Patent Application
20070067360
This invention relates to communication of metadata from a test probe to a receiver and more particularly to a system and method for communicating the metadata in a manner to reduce bandwidth and conserve power.
Test and measurement systems utilize multiple probes (sensors) that produce and consume various types of data. Probes vary greatly from one to another. For example, probes can measure different parameters, or use different units of measurement for the same parameter. It is important that when using data from a probe, the user (usually a test system) know what parameters, such as units of measurement, uncertainty of the measurement, description, name, data type, etc., the probe is using. In some systems, a new probe can come ‘online’ and the existing measurement system may not know what the sensor's parameters are. In some situations, the sensor may change parameters and this change must be communicated to the measurement system. Ideally, the sensor would communicate to the system using metadata to indicate the parameters of the data. This metadata is sent in addition to the measurement data from the probe.
However, as probe become smaller and less expensive it is common for the communication channel to be either very low bandwidth or for the sensor to have limited power. That is, the device can only send a small amount of data at any one time. The probe may additionally be constrained to only transmit data and may lack the capability of receiving data from the measurement system.
Traditional solutions either embed the metadata with every transmission (making the data self-describing) or they employ some type of query/response protocol allowing the system to discover and query the probe for various types of metadata that may be needed by the measurement system.
For example, a probe that produces an integer temperature reading every 10 seconds may have metadata that is several hundred times as large (in terms of bytes) as the measured temperature itself. When sending only the data, the probe can get by with a lower bandwidth/lower power communication scheme than it could if it had to send all the metadata with every reading. One solution is to have any measurement receiving device query the probe for its metadata so the probe does not have to send the metadata very often. However, this will not work if the probe is transmit only, or if the probe has a lot of different metadata to send, or if the probe has bandwidth constraints.
In one embodiment, measurement probes are designed to provide metadata to a measurement system in an opportunistic manner. The opportunistic period can be, for example, when actual data transmission can be skipped, or when battery level is high, or when there is enough bandwidth such as when other probes are not using the full allocated bandwidth.
In one embodiment, a plurality of substantially similar probes are arranged to send only a portion of their data such that all the portions taken together form a complete metadata for all of the probes. In another embodiment, each probe only sends an identification of its type and the receiving device retrieves the full metadata from a database.
As an example, consider that probe 20-1 has twenty discrete pieces of metadata that a data collection system, such as data collection system 11, requires to properly store and to utilize measurements from probe 20-1. Probe 20-1 could, for example, allocate 0.1% of its power or communication bandwidth to metadata and send a piece of metadata after every 1000th measured data transmission message. Accordingly, after 20,000 measurements have been communicated to data collection 101, perhaps for storage in data storage 102 under control of processor 101, all of the metadata would also have been communicated with a very small impact on power or bandwidth.
In the embodiment of
One side effect of this strategy is that data collection 11 may receive a piece of data (or several pieces of data) from one or more sensors without knowing what the data really means, i.e., without the parameters obtained from metadata. In such a case, data collection 11 would store the data and then wait some random amount of time to obtain enough metadata from the probe(s) to know what to do with the stored data. This is compatible with existing implementations where the metadata is queried from a sensor when new sensor data is received. The main difference is that in the system being described the latency between receiving the data and obtaining enough metadata is unknown. However, in the long run, the metadata is eventually delivered and the system can utilize the metadata when it arrives.
Control units 201-206 allow various opportunistic metadata transfers, with each such metadata transfer usually being less than all of the metadata necessary for a data collected in a device, such as device 11
One criteria the system could use when sending metadata would be to send some metadata only when the current collected data reading is the same as a previous data reading. Thus, instead of sending the same readings over and over, the probe, under control, for example, of skip data control 202, would use the energy to send metadata instead.
If desired, metadata could be trickled out a small bit at a time, with each measurement, for example, under control of schedule control 203, so the metadata only consumes a small amount of extra bandwidth or the metadata could be sent in atomic chunks or it could be broken up into small pieces and reassembled by data collector 11,
As shown in
In some situations, combinations of metadata transfer can be used. For example, to eliminate database (or server) overload on startup, or when a high number of probes are added, some metadata could come from the probes in an opportune manner as discussed above and some metadata can be retrieved from the database as a result of an ID.
If process 302 determines there is not enough metadata already received then, process 303 determines if the received metadata portion is an ID (or points toward a server, etc.) then process 305 obtains the metadata (or the equivalent thereof). If the information received is not an ID then the metadata portion is stored by process 304. This mechanism could. also be used as a need determined acceleration of metadata retrieval. In other words, metadata can “trickle in” as noted in paragraph [0018] above until a measurement need arises where the complete metadata is necessary.
If process 302 determines that enough metadata is available for this probe such that the measured data can be further processed properly (or if metadata is available from process 305), then process 306 determines if there is stored measured data from this probe. If there is, then that data is retrieved via process 307 and all the data obtained from the sensor is processed by process 308.
Note that in this context further processing can take place at the data collection point or at other points in the system, not shown and includes manipulation of the data, storage of the data, together with its proper parameters (units of measurement, etc) or passing some or all of the data to a other locations together with the data's proper parameters.
Process 404 determines if there is enough metadata to perform proper processing of the received measured data. In this context, proper processing is any use of the measured data for any purpose where the use is dependant upon the system obtaining parameters of the data via the metadata associated with the probe from which the measured data is received.
If there is not enough metadata received then process 40 continues until there is enough. When enough metadata is retrieved, then process 406 retrieves the stored measured data proceeds to process the stored measured data.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
