface, the RSI interface, a hard drive that contains the data store or database, server control and application specific software. By including server functionality in the gateway  11 , WAN interface cost may be reduced. As will be apparent to the Ordinary Artisan, the WAN may be utilized for backup and remote operation but is not required.  
         [0043]      FIG. 2  is a diagram illustrating wireless communication between one of the gateways and one of the remote sensor interfaces of  FIG. 1 . As shown therein, the gateway  11  includes a power source  13  such as a battery or connection to an external power source for powering systems of the gateway  11 ; a central processing unit (CPU) section  15  for controlling operations of the gateway  11 ; a wake-up transmitter  18  coupled to an external patch antenna  20 , such as a 6.5 dBi omni-directional antenna, for transmitting wake-up signals; and a two-way wireless communication device  22  including an antenna  24  for two-way communications. The two-way wireless communication device  22  is preferably a standards based radio such as, for example, a Bluetooth radio, a WiFi radio, a Zigbee radio, an Ultra-Wideband (UWB) radio, or a WiMAX radio, with a Bluetooth radio being the most preferred. The CPU section  15  most predominantly includes a microprocessor and 802.11 or other communication capability, but optionally, may further include a global positioning system (GPS) and cellular telephony communications capabilities.  
         [0044]     The RSI  12  includes a wake-up receiver  26 , for receiving wake-up signals from the gateway  11  and/or other RSIs  12  and, in turn, prompting the stepped wake up sequence of  FIG. 5 , and a two-way wireless communication device  28 , including an antenna  24  etched on a printed circuit board, for two-way communications. The two-way wireless communication device  28  is preferably a standards based radio such as, for example, a Bluetooth radio, a WiFi radio, a Zigbee radio, an Ultra-Wideband (UWB) radio, or a WiMAX radio, but which in any case is generally selected to match the two-way wireless communication radio  22  of the gateway  11 . The wake-up receiver  26  further includes an ultra-low power consumption receiver and includes, for example, an etched antenna on a printed circuit board.  
         [0045]     In general, wireless communication between the gateway  11  and the RSI  12  may be carried out as follows. The gateway  11  first transmits, via the wake-up transmitter  18 , a wake-up signal  14  to the RSI  12 . At the RSI  12 , the wake-up signal  14  is received by a wake-up receiver  26  of the RSI  12 , which executes a stepped wake up sequence as shown in  FIG. 5  in accordance with the present invention. Upon full wake-up of the RSI  12 , the gateway  11  and RSI  12  engage in the two-way communications  16  using the standards based radios  22 ,  28 . As shown in the illustrated embodiment, the standards based radios  22 ,  28  that are used are Bluetooth radios. Each of the gateway  11  and RSI  12  are furthermore capable of two-way communications with other RSIs  12  or gateways  11  of a network.  
         [0046]     The RSI  12  may be associated with one or more sensors  17 , or the RSI  12  itself may serve as a gateway to other RSIs  12 . One particularly common application for RSIs  12  is in the tracking of various assets, wherein each of a plurality of RSIs  12  is associated with a particular asset and/or an RSI  12  is associated with an asset, such as a shipping container, pallet, or the like, that carries or contains other assets. The use of devices similar to RSIs  12  to track assets has been described in U.S. Patent Application Publication No. 2005/0093702 A1, in which such devices are often generally referred to as “wireless transceivers” or “WRTs.” Insofar as the RSI  12  is associated with assets, such as shipping containers and/or contents thereof, the RSI  12  further preferably is capable of interfacing or interacting with asset monitoring sensors  17  that monitor conditions, phenomena, or the like inside or outside the container and/or inside or outside a particular asset in the container. Such sensors  17  may include, without limitation, electronic seals capable of detecting openings and/or closures of the container, cameras, microphones, RF signal detectors, light detectors, temperature sensors, radiation sensors, chemical sensors, and motion detectors. The particular use and implementation of RSIs in shipping containers has been further described in U.S. patent application Ser. No. 11/306,765. The RSI  12  preferably includes a sensor board having circuitry for interfacing with such asset monitoring sensors  17 . The two-way communications  16  convey commands and queries from the gateway  11  to the RSI  12  and convey data, which may include sensor data acquired from the monitoring sensors  17 , from the RSI  12  to the gateway  11 . As the RSI  12  is preferably deployed and mobile with assets and asset containers, the RSI  12  preferably includes the wake-up receiver  26  and executes the stepped wake up sequence of  FIG. 5  in order to minimize power consumption of the RSI  12 , which avoids frequent servicing (such as the changing of a battery).  
         [0047]     A wake-up signal may be specifically directed toward a particular RSI  12  as identified by a unique identifier of the RSI  12 . In this regard, the wake-up signal would include a unique identifier of the RSI  12 .  
         [0048]     Alternatively, a wake-up signal may be specifically directed toward a particular class of RSIs  12  as identified by a class designation. In this regard, the wake-up signal would include the class to which the wake-up signal is directed.  
         [0049]     In yet another alternative, a wake-up signal may be directed to all RSIs  12 . In this regard, the wake-up signal would include an indication to this effect. Preferably in class based systems, such a wake-up signal would include a class designation that includes, as members of the class, all of the RSIs  12  (i.e., an all encompassing or root class).  
         [0050]      FIG. 3  is a block diagram of a first exemplary implementation of a wake-up transmitter  18  for use in the gateway  11  of  FIG. 2 . A microcontroller  30 , which may be, for example, a RISC-type microcontroller such as the PIC-16F88, available from Microchip Technology of Chandler, Ariz., receives input signals  32  from, for example, the CPU section  15  of a gateway  11  that conveys digital information, such as class and other data, to be transmitted by the wake-up transmitter  18 . An output  34  of the microcontroller  30  passes the digital information to be transmitted to an encoder  36 . Another output  38  of the microcontroller  30  dictates channel selections, dwell times, which are generally less than 0.4 seconds, and modulation levels for frequency hopping by the wake-up transmitter  18  in its transmissions. An ultra-low power frequency synthesizer  40 , for example the LMX2310U Synthesizer, available from National Semiconductor, coupled to a reference oscillator  42 , receives the frequency hopping related output  38  of the microcontroller  30 . The synthesizer  40 , in a feedback controlled loop  43  with a filter  44  and a voltage-controlled oscillator (VCO)  46 , operating, for example, in a 2 to 3 Gigahertz (GHz) range, establishes the frequency of the VCO output  48  according to the frequency hopping scheme dictated by the output  38  of the microcontroller  30 . A digital attenuator  50  then modulates the VCO output  48  according to an output  52  of the encoder  36 . For example, a 5-bit digital attenuator is used for 70% modulation. The output  54  of the digital attenuator  50  conveys the digital information to be transmitted by the wake-up transmitter  18 , at the output frequency of the VCO  46 , to an amplifier  56 . The amplifier  56  regulates the power of transmissions of the antenna  20 , namely, the wake-up signals  14  that convey the digital information to a wake-up receiver  26  of, for example, an RSI  12 .  
         [0051]     The frequency hopping scheme dictated by the microcontroller  30  is preferably in compliance with applicable regulations, such as those promulgated by the Federal Communications Commission (FCC). For example, one frequency hopping scheme suitable for use in a preferred embodiment of the present invention is the frequency hopping spread spectrum (FHSS) convention, in which the 2.4000 to 2.4825 GHz ISM (Industrial, Scientific, and Medical) band is broken into a minimum of 75 channels (in Bluetooth communications, for instance, 79 hopping channels are utilized), each 1 Mega-Hertz (MHz) wide, with a 2 MHz lower guard band and a 3.5 MHz upper guard band. FHSS systems generally operate on time-division multiple access (TDMA) schemes with varying standards with regard to the number of frequency hops per second.  
         [0052]     Modulation of the output of the VCO  46  by the digital attenuator  50  embeds the digital information to be transmitted by the wake-up transmitter  18  into the output  54  of the attenuator  50 . This modulation also is preferably in compliance with regulations. For example, Bluetooth and digital enhanced cordless telecommunications (DECT) standards utilize Gaussian frequency-shift keying (GFSK) modulation, whereas HomeRF and FHSS 802.11 use 2-level and 4-level frequency-shift keying (FSK) to take advantage of the higher efficiencies offered from saturated power amplifiers. Under current FCC regulations, an FHSS system operating in the 2.4 GHz band can deliver a maximum output power of +30 dBm (1 Watt). The regulations further specify that FHSS systems must use a minimum of 75 hopping channels, with each channel having a 20 dB bandwidth not exceeding 1 MHz, and that the average time of occupancy on any frequency must not exceed 0.4 seconds within any 30 second time period.  
         [0053]      FIG. 4  is a block diagram of a first exemplary implementation of a wake-up receiver  26  for use in the RSI  12  of  FIG. 2 . The wake-up signals  14  from, for example, the wake-up transmitter  18  of the gateway  11  of  FIG. 2 , along with other electromagnetic noise signals, are received by an antenna  60 , and are boosted by a low noise amplifier (“LNA”)  62  of the wake-up receiver  26 . An internal power source  61  comprising, for example, a battery, powers the LNA  62  and other components or circuits of the wake-up receiver  26  through a power management module  63 . A broadband detector  64  receives the output of the LNA  62  and, when it detects the likely presence of a wake-up signal over other electromagnetic noise signals, the detector  64  passes the LNA output to a high gain amplifier  66 . The output of the high gain amplifier  66 , specifically, the wake-up signal boosted by the LNA  62  and high gain amplifier  66 , is passed to a conditional gate  68 . A threshold circuit  70  dictates a threshold criterion to the conditional gate  68  that controls the opening of the gate  68  whereby the gate  68  is opened when the output of the high gain amplifier  66  satisfies the threshold criterion.  
         [0054]     Signals reaching the gate  68  and satisfying the threshold criterion are then passed to the decoder  72  that extracts the digital information therein, such as class and/or other data embedded in signals by, for example, the encoder  36  of the wake-up transmitter  18  of  FIG. 3 . Thus, the decoder  72  preferably operates according to the same standard, such as GFSK or FSK, as the encoder  36  of the wake-up transmitter, such as the one illustrated in  FIG. 3 .  
         [0055]     A first output  74  of the decoder  72  conveys the extracted digital information to a multi-point control unit (“MCU”)  76 . The MCU  76  passes the extracted digital information to, for example, the two-way wireless communication device  28  (the standards based radio) of the RSI  12  of  FIG. 2 , thereby providing the data interface to the radio  28 . The MCU  76  also drives the gain control circuits (not shown) of the two-way wireless communication device  28 . A second output  78  of the decoder  72  prompts an output driver  80  to send an internal wake-up signal  82  to the two-way wireless communication device  28  of the RSI  12  causing the standards based radio thereof to enter active receive mode and/or active transmit mode.  
         [0056]      FIG. 5  is a graphical representation of a stepped wake-up sequence, performed by the wake-up receiver  26  of  FIG. 4 , in accordance with a preferred embodiment of the present invention.  FIG. 5  illustrates, in general, the operation of any standards based radio that may be utilized. In order to reduce unnecessary power consumption by the RSI  12 , and, in particular, to reduce power consumption of the standards based radio  28  of the RSI  12  that is used for two-way wireless communications  16  ( FIG. 2 ), the standards based radio  28  generally resides in a low or no power consumption state. The standards based radio  28  may sometimes be referred to as being in a standby mode or a sleep mode when in the low power consumption state, and may sometimes be referred to as being turned off when in the no power consumption state (i.e., so that no power is consumed by it while it otherwise would be idle). While the standards based radio  28  is in either of these states, the wake-up receiver  26  preferably operates or resides in the first domain “A” of  FIG. 5  (subdivided into subdomains “A 1 ” and “A 2 ”), wherein the RSI  12  draws electrical current that is only on the order of magnitude of tens of microamps.  
         [0057]     In the first subdomain “A 1 ” of domain “A 1 ,” the LNA  62  of the wake-up receiver  26  passes signals to the detector  64  while other components of the wake-up receiver  26 , such as the high gain amplifier  66  and the standards based radio  28 , remain in an inactive state. When the detector  64  determines that a wake-up signal is likely present, for example, by way of a measured signal strength that prevails over any present RF noise, the RSI  12  and, specifically, the wake-up receiver  26  enters the second subdomain “A 2 ” of  FIG. 5 .  
         [0058]     In the second subdomain “A 2 ” of  FIG. 5 , the RSI  12  overall draws on the order of tens of microamps of electrical current from the battery  61 , primarily due to the increased activity of the wake-up receiver  26 . Specifically, in this subdomain “A 2 ”, the wake-up receiver  26  evaluates the signal for one or more particular criteria, such as the presence of a particular modulation in the possible wake-up signal detected in subdomain “A 1 ”, which signal may convey digital information. In this regard, the high gain amplifier  66 , threshold circuitry  70 , and conditional gate  68  are activated and the signal is analyzed with regard to amplitude, frequency and/or phase to determine if the signal is modulated according to the applicable standard, such as GFSK or FSK, that is being utilized in the operation of the decoder  72 . This determination is typically completed within 30 microseconds of the RSI  12  entering the second subdomain “A 2 ”. If the signal is not modulated according to the applicable standard (a situation where digital information is not going to be extracted from the signal by the decoder  72 ), then the signal is deemed not to be a wake-up signal and the RSI  12  returns to the first operational subdomain “A 1 ”. On the other hand, if the signal is modulated according to the standard of the decoder  72 , then the RSI  12 , and specifically the wake-up receiver  26 , enters the second domain “B” of  FIG. 5 .  
         [0059]     In the second domain “B” of  FIG. 5 , the RSI  12  overall draws on the order of magnitude of hundreds of microamps of electrical current from the battery  61 , primarily due to still greater activity of the wake-up receiver  26 . In this domain, the wake-up receiver  26  receives a modulated signal and extracts and interprets digital information therefrom. In this regard, the decoder  72  is activated and extracts digital preamble information from the modulated signal. For example, the digital preamble information embedded in the wake-up signal  14  transmitted by the gateway  11  of  FIG. 2  may include an indication of whether the signal or message is of a type intended for RSIs  12 , such indication being determinative of whether the RSI  12  enters the third domain “C” or returns to the first domain “A,” wherein if the preamble of the wake-up signal is of a type intended for RSIs  12 , then the third domain “C” preferably is entered, and if the preamble of the wake-up signal is not of a type intended for the RSI  12 , then the first domain “A” preferably is re-entered.  
         [0060]     In the third domain “B” of  FIG. 5 , the RSI  12  overall draws on the order of magnitude of a milliamp of electrical current from the battery  61 , primarily due to still greater activity of the wake-up receiver  26 . In this domain, the wake-up receiver  26  receives a modulated signal and extracts and interprets digital information therefrom. In this regard, the decoder  72  is activated and extracts digital information such as class and/or other data from the modulated signal. The extraction is typically completed within 300 microseconds. For example, the digital information embedded in the wake-up signal  14  transmitted by the gateway  11  of  FIG. 2  may include a class that is determinative of whether the RSI  12  enters the fourth domain “D” or returns to the first domain “A,” wherein if the class of the wake-up signal matches a class of the RSI  12 , then the fourth domain “D” preferably is entered, and if the class of the wake-up signal does not match a class of the RSI  12 , then the first domain “A” preferably is re-entered.  
         [0061]     In the fourth domain “D” of  FIG. 5 , the RSI  12  overall draws on the order of tens to hundreds of milliamps of electrical current from the battery  61 , primarily due to the standards based radio  28  actively receiving data. In this domain, the wake-up receiver  26  prompts further activation of RSI circuits to receive wireless communications from the gateway  11  or other RSIs  12 .  
         [0062]     In particular, the wake-up receiver  26  “wakes up” the standards based radio of the RSI  12  whereby the RSI  12  preferably returns to a state in which it begins to actively receive data in communications from a gateway  11  or another RSI  12 . The RSI  12  may be awakened from a standby or sleep mode or, preferably, from a no power consumption state where the standards based radio  28  is turned off. Such communications received by the RSI  12  may configure the RSI  12  with regard to sensors  17  with which the RSI  12  is associated. Alternatively, the commands received may configure the RSI  12  with regard to a periodic wake-up schedule for periodic exchanges of communications with the gateway  11 . The communications received further may alter a class designation of the RSI  12 , may prompt the RSI  12  to communicate with other RSIs  12 , may relate to network formations among multiple RSIs  12 , or the like.  
         [0063]     The fifth domain “E” is entered when the standards based radio  28  actively transmits data. In this fifth domain “E”, the RSI  12  overall draws on the order of magnitude of hundreds to thousands of milliamps of electrical current from the battery  61 , primarily due to the active transmission of data by the standards based radio. In particular, the two-way wireless communication device  28  of the RSI  12  actively transmits wireless communications to the gateway  11  or to one or more other RSIs  12 . Thus, though the two-way wireless communication device  28  of the RSI  12  is active in both the fourth domain “D” and the fifth domain “E”, the two domains are distinguished because actively transmitting signals (domain “E”) generally draws substantially more electrical current than actively receiving signals (domain “D”).  
         [0064]     With particular regard to some examples of specific standards based radios, Bluetooth class 1 radios draw, on average, approximately 40 milliamps when actively receiving data and draw, on average, approximately 100 milliamps when actively transmitting data; WiFi radios draw, on average, approximately 175 milliamps when actively receiving data and draw, on average, approximately 400 milliamps when actively transmitting data; and Zigbee class 2 radios draw, on average, approximately 30 milliamps when actively receiving data and draw, on average, approximately 65 milliamps when actively transmitting data.  
         [0065]     As will be appreciated by the Ordinary Artisan, the RSI  12  will operate or reside a majority of the time within the first, second, and third domains (domains “A”, “B” and “C”) and the overall power consumption rate of the RSI  12  arising primarily from operation of the wake-up receiver  26  will be much less than if only the standards based radio  28  were used to monitor for communications intended for the RSI  12 . Moreover, by utilizing a stepped wake-up sequence in the wake-up receiver  26 , an even lower power consumption rate is realized. Indeed, it is believed that a majority of the time the RSI  12  will reside within the first domain “A”, during which time the RSI  12  as a whole will draw only on the order of tens of microamps of current. Indeed, by first detecting for the presence of a likely signal within a noisy RF environment, substantial power savings can be achieved using this preferred stepped wake-up sequence because the attempt to extract meaningful data from a received signal, which is an exercise that results in significantly increased power consumption, is not attempted if the signal is determined to be noise.  
         [0066]     As a result of the present invention, the RSI  12  enjoys improved power consumption (lower power consumption) and an extended life of the power source of the RSI  12  is promoted. Indeed, it is believed that an RSI  12  may operate for several years even in an RF noisy environment, thereby even possibly outlasting the useful life of its power source.  
         [0067]      FIG. 6  is a block diagram of a second exemplary wake-up transmitter  88  for use in the gateway of  FIG. 2 . As with the first exemplary wake-up transmitter  18 , a microcontroller  30  receives input signals  32  from, for example, the CPU  15  of a gateway  11  that conveys digital information, such as class and other data, to be transmitted by the wake-up transmitter  88 . However, the transmitter  88  of  FIG. 6  utilizes a synthesizer  90 , which may be a 2.4 GHz synthesizer, into which other components and functions illustrated in the block diagram of  FIG. 3  have been consolidated. For example, the filter  44 , VCO  46 , digital attenuator  50 , and encoder  36  of  FIG. 3  may be consolidated into the functioning of the synthesizer  90  through appropriate programming (e.g., software). The synthesizer  90  of  FIG. 6  is coupled to a reference oscillator  42 , and the output of the synthesizer  90  is modulated under the control of the microcontroller  30  using an RF amplifier  92  whose output is conveyed through a band pass filter  94  to the antenna for transmission.  
         [0068]      FIG. 7  is a block diagram of a second exemplary wake-up receiver  96  for use in the RSI  12  of  FIG. 2 . As with the first exemplary wake-up receiver  26 , the wake-up signals  14  from, for example, the first or second exemplary wake-up transmitter  18 ,  88  of the gateway  11  of  FIG. 2 , along with other electromagnetic noise signals, are received by an antenna  60 , and are boosted by a low noise amplifier (“LNA”)  62  of the wake-up receiver  96 . An internal power source  61  comprising, for example, a battery, powers the LNA  62  and other components or circuits of the wake-up receiver  96  through a power management module  63 . A broadband detector  64  receives the output of the LNA  62  and, when it detects the likely presence of a wake-up signal over other electromagnetic noise signals, the detector  64  passes the LNA output to a high gain amplifier  66 . The output of the high gain amplifier  66 , specifically, the wake-up signal boosted by the LNA  62  and high gain amplifier  66 , is passed to a conditional gate  68 . A threshold circuit  70  dictates a threshold criterion to the conditional gate  68  that controls the opening of the gate  68  whereby the gate  68  is opened when the output of the high gain amplifier  66  satisfies the threshold criterion.  
         [0069]     It will be appreciated by the Ordinary Artisan that certain components and functions of the block diagram of  FIG. 4  may be consolidated into the functioning of a microcontroller device  98 . For example, the threshold circuitry  70 , decoder  72 , and MCU  76  of  FIG. 4  may be consolidated into the functioning of the microcontroller device  98  through appropriate programming (e.g., software). This may readily be recognized by comparing the block diagram of  FIG. 7  for the second exemplary wake-up receiver  96  with the block diagram of  FIG. 4  for the first exemplary wake-up receiver  26 . In this case, the microcontroller device  98  could be, for example, a PLL decoder and control processor whose output drives the wake-up circuitry  99  that enables the two-way wireless communication device  28  of the RSI  12 . Alternatively, the microcontroller device  98  could be a programmable logic device and processor.  
         [0070]      FIG. 8  is a graphical representation of an alternative stepped wake-up sequence, performed by the wake-up receiver  96  of  FIG. 7 , in accordance with another preferred embodiment of the present invention. In consolidating functioning into the microcontroller device  98  in the wake-up receiver  96  as illustrated in  FIG. 7 , the domains “B” and “C” of  FIG. 5  may be merged as illustrated in  FIG. 8 , wherein only four domains are shown. As with the sequence of  FIG. 4  for the first exemplary wake-up receiver  26 , the second exemplary wake-up receiver  96  will continue to draw electrical current on the order of tens of microamps while listening for the presence of a wake-up signal, for example, by way of a measured signal strength that prevails over any present RF noise, and will draw only hundreds of microamps, on average, while determining whether a signal contains data. However, the second exemplary wake-up receiver  96  will still draw only hundreds of microamps, on average, while determining whether the data, once extracted from a signal detected out of RF noise, in fact indicates that the RSI  12  is an intended recipient of a communication such that the standards based radio of the RSI  12  should be woken by the wake-up receiver  96 . It is believed that, by enabling the microcontroller device  98  to make the latter determination rather than through the circuitry of the wake-up receiver  26  of  FIG. 4 , an overall decrease in the power consumption rate may be achieved on behalf of the wake-up receiver  96  (and thus the RSI  12 ) during this determination.  
         [0071]     With further regard to FCC rules (47 CFR § 15), Part 15, Section 249 thereof relates to operation within the 2400-2483.5 MHz range and to field strengths of emissions from intentional radiators. Part 15, section 205 relates to restricted bands of operation, wherein only spurious emissions are permitted, such as the 2310-2390 MHz and 2483.5-2500 MHz ranges. Part 15, section 245 relates to operation within the 2407.5-2417.4 MHz band for intentional radiators used as field disturbance sensors, excluding perimeter protection systems. Part 15, section 247 relates to intentional radiators in the 2400-2483.5 MHz range.  
         [0072]     In any 100 kilo-Hertz (kHz) bandwidth outside the frequency band in which the spread spectrum or digitally modulated intentional radiator is operating, the radio frequency power that is produced by the intentional radiator shall be at least 20 dB below that in the 100 kHz bandwidth within the band that contains the highest level of the desired power, based on either an RF conducted or a radiated measurement.  
         [0073]     Based on the foregoing information, it is readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those specifically described herein, as well as many variations, modifications, and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing descriptions thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for the purpose of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended to be construed to limit the present invention or otherwise exclude any such other embodiments, adaptations, variations, modifications or equivalent arrangements; the present invention being limited only by the claims appended hereto and the equivalents thereof. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for the purpose of limitation.