Source: https://patents.google.com/patent/WO2002008866A2/en
Timestamp: 2019-12-07 06:06:47
Document Index: 695079697

Matched Legal Cases: ['art 15', 'art 15', 'art 15', 'art 15', 'art 15', 'art 15', 'art 15', 'art 15', 'art 15', 'art 15']

WO2002008866A2 - Spread spectrum meter reading system utilizing low-speed/high-power frequency hopping - Google Patents
WO2002008866A2
WO2002008866A2 PCT/US2001/023303 US0123303W WO0208866A2 WO 2002008866 A2 WO2002008866 A2 WO 2002008866A2 US 0123303 W US0123303 W US 0123303W WO 0208866 A2 WO0208866 A2 WO 0208866A2
PCT/US2001/023303
WO2002008866A3 (en
2000-07-21 Priority to US60/220,015 priority
2001-07-23 Application filed by Itron, Inc. filed Critical Itron, Inc.
2002-01-31 Publication of WO2002008866A2 publication Critical patent/WO2002008866A2/en
2002-06-20 Publication of WO2002008866A3 publication Critical patent/WO2002008866A3/en
239000005020 polyethylene terephthalate Substances 0 abstract description 140
108060003870 IFT56 family Proteins 0 description 14
108060006704 JAK family Proteins 0 description 14
102100004894 STIP1 Human genes 0 description 14
A spread spectrum meter reading system enables the use of high power frequency hopping spread spectrum (HFSS) transmission at both the encoder transmitter and repeater levels of the meter reading system. A plurality of end point encoder transmitter devices (RF devices) are each connected to a utility meter and transmit high power FHSS signals containing metering data for the corresponding utility meter. A plurality of intermediate transceiver units (PET Repeaters) both receives and retransmits the high power FHSS signals. The base station (PETRC Base Unit) can receive the high power FHSS signals from both the encoder transmitter devices and the intermediate transceiver units. The intermediate transceiver units aggregates metering data from multiple encoder transmitter devices prior to block retransmission of the metering data to the base station. The high power FHSS signals are transmitted at a maximum hopping rate to reduce power consumption and increase battery life of the devices.
Field of the Invention The present invention relates to utility metering systems and, more particularly, to a utility metering system that utilizes frequency hopping spread spectrum wireless communication to transmit utility consumption data.
Wireless automatic meter reading systems are well known. Typically, each utility meter is provided with a battery-powered encoder that collects meter readings and periodically transmits those readings over a wireless network to a central station. The power limitations imposed by the need for the encoder to be battery powered and by regulations governing radio transmissions effectively prevent direct radio transmissions to the central station. Instead, wireless meter reading systems typically utilize a layered network of overlapping intermediate receiving stations that receive transmissions from a group of meter encoders and forward those messages on to the next higher layer in the network as described, for example, in U.S. Patent No. 5,056,107. These types of layered wireless transmission networks allow for the use of lower power, unlicensed wireless transmitters in the thousands of encoder transmitters that must be deployed as part of a utility meter reading system for a large metropolitan area. i 1985, as an attempt to stimulate the production and use of wireless network products, the FCC modified Part 15 of the radio spectrum regulation, which governs unlicensed devices. The modification authorized wireless network products to operate in the industrial, scientific, and medical (ISM) bands using spread spectrum modulation. The ISM frequencies that maybe used include 902 to 928 MHz, 2.4 to 2.4835 GHz, and 5.725 to 5.850 GHz. The FCC allows users to operate wireless products, such as utility metering systems, without obtaining FCC licenses if the products meet certain requirements. This deregulation of the frequency spectrum eliminates the need for the user organizations to perform cost and time-consuming frequency planning to coordinate radio installations that will avoid interference with existing radio systems.
U.S. Patent No. 5,661,750 describes a DSSS system for utility metering that is designed to utilize a high power transmitter and still meet the requirements of FCC Part 15.247. Specifically, in this system, the transmitter utilizes a modulator to modulate the transmission signal with a pseudo-random pattern to spread the signal across a broader bandwidth than the original signal and uses a second modulator to modulate a preamble of the signal with a phase reversal pattern. The phase reversal pattern increases the number of spectrum lines produced by the transmitter and thereby decreases the power density of the broadcast signal, which for DSSS is +8 dBm in any three KHz bandwidth. However, while the phase reversal pattern addresses the low power density requirement, it does not address of the increased cost associated with DSSS — in fact, the addition of a phase reversal modulator likely adds to the cost of the transmitter. Further, it does not address that the DSSS receiver is still significantly vulnerable to noise, and it does not address the issue that only time, rather than time and frequency, may be used for signal collision avoidance; features which are significant and important in a utility sub-metering application.
U.S Patent Nos. 5,430,759, 5,499,266, 5,546,422, 5,712,867 and 5,870,426 describe a FHSS system for a paging network to provide low power communications to mobile pagers over an extended coverage area. Although utility metering is identified in these patents as a potential application for the paging network, there are important differences between paging systems and utility meter reading systems that restrict the ability to successfully utilize paging network FHSS technology in a utility meter reading application. Unlike paging systems in which the pager is mobile, the utility meter encoder transmitter is fixed in a single location and reception coverage areas are effectively dictated by the antenna pattern available from that location. While two-way paging system can provide limited communication from a pager to the network, the paging system is not designed to handle continuous periodic reporting of large amounts of data by a large number of units concentrated in a relatively small area.
One meter reading system which has been developed for the sub-metering application
is the Inovonics Tap Watch® system. In this system, the end point encoder transmitters
attached to each utility meter utilize a low power FHSS transmitter having less than 0.5 mW of power and operating under FCC Part 15.249. A network of intermediate repeaters receive the low power FHSS transmissions from the end point transmitters and convert these transmission to DSSS transmissions that are retransmitted by high power transmitter operating under FCC Part 15.247 to base stations for collection and processing. While this approach allows for the use of lower cost end point encoder transmitters, it increases the costs of the intermediate repeaters. Moveover, because the end point encoder transmitters are low power, their transmission range is limited and more intermediate repeaters are required for effective coverage in a sub-metering utility application, for example, thereby further increasing the overall costs of the system. In view of the above, there is a need for a utility meter reading system that is particularly suited to utility sub-metering, that complies with Part 15.247 of the FCC rules governing spread spectrum devices and that enables a lower overall system while allowing for use of long life battery-operated end-point transmitters and intermediate repeaters, and that also enables improved signal collision avoidance.
In still another embodiment, the meter end point encoder transmitter device transmits consumption data to at least the base unit such that the transmitted consumption data is in the form of a plurality of buckets of data, each bucket representing a period of time of consumption data from which the base unit may retrieve desired consumption data. In still another embodiment, each of the encoder transmitter devices and the transceiver units incorporates a transmission counter value that is maintained by that device or unit and is used to calculate latency information. The base station time stamps each received transmission with a real time clock such that accurate calculation of the actual meter reading time can be determined from the combination of the time stamp and the latency information.
Fig. 9 is another example of a message structure supported by the system of the present invention. Fig. 10 is a block diagram of the main components that comprise the logic board of both the base unit and the repeater unit of the system of the present invention.
Description of the Preferred Embodiments The utility metering system of the present invention operates to monitor and retain data on a plurality of water, electric, and gas utility meters, e.g., up to 1000 utility meters, that are typically located within multi-dwelling or high-rise environments.
L A. PET Module
Each PET module 22 is preferably a radio frequency (RF) transmit-only device that gathers and encodes utility consumption and tamper information, then transmits this data with other information via RF to the repeater units 24 or base units 26 periodically, for example, every 10 to 15 minutes using a high power frequency hopping spread spectrum (FHSS) technology. The electric PET modules 223 are preferably installed under the glass of standard meters and do not require battery power. The PET modules 221 and 222 for gas and water, respectively, are preferably self-contained low power units that are powered by long- life batteries; the PET modules 221 and 222 utilize a very slow "bubble up" rate to minimize power consumption and extend the life of the batteries as well as minimize unnecessary RF interference to other users in the RF band. Each of the PET modules 22 is designed to be installed by the meter manufacturer during the manufacturing process or to be easily retrofitted into existing meters.
The PET module 22 complies with Part 15.247 of the FCC rules governing high power spread spectrum devices (i.e., frequency hopping spread spectrum devices having power outputs of greater than 0.5 mW). The PET module 22 operates in the 900 MHz unlicensed band at a maximum peak power level of 40 milliwatts with a transmission rate not to exceed 50 milliseconds. The PET module 22 is to be permanently mounted such that it retains a distance of 20 centimeters (7.9 inches) from all persons in order to comply with FCC RF exposure levels. The PET module 22 preferably cannot be modified in any way and contains no user serviceable parts. LB. Repeater Unit
Each repeater unit 24 collects water, electric, gas and usage data via RF from the PET modules 22 and forwards that data to a base unit 26 via RF. This is preferably accomplished by a store and forward functionality that groups transmissions from multiple PET modules together in a block transmission format, although single store and forward or even immediate retransmission approaches can also be used. Specifically, each repeater unit 24 receives PET module RF transmissions from surrounding PET modules 22, adds a time stamp, and upon a predetermined time, forwards the stored PET module data to other repeater units 24 or base units 26. The repeater unit 24 utilizes frequency hopping spread spectrum (FHSS) on a timed basis to transmit its collected data. Preferably, the transmissions are relatively short, e.g. less than 400 milliseconds, and communicate up to 45 PET module messages per transmission.
The repeater unit 24 also provides an identification number with each transmission. The identification numbers of all repeater units 24 in the system 20 are entered into the base unit
26 to allow reception into the system database.
The repeater units 24 are used to counteract antenna interference that may occur in one direction. If the antenna signal of a PET module 22 is blocked by an obstruction, a receiver can not receive the PET module message. The use of the repeater units 24 provides azimuth diversity, i.e., the signal blocked by obstructions can be captured by one or many other repeater units 24 whose antenna patterns overlap that of the PET module 22. I. C. Base Unit
I. D. Meter Reading Analysis Device
Further details regarding installation and mounting of the components of the system 20 may be found in the Itron "Installation Guide for the PETRC and PET Repeater Units used in the PETNET Submetering System", February 20, 2001, which is hereby incorporated by reference. π. System Operation H A. PET Module - Hardware Detail
The PET module 22 is a fully synthesized FM transmitter that operates in the 902 to 928 MHz frequency band. The PET module 22 operates pursuant to FCC rule part 15.427 as a frequency hopper capable of utilizing twenty-five channels. The RF nominal output power of the PET module 22 is +15 dBm with a modulation of +/- 75 KHz and a message transmission time of 50 milliseconds. The PET module 22 is fully self-contained, including the antenna, and has no user serviceable parts. The PET module operates in an asynchronous mode with a message transmit rate of 10-15 minutes, most preferably 10 minutes, and provides an estimated battery life of five years. The PET modules 22 transmit on a pseudorandom frequency and time, and while capable of sequencing tlirough the twenty-five random frequencies, preferably utilizes only six of the twenty-five acquisition channels, i.e., three lower and three upper acquisition channels through which the PET module rotates. However, any one of the twenty-five channels can be considered an acquisition channel and is dependent on the base unit 26 configuration.
A block diagram depicting the major components of the transmitter of the PET module 22 is provided in Fig. 2. As shown, the PET module 22 utilizes an RF subsystem 30 in combination with a digital subsystem 32. The RF subsystem 30 includes a voltage controlled oscillator (VCO) 34 followed by pin diode attenuators (a.k.a. an RF switch) 36. The RF switch 36 is followed by an RF power amplifier 38 which is followed by a low pass filter 40 for harmonic suppression. The low pass filter 40 is followed by a quarter- wave dipole antenna 42. A frequency synthesizer 44 is provided and operates to tune the VCO 34 to the proper channel and maintain the channel under varying load conditions.
The RF switch 36 is preferably comprised of two PIN diodes that are used as a shut type reflective switch. The PTN diodes are preferably in parallel for RF to reduce their combined "on" impedance to ground, and in series for DC to reduce the current required to operate them. The RF switch 36 is controlled by an emitter follower that is driven by a low pass filter to control the rate at which it turns on and off.
The low pass filter 40 is preferably a fifth order low pass filter that is used to reduce harmonic emissions, hi its preferred configuration, the low pass filter 40 utilizes transmission lines instead of inductors, and utilizes two capacitors at each of the three nodes of the filter due to the low self-resonance frequency of the capacitors. This self-resonance occurs in the stopband near the second harmonic, which actually helps to improve the filter performance over what it would otherwise be. The resulting filter has a rather narrow passband response and has an insertion loss around 1 dB.
The digital subsystem 32 further includes meter input conditioning circuitry 60, i.e., a sensor interface circuit, such as a debounce and divide-by-two circuit to capture short duration pulses without requiring rapid sampling by the main processor 46. However, numerous other types of sensor interface circuits, e.g., register type sensors, maybe used as appropriate or desired without departing from the spirit or scope of the invention.
The transmitter power supply charge circuit, indicated in Fig. 2 by block 52 labeled power control, is able to supply a regulated five volts at up to 200 milliAmps during transmission of the PET module message, however current PET module design requires only 50 milliAmps. The nominal charge current for the transmitter power supply charge circuit varies between three milliamps and less than one milliAmp during a charge cycle. The transmitter power supply charge circuit uses a charge pump to slowly charge a large value capacitor, e.g., 4700 microFarads, to approximately six volts. During transmission of the
PET module message, the power amplifier 38 runs off of this capacitor allowing the PET module 22 to have a high power transmitter while limiting battery drain.
The PET module transmitter 22 described above is preferably manufactured using a two-sided PC board design. The two-sided design, while more difficult than a multi-layer board design, greatly reduces production costs. Design considerations pertinent to the two- sided design include providing no traces through the ground plane in the RF section, this is a feature that is critical to reliable and repeatable RF performance. Further design considerations include limiting the overall number of traces on the ground plane side of the board for further improved RF performance and utilizing large diameter via holes for RF connections to the ground plane to reduce inductance. H B. PET Module - Operation
At the time of transmission and having received an indication of a fully charged capacitor, the main processor 46 initiates operation of the "bubble-up" architecture of the PET module transmitter by turning on the COMM processor 48 and awaiting a response therefrom; if no response is returned, the main processor 46 turns off the COMM processor 48. Upon receiving a response from the COMM processor 48, which comes in the form of a request for PET module message data and frequency transmission data, the main processor 46 replies to the request. After receiving the requested data, the COMM processor 48 checks an inter-processor checksum to determine if it should continue with its message sending operations.
If the COMM processor 48 determines that it should continue per the checksum, the COMM processor 48 goes through a sequenced turn-on, or "bubble-up" operation, of the transmitter to avoid out-of-band spurious generation. The entire turn-on, send message, and turn-off sequence takes approximately 40 milliseconds. The turn-on sequence preferably occurs as follows:
1. The RF switch 36 between the VCO 34 and power amplifier 38 is turned off, which attenuates the RF to the power amplifier 38 by approximately 10 dB. (Note: The RF switch 36 draws DC current while it is in the "off state. It does not draw current while it is in the "on" state).
The use of the above-described "bubble-up" operation not only provides a transmitter that creates very little co-channel band interference but also provides for a PET module transmitter that has a five year life span without battery replacement (presuming transmissions of once every 600, i.e., 10 minutes, to 900 seconds, i.e., 15 minutes).
8. The COMM processor 48 then goes into a sleep mode to conserve current. The use of frequency modulation by the PET module 22 provides for number of benefits, e.g., a frequency synthesized transmit frequency that can be accurately controlled
and for a carrier stability of ±100 PPM. Further the use of frequency modulation allows for a
simplified manufacturing process of the PET module 22 because the intrinsic accuracy and stability requirements of the microwave VCO are significantly reduced over a free-running design. Additionally, the use of frequency modulation enables the use of narrower receiver bandwidths, e.g., 360 KHz, resulting in improved sensitivity, and allows for a faster more reliable hop synchronization process because the location of each acquisition channel is precisely known, which vastly simplifies the base unit receiver signal processing requirements over what they would be if an FCC Part 15.249 design using a non-synthesized architecture were employed.
As indicated above, the nominal output power of the PET module transmitter is +15
dBm with a narrower band receiver (-110 dBM). When compared to the existing Itron ERT®
(-6dBM with a broader band receiver of -105dBM) which operates at the power limit of FCC Part 15.249, the present invention offers up to 400 times more "available" power than the
Itron ERT®. This increase h effective power is used to improve the existing unacceptably
poor link margin and a R"4 propagation constant. The transmission range of the PET module
22 transmitter, as compared to an Itron ERT® or any other lower power device operating
under FCC Part 15.429, is increased by approximately a factor of up to six times. This reduces the number of intermediate coverage zones (coverage zones created by location of a repeater unit 24 of base unit 26) required by a factor of between five to twenty five times (coverage area increases as a square of an increase in the transmission radius). As such, due to the increased range of the PET module 22 transmitter and the reduced number of intermediate coverage zones required. By reducing both the cost per transceiver and the number of transceivers required to provide effective coverage for a utility meter reading system, the overall cost of system 20 of the present invention is significantly lower than the overall system cost of a utility meter reading system implemented using prior encoder
transmitter technology, such as the Itron ERT® modules.
The PET module 22 transmitters preferably support multiple message types, allowing an entirely different message structure to be used by merely changing the message type field. A dotting pattern preferably precedes the message and helps to improve receiver and encoder performance. Figs. 4-9 provide diagrams of the bit sequences that comprise the various message types. Fig. 4 is a type "10" (decimal) message type, Fig. 5 is a type "11" (decimal) message type, Fig. 6 is a type "12" (decimal) message type, Fig. 7 is a type "13" (decimal) message type, Fig. 8 is a type "14" (decimal) message type, and Fig. 9 is a type "17" '
(decimal) message type. The type of message utilized determines what data is used and what hop sequence is used to transmit the data.
For example, a type "10" message, Fig. 4, transmits the consumption pulse count of register one of the utility meter to which the PET module 22 is connected according to a first pre-programmed hop sequence table. The type "10" message includes a dotting pattern field 86, a message preamble field 88 of four bits, a message length field 90 of eight bits, a one's complement message length field 92 of eight bits and a message 94. The message 94 includes a message type field 96 of eight bits, a message body field 98 of variable length, and a CRC 108 of 16 or 32 bits. The message body field 98 preferably includes the thirty-two bit PET module identification/serial number in field 100, a thirty- two bit consumption pulse count 102 of register one of the utility meter to which the PET module 22 is connected, a hardware field 104 indicating the PET module hardware type, and an eight bit field 106 for flags and tamper bits.
A type "11" message, as shown in Fig. 5, transmits the consumption pulse count of register one of the utility meter to which the PET module 22 is connected according to a first pre-programmed hop sequence table and additionally transmits nine buckets of "delta" consumption data. Each of the nine buckets transmitted represents five minutes of register data wherein bucket "0" is five minutes old and transmitted first while bucket "8" is 45 minutes old and transmitted last. The use of buckets enables the base unit 26 receiver to go back to a desired point in time and reconstruct the consumption data no matter the time at which the base unit 26 actually receives the PET module message transmission. The fields within the message structure are similar to that of the type "10" message with the addition of the nine bytes comprising the nine buckets the message body field 98. A type "12" message, as shown in Fig. 6, transmits the consumption pulse count of register one and two of the utility meter to which the PET module 22 is connected according to a second pre-programmed hop sequence table. The fields within the message structure are similar to that of the type "10" message with the addition of a second thirty-two bit consumption pulse count field 102 for the consumption data within register two of the utility meter to which the PET module 22 is connected.
A type "13" message, as shown in Fig. 7, is a repeater message type that resends a previously transmitted message. The fields within the message structure are similar to that of the type "10" message with the exception that the message body field 98 incorporates the message type field 96 as well as an eight bit route field 112, an eight bit group field 114, an eight bit sub-group field 116, the original message data that was previously sent within field 118. The use of route, group and subgroup coding allows for minimization of crosstalk between systems and within a system minimizes redundant data in overlapping coverage areas, thereby improving coverage and channel efficiency. The original message data within field 118 includes the original message type, up to but not including the original CRC 108.
A type "14" message, as shown in Fig. 8, is identical in message structure to that of a type "12" message, described above. However, a type "14" message is transmitted according to a second pre-programmed hop sequence table that is different from the first preprogrammed hop sequence table. Multiple hop tables can be programmed into the Pet module to further minimize collisions which further improves RF channel utilization and efficiencies.
A type "17" message, as shown in Fig. 9, is a large block mode message type, wherein up to 45 PET module messages may be transmitted in a single large block. The start of the message structure is similar to that above including fields 86, 88, 90 and 92, as well as a message type field 96. The message length is preferably repeated twice (original and compliment) to improve accuracy of decoding the proper message prior to decoding the full CRC protected message. By utilizing this test early in the message, long false message lengths are greatly minimized and efficient decode recovery for new messages is attained. The source is preferably the local serial number of the unit transmitting. The destination is originally set to zero and within the receiver decoder circuitry, the receiver may be selectively configured to enable the source destination. The primary and secondary payload are block identifiers. The primary payload is defaulted to one, and the second payload is set to the number of PET transmissions contained in that block. The next packet interval preferably identifies a subsequent time for the interval to the next transmission. This interval information allows for selective adjustment of the block transmissions between the repeater and the base station to optimize performance. The transmission counter is used to calculate latency of retiansmission so that latency between each retransmission or the original read can be determined. Preferably, the transmission counter of that unit is appended at each retiansmission step in the network. At the head end, this information is accurately time stamped with a real time clock that is appended with the latency information to allow for accurate calculation of the actual meter reading time.
While the above represent the structures of the preferred and most often used messages it should be noted that other message types may be used without departing from the spirit or scope of the invention. π. C. Repeater Unit and Base Unit - Hardware Detail
Figure 10 provides a block diagram of the main components that comprise the base unit 26 logic board, and likewise, the repeater unit 24 logic board. As shown, base unit 26 generally comprises a main controller 130, an encoder 132, a decoder 134, and a transceiver 136. The main controller 130 is connectable via an RS-232 communication line 138 to a console for user programming. Further, the main controller 130 is preferably supported by three different memories: an EEPROM 140, RAM 142, and ROM 144. The main controller 130 generally runs the application and diagnostic software of the base unit 26 as well as handling all external user interfaces. The main controller 130 also controls the actions of the lower level processors on the logic board, which in turn control the base unit's transceiver
The encoder 132 generally handles the low level interface to the RF board of the transceiver 136. The encoder 132 is generally responsible for communications to the synthesizers on the RF board of the transceiver 136 along with controlling the RAKON on the RF board. The decoder 134 generally operates to take raw data from the transceiver 136, to attempt to decode a valid message preamble, and then to buffer that message for transfer to the main controller 130 through use of a sliift register microchip 146. The DC inputs 148 and AC inputs 150 for the base unit 26 are regulated as needed by a power supply regulator 152.
The main controller 130 is preferably a Dallas 80C320 and communicates via a single communication protocol with both the encoder 132, preferably a PIC 16C77, and the decoder 134. There are four configuration memory areas that are utilized for the operating parameters of the main controller 130. The default configuration of the base unit 26 is stored in ROM 144 as part of the program code for the main controller 130 and provides the starting point for initializing a new base unit 26. The remaining three areas reside in the EEPROM 140 and allow for changes during the installation process of the base unit 26. Specifically, the remaining three configuration memory areas include a primary configuration table that provides the primary configuration parameters for the main controller 130, a backup configuration table that provides a backup copy of the configuration parameter and is utilized if the primary configuration table is deemed "bad", and a factory setting area that has been programmed with settings for completing a diagnostic mode of operation of the base unit 26.
The encoder 132 controls the tiansceiver 136 operation and performs the low level activities such as loading the synthesizers, setting the various power levels, switching between transmit and receive operation, and converting the transmitted data stieams to
Manchester encoded data.
Raw noisy radio data is applied to the input of device 156. The signal is synchronized to a 19.6608 MHz clock 160 and fed through a digital integrator 162 to filter any high frequency noise. This filtered signal is sent through the delay shift register microchip 146 . After the shift register, the now delayed data signal is resynchronized in device 156. The two existing data stieams, i.e., the filtered data signal and the delayed data signal, can be selected by steering logic 164 within device 156 to allow a phase locked loop (PLL) within the microcontroller 158 to lock onto either data signal. Note that the delayed data is always connected to the data integrator 162. The data integrator 162 samples the delayed data at a 16x clock rate and filters each data bit for sampling by microcontroller 158. A digital, nonretriggerable one-shot is configured in the device 156 to provide a raw, noisy clock for the PLL algorithm. The microcontroller 158 provides the PLL for data stream synchronization and assembles the transmitted data bits into data packets. The digital PLL has a frequency lock range of +/- 2%. A programmable counter within microcontroller 158 is used to sample each edge of a clock level input. The time between edges (phase) is monitored by microcontroller 158 and an output reconstructed PLL clock produced by microcontroller 158 is adjusted accordingly to provide the final PLL clock used to sample the data stream.
The transceiver 136 includes an FM receiver with automatic frequency control (AFC) for PET module 22 tracking and an FM transmitter that utilizes inter-concentrator forwarding. The FM receiver is preferably a dual conversion super-heterodyne FM receiver with approximately 1.3 MHz intermediate frequency (IF) bandwidth in the high IF, a 360 KHz bandwidth in the low IF and a 20 KHz post-detection bandwidth. The receiver scans the 902 to 928 MHz band by using a synthesized stepping local oscillator (LO) to produce an intermediate 110.6 MHz high IF. The 110.6 MHz IF is buffer amplified and applied to a second mixer in conjunction with a 99.9 second LO which down-converts to a 2nd IF frequency of 10.7 MHz. The 360 KHz IF minimum bandwidth is required to match the 20 dB occupied bandwidth of the PET module 22 and the repeater unit 24 transmitters as well as provide the additional allowance for frequency stability,a component variations, and aging of the base unit 26, the repeater unit 24, and PET module 22. The FM signal is demodulated with a quadrature detector and applied to a data sheer to produce hard-limited 5 volt 16 Kilobits per second data. The data is transferred to the base unit 26 or repeater unit 24 logic board for further processing.
Fig. 12 provides a detailed block diagram of the transceiver 136. A corresponding pictorial diagram of a preferred embodiment of the RF circuit board 138 implementing transceiver 136 is shown in Fig. 14. The RF board 138 is preferably enclosed within a clamshell 140 as shown in Fig. 15. The clamshell 140 has partitions 142 defined therein that are used for shielding and isolation between various circuits on the RF board 138. The partitions 142 mate with corresponding grounding structures 144 on the RF board 138 to isolate the various portions of the circuitry of RF board 138 when mated with the clamshell 140. Extensive use of feedthroughs are made to eliminate crosstalk between compartments. TIC.1 Transceiver Hardware - 900 MHz Receiver
Mixer 205 is a passive doubly balanced diode mixer with an input IP3 of +18 dBm and conversion loss of approximately 9 dB. Because of the high dynamic range, a medium power LO drive level of +17 dBm is required, this is supplied by the Power Amplifier 253.
This Amplifier also provides the PA function for the transmitter. The synthesized stepping
VCO 250 operates from approximately 790 MHz to 816 MHz. It is phase-locked to the reference oscillator and is temperature compensation to maintain frequency stability over temperature. The VCO 250 tuning voltage is derived from the synthesizer that is controlled by signals from the logic board. Currently the number of channels in which the unit operates is 25, which are specified in Table 1. PET Channels Table 1
The channels indicated in bold in Table 1 are channels identified as acquisition channels which are scanned on a rotating basis. Preferably, there are only 6 acquisitions channels, 3 upper frequency channels and 3 lower frequency channels. The acquisitions channels are selected at the upper and lower ends of the transmission spectrum to allow for backward compatibility with existing Itron ERT® technology by avoiding use the center frequencies used by that technology as acquisition channels for the present invention. Preferably, there are two or more sets of acquisition channels that can be alternated to enable the deployment of multiple utility meter reading systems 20 over the same coverage area without creating interference between the two or more systems. The transceivers 136 are programmed with the acquisition channels. Amplifier 206 have approximately 14 dB gain and serve to buffer the 110.6 MHz IF signal prior to SAW filter 303; the amplifier 206 has an output IP3 of +30 dBm which maintains the system dynamic range requirement. Filter 303 is the band-limiting device in the 900 MHz receiver to reduce image frequencies and establishes the both input thermal noise floor as well as the nominal selectivity to incoming PET and PET Repeater messages.
Filter 303 has a 3 dB bandwidth of 1.5 MHz with a loss of 8.5 dB. An additional 14 dB of IF gain is provided by amplifier 207. The output of amplifier 207 is then down-converted to
10.7 MHz by mixer 208. The LO for conversion by mixer 208 is provided from a synthsized
99.9 MHz VCO 251. The 10.7 MHz signal is then filtered by a 16 MHz Low pass filter 304 and then buffer amplified by amplifier 209 with 23 dB of gain. The signal then is impedanced match to the 3 each- 360 KHz bandpass ceramic filters 305 with a loss of 7dB and presented to the FM detector circuitry 211.
Detector circuitry 211 is a limiting IF amplifier with approximately 70 dB gain. It features a fast RSSI output and is used for the PETRC unit logic board to determine PET module transmission RF signal strength. The transfer curve of the RSSI output and the RF is logarithmic which means the demodulated amplitude is non-linear with respect to the IF signal amplitude. The RF dynamic range is approximately equal to the gain i.e. 70 dB. The particular detector used requires approximately 40 dB of system gain preceding it in order to operate on the most "linear" portion of the tiansfer curve and to ensure the system noise figure is not gain limited.
The FM information is derived from the Quadrature detector 215 and is applied to a low pass filter made up of 312a and 312b. The demodulated signal is lowpass filtered to improve the baseband signal to noise ratio, and then is applied to comparator 214a which functions as the threshold detector/bit sheer. The 5 volt digital logic is then combined with the exclusive "OR" gate and a FM phasing level to provide the correct phasing of the PET
Manchestor coded data to the logic board decoder circuitry. π.C.2 Transceiver Hardware - 900 MHz Transmitter
In the transmit mode, modulation data originating from the logic board's microprocessor is applied to resistor 543. Resistor 543 provides deviation adjustment for the transmitter's modulator circuitry 510. The tiansmitter's modulated circuitry 510 is composed of primarily ceramic resistor 544 which is loosely capaticitively coupled to the transmit VCO
400 in order to FM modulate the transmitter. Typically, the modulation setting is +/- 75
KHz. n.C.3 Transceiver Hardware - Reference Frequency Oscillator
Amplifiers 229A and 229B operate as a buffer amplifier and level shifter to provide 5 volt TTL levels to the divide by 4 circuitry 230 A and 230B. The output of circuitry 230 is a 4.1 MHz TTL signal that isa pplied to Amplifier 229 C,D,E inputs which isolate drive levels to individual circuits throughout the transciever board 138.
Oscillator 219 can also be modulated during the receive mode by the AFC (Automatic Frequency Control) circuitry. This is accomplished by combining the AFC output signal with the oscillator 219 DAC output. This is accomplished by circuits 228C and 228D. The output of circuit 228D is then reapplied to the oscillator 219 DAC input. IT.C.3 Transceiver Hardware - Automatic Frequency Control (AFC) AFC allows proper decoding of PET data transmissions with carrier frequencies separated by as far as +/- 60 KHz. This further reduces the cost of the PET module by allowing lower cost less stable crystals as reference frequency. This is preferably accomplished by microprocessor 218 (a single chip microprocessor) and its associated circuitry. The system is triggered by signal detect which is an RSSI threshold level that is determined by the logic board microprocessor. The threshold level adjustment is accomplished through the combination of two band pass filter sections made up of filters
332A, 332B, 332C, and 332D. Microprocessor 218, upon detection of the signal flag, controls analog gates 231 A, 23 IB, and 23 IC. These gates change the band pass characteristics of filter 328 A and 328B which provide an offsetting DC voltage that is proportional to the carrier offsets of the PET transmitter and PET receiver. The offset DC voltage is applied to filter 328C which modulates the reference oscillator 219. π.C.3 Transceiver Hardware -Power Regulation
The power supply 152 essentially comprises an unregulated supply that provides the input power to three single chip buck switch regulators (not shown). These switcher regulators supply the system +6 volts, +6 volts (PA) and variable supply to charge the system batter if one is connected. From the +6 volt supply, a +5 volt supply is generated from a low overhead linear regulator. Further, a -5 Volt bias supply is then generated from the +5 Volt supply. A +3 Volt reference supply is generated from the +6 Volt supply. A system temperature reference and battery voltage, and current monitor are built into the power supply
152 for use by the main controller 130 so that information can be used to control battery charging in a totally closed loop system. Hard wired voltage comparators (not shown) manage the operation from either the unregulated DC supply 148 or the battery. π. D. Repeater Unit and Base Unit — Operation The base units 26 and repeater units 24 utilize transceivers that monitor user configurable acquisition channels until reception of a PET module transmitted message occurs. Once a PET message is decoded the base unit 26 tracks the hopping tiansmissions by information stored in the base unit 26 memory regarding the pseudo-random hop sequence and time of arrival. Specifically, each PET module 22 hops on its own timing sequence for a certain frequency. The transceiver monitors the PET module messages, which provide a PET module identification/serial number and based on that identification/serial number the unit 24 or 26 knows the time and frequency of transmission of that specific PET module 22. This also allows the unit 24 or 26 to know when collisions in time and frequency may occur and to adjust reception of the PET module messages accordingly.
In operation, the base unit and repeater units are first initialized. Specifically, within the main controller 130 all timers, counters, and a transmit and receive interval is set. The modem, within the base unit 26, is initialized. Further, the main contioller 130 establishes its expected PET module message arrival list wherein message arrival times are determined, arrival channels are determined, receiver windows are determined.
An example of receiver window timing is provided in Fig. 14 as related to the interval timing of Fig. 13. As shown, the transceiver 136 of the repeater unit 24 or base unit 26 requires a minimum window of 380 milliseconds to compensate for oscillator crystal tolerances and the preamble detection of the PET module message in order to receive the
PET module message. Knowing the first interval timing 218, the main controller 130 can direct the transceiverl36 to start receiving 180 milliseconds before the data transmission, allow 20 milliseconds for preamble detection, and provide another 180 milliseconds after preamble detect.
Initialization of the main contioller 130 also includes establishing how missed PET module messages will be handled, when PET modules will be dropped from an expected arrival list, and how to adjust for drift. The parameters for receiving large blocks through transceiver 136 are also established. For example, upon receiving a large block of data through transceiver 136 it is decoded and the main controller 130 operates to verify the integrity of the data. From the verified data the main controller 130 then compares the PET module identification/serial numbers to the main controller's local list of PET modules 22. The main controller 130 also determines the timing interval from the data as well as the hopping sequence being used, and calculates the arrival time for the next large block data receive. This calculation is adjusted by the main controller if the receive window is missed. Finally, the main controller enters and stores the data within its PET module database for later transmission.
Additional initialization parameters for the main controller 130 include how to manage PET module messages to be forwarded, e.g., placed within PET module database, and how to manage the transmitting schedule for large blocks, and database management, e.g., how long should a PET module live within the database, how the database should be updated with new PET modules, and how the database is to be cleaned up on a regular interval. The main controller 130 is also preferably initialized to count the number of successful hits on each acquisition channel. Once initialized, the main controller 130 checks the CRC in the primary configuration table of EEPROM 140. If the CRC is valid then the configuration parameters in the primary configuration table are loaded into the main controller. Otherwise, the main contioller checks the CRC in the backup configuration table of EEPROM 140 and, if valid, re-writes the primary configuration table from the back-up table whereby the configuration parameters are then loaded into the main contioller 130. With the configuration parameters loaded, the main controller operates to format a PET module data table and additionally commands that the decoder 134 start operation to decode those PET module messages that have been received by the transceiver 136.
4. Shifting the remainder of the message packet, i.e. the portion beyond the preamble, into the decoder microcontroller 158 where it is tiansmitted to the main controller 130.
If a valid, decoded data packet from a PET module 22 is available from the decoder 134, the main controller 130 operates to read the data packet and determine if it is to be processed by the unit 24 or 26. hi the case of a repeater unit 24, the repeater unit 26 builds a record and stores the decoded data therein. Upon reaching the time at which the current repeater unit 24 is to transmit, the stored PET module message data is encoded by the encoder 132 and forwarded to the next repeater unit 24 or base unit 26 via FHSS RF. This process is repeated until all current PET module messages have been sent to a base unit 26.
The encoder 132 receives its commands and data via the PSP (parallel slave port) from the main contioller 130. During the encoding process, data arrives at the encoder 132 in a binary format and is converted to a Manchester encoded format for transmission; the method of modulation is FM and the Manchester data provides an FM deviation modulation technique. The main controller 130 maintains a steady flow of "bytes to transmit" as the encoder clocks the bits out at an accurate pace thereby controlling the modulation input to the transmitter of the transceiver 136. At the start of the data stream the main controller 130 preferably includes a length byte and a transmitter tuning byte to direct the encoder's setup operation, hi return, the encoder 132 sends a response to the main controller 130 for every command or string of data it receives to ensure that a complete transaction has occurred. The encoder 132 preferably responds with the first character of the received data as the transaction acknowledgement.
Upon the PET module message data reaching a base unit 26 via a PET module 22 or repeater unit 24, the main controller 130 of that base unit 26 determines if the PET module 22 that originated the message is within its PET module data table. If so, the data buffer for this PET module 22 within the table is updated with the new PET module data after having been decoded, the data is time-stamped with the current timer value, and the number of message receives for this PET module 22 is incremented. If the PET module 22 that sent the message has not been previously established within the main controller's data table, and there is room for a new table entry, the main controller 130 operates to create that new table entry for the PET module, to store the message data in the data buffer, set the message receive count to one, and time stamp the data. If the main contioller has no room for a new PET module, the message data is simply discarded by the main controller 130. Upon establishing and storing PET module messages, the base unit 26 operates to transmit the message data, including the time stamp and message receive counts, per PSTN or cellular telephone to the head-end meter reading software 28 for analysis and other desired uses.
The present invention may be embodied in other specific forms without departing from the spirit of the essential attributes thereof; therefore, the illustrated embodiments should be considered in all respects as illustiative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.
1. A spread spectrum meter reading system, comprising: a plurality of end point encoder transmitter devices each of which is operably connected to a utility meter and transmits high power frequency hopping spread spectrum signals containing at least metering data for the corresponding utility meter; a plurality of intermediate tiansceiver units, wherein the number of intermediate transceiver units is less than the number of end point encoder transmitter devices and wherein each of said intermediate transceiver units receives and retransmits the high power frequency hopping spread spectrum signals; and a base station having a receiver that receives the high power frequency hopping spread spectrum signals.
3. The system of claim 1 , wherein the high power frequency hopping spread spectrum signals are transmitted at a maximum hopping rate of at least one minute per hop.
4. The system of claim 1 , wherein the high power frequency hopping spread spectrum signals include at least twenty five channels, at least two of which are reserved as acquisition channels.
5. A meter end point encoder transmitter device, wherein the device is operably coupled to a utility meter that forms part of a utility meter reading system, the device comprising: a radio frequency sub-system that transmits consumption data from the utility meter using frequency hopping spread spectrum signal; and a digital subsystem, wherein the digital sub-system includes a first processor and a second processor, wherein the first processor runs continuously and contiols the operation of the radio frequency sub-system, and wherein the second processor runs only upon utilization of the radio frequency sub-system.
8. A meter end point encoder tiansmitter device, wherein the device is operably coupled to a utility meter that forms part of a utility meter reading system, the device comprising: a radio frequency sub-system that transmits consumption data from the utility meter using frequency hopping spread spectrum signal; and a digital subsystem, wherein the digital subsystem is powered by a battery and wherein upon nearing a time for the radio frequency sub-system to tiansmit the digital subsystem directs a charge pump capacitor to charge, and once the charge pump capacitor is charged the digital sub-system enables at least a portion of the radio frequency sub-system to run off the charge pump capacitor during the consumption data transmission.
10. The device of claim 8, wherein the digital subsystem includes a first low-speed processor and a second high-speed processor, and wherein the first low-speed processor monitors the status of the battery and tiansfers the status of the battery to the second highspeed processor.
11. A utility meter reading system, comprising: a plurality of meter end point encoder tiansmitter devices each of which is operably connected to a utility meter and transmits data using a low-speed frequency hopping spread spectrum mode; and at least a base unit that receives tiansmissions from the plurality of encoder tiansmitter devices, wherein upon installation of one of said plurality of meter end point encoder transmitter devices, the installed meter end point encoder transmitter device operates for an initial period of time in a installation mode that uses a high-speed frequency hopping spread spectrum mode.
12. A utility meter reading system, comprising: a meter end point encoder transmitter device operably connected to a utility meter; and at least a base unit, wherein the meter end point encoder transmitter device transmits consumption data to at least the base unit by utilizing frequency hopping spread spectrum and wherein the transmitted consumption data is in the form of a plurality of buckets of data, each bucket representing a period of time of consumption data from which the base unit may retrieve desired consumption data.
13. The system of claim 12, wherein the base unit utilizes a time and frequency transmission collision avoidance scheme in combination with the bucket tiansmission.
14. A spread spectrum meter reading system, comprising: a plurality of end point encoder tiansmitter devices each of which is operably connected to a utility meter and transmits frequency hopping spread spectrum signals containing at least metering data for the corresponding utility meter; a plurality of intermediate transceiver units, wherein the number of intermediate tiansceiver units is less than the number of end point encoder tiansmitter devices and wherein each of said intermediate tiansceiver units receives and retransmits the frequency hopping spread spectrum signals; and a base station having a receiver that receives the high power frequency hopping spread spectrum signals, wherein each of the encoder transmitter devices and the tiansceiver units incorporates a transmission counter value maintained by that device or unit that is used to calculate latency information, and wherein the base station time stamps each received transmission with a real time clock such that accurate calculation of the actual meter reading time can be determined from the combination of the time stamp and the latency information.
PCT/US2001/023303 2000-07-21 2001-07-23 Spread spectrum meter reading system utilizing low-speed/high-power frequency hopping WO2002008866A2 (en)
US60/220,015 2000-07-21
KR10-2003-7000922A KR20030082536A (en) 2000-07-21 2001-07-23 Spread spectrum meter reading system utilizing low-speed/high-power frequency hopping
EP01959155A EP1320793A2 (en) 2000-07-21 2001-07-23 Spread spectrum meter reading system utilizing low-speed/high-power frequency hopping
MXPA03000516A MXPA03000516A (en) 2000-07-21 2001-07-23 Spread spectrum meter reading system utilizing low-speed/high-power frequency hopping.
CA2414777A CA2414777C (en) 2000-07-21 2001-07-23 Spread spectrum meter reading system utilizing low-speed/high-power frequency hopping
JP2002514502A JP2004518313A (en) 2000-07-21 2001-07-23 Spread spectrum meter reading system utilizing frequency hopping slow / High Power
BR0112613-0A BR0112613A (en) 2000-07-21 2001-07-23 System spread spectrum meter reading, transmitting device endpoint encoder meter, and utility meter reading system
AU2001280740A AU2001280740B2 (en) 2000-07-21 2001-07-23 Spread spectrum meter reading system utilizing low-speed/high-power frequency hopping
AU8074001A AU8074001A (en) 2000-07-21 2001-07-23 Spread spectrum meter reading system utilizing low-speed/high-power frequency hopping
WO2002008866A2 true WO2002008866A2 (en) 2002-01-31
WO2002008866A3 WO2002008866A3 (en) 2002-06-20
PCT/US2001/023303 WO2002008866A2 (en) 2000-07-21 2001-07-23 Spread spectrum meter reading system utilizing low-speed/high-power frequency hopping
AU (2) AU2001280740B2 (en)
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