WO2009025641A1 - Systems and methods for resampling unreliable data - Google Patents
Systems and methods for resampling unreliable data Download PDFInfo
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- WO2009025641A1 WO2009025641A1 PCT/US2007/018556 US2007018556W WO2009025641A1 WO 2009025641 A1 WO2009025641 A1 WO 2009025641A1 US 2007018556 W US2007018556 W US 2007018556W WO 2009025641 A1 WO2009025641 A1 WO 2009025641A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/0016—Arrangements for synchronising receiver with transmitter correction of synchronization errors
- H04L7/002—Arrangements for synchronising receiver with transmitter correction of synchronization errors correction by interpolation
- H04L7/0029—Arrangements for synchronising receiver with transmitter correction of synchronization errors correction by interpolation interpolation of received data signal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/04—Speed or phase control by synchronisation signals
- H04L7/041—Speed or phase control by synchronisation signals using special codes as synchronising signal
- H04L7/042—Detectors therefor, e.g. correlators, state machines
Definitions
- This disclosure relates to digital signal processing. More particularly, this disclosure relates to systems and methods for changing the sample rate of a digital signal. This disclosure also relates to data reception and coordination with time. Brief Description of the Drawings
- FIG. 1 is a block diagram illustrating a first intelligent electronic device (IED) used in a power system and configured in certain embodiments to provide sampled data and information for resampling the data to a second IED;
- IED intelligent electronic device
- FIG. 2 is a block diagram of a system for resampling transmitted data according to one embodiment
- FIG. 3 is a block diagram illustrating a second IED configured to receive sampled data, resample the sampled data, and process resampled data according to one embodiment
- FIGS. 4A and 4B are block diagrams of the resample data component shown in FIG. 2 configured to resample data using index values sent from the transmitter to the receiver according to one embodiment;
- FIG. 5 is a block diagram of the resample data component shown in FIG. 2 configured to resample data using time stamps according to one embodiment
- FIG. 6 is a plot illustrating an interpolation according to one embodiment
- FIG. 7 is a schematic diagram representing a data matrix as it may be stored and used according to one embodiment
- FIGS. 8A, 8B and 8C are flow charts illustrating a method for resampling data using synchronized index values according to one embodiment
- FIGS. 9A and 9B are flow charts illustrating a method for resampling data using time stamps according to one embodiment.
- FIG. 10 is a flow chart illustrating a method for resampling data by basing a receiver's time stamp on an arrival time instant according to one embodiment.
- Data resampling is an operation that converts a signal from one sampling frequency to another sampling frequency.
- data sampled at one frequency e.g., for a digital music recording
- recording media e.g., hard drive, floppy disc, compact disc (CD), digital versatile disc (DVD), flash memory, magnetic tape, or other memory device.
- power system information at one location may be initially sampled at a first frequency and resampled at a second frequency before being transmitted, stored or compared with other sampled power system information.
- the resampling may be done such that the sampled data is synchronized in time with another set of sampled or resampled data.
- digital signal processing systems uniformly sample an analog signal at a fixed and known rate in order to apply mathematical relationships to the analysis and processing of the data.
- signal processing operations process the data at different rates in various sections of the system.
- Many well-known resampling algorithms are available to provide conversion of data between rates. For example, Oppenheim and Schafer (Discrete-Time Signal Processing, Prentice Hall, 1989, pg.
- 111 - 112 describe a system whereby the data is first interpolated to insert L-1 zero values between each sample, followed by discrete time filtering with a low pass filter of gain L and with cutoff frequency the minimum of pi/L and pi/M radians, followed by removing M-1 out of every M values. The overall rate is changed by a factor of L/M.
- these signal processing operations are all performed within a single processing element.
- a computer aided design application executing on a single desktop computer may provide resampling capabilities.
- the data is communicated from one location to another and the resampling is provided at either the transmission or the reception end of the communication channel. When resampling is required after receiving data, it is generally important for the receiver to guarantee that the data arrives reliably and uncorrupted.
- Many communication algorithms such as equalization filtering, error correction codes, and repeated transmission handshakes have been developed to ensure reliable reception.
- Unreliable data may be any data wherein data points are missing, data points are out of order, the data is not readily available, and the like.
- IEDs intelligent electronic devices
- microprocessors in embedded systems logic devices such as FPGAs 1 communication system processors, servers, workstations, desktop computers, laptop computers, personal digital assistants (PDAs), cellular telephones, kiosks, point-of-sale terminals, and other computing devices.
- logic devices such as FPGAs 1 communication system processors, servers, workstations, desktop computers, laptop computers, personal digital assistants (PDAs), cellular telephones, kiosks, point-of-sale terminals, and other computing devices.
- PDAs personal digital assistants
- an IED configured to resample data includes a microprocessor-based power system control, monitoring, protection, communication and/or automation device. Accordingly, although the systems and methods for resampling data disclosed herein may be used in any IED that requires resampling, several of the disclosed embodiments illustrate the use of resampling methods in terms of power system data handling.
- the IED may be a power system protection, automation and control device such as an SEL-421, or a synchrophasor processor such as an SEL-3306 (both available from Schweitzer Engineering Laboratories, Inc., Pullman, Washington).
- the systems and methods disclosed herein may be implemented into an IED running software used for resampling audio files.
- IED running software used for resampling audio files.
- a software module or component may include any type of computer instruction or computer executable code located within a memory device and/or transmitted as electronic signals over a system bus or wired or wireless network.
- a software module or component may, for instance, comprise one or more physical or logical blocks of computer instructions, which may be organized as a routine, program, object, component, data structure, etc., that performs one or more tasks or implements particular abstract data types.
- a particular software module or component may comprise disparate instructions stored in different locations of a memory device, which together implement the described functionality of the module.
- a module or component may comprise a single instruction or many instructions, and may be distributed over several different code segments, among different programs, and across several memory devices.
- Some embodiments may be practiced in a distributed computing environment where tasks are performed by a remote processing device linked through a communications network.
- software modules or components may be located in local and/or remote memory storage devices.
- data being tied or rendered together in a database record may be resident in the same memory device, or across several memory devices, and may be linked together in fields of a record in a database across a network.
- Embodiments may be provided as a computer program product including a machine-readable medium having stored thereon instructions that may be used to program a computer (or other electronic device) to perform processes described herein.
- the machine-readable medium may include, but is not limited to, hard drives, floppy diskettes, optical disks, CD-ROMs, DVD-ROMs, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, solid-state memory devices, or other types of media/machine- readable medium suitable for storing electronic instructions.
- FIG. 1 is a block diagram illustrating a first intelligent electronic device (IED) 100 used in a power system and configured in certain embodiments to provide sampled data and information for resampling the data to a second IED.
- the first IED 100 may be used, for example, in the power system's protection, automation, control, and/or metering applications to gather analog data directly from a conductor (not shown) using a current transformer 104 and/or a voltage transformer 106.
- the voltage transformer 106 may be configured to step-down the power system's voltage (V) to a secondary voltage waveform 108 having a magnitude that can be readily monitored and measured by the first IED 100 (e.g., to step-down the distribution line voltage from approximately 13kV to approximately 120 V).
- the current transformer 104 and a resistor 109 may be configured to proportionally step-down the power system's line current (I) to a secondary current waveform 110 having a magnitude that can be readily monitored and measured by the first IED 100 (e.g., to step-down the distribution line current from approximately 200 amps to approximately 0.2 amps).
- Low pass filters 114, 116 respectively filter the secondary current waveform 110 and the secondary voltage waveform 108.
- An analog-to-digital converter 120 then multiplexes, samples and digitizes the filtered waveforms to form a corresponding digitized current and voltage signals 124.
- the digitized current and voltage signals 124 are received by a microcontroller 130 configured to perform digital signal processing.
- the microcontroller 130 may use Cosine filters to eliminate DC and unwanted frequency components from the digitized current and voltage signals 124.
- the microcontroller 130 includes a central processing unit (CPU) or microprocessor 132, a program memory 134 (e.g., a Flash EPROM), and a parameter memory 136 (e.g., an EEPROM).
- CPU central processing unit
- microprocessor 132 e.g., a Flash EPROM
- a parameter memory 136 e.g., an EEPROM
- other suitable microcontroller configurations may be used.
- FPGA field-programmable gate array
- ASIC application specific integrated circuit
- the microprocessor 132 by executing a computer software program or logic scheme, processes the digitized current and voltage signals 124 to extract phasors representative of the measured secondary voltage waveform 108 and the secondary current waveform 110. The microprocessor 132 then performs various calculations and digital signal processing algorithms using the phasors. The microprocessor 132 may also provide outputs 140 based on the results of the calculations and digital signal processing.
- the first IED 100 is also configured to transmit the digitized current and voltage signals 124 for further signal processing and/or resampling.
- the first IED 100 is configured to transmit information with the digitized current and voltage signals 124 to assist with resampling.
- the first IED 100 may be configured to transmit an index representing a predetermined sampling time instant, a time stamp with an encoded time instant, and/or other information described herein for use by another IED to resample the digitized current and voltage signals 124.
- an artisan will recognize from the disclosure herein that the first IED 100 shown in FIG.
- FIG. 2 is a block diagram of a system 200 for resampling transmitted data according to one embodiment.
- the system 200 includes a transmit data component 210, a communication channel 212, a receive data component 214, a resample data component 216, and a further processing component 218.
- the transmit data component 210 is located in a first IED (e.g., the first IED 100 shown in FIG. 1) and the receive data component 214, resample data component 216, and the further processing component 218 are located in a second IED (e.g., the second IED 300 shown in FIG. 3).
- the first IED 100 is configured to sample data at a first sample rate and the second IED 300 is configured to resample the data at a second sample rate.
- the first and second sample rates may or may not be equal.
- the transmit data component 210 is configured to transmit sampled data 220 through the communication channel 212, to the receive data component 214.
- the communication channel 212 may include, for example, a direct connection (e.g., through a universal serial bus (USB) or the like), a local area network (LAN), a wide area network (WAN), a Public Switched Telephone Network (PSTN), a cable television (CATV) network, the Internet, or other connection services and network variations such as the world wide web, the public internet, a private internet, a private computer network, a secure internet, a private network, a public network, a value-added network, combinations of the foregoing, or the like.
- USB universal serial bus
- PSTN Public Switched Telephone Network
- CATV cable television
- the data is communicated through the communication channel 212 in accordance with International Standard IEC 61850 Part 9, Section 2.
- the receive data component 214 is configured to receive the sampled data 220 from the communication channel 212 and to provide the sampled data 214 to the resample data component 216.
- the resample data component 216 is configured to resample the sampled data 220 and to provide resampled data 222 to the further processing component 218.
- the further processing component 218 generically indicates any other processing of the resampled data 222 or other functionality that is encompassed in the second IED 300 or another device.
- the second IED 300 is a block diagram illustrating a second IED 300 configured to receive sampled data 220, resample the sampled data 220, and process resampled data 222 according to one embodiment.
- the second IED 300 may receive the sampled data 220 through the communication channel 212.
- the second IED 300 includes a microcontroller 330 that includes a central processing unit (CPU) or microprocessor 332, a program memory 334 (e.g., a Flash EPROM), and a parameter memory 336 (e.g., an EEPROM).
- CPU central processing unit
- program memory 334 e.g., a Flash EPROM
- a parameter memory 336 e.g., an EEPROM
- the microcontroller 330 includes the receive data component 214, the resample data component 216, and the further processing component 218 discussed above.
- the resampling may provide any arbitrary ratio of output to input rates, from a downsampling relationship, to an upsampling relationship, and with integer or non-integer ratios.
- Example resampling methods are discussed in detail below. Various of the resampling embodiments are described in terms of a communication system, but the present disclosure is not so limited.
- example methods are provided for resampling data sent from a transmitter to a receiver.
- the transmitter includes the transmit data component 210 discussed above.
- the transmitter includes the first IED 100 shown in FIG. 1.
- the receiver includes at least the receive data component 214 and the resample data component 216 discussed above.
- the receiver includes the second IED 300 shown in FIG. 3.
- the receiver may also include the further processing component 218 discussed above.
- sampling time instants are synchronized between the transmitter and the receiver. In other embodiments, the sampling time instants are not synchronized between the transmitter and the receiver.
- data is sampled at time intervals that are predetermined between the transmitter and the receiver.
- Synchronization may include the use of synchronized clocks in both the transmitter and the receiver to correlate data sampled at a particular time instant at the transmitter with sampled data received at the receiver.
- the transmitter and the receiver may each include an internal clock synchronized with a global positioning system (GPS) time standard.
- GPS global positioning system
- the transmitter is configured to assign an index value to each data sample and to transmit the index values to the receiver with the sampled data. Each index represents one of a plurality of the predetermined sampling time instants.
- the sampling time instants are encoded as time stamps and the transmitter is configured to transmit the time stamps to the receiver with the sampled data.
- the receiver uses the received index values or time stamps to correlate the received sampled data with the respective time instants based on the synchronized GPS time.
- the receiver may then resample the received data at a predetermined or user-selected resampling rate.
- Synchronized Index Values [0044] Providing an index representing a sampling time instant requires less communication bandwidth than that required for conventional communication systems that use, for example, equalization filtering, error correction codes and/or repeated transmission handshakes.
- an index representation size may be limited according to certain embodiments by allowing the index to roll over at predetermined time instants. For example, the index may start counting from a zero value at a first one second instant and may continue counting at the receive data rate until the next one second instant, at which time it again is assigned a zero value.
- the predetermined time instants are not limited to one second intervals and that any predetermined interval, including fractions or multiples of a second, may be used.
- FIGS. 4A and 4B are block diagrams of the resample data component 216 shown in FlG. 2 configured to resample data using index values sent from the transmitter to the receiver according to one embodiment.
- the resample data component 216 includes an assign count value component 410, an assign data component 412, an interpolate component 414, and a random access memory (RAM) 416. While the RAM 416 is shown as the memory device in this and other embodiments disclosed herein, an artisan will recognize that any other read-writable media may also be used. Some example memory devices include magnetic disk drive storage or FLASH memory.
- the resample data component 216 according to this embodiment also includes a count value generator component 418. [0046] (i) Assign Count value
- the assign count value component 410 assigns a count value (generated by the count value generator 418 illustrated separately in FIG. 4B) associated with a time input value.
- the time input value is synchronized with the transmitter and may be communicated and encoded, for example, with Inter Range Instrumentation Group (IRIG) time codes.
- IRIG Inter Range Instrumentation Group
- the time input value does not necessarily have to be communicated over the same channel as the sampled data. Further, the time input value does not necessarily have to be an absolute global (e.g., GPS) time, as long as the time is synchronized between the transmitter and receiver. Fixed errors (such as, for example, the transmitter being in a different time zone) in the time input value between the transmitter and receiver may be easily corrected, as is known in the art.
- the count value generator 418 is configured to generate the count value provided to the assign count value component 410 and the interpolate component 414.
- the count value generator 418 counts at a faster rate relative to a received data rate and includes a rollover time that is longer than a maximum interpolation interval.
- the assign count value component 410 monitors the time input value and latches the count value to its output for storage in the RAM 416 each instant that the time input value equals one of a plurality of predetermined sampling time values.
- the assign count value component 410 also generates an index that it stores in the RAM 416 with the associated count value.
- the RAM 416 comprises a data structure (see FIG. 7) that includes an expected receive index and a validation bit. Due to the synchronization, the index stored by the assign count value component 410 matches the expected receive index for the corresponding predetermined sampling time. Because the count value is not associated with a received data sample when the assign count value module 410 stores it in the RAM 416, the assign count value block 410 simultaneously invalidates the validation bit. [0050] (ii) Assign Data
- the assign data component 412 receives a datain signal that includes sampled data and a corresponding index value.
- the datain signal may be received, for example, by the receive data component 214 shown in FIG. 2.
- the assign data component 412 is configured to search the RAM 416 using a search algorithm to locate an index value stored by the assign count value component 410 that corresponds to the index value received in the datain signal.
- the assigned data component 412 then stores the sampled data in the RAM 416 at a location that corresponds to the stored index value that matches the received index value.
- the assign data component 412 then validates the validation bit.
- the assign data component 412 may invalidate the validation bit if the communication channel 212 had an uncorrectable error for the sampled data. In addition, or in another embodiment, the assign data component 412 may use an expanded set of valid information to store information regarding the sampled data's confidence. [0052] In certain embodiments, it is not required that the data from the datain signal arrive in any particular order. The search ⁇ algorithm properly orders the data regardless as to the order in which it was received. To be used for resampling or further processing, the assign data component 412 stores the data in the RAM 416 prior to the interpolation step discussed below. However, data that is delayed such that it is not stored in the RAM 416 before the interpolation step, or data that is otherwise missing during the interpolation step, is automatically accounted for in the interpolation algorithm by increasing an interpolation step interval.
- FIG. 7 shows a possible arrangement of the data in the RAM 416 for the case when each received index corresponds to a set of four data.
- each row corresponds to one set of receive data from the receive data component 214 shown in FIG. 2.
- each data in the set has its own related validation bit.
- each row includes four slots for data, and corresponding four spots for the related valid bit, count value, and index. This allows each data to be interpolated according to the surrounding data that is valid.
- the system may assert a samplejiow signal. This may occur at any arbitrary rate or time instant. For example, the system may assert the sample_now signal at a rate corresponding to an upsampling or a downsampling rate.
- the interpolate component 414 records the count value generated by the count value generator 418.
- the receiver may generate the samplejiow signal in response to a predefined system resampling ratio.
- the system may not specifically require a separate samplejiow signal, but could instead use another control mechanism, as is known in the art, to control the interpolation at the desired output sampling rate.
- an entire sequence of resampled outputs may be generated simultaneously by simply indicating to the interpolate component 414 a series of time stamps (as discussed below) or index values with associate count values for each of the resampled outputs.
- the interpolate component 414 modifies the recorded count value to insert a fixed delay. By setting a fixed delay, the effect of a variable delay of the communication channel 212, through which the data is transmitted, is reduced or eliminated. As discussed above, the fixed delay in some embodiments is sufficiently long so as to allow for the arrival of out-of-order data such that the appropriate data may be used in the interpolation.
- the interpolate component 414 searches the RAM 416 for a pair of count values stored by the assign count value component 410 that straddle the count value recorded by the interpolate component 414 in response to the samplejiow signal.
- the pair of count values according to certain embodiments are the count values that are closest in time before and after the count value recorded in response to the samplejiow signal. However, if data was lost in the communication channel 212, then count values stored by the assign count value component 410 that are further apart can also be used. Once the pair is found, then the interpolate component 414 applies one of several known interpolation algorithms to determine a data value at a time instant corresponding to the sample_now signal.
- a Taylor Series approximation truncated to the linear term performs the interpolation as follows, and is illustrated in FIG. 6: where: y[T] is the desired data value and is associated with sample_now; x[l] is the data value associated with the datain value with a count value less than the count value associated with samplejiow; x[Ty] is the data value associated with the datain value with a count value greater than the count value associated with samplejiow;
- T is the count value associated with sample_now; T, is the count value associated with the data value x[T,]; and, J, is the count value associated with the data value x[T ; ].
- Some other examples of algorithms to estimate the y[T] value include fitting using more than two values, nearest neighbor interpolation, Neville's algorithm, and the like.
- the interpolate component 414 then exports a dataout signal that includes the data value at the time instant corresponding to the sample_now signal.
- the dataout signal may be referred to herein as data resampled from the sampled data available to the receiver.
- FIGS. 8A, 8B and 8C are flow charts illustrating a method for resampling data using synchronized index values according to one embodiment. The method illustrated in FIGS.
- FIG. 8A illustrates an assign count value process 810 that begins by generating 812 a count value.
- the count value may be generated using a count value generator as described above.
- the assign count process 810 then assigns 814 the count value by associating it with a predetermined time input value, which is synchronized between a transmitter and a receiver of sampled data.
- the assign count value process 810 then generates 816 an index and stores 818 the index and count value in RAM.
- the assign count value process 810 then invalidates 820 a validation bit corresponding to the saved index and count values.
- the assign data process 822 includes receiving 824 data from the transmitter.
- the data includes sampled data as well as an index value.
- the assign data process 822 searches 826 the RAM for a stored index value that corresponds with the received index value.
- the assign data process 822 also queries 828 whether the search algorithm finds the corresponding index value. If a stored index value is found, the assign data process 822 stores 830 the sampled data corresponding with the received index value along with the count value and validation bit in the RAM.
- the assign data process 822 sets 832 (validates) the validation bit. If a stored index value is not found, the assign data process 822 discards 834 the received data.
- the table includes sets of information, each set including a count value, an index value, the received sampled data (if data is received for the corresponding count value), and a validation bit that is set if the set of information is valid.
- FIG. 8C illustrates an interpolation process 836 for generating resampled data.
- the interpolation process 836 begins by receiving 838 a sample_now signal. In response to the sample_now signal, the interpolation process 836 records 840 a count value.
- the count value may be corrected for inaccuracies such as, for example, for communication channel latencies, or the like.
- the count value correction may be performed by subtracting a fixed number of count values from the recorded count value. Where the count value is corrected for a communication channel latency, the fixed number of count values that is subtracted may correspond with the channel delay in units of count values.
- the interpolation process 836 includes searching 842 the RAM for a set of information that includes a count value that corresponds to the recorded count value.
- the interpolation process 836 queries 844 whether the search finds a valid set of information (e.g., querying whether the validation bit is set). If the search 842 yields a matched count value and the validation bit is set, then the interpolation process 836 uses 846 the corresponding data value in that set of information in a dataout signal.
- the interpolation process 836 searches 848 the RAM for two sets of information with count values that straddle the recorded count value, and which both have valid sets of information (the validation bit is set). That is, sets of information with the validation bit not set are ignored. Once the two valid sets of information are found with count values that straddle the recorded count value, the interpolation process 836 interpolates 850 the data in the two valid sets of information to calculate a data point corresponding to the recorded count value. The interpolation process 836 then uses 852 the interpolated data for the dataout signal. It should be noted that the dataout signal may be used within the same microprocessor/FPGA in which the interpolation process takes place, or within another microprocessor, FPGA, or IED. [0069] 2. Synchronization with Time Stamps
- the transmitter encodes the sampled data's sampling time instant as a time stamp and transmits the time stamp with the sampled data to the receiver.
- FIG. 5 is a block diagram of the resample data component 216 shown in FIG. 2 configured to resample data using time stamps according to one embodiment.
- the sampling time instant is communicated directly with the sampled data, and does not use an index.
- the resample data component 216 according to this embodiment includes an assign time component 510, an assign data component 512, an interpolate component 514, and a RAM 516.
- the assign time component 510 When the sample_now signal asserts, the assign time component 510 outputs the corresponding time input value. Similar to the embodiment discussed above in relation to FIGS. 4A and 4B 1 the time input value is synchronized between the transmitter and the receiver and may be communicated and encoded using, for example, IRIG. The time input value does not necessarily have to be communicated over the same channel as the data. Further, the time input value does not necessarily have to be an absolute global time, as long as the time is synchronized between the transmitter and receiver. Fixed errors errors (such as, for example, the transmitter being in a different time zone) in the time input value between the transmitter and receiver may be easily corrected, as is known in the art. [0073] ( ⁇ ) Assign Data
- the assign data component 512 receives a datain signal that includes sampled data and a corresponding time stamp.
- the datain signal may be received, for example, by the receive data component 214 shown in FIG. 2.
- the assign data component 512 is configured to store the sampled data along with its time stamp in the RAM 516.
- the assign data component 512 stores the sampled data at a location that corresponds to the time stamp value received.
- the assign data component then validates a validation bit. [0075] (iin Interpolate
- the interpolate component 514 is configured to perform similar functions as the interpolate component 414 shown in FIG. 4A. However, when the sample_now signal asserts, the interpolate component 512 uses the corresponding time input value provided by the assign time component 510 as the value against which to compare the time stamps stored in the RAM 516. As discussed above, the RAM 516 includes time stamps rather than index values or count values.
- FIGS. 9A and 9B are flow charts illustrating a method for resampling data using time stamps according to one embodiment. The method illustrated in FIGS.
- FIG. 9A illustrates an assign data process 910 that begins by receiving 912 sampled data with a corresponding time stamp from a receiver.
- the assign data process 910 then stores 914 the sampled data along with the time stamp in a RAM at a location corresponding to the time stamp.
- the RAM includes the time-stamped sampled data, along with a validation bit.
- the assign data process 910 sets 916 the validation bit when it stores the sampled data.
- FIG. 9B illustrates an assign time and interpolate process 918 that begins with receiving 920 a sample_now signal.
- the process 918 records 922 a corresponding time value.
- the time value may be shifted to, for example, account for communication channel latencies. The shift may be performed by subtracting a fixed value from the time value. Where the time value is corrected for a communication latency, the fixed value may correspond with the channel delay.
- the process 918 searches 924 the RAM for stored data with a time stamp that corresponds with the time value.
- the process 918 queries 926 whether the search finds data with a corresponding time stamp.
- the process 918 uses 928 that data as the resampled data, as above, in a dataout signal. [0080] If, however, no data with the corresponding time stamp is found, then the process 918 searches 930 the RAM for time stamps that straddle the recorded time value. As above, the process 918 uses the data if the validation bit is set. The process 918 then interpolates 932 a data point corresponding to the recorded time value using the straddling recorded time values. The process 918 then uses 934 the interpolated data point for the dataout signal. [0081] (v) Example Time Stamp Embodiment Using Less Storage
- the processes 910, 918 discussed above with respect to FIGS. 9A and 9B are modified to reduce the receiver's storage requirements.
- the assign data process 910 receives 912 the sampled data with the corresponding time stamp from the receiver.
- the receiver rather than storing 914 the sampled data along with the time stamp, the receiver generates a count value from the time stamp and stores the count value in the RAM.
- the receiver uses the count value as an intermediary to the full time stamp value and the storage requirements of a full time stamp value are reduced.
- the RAM is searched (e.g., steps 924 and/or 930) for corresponding count values rather than corresponding time stamps.
- the sampling time instants are not synchronized between the transmitter and the receiver.
- the transmitter is not required to send an index or time stamp with the sampled data.
- the receiver is configured to use arrival time instants of the received data to provide sampling time information used for resampling.
- the synchronization between the transmitter and the receiver may be lost or may become inaccurate over time. For example, clocks in the transmitter and receiver may slowly drift with respect to each other such that an index sent by the transmitter no longer corresponds to the time value expected by the receiver.
- the receiver is configured to adjust the index received from the transmitter to account for the unsynchronized time condition between the transmitter and the receiver.
- the time keeping mechanism e.g., clock
- the receiver uses the arrival time instants of the received data to provide sampling time information to the resample data component 216 shown in FIG. 2. As discussed above, this embodiment does not require the datain signal (see FIGS. 4A and 5) to include an index or a time stamp. In this embodiment, the receiver takes the arrival instant of the datain signal to represent the time of the datain sample instant.
- the datain signal in one embodiment may include an array of data, with missing data marked as such or represented using an illegal encoding value.
- the receiver time-stamps the data at each arrival instant with a time corresponding to the time at the receiver (as received by the time input value) at that arrival instant.
- the sampling times are determined in advance and agreed between the transmitter and receiver.
- the receiver may snap the datain arrival time value to the nearest corresponding predetermined sampling time.
- the time input value is not synchronized between the transmitter and receiver.
- the receiver may filter the datain arrival time instants with a phase locked loop (PLL), as is well-known in the art.
- PLL phase locked loop
- Such a PLL removes jitter due to the transmitter and communication channel.
- the receiver may snap the arrival time instants to the nearest PLL generated expected arrival time instant.
- Such a PLL also generates the time interval in between samples for use with an interpolation algorithm. The receiver may then interpolate the received data and/or provide the data for further processing as described above.
- the index values discussed above are modified to account for an unsynchronized time condition between the transmitter and receiver. Such an embodiment may be appropriate, for example, when the time input value is not synchronized between the transmit data component 210 and the receive data component 214 shown in FIG. 2. Thus, the time input value does not need to be common between the transmitter and the receiver. In certain such embodiments, the receiver may continue resampling in spite of the fact that the relative time between the transmitter and the receiver is no longer synchronized (e.g., the respective clocks in the transmitter and receiver may be slowly drifting with respect to each other). [0089] Referring again to FIG.
- the assign count value module 410 is configured to adjust the index value by an offset value approximately equal to the difference between the received index value and the index value generated by the assign count value module 410. This realigns the generated index values to match those that are received and allows the resampling operations to continue.
- the offset value may be updated periodically based on the shift of the index values in the RAM 416, continuously after application of a filtering algorithm, or at some other time based on an overall goal of keeping the index values received and the index values generated close enough to each other in range to allow matches to be found in the RAM 416 and the resampling to be continued.
- the offset value provides an ability to monitor the unsynchronized condition between the transmitter and the receiver. [0090] 3.
- the receiver's time keeping mechanism e.g., clock
- the receiver uses the arrival times of the sampled data to update the time at the receiver, instead of using the time input value.
- the arrival times of the sampled data effectively become the time input value.
- a PLL or filter may be used to reduce network jitter, as is known in the art.
- basing the receiver's time on the arrival time instants of the received data effectively slaves the receiver's time stamps themselves to the arrival times. After updating the receiver time in this manner, the resampling and further processing continues according to any of the above embodiments.
- FIG. 10 is a flow chart illustrating a method 1000 for resampling data by basing a receiver's time stamp on an arrival time instant according to one embodiment.
- the method 1000 includes receiving 1010 data from a transmitter, associating 1012 the received data with a time stamp based on the arrival time instant of the data, storing 1014 the data in a RAM at a location corresponding to the time stamp, and setting 1016 a validation bit.
- the method 1000 may further process the data using the time and interpolation process 918 shown in FIG. 9B.
Abstract
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MX2009000606A MX2009000606A (en) | 2006-08-22 | 2007-08-22 | Systems and methods for resampling unreliable data. |
BRPI0715608-1A BRPI0715608A2 (en) | 2006-08-22 | 2007-08-22 | Method for re-sampling a signal received via a communication channel, data re-sampling system, and machine readable storage |
CA2661167A CA2661167C (en) | 2006-08-22 | 2007-08-22 | Systems and methods for resampling unreliable data |
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US11/894,357 US7583771B2 (en) | 2006-08-22 | 2007-08-21 | Systems and methods for resampling unreliable data |
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Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20020184277A1 (en) * | 2001-05-02 | 2002-12-05 | Ke-Chiang Chu | Resampling system and apparatus |
US7203718B1 (en) * | 1999-10-29 | 2007-04-10 | Pentomics, Inc. | Apparatus and method for angle rotation |
US20070219751A1 (en) * | 2006-03-17 | 2007-09-20 | Jonathan Huang | Sensor network data alignment with post-process resampling |
-
2007
- 2007-08-22 WO PCT/US2007/018556 patent/WO2009025641A1/en active Application Filing
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7203718B1 (en) * | 1999-10-29 | 2007-04-10 | Pentomics, Inc. | Apparatus and method for angle rotation |
US20020184277A1 (en) * | 2001-05-02 | 2002-12-05 | Ke-Chiang Chu | Resampling system and apparatus |
US20070219751A1 (en) * | 2006-03-17 | 2007-09-20 | Jonathan Huang | Sensor network data alignment with post-process resampling |
Non-Patent Citations (1)
Title |
---|
SEL-421: "High-Speed Line Protection, Automation, and Control System", SEL CELEBRATING 25 YEARS IF INNOVATION, 9 July 2001 (2001-07-09), Retrieved from the Internet <URL:http://www.selinc.com> * |
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