System and method for optimizing contiguous channel operation with cellular reuse

• US 20050053047A1
• Filed: 08/30/2004
• Published: 03/10/2005
• Est. Priority Date: 09/05/2003
• Status: Active Grant

• Current Assignee: Itron, Inc.
• Original Assignee: Itron, Inc.
• Inventors: Osterloh, Christopher L., Hovelsrud, Neil R.
• Granted Patent: US 7,376,118 B2
• Time in Patent Office: Days
• US Class Current: 370/344
• CPC Class Codes: H04Q 2209/60 for transmitting utility meters data, i.e. transmission of data from the reader of the utility meter
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 52/0219 where the power saving management affects multiple terminals
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method for communicating with automatic meter reading (AMR) endpoints in adjacent cells, when the endpoints are arranged in a cell pattern similar to a cellular telephone system, is disclosed that substantially reduces the likelihood of signal interference. A Frame ID is identified as corresponding to a particular receive frequency that a system reader (receiver/collector) uses when listening for endpoint responses. In this example embodiment of the AMR network model, all endpoints in the network listen on the same control frequency to receive commands sent out from the readers. To allow for a relatively fast network read cycle, cells that are spaced far enough away from each other as to not interfere with each other are allowed to transmit at the same time. Cells with the same Frame ID are configured to be spaced a safe distance from each other so as not to interfere with each other'"'"'s endpoint population.

Claims

1. A method of reducing signal interference in the transmission of metered data from a plurality of meter endpoint transmitters to a plurality of corresponding readers in an automatic meter reading (AMR) system, a first set of the endpoint transmitters being assigned to a first reader, a second set of the endpoint transmitters being assigned to a second reader, and a third set of the endpoint transmitters (endpoints) being assigned to a third reader, wherein the first, second and third set of endpoints are disposed within a plurality of cells, wherein each of a first, second and third cell that are adjacent to each other, the method comprising:

assigning a first Frame ID number and first response frequency channel to the first reader, a second Frame ID number and a second response frequency channel to the second reader, and a third Frame ID number and third response frequency channel to the third reader;

transmitting on at least one control frequency channel from the first reader a first wake up signal sequence comprised of a wake-up countdown timer frame, a sync and control frame corresponding to the first Frame ID number, and a dead time slot frame, the first wake up signal sequence adapted to include a response delay for the first endpoint set;

transmitting on the at least one control frequency channel from the second reader a second wake up signal sequence comprised of a second wake-up countdown timer frame, a second sync and control frame corresponding to the second Frame ID number, and a second dead time slot frame, the second wake up signal sequence adapted to include a second response delay for the second endpoint set;

transmitting on the at least one control frequency channel from the third reader a third wake up signal sequence comprised of a third wake-up countdown timer frame, a third sync and control frame corresponding to the third Frame ID number, and a third dead time slot frame, the third wake up signal sequence adapted to include a third response delay for the third endpoint set; and

receiving metered data simultaneously at the readers from the corresponding endpoint sets via the first, second and third response frequency channels,

wherein the order of transmitting the first, second and third wake-up signal sequences and the magnitude of the response delay for the respective endpoints is a function of the Frame ID number that is assigned the reader of each cell.

2. The method of claim 1, wherein the reader with the highest Frame ID number is the first to transmit the first wake-up signal sequence and the reader with the lowest Frame ID number is the last to transmit a wake-up signal sequence, the readers transmitting in a descending order as a function of the value of the Frame ID number.

3. The method of claim 1, before the step of assigning the Frame ID numbers to the readers, further comprising the steps of:

selecting a multi-cell pattern greater than two for positioning all of the endpoint sets in the selected cell pattern; and

generating a set of Frame ID numbers and an equal number of response frequencies to be assigned to the readers located within each cell of the selected multi-cell pattern.

4. The method of claim 1, before the step of transmitting the wake-up signal sequences on the at least one control frequency, further comprising the step of synchronizing the first, second and third readers so as to alleviate cell to cell interference by inserting each of respective the dead slot time frames in each of the wake-up signal sequences immediately after the respective control frame.

5. A method of claim 1, wherein the response delay for each of the endpoint sets is determined by multiplying the Frame ID number by the Nominal Frame Time such that reader with the highest Frame ID number has the longest hold off time for response by the corresponding endpoint set.

6. A system for reducing signal interference in the transmission of metered data from a plurality of meter endpoint transmitters to a plurality of corresponding readers in an automatic meter reading (AMR) system, the system including a first set of the endpoint transmitters being assigned to a first reader, a second set of the endpoint transmitters being assigned to a second reader, and a third set of the endpoint transmitters (endpoints) being assigned to a third reader, wherein the first, second and third set of endpoints are disposed within a plurality of cells, wherein each of a first, second and third cell that are adjacent to each other, the system comprising:

a first reader with an assigned first Frame ID number and first response frequency channel adapted to transmit on at least one control frequency channel a first wake up signal sequence comprised of a wake-up countdown timer frame, a sync and control frame corresponding to the first Frame ID number and a dead time slot frame, the first wake up signal sequence adapted to include a response delay for the first endpoint set;

a second reader with an assigned second Frame ID number and a second response frequency channel adapted to transmit on the at least one control frequency channel a second wake up signal sequence comprised of a second wake-up countdown timer frame, a second sync and control frame corresponding to the second Frame ID number, and a second dead time slot frame, the second wake up signal sequence adapted to include a second response delay for the second endpoint set;

third Frame ID number and third response frequency channel to the third reader, transmitting on the at least one control frequency channel from the third reader a third wake up signal sequence comprised of a third wake-up countdown timer frame, a third sync and control frame corresponding to the third Frame ID number, and a third dead time slot frame, the third wake up signal sequence adapted to include a third response delay for the third endpoint set; and

wherein the readers receive metered data simultaneously from the corresponding endpoint sets via the first, second and third response frequency channels, and wherein the order of transmitting the first, second and third wake-up signal sequences and the magnitude of the response delay for the respective endpoints is a function of the Frame ID number that is assigned the reader of each cell.

7. The system of claim 6, wherein the set of Frame ID numbers and an equal number of response frequencies assigned to the readers are generated as the endpoint sets are positioned in a selected cell pattern.

8. The system of claim 6, wherein the first, second and third readers are synchronized so as to alleviate cell to cell interference upon inserting each of respective the dead slot time frames in each of the wake-up signal sequences immediately after the respective control frame.

9. The system of claim 6, wherein the response delay for each of the endpoint sets is determined by multiplying the Frame ID number by the Nominal Frame Time such that reader with the highest Frame ID number has the longest hold off time for response by the corresponding endpoint set.

10. An automatic meter reading (AMR) system configured to transmit metered data gathered by a plurality of endpoint transmitters (endpoints) to a utility via a plurality of predefined readers disposed in a plurality of cells without a substantial loss of data caused by signal interference, the AMR system comprising:

a first set of endpoints assigned to a first reader located within a first cell of a defined communications cell pattern, the first reader having assigned thereto a first Frame ID number and first response frequency channel;

a second set of endpoints assigned to a second reader located within a second cell of the cell pattern, the second reader having assigned thereto a second Frame ID number and a second response frequency channel; and

a third set of endpoints assigned to a third reader located within a third cell of the cell pattern, wherein the first, second and third cell are disposed adjacent one another, the third reader having assigned thereto a third Frame ID number and third response frequency channel;

wherein the first reader is configured to transmit a first wake up signal sequence on at least one control frequency channel to the first set of endpoints, the second reader is configured to transmit a second wake up signal sequence on the at least one control frequency channel to the second set of endpoints, the third reader is configured to transmit a third wake up signal sequence on the at least one control frequency channel to the third set of endpoints, wherein each wake-up signal sequences is comprised of a wake-up countdown timer frame, a sync and control frame corresponding to one of the first, second or third Frame ID numbers, and a dead time slot frame,

wherein the first, second and third wake-up signal sequences are transmitted in a time staggered scheme as a function of the Frame ID number and the first, second and third endpoint sets respond simultaneously to each of the readers via their assigned response frequency, the Frame ID numbers and the response frequencies being a function of a multi-cell pattern selected for organizing all of the endpoint sets.

11. A method of reducing signal interference in the transmission of metered data from a plurality of meter endpoint transmitters disposed in a plurality of cells to at least one mobile reader in an automatic meter reading (AMR) system, a first set of the endpoint transmitters disposed within a first cell, a second set of the endpoint transmitters disposed within a second cell, and a third set of the endpoint transmitters (endpoints) disposed within a third cell, wherein each of the first, second and third cells are adjacent to each other, the method comprising:

assigning a first Frame ID number to the first set of endpoints, a second Frame ID number to the second set of endpoints, and a third Frame ID number to the third set of endpoints, wherein the endpoint sets are adapted to respond to signals received on a control frequency channel from the at least one mobile reader;

transmitting from the mobile reader on the control frequency channel a wake up signal sequence comprised of a wake-up preamble, a first command and control frame, a quiet time frame and a slotted receive time frame, wherein the command and control frame includes a group call directed to endpoint sets with at least one of the Frame ID numbers from the group consisting of the first, second and third Frame ID numbers;

receiving metered data at the mobile reader from the first endpoint set via a first random response frequency channel at a first random time slot;

receiving metered data at the mobile reader from the second endpoint set via a second random response frequency channel at a second random time slot; and

receiving metered data at the mobile reader from the third endpoint set via a third random response frequency channel at a third random time slot;

wherein the response frequency channel used by each of the endpoint sets is randomly selected from a list of channels in the command and control frame and the order of transmitting the metered data from each of the first, second and third endpoint sets is randomly selected from a plurality of time slots provided by the slotted receive time frame.

12. The method of claim 11, upon receiving a response from one of the set of endpoints, further comprising the step of transmitting a second command and control frame that includes a standard command frame and an extended control frame, thereby allowing the mobile reader to access the most endpoints in a single pass.

13. The method of claim 11, during the step of transmitting the wake up signal sequence from the mobile reader, further comprising the step of waking up the receivers at the endpoints at a higher rate than normal so as to improve mobile data collection.

14. The method of claim 11, during the step of transmitting the wake up signal sequence from the mobile reader, further comprising the step of synchronizing the receivers at the endpoints to the first command and control frame so as to improve mobile data collection.

15. The method of claim 12, further comprising the step of transmitting metered data to the mobile reader from a plurality of endpoints via response channels distinct from the first, second and third channels and at timeslots distinct from the first, second and third timeslots.

16. A system for reducing signal interference in the transmission of metered data from a plurality of meter endpoint transmitters disposed within adjacent cells in an automatic meter reading (AMR) system, the system comprising:

a first set of the endpoint transmitters (endpoints) disposed within a first cell and having an assigned first Frame ID number, the first endpoint set adapted to respond to signals received on a control frequency channel that includes the first Frame ID number;

a second set of the endpoint transmitters disposed within a second cell and having an assigned second Frame ID number, the second endpoint set adapted to respond to signals received on the control frequency channel that includes the second Frame ID number;

a third set of the endpoint transmitters (endpoints) disposed within a third cell and having an assigned third Frame ID number, the third endpoint set adapted to respond to signals received on the control frequency channel that includes the third Frame ID number; and

at least one mobile reader adapted to transmit on the control frequency channel a wake up signal sequence comprised of a wake-up preamble, a first command and control frame, a quiet time frame and a slotted receive time frame, the command and control frame including a group call directed to endpoint sets with at least one of the Frame ID numbers from the group consisting of the first, second and third Frame ID numbers;

wherein the response frequency channel used by each of the endpoint sets is randomly selected from a list of channels in the command and control frame and the order of transmitting the metered data from each of the first, second and third endpoint sets is randomly selected from a plurality of time slots provided by the slotted receive time frame.

17. The system of claim 16, wherein the at least one mobile reader is adapted to receive metered data from the first endpoint set via a first random response frequency channel at a first random time slot, metered data from the second endpoint set via a second random response frequency channel at a second random time slot, and metered data from the third endpoint set via a third random response frequency channel at a third random time slot.

18. The system of claim 17, wherein the mobile reader is adapted to transmit a second command and control frame, which includes a standard command frame and an extended control frame, thereby allowing the mobile reader to access the most endpoints in a single pass, upon receiving a response from one of the set of endpoints.

19. The system of claim 16, wherein the receivers at the endpoints bubble up at a higher rate than normal so as to improve mobile data collection at the mobile reader.

20. The system of claim 16, wherein the receivers at the endpoints are synchronized to the first command and control frame so as to improve mobile data collection at the mobile reader.

21. A method of reducing signal interference in the transmission of metered data from a plurality of meter endpoint transmitters (endpoints) to a plurality of corresponding readers disposed in a plurality of cells in an automatic meter reading (AMR) system, various sets of the endpoint transmitters disposed within distinct cells that are adjacent to each other, the method comprising:

assigning a list of operating frequencies and timeslots to a first set of endpoints, wherein each timeslot has a slot length;

transmitting on a control frequency channel from a first reader a first wake up signal sequence comprised of a wake-up preamble frame, at least one sync and control frame and a plurality of assigned slot times, wherein each of the assigned slot times is assigned at least one endpoint;

scanning the list of operating frequencies at the first endpoint set until establishing a match with the control frequency channel and the wake-up preamble; and

transmitting the metered data from the first endpoint set during one of the assigned timeslots via one of the assigned operating frequencies, wherein each transmission has a transmit time of TX time;

wherein each timeslot is assigned an X number of endpoints according to the following formula;

X=0.45*^{(Slot Length)/(TX time)}

22. The method of claim 21, wherein the factor in the formula is increased to 0.75 for dense endpoint systems.

23. The method of claim 21, before the step of scanning, further comprising the step of transmitting multiple times the sync and control frame and information.

24. The method of claim 21, before the step of transmitting the metered data, further comprising the step of selecting one of the assigned frequencies with the highest return signal strength indication (RSSI).

25. A system for reducing signal interference in the transmission of metered data from a plurality of meter endpoint transmitters (endpoints) to a plurality of corresponding readers disposed in a plurality of cells in an automatic meter reading (AMR) system, various sets of the endpoint transmitters disposed within distinct cells that are adjacent to each other, the system comprising:

a first set of endpoints with an assigned list of operating frequencies and timeslots, wherein each timeslot has a slot length; and

a first reader adapted to transmit on a control frequency channel a first wake up signal sequence comprised of a wake-up preamble frame, at least one sync and control frame and a plurality of assigned slot times, wherein each of the assigned slot times is assigned at least one endpoint;

wherein the first endpoint set is adapted to scan the list of operating frequencies until establishing a match with the control frequency channel and the wake-up preamble and thereafter transmit the metered data during one of the assigned timeslots via one of the assigned operating frequencies;

wherein each transmission has a transmit time of TX time, each timeslot being assigned an X number of endpoints according to the following formula;

X=0.45*^{(Slot Length)/(TX time)}

26. A method of reducing signal interference in the transmission of metered data from a plurality of meter endpoint transmitters to a plurality of corresponding readers in an automatic meter reading (AMR) system among a plurality of cells, wherein a first set of the endpoint transmitters is assigned to a first reader, a second set of the endpoint transmitters is assigned to a second reader, and a third set of the endpoint transmitters (endpoints) is assigned to a third reader, wherein the first, second and third set of endpoints are disposed within each of a first, second and third cell that are adjacent to each other, the method comprising:

assigning a first Frame ID number and first response frequency channel to the first reader, a second Frame ID number and a second response frequency channel to the second reader, and a third Frame ID number and third response frequency channel to the third reader;

transmitting on at least one control frequency channel from the first reader a first wake up signal sequence comprised of a wake-up countdown timer frame, a sync and control frame corresponding to the first Frame ID number, and a dead time slot frame, the first wake up signal sequence adapted to include a response delay for the first endpoint set;

transmitting on the at least one control frequency channel from the second reader a second wake up signal sequence comprised of a second wake-up countdown timer frame, a second sync and control frame corresponding to the second Frame ID number, and a second dead time slot frame, the second wake up signal sequence adapted to include a second response delay for the second endpoint set;

transmitting on the at least one control frequency channel from the third reader a third wake up signal sequence comprised of a third wake-up countdown timer frame, a third sync and control frame corresponding to the third Frame ID number, and a third dead time slot frame, the third wake up signal sequence adapted to include a third response delay for the third endpoint set;

receiving metered data simultaneously at the readers from the corresponding endpoint sets via the first, second and third response frequency channels; and

assigning a new Frame ID number to the reader in a fourth cell upon detecting an interference of the received meter data between the fourth cell and one of the first, second and third cells, wherein the new Frame ID number corresponds to a fourth response frequency having a predefined response delay;

wherein the order of transmitting the first, second and third wake-up signal sequences and the magnitude of the response delay for the respective endpoints is a function of the Frame ID number that is assigned the reader of each cell.

27. The method of claim 26, where the number of cells exceeds the number of response frequencies in the AMR system, the step of assigning a new Frame ID number includes assigning to the new Frame ID number a previously assigned response frequency that further includes a higher offset value than that of the previously assigned response frequency corresponding to a previously assigned Frame ID number, thereby avoiding signal collision.

28. The method of claim 27, wherein additional cells that are added to the AMR system are configured to respond to Frame ID numbers that initiate a simultaneous response from the cells on previously assigned frequencies but at an offset time period.

29. The method of claim 26, wherein the step of assigning a new Frame ID number includes assigning the fourth response frequency that corresponds to an unused response frequency available in the AMR system.