U.S. patent application number 13/427146 was filed with the patent office on 2012-07-12 for data communication protocol in an automatic meter reading system.
This patent application is currently assigned to ITRON, INC.. Invention is credited to Christopher Nagy, Christopher L. Osterloh.
Application Number | 20120176253 13/427146 |
Document ID | / |
Family ID | 34139059 |
Filed Date | 2012-07-12 |
United States Patent
Application |
20120176253 |
Kind Code |
A1 |
Osterloh; Christopher L. ;
et al. |
July 12, 2012 |
DATA COMMUNICATION PROTOCOL IN AN AUTOMATIC METER READING
SYSTEM
Abstract
Automatic meter reading (AMR) systems and methods in which
readers communicate with endpoints interfaced to utility meters. In
operation, the reader and the endpoint communicate with one another
via radio frequency (RF) communication according to a communication
protocol. Aspects of the invention are directed to packetization,
command and control, and messaging arrangements.
Inventors: |
Osterloh; Christopher L.;
(Waseca, MN) ; Nagy; Christopher; (Waseca,
MN) |
Assignee: |
ITRON, INC.
Liberty Lake
WA
|
Family ID: |
34139059 |
Appl. No.: |
13/427146 |
Filed: |
March 22, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11981775 |
Oct 31, 2007 |
8164479 |
|
|
13427146 |
|
|
|
|
10915706 |
Aug 10, 2004 |
7336200 |
|
|
11981775 |
|
|
|
|
60500550 |
Sep 5, 2003 |
|
|
|
Current U.S.
Class: |
340/870.02 |
Current CPC
Class: |
Y04S 20/30 20130101;
G01K 1/024 20130101; Y02B 90/20 20130101; Y02B 90/243 20130101;
Y04S 20/325 20130101; G01D 4/006 20130101; G01K 1/026 20130101 |
Class at
Publication: |
340/870.02 |
International
Class: |
G08C 15/06 20060101
G08C015/06 |
Claims
1. An automatic meter reading (AMR) system, comprising a reader;
and an endpoint interfaced to a utility meter; wherein in
operation, said reader and said endpoint communicate with one
another via radio frequency (RF) communication according to a
communication protocol that includes a transport layer, wherein
said transport layer provides slot assignments, timing, and
packetization for all data transferred between said reader and said
endpoint; wherein said packetization defines packets to include: a
preamble field; a preface following the preamble field, wherein the
preface includes at least a message type field; an endpoint type
field following the message type field; a message field following
the endpoint type field; and a validation field.
2. The system of claim 1, wherein said packetization further
defines the packets to include a packet length identifier field;
and wherein when a message to be carried by at least a first packet
has a length greater than 254 bytes, a value of a packet length
identifier field of the first packet is set to 0xFF, and a message
field of the first packet is set to include a packet number byte
representing: (a) a total number of packets used to communicate the
message, and (b) a packet number identifier of the first
packet.
3. The system of claim 1, wherein the packetization further defines
the packets to include at least one flag having a grouping of 8
bits, wherein the 8 bits consist of: a first two bits; a second two
bits that represent an encoder number associated with a utility
meter endpoint; a fifth bit that represents a status of an event; a
sixth bit that represents a security state; a seventh bit that
represents a relay state; and an eighth bit that represents a
resend state.
4. The system of claim 1, wherein the validation field includes at
least one cycle redundancy check identifier, wherein a cycle
redundancy check polynomial is 0x1021.
5. An automatic meter reading (AMR) system, comprising: a reader;
and an endpoint interfaced to a utility meter; wherein in
operation, said reader transmits a command and control frame to
said endpoint via radio frequency (RF) communication, wherein the
command and control frame includes: a system ID that indicates a
specific AMR system with which said endpoint is associated; a frame
ID that indicates a position in a wake-up sequence of said reader;
and a cell ID that indicates at least one subset of said specific
AMR system.
6. The AMR system of claim 5, wherein said command and control
frame issues commands to said endpoint.
7. The AMR system of claim 5, wherein said command and control
frame realigns a real-time clock within said endpoint.
8. The AMR system of claim 5, wherein said command and control
frame includes a command set field.
9. The AMR system of claim 8, wherein said command set includes
universal commands and type specific commands.
10. The AMR system of claim 5, wherein said command and control
frame includes a command body, wherein said command body provides
at least one command selected from the group consisting of:
reporting a status of said endpoint; changing a system number of
said endpoint; changing a group number of said endpoint; changing a
system slot number of said endpoint; changing a cell ID of said
endpoint; providing a reporting slot number to said endpoint;
requesting resending of identified packets of data from said
endpoint; setting a bubble-up channel of said endpoint;
configuration a transmission power of said endpoint; and setting a
channel frequency of said endpoint.
11. The AMR system of claim 5, wherein said command and control
frame includes a command body, wherein said command body provides
at least one command selected from the group consisting of:
requesting a report of consumption data from said endpoint;
requesting a report of time of use data from said endpoint;
requesting a report of logged data from said endpoint; requesting a
report of tamper data from said endpoint; setting a configuration
flag within said endpoint; initializing consumption within said
endpoint; request a report of an event summary from said endpoint;
performing an endpoint diagnostic check; and requesting a report of
memory content of said endpoint.
12. The AMR system of claim 5, wherein said command and control
frame includes a plurality of fields, and wherein said plurality of
fields are selected from: a frame ID field, a cell ID, a real-time
clock field, a command flag field, a slot offset field, an
unsolicited message field, an endpoint ID field, a security field,
a command set field, a command body field, or a response frequency
field.
13. The AMR system of claim 5, wherein said command and control
frame designates a response frequency for said endpoint.
14. The AMR system of claim 5, wherein said command and control
frame comprises a one-way programming frame or a two-way command
and control frame.
15. The AMR system of claim 5, wherein said command and control
frame provides a test command to said endpoint.
16. The system of claim 5, wherein said command and control frame
issues a command selected from a command set having a plurality of
different commands, and wherein the system is adapted to support a
plurality of different command sets.
17. The system of claim 16, wherein a command set is divided into a
plurality of groups including a universal group applicable to all
endpoint types, and a type specific group applicable corresponding
types of endpoint devices.
18. The system of claim 5, wherein the command and control frame
includes: a system identification field; a frame identification
field; a cell identification field; a plurality of coordinated
universal time (UTC) fields; a plurality of command flags fields; a
slot offset field that defines the number of slots between packets
in multi-packet messages; at least one field that defines a first
unsolicited message; a plurality of fields that provide at least
one endpoint ID of at least one endpoint with which that the reader
is to communicate; at least one security field; a command set
field; a plurality of command and command body fields; at least one
field that provide a response frequency for at least one endpoint;
a reserved field; a field that indicates a length of extended
control frame; and at least one cyclical redundancy check
field.
19. The system of claim 18, wherein at least one of the plurality
of the command flag fields includes: a first three bits that define
a slot length; a fourth bit that is a forward error correction bit;
a fifth bit that provides a slot mode; a sixth bit that defines a
data type; and a seventh bit and an eighth bit that are a command
target bits.
20. The system of claim 18, wherein at least one of the plurality
of command flag fields comprises: a first four bits; a fifth bit
and a sixth bit that define an encoder number; and a seventh bit
and an eighth bit that define a transmit mode.
21. The system of claim 18, wherein the plurality of command and
command body fields provide at least one indication selected from
the group consisting of: reporting a status, changing a system
number to a new system number, changing a group number to a new
group number, changing a system slot number to a new system slot
number, changing a cell identification to a new cell
identification, reporting slot numbers, resending identified
packets of data, setting a receiver bubble-up period, setting a
bubble-up channel, setting a bubble-up time, configuring a
transmission power, setting a channel frequency, reporting
consumption data, reporting time of use data, reporting logged
data, reporting temperature, reporting tamper data, setting
configuration flags, initializing consumption, reporting an event
summary, performing an endpoint diagnostic check, reporting memory
contents, or any combination thereof.
22. The system of claim 5, wherein the system ID, the frame ID, and
the cell ID are utilized to determine cell reuse.
23. An automatic meter reading (AMR) system, comprising a reader;
an endpoint interfaced to a utility meter, wherein said reader
transmits a RF communication to said endpoint; wherein said RF
communication occurs through the use of at least one packet that
includes a message type field and a message field, wherein the
message type field indicates a command type of a first command to
be carried out that is selected from a predetermined set of
commands, and wherein the message field indicates specific data
associated with the first command.
24. An automatic meter reading (AMR) system, comprising a reader;
an endpoint interfaced to a utility meter, wherein said endpoint
and reader communicate with one another via a radio frequency (RF)
communication; wherein said RF communication occurs through the use
of at least one packet that includes a message type field and a
message content field that is distinct from the message type field,
wherein the message type field indicates a message type indicator
of a first message to be conveyed that is selected from a
predetermined set of messages, and wherein the message content
field indicates specific data associated with the first
message.
25. In an automatic meter reading (AMR) system that includes a
reader and an endpoint interfaced to a utility meter, a method of
communicating between the endpoint and the reader, said method
comprising: transmitting, by at least one of the reader and the
endpoint, a packetized radio frequency (RF) communication that
comprises a first packet; providing, in the first packet, a message
type field and a message content field that is distinct from the
message type field; indicating, in the message type field, a
message type of a first message to be conveyed that is selected
from a predetermined set of messages; and indicating, in the
message content field, specific data associated with the first
message.
26. An automatic meter reading (AMR) system, comprising a reader;
and an endpoint interfaced to a utility meter; wherein in
operation, said reader and said endpoint communicate with one
another via radio frequency (RF) communication according to a
communication protocol that includes a transport layer, wherein
said transport layer provides slot assignments, timing, and
packetization for all data transferred between said reader and said
endpoint; wherein said packetization defines packets to include: a
preamble field; a preface following the preamble field, wherein the
reface includes at least a message type field; an endpoint type
field following the message type field; a message field following
the endpoint type field; and a validation field.
27. The system of claim 26, wherein said packetization further
defines the packets to include a packet length identifier field;
and wherein when a message to be carried by at least a first packet
has a length greater than 254 bytes, a value of a packet length
identifier field of the first packet is set to 0xFF, and a message
field of the first packet is set to include a packet number byte
representing: (a) a total number of packets used to communicate the
message, and (b) a packet number identifier of the first
packet.
28. The system of claim 26, wherein the packetization further
defines the packets to include at least one flag having a grouping
of 8 bits, wherein the 8 bits consist of: a first two bits; a
second two bits that represent an encoder number associated with a
utility meter endpoint; a fifth bit that represents a status of an
event; a sixth bit that represents a security state; a seventh bit
that represents a relay state; and an eighth bit that represents a
resend state.
29. The system of claim 26, wherein the validation field includes
at least one cycle redundancy check identifier, wherein a cycle
redundancy check polynomial is 0x1021.
30. An automatic meter reading (AMR) system, comprising a reader;
an endpoint interfaced to a utility meter, wherein said reader
transmits a RF communication to said endpoint; wherein said RF
communication occurs through the use of at least one packet that
includes a message type field and a message field, wherein the
message type field indicates a command type of a first command to
be carried out that is selected from a predetermined set of
commands, and wherein the message field indicates specific data
associated with the first command.
31. An automatic meter reading (AMR) system, comprising a reader;
an endpoint interfaced to a utility meter, wherein said endpoint
and reader communicate with one another via a radio frequency (RF)
communication; wherein said RF communication occurs through the use
of at least one packet that includes a message type field and a
message content field that is distinct from the message type field,
wherein the message type field indicates a message type indicator
of a first message to be conveyed that is selected from a
predetermined set of messages, and wherein the message content
field indicates specific data associated with the first
message.
32. In an automatic meter reading (AMR) system that includes a
reader and an endpoint interfaced to a utility meter, a method of
communicating between the endpoint and the reader, said method
comprising: transmitting, by at least one of the reader and the
endpoint, a packetized radio frequency (RF) communication that
comprises a first packet; providing, in the first packet, a message
type field and a message content field that is distinct from the
message type field; indicating, in the message type field, a
message type of a first message to be conveyed that is selected
from a predetermined set of messages; and indicating, in the
message content field, specific data associated with the first
message.
Description
CLAIM TO PRIORITY
[0001] The present application is a Divisional of U.S. patent
application Ser. No. 10/915,706, filed Aug. 10, 2004, and entitled
"DATA COMMUNICATION PROTOCOL IN AN AUTOMATIC METER READING SYSTEM,"
which claims priority to U.S. Provisional Patent Application No.
60/500,550, (Attorney Docket No. 1725.161US01), filed on Sep. 5,
2003, and entitled, "DATA COMMUNICATION PROTOCOL IN AN AUTOMATIC
METER READING SYSTEM," each of which is incorporated by reference
herein in its entirety.
RELATED APPLICATIONS
[0002] This application is related to commonly assigned U.S.
Provisional Application No. 60/500,507, filed on Sep. 5, 2003,
entitled, "SYSTEM AND METHOD FOR DETECTION OF SPECIFIC ON-AIR DATA
RATE," U.S. Provisional Application No. 60/500,515, filed Sep. 5,
2003, entitled, "SYSTEM AND METHOD FOR MOBILE DEMAND RESET," U.S.
Provisional Application No. 60/500,504, filed Sep. 5, 2003,
entitled, "SYSTEM AND METHOD FOR OPTIMIZING CONTIGUOUS CHANNEL
OPERATION WITH CELLULAR REUSE," U.S. Provisional Application No.
60/500,479, filed Sep. 5, 2003, entitled, "SYNCHRONOUS DATA
RECOVERY SYSTEM," U.S. Provisional Application No. 60/500,550,
filed Sep. 5, 2003, entitled, "DATA COMMUNICATION PROTOCOL IN AN
AUTOMATIC METER READING SYSTEM," U.S. patent application Ser. No.
10/655,760, filed on Sep. 5, 2003, entitled, "SYNCHRONIZING AND
CONTROLLING SOFTWARE DOWNLOADS, SUCH AS FOR COMPONENTS OF A UTILITY
METER-READING SYSTEM," and U.S. patent application Ser. No.
10/655,759, filed on Sep. 5, 2003, entitled, "FIELD DATA COLLECTION
AND PROCESSING SYSTEM, SUCH AS FOR ELECTRIC, GAS, AND WATER UTILITY
DATA," each of which is incorporated by reference herein in its
entirety.
FIELD OF THE INVENTION
[0003] The present invention relates to automatic meter reading
systems and, more particularly, to the communication protocol used
for communications between endpoints and readers of the automatic
meter reading system.
BACKGROUND OF THE INVENTION
[0004] Current automatic meter reading (AMR) systems are
significantly limited in the information that can be obtained from
the meter. Generally the AMR system comprises a reader and an
endpoint that is interfaced to a meter. In a typical system, the
endpoint obtains the consumption reading from the meter and then
bubbles up every few seconds to send that consumption reading, via
RF signal, to the reader. Alternatively, the endpoint receives a
wake-up tone from the reader that prompts the endpoint to send the
consumption reading to the reader.
[0005] All that is obtained from this configuration is a single
consumption reading from the meter and that reading is based on
what meter register the endpoint was programmed with initially at
the factory.
[0006] As such, there is a need for an AMR system that enables the
user of the system to have more access to and more control over the
information that the meter and endpoint can provide.
SUMMARY OF THE INVENTION
[0007] One aspect of the invention is directed to an automatic
meter reading (AMR) system that includes a reader and an endpoint
interfaced to a utility meter. In operation, the reader and the
endpoint communicate with one another via radio frequency (RF)
communication according to a communication protocol. The
communication protocol includes a transport layer that provides
slot assignments, timing, and packetization for all data
transferred between the reader and the endpoint. The packetization
defines packets to include the following fields: a preamble field;
a preface following the preamble field that includes at least a
message type field; an endpoint type field following the message
type field; a message field following the endpoint type field; and
a validation field.
[0008] In an AMR system comprising a reader and an endpoint
interfaced to a utility meter according to another aspect of the
invention, in operation, the reader transmits a command and control
frame to the endpoint via radio frequency (RF) communication. The
command and control frame includes a system ID that indicates a
specific AMR system with which the endpoint is associated; a frame
ID that indicates a position in a wake-up sequence of the reader;
and a cell ID that indicates at least one subset of the specific
AMR system.
[0009] In a further aspect of the invention, a RF communication
sent by an AMR system reader to an endpoint occurs through the use
of at least one packet that includes a message type field and a
message field. The message type field indicates a command type of a
first command to be carried out that is selected from a
predetermined set of commands. The message field indicates specific
data associated with the first command.
[0010] According to another aspect of the invention, in an AMR
system comprising a reader and an endpoint interfaced to a utility
meter, the endpoint and reader communicate with one another via a
RF communication. The RF communication occurs through the use of at
least one packet that includes a message type field and a message
content field that is distinct from the message type field. The
message type field indicates a message type indicator of a first
message to be conveyed that is selected from a predetermined set of
messages, and wherein the message content field indicates specific
data associated with the first message.
[0011] Another aspect of the invention is directed to a method of
communicating between the endpoint and the reader. At least one of
the reader and the endpoint transmits a packetized RF communication
that includes a first packet. In the first packet, a message type
field and a message content field that is distinct from the message
type field are provided. In the message type field, a message type
is indicated for a first message to be conveyed that is selected
from a predetermined set of messages. In the message content field,
specific data associated with the first message is indicated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 depicts a radio-based automatic meter reading system
that utilizes the data communication protocol of the present
invention.
[0013] FIG. 2 is a table containing the physical layer
specifications of the reader.
[0014] FIG. 3A is a table containing the physical layer
specifications of the endpoint at data rate 1.
[0015] FIG. 3B is a table containing the physical layer
specification of the endpoint at data rate 2.
[0016] FIG. 4 is a table containing the physical layer
specifications of the endpoint in a one-way AMR system.
[0017] FIG. 5 is a diagram of a Manchester encoding structure.
[0018] FIG. 6 is an example of a Sequence Inversion Keyed Countdown
Timer.
[0019] FIG. 7 diagrams the data packet structure.
[0020] FIG. 8 diagrams a high power pulse data packet
structure.
[0021] FIG. 9A diagrams a two-way command and control frame.
[0022] FIG. 9B diagrams a one-way command and control frame.
[0023] FIG. 10 is a table containing universal command types for
the data communication protocol of the present invention.
[0024] FIG. 11 is a table containing type specific commands for the
data communication protocol of the present invention.
[0025] FIG. 12 diagrams command 48 of the data communication
protocol, Multiple Ungrouped Endpoint Command.
[0026] FIG. 13 diagrams command 49 of the data communication
protocol, Vector and Listen Frame.
[0027] FIG. 14 diagrams command 50 of the data communication
protocol, Multiple Commands to Individual Endpoint.
[0028] FIG. 15 is a diagram of the channel spectrum of the
system.
[0029] FIG. 16 is example of a timing diagram for a staged wakeup
sequence for a three cell reuse pattern.
[0030] FIG. 17 is an example of a three-cell cellular reuse
pattern.
[0031] FIG. 18 is an example of a four-cell cellular reuse
pattern.
[0032] FIG. 19 is an example of a five-cell cellular reuse
pattern.
[0033] FIG. 20 depicts mobile operation of the system over five
channels.
[0034] FIG. 21 depicts coverage rings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] The present invention is a data communication protocol for
automatic meter reading (AMR) systems. The protocol is designed to
be flexible and expandable enabling both one-way and two-way meter
reading in both fixed and mobile meter reading systems.
I. System Components
[0036] In an AMR system 100, as depicted in FIG. 1, that is
utilized with the present invention, the components generally
include a plurality of telemetry devices including, but not limited
to, electric meters 102, gas meters 104 and water meters 106. Each
of the meters may be either electrically or battery powered. The
system further includes a plurality of endpoints 108, wherein each
corresponds and interfaces to a meter. Each of the endpoints 108
preferably incorporates a radio receiver/transmitter, e.g., the
Itron, Inc. ERT. The system additionally includes one or more
readers that may be fixed or mobile, FIG. 1 depicts: (1) a mobile
hand-held reader 110, such as that used in the Itron Off-site meter
reading system; (2) a mobile vehicle-equipped reader 112, such as
that used in the Itron Mobile AMR system; (3) a fixed radio
communication network 114, such as the Itron Fixed Network AMR
system that utilizes the additional components of cell central
control units (CCUs) and network control nodes (NCNs); and (4) a
fixed micro-network system, such as the Itron MicroNetwork AMR
system that utilizes both radio communication through concentrators
and telephone communications through PSTN. Of course other types of
readers may be used without departing from the spirit or scope of
the invention. Further included in AMR system 100 is a head-end,
host processor 118. The host processor incorporates software that
manages the collection of metering data and facilitates the
transfer of that data to a utility or supplier billing system
120.
[0037] The AMR system 100 and the data protocol is usable in both
one-way meter reading and in two-way meter reading. The one-way
meter reading system enables the reader to listen to messages sent
asynchronously from the endpoint while the two-way meter reading
system enables the reader to communicate with and command the
endpoint while also enabling the endpoint to respond to the
reader.
II. System Protocol
[0038] The present communication protocol will be described with
reference to the 1430 MHz band that may be utilized within North
America, however, it should be understood that any other radio
frequency band may be used, as suitable, without departing from the
spirit or scope of the invention. The present communication
protocol will also be described with reference to the Open Systems
Interconnection (OSI) protocol stack of the International Standards
Organization which includes: (1) the physical layer; (2) the data
link layer; (3) the network layer; (4) the transport layer; (5) the
session layer; (6) the presentation layer; and (7) the application
layer.
II.A. System Protocol--Physical Layer
[0039] The physical layer describes the physical characteristics of
the communication. This layer conveys the bit stream through the
network at the electrical and mechanical level. It provides the
hardware means of sending and receiving data on a carrier. The
physical layer specifications for the reader may be found in FIG. 2
wherein: (1) the operational modes; (2) the frequency band; (3) the
channel bandwidth; (4) the modulation scheme; (5) the deviation;
(6) the encoding; (7) the bit rate; (8) the frequency stability;
(9) the minimum reception sensitivity; (10) the transmission power;
(11) the preamble length; and (12) the transmission modes are
provided.
[0040] The physical layer specification for the endpoint in a
two-way AMR system, at a first data rate and a second data rate,
are found in the tables of FIG. 3A and FIG. 3B, respectively. The
specifications provided include: (1) the operational modes; (2) the
frequency band; (3) the channel bandwidth; (4) the modulation
scheme; (5) the deviation; (6) the encoding; (7) the bit rate; (8)
the frequency stability; (9) the minimum reception sensitivity;
(10) the minimum preamble length; and (11) the factory default
frequency. The physical layer specification for the endpoint in a
one-way AMR system is provided, similarly, in the table of FIG. 4.
However, it should be understood that any other physical layer
specifications may be used, as suitable, without departing from the
spirit or scope of the invention.
II.B. System Protocol--Data Link Layer
[0041] The data link layer specifies how packets are transported
over the physical layer, including the framing, i.e., the bit
patterns that mark the start and end of packets. This layer
provides synchronization for the physical level. It furnishes
transmission protocol knowledge and management. In the present data
communication protocol, all outbound data transmissions, i.e., all
communications from the reader's central radio to endpoint, are
Manchester encoded with the guaranteed transition mid-bit and each
data bit encoded as a.sub.na.sub.n(bar). (See FIG. 5 for the
Manchester Encoding Structure). Inbound transmissions from the
endpoint are either transmitted as Manchester encoded data,
identical to outbound transmissions, or are transmitted as NRZ
(non-return to zero) data. Selection is based on the value of the
MCH flag in the command and control frame.
[0042] The data link layer provides a countdown timer. The
countdown timer uses Sequence Inversion Keying to represent timer
bits. Each system is assigned a 10-bit pseudo noise (PN) sequence
(for valid sequences, see Table 1 below). That sequence in the data
stream represents a timer bit value 0 and the inverse of that
sequence in the data stream represents a timer bit value 1. Timer
values are composed of 10 timer bits, or 100 data bits. The
countdown timer begins at 1023, or 1111111111 binary, and counts
sequentially to zero, encoding all timer bits as either the system
PN sequence or its inverse. The total counter time, in seconds, is
102400/r, where r is the bit rate, in bits per second. FIG. 6
provides an example of a Sequence Inversion Keyed Countdown
Timer.
TABLE-US-00001 TABLE 1 PN Sequences Sequence Inverted Number Usage
Sequence = 0 Sequence = 1 0 Factory Default 0000000010 1111111101 1
Electric Devices 0000000110 1111111001 2 Electric Devices
0000001010 1111110101 3 Electric Devices 0000001110 1111110001 4
Electric Devices 0000011010 1111100101 5 Electric Devices
0000010110 1111101001 6 Electric Devices 0000111010 1111000101 7
Battery Devices 0000101110 1111010001 8 Battery Devices 0001110110
1110001001 9 Battery Devices 0001101110 1110010001 10 Battery
Devices 0000011110 1111100001 11 Battery Devices 0001011110
1110100001 12 Battery Devices 0001111010 1110000101
All inbound packet transmissions are preceded by a 24-bit or 25 bit
preamble and appended with a 16-bit CRC code, which is inclusive of
all header information, but not the preamble, length, or length_bar
bytes. The CRC polynomial is 0x1021. The CRC initialization value
is 0x0000. CRC processing is performed most significant byte (MSB)
first, and the final checksum is not inverted.
II.C. System Protocol--Network Layer
[0043] The network layer specifies how packets get from the source
network to the destination network. This layer handles the routing
of the data (sending it in the right direction to the right
destination on outgoing transmissions and receiving incoming
transmissions at the packet level). The network layer does routing
and forwarding. In the present data communication protocol, the
network layer functionality is only implemented in electric
endpoints, i.e., it is not used for battery-powered endpoints, or
in any endpoint that acts as translator or repeater. This layer
controls the hopping functions that need to occur between a reader
and any endpoint in order to transfer data. This hopping protocol
is currently used within the Itron AMR systems and is therefore not
described in detail herein.
II.D. System Protocol--Transport Layer
[0044] The transport layer is used to solve problems like
reliability ("did the data reach the destination?") and ensure that
data arrives in the correct order. This layer manages the
end-to-end control (for example, determining whether all packets
have arrived) and error-checking. It ensures complete data
transfer. In the present data communication protocol, slotting
control is handled in the transport layer. This includes slot
assignments, timing, and any necessary packetization. FIG. 7
details the packet structure. The message, message type, and flags
are received from the presentation layer, and broken into
appropriately sized packets. Each packet is prefaced with the
endpoint ID, flags, message type; endpoint type, and packet length.
The packet length reflects the number of bytes in the message
itself, exclusive of header information. In the case where more
than 254 bytes are required in a packet, the value of the length
field is set to 0xFF, and the actual length of the message
structure is placed in bytes 14 (high byte) and 15 (low byte), with
the message bytes to follow. All packets must have a whole number
of bytes in the message.
[0045] The packet number byte, when used as part of the message, is
configured as below in Table 2, wherein the first four bits
comprise the total number of packets in this message and the last
four bits comprise the packet number.
TABLE-US-00002 TABLE 2 Packet Number T T T T N N N N MSB LSB
[0046] The flags byte is configured as below in Table 3. The first
two bits are reserved while the second two bits provides the
encoder number (for multi-encoder units), wherein 00=encoder 0,
01=encoder 1, 10=encoder 2, and 11=encoder 3. The fifth bit
signifies the status of a pending event, wherein 0=no pending event
and 1=a pending event. The sixth bit comprises the security bit,
wherein 0=security disabled and 1=security enable. The seventh bit
comprises the relay bit, wherein 0=message from originating
endpoint and 1=message via relay. The eighth bit comprises the
resend bit, wherein 0=first attempt at packet transmission and
1=resend attempt.
TABLE-US-00003 TABLE 3 Flags R R ENC ENC EVT SEC RLY RSD MSB
LSB
[0047] Some endpoints in the system have the option of sending out
an infrequent (several times a day) fixed format message at a
higher power level, for use in 1-way fixed network applications.
The message has its own structure, as defined in FIG. 8. The custom
packet is then BCH (255, 139, 15) encoded, prior to transmission.
The encoding polynomial is
0x461407132060175561570722730247453567445.sub.8. For multi-encoder
endpoints this packet is generated and sent for each individual
encoder. The flags for the high power pulse data packet structure
are configured as shown in Table 4 below. The first four bits are
reserved while the fifth and sixth bits provide the encoder number,
wherein 00=encoder 0, 01=encoder 1, 10=encoder 2, and 11=encoder 3.
The seventh bit comprises the relay bit, wherein 0=message from
originating endpoint and 1=message via relay. The eighth bit
comprises the error code indicating that a critical endpoint error
has occurred.
TABLE-US-00004 TABLE 4 Flags R R R R ENC ENC RLY ERR MSB LSB
[0048] The endpoints may also be set to send out any preprogrammed
message type in place of the fixed format message described
above.
II.E. System Protocol--Session Layer
[0049] The session layer sets up, coordinates, and terminates
conversations, exchanges, and dialogs between the applications at
each end. It deals with session and connection coordination. In the
present data communication protocol, the session layer generally
comprises the command and control frame that is sent from the
reader to the endpoint.
II.E.i. System Protocol--Session Layer/Two-Way Command and
Control
[0050] The command and control frame is used to issue command to
two-way endpoints either individually or in groups. It also serves
to realign the endpoint real-time clock. FIG. 9A diagrams the
two-way communication command and control frame. As shown, the
command and control frame transmission is preceded by a 24-bit
preamble, as indicated by the three "P" fields within the frame.
The first 16 bits are preferably an alternating pattern, AAAAh, and
are used for clock recovery. The last 8 bits are used for frame and
timing synchronization.
[0051] Field "0" of the command and control frame comprises the
system identification (ID). Each system is issued an 8-bit ID
value, which is stored in the endpoint, to distinguish different
systems within geographic proximity. The endpoints are designed to
respond to commands from their own system or to commands that
address them specifically by ID number, proper security password,
and have a 0x00 in field "0". The system ID functions nearly
identically to the cell ID, described below. However, the system ID
is universal, while the cell ID is local, i.e., a single system
will have multiple cells each having the same system ID but a
different cell ID.
[0052] Field "1" of the command control frame comprises the frame
ID. Each reader within the system is assigned a frame ID to use
based on its position in the wake-up sequence. The position in the
wakeup sequence is directly related to the frequency reuse pattern
that is used in a given system. Table 1, described earlier,
correlates the frame ID to the channel, which is correlated to the
cell reuse ratio.
[0053] Field "2" of the command and control frame comprises the
cell ID. Each cell is issued an 8-bit ID value, which is stored in
the endpoint, to distinguish different systems within geographic
proximity.
[0054] Fields "3" through "6" of the command and control frame is
the RTC, which is defined as UTC time (coordinated universal time),
which is a 32-bit value representing the number of seconds since
midnight (00:00:00) on Jan. 1, 1970 GMT.
[0055] Field "7" is the command flags 1 field, wherein the first
three bits define a slot length according to Table 5.
TABLE-US-00005 TABLE 5 Slot Lengths Value of Length Bits Nominal
Length in Ticks* Nominal Length in ms 000 819 24.99390 001 1638
49.98779 010 3277 100.00610 011 6553 199.98169 100 9830 299.98780
101 16384 500.00000 110 32768 1000.00000 111 163840 5000.00000
*Defined as ticks of an ideal 32,768 Hz clock.
The fourth bit is the forward error correction bit, wherein 0=no
forward correction error and 1=forward error correct all responses.
The fifth bit provides the slot mode, wherein 0=respond to command
in pseudo-random slot (Slotted Aloha) and 1=respond to command in
the defined slot. The sixth bit of field "7" defines the data type,
wherein 0=NRZ response from endpoint and 1=Manchester encoded from
the endpoint. The seventh and eighth bits of field "7" comprise the
command target, wherein 00=the entire cell, 01=the group defined in
EPID_HI (field "12"), 10=the group defined in EPID_LO (field "15"),
and 11=the endpoint defined by EPID (including HI/LO), fields "12"
through "15". It should be noted that in single endpoint
communications the command target (TGT) is set to 11 and the
endpoint responds immediately after command processing with a
minimum of 25 milliseconds between this frame and the endpoint
response.
[0056] Field "8" of the command and control frame is the command
flags 2 field, wherein the first four bits are reserved. The fifth
and sixth bits defined the encoder number, wherein 00=Encoder 0,
01=Encoder 1, 10=Encoder 2, and 11=Encoder 3. The final seventh and
eighth bits define the transmit mode, wherein 00=transmit mode 1,
e.g., mobile response required, 01=transmit mode 2, e.g., fixed
network response required, and 10/11 are reserved. Also see section
V below.
[0057] Field "9" of the command and control frame comprises the
slot offset. Slot offset defines the number of slots between
packets in multi-packet messages. For example, if the endpoint has
an initial slot number of 50, and the slot offset is 120, a
three-packet message would be transmitted in slots 50, 170, and
290.
[0058] Fields "10" and "11" of the command and control frame define
the first unsolicited message. Specifically, they define the slot
number where the unsolicited messages (UMs) are to begin. Any UMs
generated during the cell read would be reported in a
pseudo-randomly selected slot after the slot defined here. If the
value of this field is 0x0000, no UMs are sent from the
endpoint.
[0059] Fields "12" through "15" of the command and control frame
provide the endpoint IDs for those endpoints that the reader is
desiring to communicate with.
[0060] Fields "16" and "17" are the security fields and are
described further in relation to the presentation layer.
[0061] Field "18", defines the command set. The commands are
divided into two groups: (1) universal and (2) type-specific.
Universal commands are numbered 0-63 and are applicable to all the
system endpoints. Type specific commands are numbered 64-255 and
vary depending on the lower nibble of the command set field in
accordance with Table 6 below.
TABLE-US-00006 TABLE 6 Command Sets Command Set CDS Value Usage 0
(default) 0000 Utility Metering Endpoints 1 0001 Repeaters and
Translators 2 0010 Telemetry Devices 3-14 0011-1110
<<Reserved>> 15 1111 <<Reserved Engineering Use
Only>>
[0062] Fields "19" through "21" of the command and control frame
define the command and command body. Specifically, the eight
command bits of field "19" indicate the command type, wherein the
numbers 0-63 are universal commands and 64-255 are the type
specific commands. Fields "20" and "21" provide sixteen bits
wherein any data needed to carry out the command type is provided.
The tables in FIGS. 10 and 11 indicate the command types and
command bodies that are possible with the system of the present
invention. Referring to the universal commands (FIG. 10), it can be
seen that the present system is capable of but not limited to: (1)
reporting a status; (2) changing a system number to a new system
number; (3) changing a group number to a new group number; (4)
changing a system slot number to a new system slot number; (5)
changing the cell ID to a new cell ID; (6) reporting slot numbers;
(7) resending identified packets of data; (8) setting the receiver
bubble-up period; (9) setting the bubble-up channel; (10) setting
the bubble-up time; (11) configuring the transmission power; (12)
setting the channel frequency; etc.
[0063] Referring to the type specific commands (FIG. 11), numerous
other commands are available including but not limited to: (1)
reporting consumption data; (2) reporting time of use (TOU) data;
(3) reporting logged data; (4) reporting temperature; (5) reporting
tamper data; (6) setting configuration flags; (7) initializing
consumption; (8) reporting an event summary; (9) performing an
endpoint diagnostic check; (10) reporting memory contents; etc.
[0064] Fields "22" and "23" of the command and control frame
designate the response frequency for the endpoint. The response
frequency is configured as 16 bit flags, identifying valid response
frequencies for the endpoint. For example, if the response
frequency has a value of 0x00C1 (bits, 7, 6, and 0 are set), the
endpoint may respond on channel, 7, channel 6, or channel 0.
[0065] Field "24" is reserved for later use.
[0066] Field "25" indicates the length of the extended control
frame in bytes. A value of 0 indicates that no extended frame is
present.
[0067] Fields "26" and "27" of the command and control frame
provides the cyclic redundancy check (CRC). Specifically, fields
"26" and "27" provide a 16-bit CRC. The CRC is preferably a
polynomial defined as 0x1021. The CRC initialization value is
0x0000. CRC processing is performed most significant bit (MSB)
first, and the final checksum is not inverted.
II.E.ii. System Protocol--Session Layer/One-Way Command and
Control
[0068] For simplicity one-way devices may opt to use the
programming frame shown in FIG. 9B. The command and command body
bytes are similar to that described above with reference to the
two-way devices. The byte for number of commands provides the total
number of commands to follow in this frame, with a maximum value of
8. The command flags are diagrammed in Table 7 below. The first two
bits indicate the transmit mode, wherein 00=transmit mode 0,
01=transmit mode 1, and 10/11 are reserved. The third bit
designates the data logging, wherein 0=data logging is disabled and
1=data logging is enabled. The fourth bit designates the forward
error correction, wherein 0=disable forward error correction on
response and 1=enable forward error correction on response. The
fifth and sixth bits designate the mode set, wherein 00=stock mode,
01=test mode, 10=reserved mode, and 11=normal mode. The seventh and
eighth bits are reserved.
TABLE-US-00007 TABLE 7 Command Flags TXM TXM DLG FEC MDE MDE R R
MSB LSB
II.E.iii. System Protocol--Session Layer/Special Commands--Channel
Frequency
[0069] Certain of the commands provided in the command and control
frame are described in detail below. For instance, Command 33,
which is the set channel frequency. Each of the system endpoints
support up to 16 channels, which are set individually. They may or
may not be contiguous channels. The channel numbering differs based
on frequency band. For example, in the present implementation of
the invention, the 1427-1432 MHz band is divided into 6.25 kHz
frequency channels, with frequency channel 0 centered at 1427.000
MHz, frequency channel 1 centered at 1427.00625 MHz, etc. If
endpoint channel 15 is programmed to a value of 480, that endpoint
receiver will always operate at 1427.000+(0.00625*480)=1430.000
MHz. This may be extended to other frequency bands. For example,
the 433-435 MHz band is divided into 25 KHz frequency channels with
the frequency channel 0 centered at 433.000 MHz, frequency channel
1 centered at 433.025 MHz and so on.
[0070] The command body of the set channel frequency command is
detailed below in Table 8:
TABLE-US-00008 TABLE 8 Command Body/Channel Frequency CHN CHN CHN
CHN FRQ FRQ FRQ FRQ FRQ FRQ FRQ FRQ FRQ FRQ FRQ FRQ MSB LSB
Individual frequencies are programmed into the endpoint by
selecting the channel being programmed (1-15) with the top nibble,
and the frequency number in the lower 12 bits. Endpoint channel 0
is preferably the manufacturing default frequency, and may not be
edited. Endpoint channel 15 is the receiver frequency. It is
initialized to the same frequency as channel 0 at manufacture, and
is preferably programmed prior to or at installation. The endpoint
channel uses are defined in Table 9 below:
TABLE-US-00009 TABLE 9 Endpoint Channel Use Endpoint Channel
Channel Use 0 Factory Default. This channel is not reprogrammable.
1 General use Tx/Rx (Transmission/Reception) 2 General use Tx/Rx 3
General use Tx/Rx 4 General use Tx/Rx 5 General use Tx/Rx 6 General
use Tx/Rx 7 General use Tx/Rx 8 General use Tx/Rx 9 General use
Tx/Rx 10 General use Tx/Rx 11 General use Tx/Rx 12 General use
Tx/Rx 13 General use Tx/Rx 14 Default UM Channel (unsolicited
message) 15 Default Rx Channel
[0071] The configuration flag commands, i.e., commands 90, 91, and
92 are used for setting individual flags in the endpoints. Each
flag command includes an 8-bit flag mask and an 8-bit flag as shown
below (the configuration flags 1 command body):
TABLE-US-00010 TABLE 10 Flag Mask MSK MSK MSK MSK MSK MSK MSK MSK
MSB LSB
TABLE-US-00011 TABLE 11 Flags R R R TxB UMC FN FEC MMI
The flag mask field determines which flags are to be modified by
this command. A "1" in any bit position means the associated value
in the flags field should be modified. For example, A value of 0x17
(bits 4,2,1 and 0 are high) means that the values in the Flags
field, bits 4, 2, 1, and 0 must be written to the associated flags
in the endpoint. With regard to the flags field of Table 7, the
first three bits are reserved for future growth while the fourth
bit, TxB, determines if the endpoint is in transmit bubble up mode,
the fifth bit, UMC, defines the unsolicited message channel, i.e.,
UMC=0 then transmit UMs on Channel 14, and UMC=1 then transmit UMs
on channel 15. The sixth bit of the flags field defines the fixed
network mode, wherein 0=this endpoint operates in Mobile/Handheld
mode only and 1=this endpoint operates in mobile/handheld/fixed
network mode. The seventh bit of the flags field defines the
forward error correction, wherein 0=no forward error correction
applied to the high power pulse and 1=forward error correction is
applied to the high power pulse. The eighth bit of the flags field
defines the multiple message integration, wherein 0=no multiple
message integration applied to high power pulse and 1=multiple
message integration applied to high power pulse. II.E.iv. System
Protocol--Session Layer/Special Commands--Test Commands
[0072] The present data communication protocol provides at least
two commands for use in system testing and analysis. The first
command is command 210, i.e., Generate UM (unsolicited message).
This command automatically generates an unsolicited message in all
endpoints addressed by the command and control frame. It generates
the lowest numbered UM supported by the endpoint. The second
command is command 211, i.e., Enter Screaming Viking Mode.
Screaming Viking Mode is a constant transmission mode, to be used
for test only. When this command is received, the endpoint
repetitively transmits its ID for the number of minutes declared in
the command. If a value of 0 is sent, the mode is active for 15
seconds.
II.E.v. System Protocol--Session Layer/Special Commands--Extension
Commands
[0073] Commands 48, 49, 50 and 51 of the data communication
protocol are implemented as extensions to the command and control
frame. The extension commands immediately follow the command and
control frame in the same transmit session. Command 48 is the
multiple ungrouped endpoint command. In the case where the system
needs to command a group of specific endpoints and vector them to
specific slots, command 48 is issued. The central radio then issues
commands to these endpoints, as shown in FIG. 12. This command can
be used to address a maximum of 16 distinct endpoints. The packet
length reflects the number of endpoints addressed by the message.
Note that the command 48 may not be used for any command that
requires the security password. The structure of command 48
provides for an 8-byte preamble having the value of 0xAAAA AAAA
AAAA AA96, the length, the endpoint IDs, and the command bodies for
each of the endpoints and a response byte for each of the
endpoints. The response byte is diagrammed in Table 12 below:
TABLE-US-00012 TABLE 12 Response Byte R R R R CHN CHN CHN CHN MSB
LSB
The response byte reserves the first four bits and utilizes the
last four bits to define the response frequency nibble.
Specifically, the four bit flags define which of the pre-programmed
channels the endpoint may respond on. If CHN=0000, then use the
response frequency byte from the original command and control
frame. The structure of the command 48 also includes the CRC as
described earlier.
[0074] Command 49, i.e., the vector and listen frame, is issued in
the instance where the central radio or reader need to download an
arbitrary block of data to the endpoint. The endpoint, upon
receiving this command receives a data frame, as defined in FIG.
13. This command is valid only when the endpoints are individually
addressed (i.e., TGT=11). The data is endpoint-type specific. Note
that the vector and listen frame has an 8-byte preamble with a
value of 0xAAAA AAAA AAAA AA96. Further, note that the packet
length reflects the number of bytes in the message itself,
exclusive of header information, and that the CRCs computed over
all bytes in the message body.
[0075] Command 50, the multiple command to individual endpoint
command, is used in the case where the central radio or reader need
to download a series of commands to one specific endpoint. The
endpoint, upon receiving this command, receives a data frame as
defined in FIG. 14. This command is only valid when the endpoints
are individually addressed (i.e., TGT=11). Up to 24 commands may be
issued to an endpoint using this structure. Note that the packet
length reflects the number of commands to be issued within this
structure.
[0076] Command 51, the Extended Frame Mobile Read command, uses the
multiple ungrouped endpoint command structure, with a Slotted-ALOHA
period between the extended frame and the queried response slots.
All endpoints which recognize the command respond. If the endpoint
is among those addressed by the extended frame, it responds as
commanded, being offset by 16 slots. If the endpoint is not
specifically addressed it responds in the Slotted-ALOHA section
with its programmed default message.
II.F. System Protocol--Presentation Layer
[0077] The presentation layer, which is usually part of an
operating system, converts incoming and outgoing data from one
presentation format to another and it is sometimes called the
syntax layer. In the present data communication protocol, the
presentation layer handles data security and any necessary data
compression and decompression.
[0078] The data security is preferably a simple two-level protocol,
which may be enabled or disabled by the customer. Level 1 provides
simple encryption for the transfer of normal data while level 2
provides write security to the endpoint to prevent unauthorized
users from changing endpoint parameters.
[0079] Level 1 is intended for use on ordinary data being
transmitted from the endpoint to the head end. All data is
encrypted with a simple 8-bit XOR mask. The level 1 security
enables flag and encryption mask and are editable by a level 2
parameter write. The factory default for the XOR mask is the bottom
8 bits of the serial number. Level 1 security is applied only to
the message itself and not to the EPID, flags, or message type.
Level 1 security may be disabled by setting the mask value to
0.
[0080] Level 2 security is intended for use on any head end
commands to change endpoint parameters. It includes modification of
operational, security and reprogramming parameters. Level 2
functionality is independent and can be applied with or without
Level 1 functions enabled. Each endpoint has a 16-bit password.
This password is originally defined at install, and can be edited
by a valid Level 2 command. Any write command must include the
current password to be considered valid by the endpoint. For added
security, the Level 1 encryption mask may be applied to the
password, if Level 1 functionality is active. There is no
compression performed on packet data.
II.G. System Protocol--Application Layer
[0081] The application layer is the layer at which communication
partners are identified, quality of service is identified, user
authentication and privacy are considered, and any constraints on
data syntax are identified. (This layer is not the application
itself, although some applications may perform application layer
functions.) In the present data communication protocol, an endpoint
application layer is used in conjunction with the application
programming interface (API). When data is requested by the
presentation layer, via the API, the application layer performs its
processing and returns the requested message as a single block,
along with one 8-bit value. The value represents the message
type.
III. System Operation
[0082] The two-way AMR system of the present invention, at 1430
MHz, is designed to operate most efficiently in five contiguous RF
channels. This allows the use of a cheaper (wider) receiver section
in the endpoint while still maintaining the FCC mandated 50 KHz
maximum transmit spectrum. The transmit spectrum in all devices,
endpoints, and readers, must maintain a 50 KHz or less occupied
bandwidth during transmit. The receiver in the reader must also
have a good selectivity on the channel of interest. The endpoint
receiver is allowed to accept a wider receive bandwidth primarily
to reduce the cost of the endpoint.
[0083] Refer to FIG. 15 to observe the 250 KHz of spectrum
allocated to the system. As shown, the spectrum is divided in to
five 50 KHz channels. The center channel, i.e., channel 3, is
designated as the control channel for the system 100. All endpoints
106 listen on this channel. As such, if the readers are
quasi-synchronized in their outbound transmissions the center
channel approach allows the endpoints to use a wider receive
bandwidth while avoiding the interference that would normally be a
problem (synchronization is described in further detail below). The
diagram of FIG. 15, illustrates the bandwidth differences
graphically. Since the reader has good selectivity the endpoints
can respond on a different channel in each cell simultaneously
allowing the maximum data throughput in the system (cell re-use is
described in further detail below).
[0084] By utilizing an appropriate RF ASIC, the architecture can be
reduced to three contiguous channels with the reaming two or more
channels scattered throughout the band to ease spectrum allocation
requirements. With a reduction in the interference protection to
the end point, a completely separated channel model could be used
in an alternative configuration. However, in the separate channel
model, the endpoint requires additional base band filtering and is
still slightly more susceptible to adjacent channel interference on
the control channel especially if operating in the high power
portion of the band. The separate channel option also allows
multiple control channels in the system when mobile operation is
used with multiple outbound channels. When using the separate
channel model, channels 2 and 4, of a 5-channel block, are used for
control signals.
[0085] To alleviate cell-to-cell interference in a system with a
single control channel the readers must be synchronized in time so
that the control frames, which are described in further detail
below, do not overlap. The addition of "dead time" in between
sequential control frames allow for the receivers to be
quasi-synchronized instead of in perfect lock step. In the
preferred embodiment, quasi-synchronized means that the receivers
are within 0.5 seconds of each other, which can easily by achieved
via protocols such as NTP (network time protocol). Other
quasi-synchronization times may be used without departing from the
spirit or scope of the invention. As such, a GPS or other high
accuracy time base is not required within the readers.
[0086] Within the AMR system, each reader is assigned a frame ID to
use based on its position in a wakeup sequence. The position in the
wakeup sequence is directly related to the frequency reuse pattern
used in a given system. The timings in the diagram of FIG. 16 are
provided as an example of a staged wakeup sequence for three cell
reuse. As shown, the timings are for an endpoint to endpoint clock
accuracy of +1-0.5 seconds, if the value obtainable is only +/-1
second then the dead time must be increased to 5 and the nominal
frame time to 22.5 seconds. All other timings remain the same. If
GPS is available in the reader, the dead time can be reduced and
the time frame timing can be shortened. In any case, the minimum
dead time is preferably 0.5 seconds.
[0087] As shown in FIG. 16, the first wake-up sequence is initiated
at time T=0. For the first 18.5 seconds, get wakeup (SIK countdown
timer), next 0.25 seconds (command and control, frame 2), and last
2.5 second is dead time. The remaining time in the timeline is the
hold off time for response slots, which is the frame number*the
nominal frame time, or 2*20=40 seconds of hold off time. At T=20,
the second wake-up sequence is initiated. Similarly, the first 18.5
seconds, get wakeup (SIK countdown timer), next 0.25 seconds
(command and control, frame 1), and the last 2.5 seconds is dead
time. The hold off time for response slots in this instance is,
again, the frame number*the nominal frame time, which is 1*20=20
seconds off hold off time. At T=40, the third wake-up sequence is
initiated. For the first 18.5 seconds, get wakeup (SIK countdown
time), the next 0.25 seconds (command and control, frame 0), and
the last 2.5 seconds is dead time. The hold off time for response
is calculated as follows, frame number*nominal frame time, or
0*20=0 seconds hold off time meaning the endpoints have 2.5 seconds
before the beginning of slot 0 in this cell.
[0088] As mentioned, the example of FIG. 16 is for a three cell
reuse pattern. However, the example can be easily extended to
higher cellular reuse ratios by adding more frames as appropriate.
In the 1430 MHz system, the maximum recommended cellular reuse is
5. This leads to a hold off time of 100 seconds in the first cell
transmitted which is short enough for the endpoint to maintain
accurate timing with regard to slot timings.
[0089] Unless otherwise specified by the system, the frame ID is
preferably tied to the cellular frequency used based on Table 13
below:
TABLE-US-00013 TABLE 13 Frame ID Cell Reuse Ratio Channel to Frame
ID mapping 3 Cell Channel 1 = Frame ID 0 Channel 3 = Frame ID 1
Channel 5 = Frame ID 2 4 Cell Channel 1 = Frame ID 0 Channel 2 =
Frame ID 1 Channel 4 = Frame ID 2 Channel 5 = Frame ID 3 5 Cell
Channel 1 = Frame ID 0 Channel 2 = Frame ID 1 Channel 3 = Frame ID
2 Channel 4 = Frame ID 3 Channel 5 = Frame ID 4
[0090] To maximize throughput in the system 100, a cellular reuse
scheme is employed in the 1430 MHz band. The reuse ratio is
preferably a 3, 4, 5, 7, or 9 cell pattern. Smaller patterns are
preferred from a delay perspective, however, the final choice is
preferably made during the RF planning and installation of actual
systems in the field. The 7 and 9 patterns are preferably used in
the virtual cell model. The reuse patterns are provided in FIGS.
17, 18, and 19 depicting three-cell (ABC), four-cell (ABCD), and
five-cell reuse patterns (ABCDE), respectively.
IV. Mobile and Hand-Held Operation
[0091] When operating in the mobile or hand-held mode, the 2.5
seconds of "dead time" does not apply. Rather slot "0" occurs at
the end of the command and control frame plus 25 milliseconds.
Note, that due to time required to read the attached meter and/or
bring the charge pump to full operation the endpoint may or may not
respond in slot "0" even if told to respond immediately.
[0092] In programming mode, the hand-held control may reduce its
sensitivity by as much as 30 dB to avoid overload conditions at
close programming distances. The hand-held and endpoint must work
with programming distances as close as 0.5 meters and as far as 300
meters when in the mobile mode of operation with a line of site
propagation path.
[0093] In mobile operation the wake-up sequence, the command &
control data, and the receive portions of a standard read cycle are
continuously repeated as the mobile moves through the system. The
timing is preferably in the range of a one to five second cycle.
The diagram depicted in FIG. 20 gives a general over view of the
mobile operation over the five channels.
[0094] The command & control frame preferably contains a group
call read that solicits a consumptive type reading from all of the
endpoints that can hear the mobile and that have the correct system
ID. The endpoint responds to the group call in a random slot, on a
random channel. The random channel is chosen from the list of
available channels that is provided in the command & control
frame. The random slot is one of the 50 ms slots in the
Slotted-ALOHA portion of the frame. (Slotted ALOHA is a random
access scheme just like regular ALOHA except that the transmissions
are required to begin and end within the predefined timeslot. The
timeslots are marked from the end of the command & control
frame just like in the fixed network).
[0095] When the reader hears a response from a given endpoint, it
knows that it is within range and can request a specific response
from the endpoint in the next command & control frame. The
command & control frame is expected to contain both a standard
command frame and an extended control frame to allow for the mobile
to access the most endpoints possible in a single pass. When the
mobile requests a response from the end point it will tell it the
channel and time slot that it is supposed to respond on. This is to
minimize the chances of a collision on the longer messages that can
be delivered in the MDP type of responses. During the mobile cycle,
battery endpoints may be required to bubble up their receivers up
at a higher rate than normal or synchronize to the first command
& control frame to improve mobile performance.
[0096] If the van is moving at a maximum of 30 miles per hour it
will travel 440 feet in 10 seconds. The van will also have a
communications radius of approximately 500 feet give a 1400 MHz
system operating at a data rate of 22.6 Kchips/second, with the
expected power levels and receiver sensitivities (e.g., +14 dBm
endpoint TX power, -110 dBM RX sensitivity in the van, 20 dB
margin, endpoint at 5'). The margin is included because the MDP
data packet is much longer than the current SCM type messages and
is not repeated unless an error occurs. To achieve a low re-try
rate, it is desirable to bring the BER down to 0.01%. To do this
under normal situations would require an additional 20 dB of
margin, however, a diversity setup on the van receivers can be used
to achieve the same results. This requires two antennas on the van
placed five to six feet apart along with an additional receiver
demodulator chain per channel. For SCM data that is repeated
multiple times, the system can operate at a much lower margin and
still achieve excellent read reliability in the van. A coverage
radius of about 1200 feet is obtained for the system when
collecting standard consumptive data.
[0097] The diagram of FIG. 21, shows the coverage rings for low
margin SCM messages and for the 20 dB margin IDR messages for the
present system in comparison with the current 0 dB margin SCM
messages from the ERT.
[0098] With the current mobile protocol each endpoint is, on
average, in the range of the van for approximately 12 to 25
seconds. This is an appropriate amount of time to wake up the
endpoint, identify who it is, request an MDP (mobile data
packet=250 bytes of raw data maximum) to be sent, receive the MDP
and potentially retry the request and receive portions of the
process if necessary.
[0099] In the basic system, there are five channels at a maximum
75% utilization for MDP responses. This gives an effective data
rate of 42375 BPS or 5296 bytes per second or 21 blocks per second.
Since the system is looking at a single block per meter, the system
can support 21 new meters per second. The mobile then has a nominal
range of 500 feet. This gives the system of about 175 meters in
range at any given time, even in the densest specified systems. If
the van is moving at 30 mph, the system gets 44 feet of new meters
per second. In performing a geometric approximation, the result is
about 12 new meters per second. So, the system can handle 21 new
meters per second but can only get in the range of 10 to 12 meters
per second. This allows for a full set of retries in a dense
system. (This assumes the low 11.36363 KBPS data rate and the full
250 byte MDP, for smaller packets and with the higher data rate
option, the situation is even better.
V. Response Optimization for Mobile and Fixed Network Operation
[0100] In order to optimize the batter efficiency, range, and
overall system robustness for endpoints that must operate in both a
mobile and fixed network scenario without reprogramming, the
following methodology is preferably used. The outbound transmission
from the reader includes a flag that states the response mode of
the endpoint. When the response mode flag is set to "mobile" the
endpoint responds at a lower power (e.g., +14 dBm) and in a
dynamically randomized slot determined as described above. When the
endpoint sees the "fixed network" flag set it responds in its
assigned slot at high power (e.g., +30 dBm). The advantage provided
by this scenario is that in the mobile case the reader is not
burdened with slot dynamic allocation of multiple, which can be
computationally intensive and consume additional air time to
successfully communicate to all the in-range endpoints. It also
allows the endpoint to conserver power and reduce interference.
This leads to the ability to transmit more data with less retries.
In the fixed network case, the high power mode enables the system
to get maximum range from the device (reducing infrastructure
costs) while interference is mitigated by assigned slots. The slots
are efficiently assigned in the fixed network case because of the
pseudo-static nature of the system. Note that prior art systems
enabled only static programming of the endpoint to operate in one
mode or the other. As such, the previous methodology did not allow
for mixed mode operation without reprogramming the endpoint. Thus,
the present invention presents the combination of low power
operation and dynamic slot assignment for mobile operation with the
high power slotted operation for the fixed network all controlled
by a flag in the outbound wakeup data. Refer to field "8," bits 7
and 8, of the command & control frame that define the
transmit/response mode.
[0101] The present invention may be embodied in other specific
forms without departing from the spirit of the essential attributes
thereof; therefore, the illustrated embodiment should be considered
in all respects as illustrative and not restrictive, reference
being made to the appended claims rather than to the foregoing
description to indicate the scope of the invention.
* * * * *