WO2020244831A1

WO2020244831A1 - Method and apparatus for precise power and energy consumption measurements of communication modems

Info

Publication number: WO2020244831A1
Application number: PCT/EP2020/059491
Authority: WO
Inventors: Peter Müller; Thomas Fliess
Original assignee: Commsolid Gmbh
Priority date: 2019-06-07
Filing date: 2020-04-03
Publication date: 2020-12-10

Abstract

The invention discloses a method and an apparatus for precise power and energy consumption measurements of communication modems during operation. The objective of the invention to provide a method and an apparatus which supports a sufficient dynamic range for current measurement of current drawn by a communication modem is solved by an apparatus performing the method for precise power and energy consumption measurements of communication modems during operation comprising a device under test (DUT) to become configured an tested in various test scenarios to measure its power and energy consumption, a power supply configured to power the DUT and a measurement unit configured to measure a provided voltage to the DUT by the power supply and a current drawn by the DUT, wherein the apparatus further comprises a radio communication tester configured to derive an operation mode of the DUT or to create a desired power and energy scenario for the communication modem and a measurement control unit for dynamically selecting one shunt resistor of at least two shunt resistors, whereas the selection of the shunt resistor is based on the estimation of the current drawn by querying the operation mode of the DUT or the desired power and energy scenario either directly from the DUT or indirectly either from the radio communication tester or a base station of a live network to which the DUT is connected to.

Description

Method and apparatus for precise power and energy consumption measurements of communication modems

The invention relates to a method and an apparatus for precise power and energy consumption measurements of communication modems during operation.

The power consumption measurement comprises generally a current and a voltage measurement. To measure the energy a device under test (DUT) is consuming for a dedicated task or over a dedicated time period with some predefined states, the power consumption must be monitored over a defined time period .

Measuring the voltage is not critical as the voltage is supposed to be constant, or in case a battery is used the voltage variation is quite small.

The range of the current to be measured is much wider; it is in a range of 0.2mA to 500mA. There are quite some solutions in the state-of-the-art known to deal with this problem. A common approach to dynamically measure and log current drawn by DUT are shunt resistors in the current path and data loggers or scopes to measure the voltage over these shunt resistors as it is illustrated in figure 1. The current consumed by the DUT can be calculated by I = Ui / R_Shunt and the power consumed by DUT can be calculated by P = U2*I.

A similar principle to measure dynamic currents uses current probes that have a shunt resistor built in together with oscilloscopes. Another approach is to statically or quasi

- statically measure currents with multimeters or special power supplies with some sort of data logging. Here, the sensitivity is increased and may be enough but dynamic measurements for dedicated procedures e.g. the attach process or the dynamic switch to power save are not really doable .

More sophisticated implementations (like in R&S Probe RT-ZVC A series) a feature so-called auto-ranging where the measurement equipment switches for instance its internal analog gains over time to obtain a wider dynamic range than the analog-to-digital converter would natively provide. Pre requisite for such auto-ranging is that the current changes of the DUT do not happen too fast and switching circuitry does not impact measurement accuracy too much. The latter limits the available dynamic range, e.g. in Keysight N6782A where the lowest measurement range is not available for auto-ranging or in R&S RT-ZVC where the resulting

measurements possess a high noise in the lowest range.

The invention deals with the problem of dynamic measurement of currents with high dynamic range from 0.2mA to 500mA or even higher.

Internet-of-Things (IoT) devices are rather new. Currents to be measured to determine the device power consumption possess a high dynamic range. A state-of-the-art IoT device requires supply currents of several 100mA during active radio transmissions, several 1mA during active radio reception or activities on application processor, and down to a few lOOnA during sleep phases.

These are different operation modes of the IoT devive (UE) . Since sleep phases are much longer than phases with activity in most use cases, total energy consumed in sleep phases may dominate the entire energy budget. Hence, it is necessary to measure very small sleep currents with high accuracy. At the same time, the measurement setup must support maximum supply currents for active transmissions since test

scenarios, e.g. DUT in live network operation, usually include phases with active radio transmissions. Live network operation is understood to mean that the device under test (DUT) is operated in a public telecommunications network that is provided by a commercial service provider.

Particularly challenging for autonomous power measurement is that an IoT device changes its state of operation at times unknown to the power measurement equipment. On top, the corresponding change of supply current can happen very fast, e.g. within a few micro seconds.

Dynamic range of current measurement equipment is determined on the upper end by the maximum amount current it can support and on the lower end by resolution of Analog-to- Digital converter (ADC) and the amount of various kinds of noise and unknown offsets which is introduced by wiring, analog circuitry etc.

With present solutions on the marked, R&S Probe RT-ZVC4 series, the Nordic Data Logger, multimeters or quasi static power supplies e.g. Keysight N6782A, etc. the full dynamic range is not supported with existing auto-ranging

implementations .

These either support limited dynamic range in time-variant operation or static measurements where the DUT is put into a dedicated state or operation mode (e.g. sleep mode) that is not changing while the current is measured.

The objective of the invention is to find a solution which helps to overcome this problem, hence to provide a method as well as an apparatus which support sufficient dynamic range for the current measurement of current drawn by a

communication modem which is the device under test (DUT) .

The objective of the invention is solved by a method for precise power and energy consumption measurements of communication modems during operation, the method comprising the following steps:

- querying information of an operation mode or a power and energy scenario of a device under test (DUT) , either

- directly from the DUT, or

- indirectly either from a radio communication tester, or

- a base station (eNodeB) of a live network to which the DUT is connected to, whereas

- depending on the queried information a measurement control unit of the communication modem dynamically selects one shunt resistor of at least two shunt resistors for

increasing a dynamic range of power consumption

measurements for dynamic DUT operation.

Before measuring the current drawn of the DUT, the expected measured value is estimated by querying information in which state the DUT is at the time of measurement. This can be realized either by querying the information directly from the DUT about its operation mode/state or indirectly if the DUT, for example is in a sleep mode and cannot by directly reached. So, 'indirectly querying' in the sense of this invention means that in a first variant the information about the operation mode/state of the DUT can be obtained by a radio communication tester which knows the operation mode of the DUT due to instructions the radio communication tester has given to the DUT. Or in a second variant the information about the operation mode/state of the DUT can be obtained from a base station of a live network to which the DUT is connected to, whereas for the second variant a recording means is used for recording the communication instruction between the base station and the DUT and to derive thereof the operation mode/state of the DUT. This allows flexibly adapting the configuration for testing to the expected (current) measured value and thus achieves very high measurement accuracy. With the inventive method it is possible to adapt the measurement accuracy according to the different variants of the application of a communication modem/DUT .

In a variant of the inventive method, the measurement control unit uses the queried information and a look-up table for estimating how much current the DUT is drawing and selecting the appropriate shunt resistor. This has the advantage to dynamically change the value of the shunt resistor while the measurement and the DUT are running, depending on the current to be measured. So, for high currents a small resistance is preferred while for low currents a higher (known) resistance is selected.

In another variant of the inventive method, a measurement unit measures a provided voltage to the DUT by a power supply and a current drawn by the DUT. According to the results and the derived operation mode, the measurement control unit selects the appropriate shunt resistor to provide an adequate and high dynamic range for every operation state of the DUT .

The objective of the invention is also solved by an

apparatus for precise power and energy consumption

measurements of communication modems during operation which is able to perform the inventive method according to the method claims, the apparatus comprising a device under test (DUT) to become configured and tested in various test scenarios to measure its power and energy consumption, a power supply configured to power the DUT, and a measurement unit configured to measure a provided voltage to the DUT by the power supply and a current drawn by the DUT, wherein the apparatus further comprises a radio communication tester configured to derive an operation mode of the DUT or to create a desired power and energy scenario for the

communication modem, and a measurement control unit for dynamically selecting one shunt resistor of at least two shunt resistors, whereas the selection of the shunt resistor is based on the estimation of the current drawn of the DUT by querying the operation mode of the DUT or the desired power and energy scenario either directly from the DUT or indirectly either from the radio communication tester or a base station (eNodeB) of a live network to which the DUT is connected to.

So, on the one hand the DUT can be queried directly about its state/operation mode. On the other hand the radio communication tester can be queried about the DUT operation mode/status or communication scenario, which means in an indirect way, as the radio communication tester signals the DUT to do a state transition (e.g. from active mode to sleep mode) if possible and/or required by the selected

communication scenario. Measuring of power consumption for communication devices is done by measuring the provided voltage and the current drawn by the device. The voltage can be measured directly by at least an Analog-to-Digital converter. Current measurement is typically conducted by converting the current into a voltage by a known shunt resistor and then measuring the voltage across that shunt resistor.

While the voltage is quite constant the dynamic range of the current drawn is usually very high. Therefore, the shunt resistor must be selected in a way that it provides enough voltage at the lowest current to be measured. At the highest current to be measured, the voltage drop due to the shunt resistor shall not affect the system operation and health. This limits the dynamic range of the current that can be measured with one shunt resistor.

The idea of the invention is to dynamically change the value of the shunt resistor while the measurement and the DUT are running, depending on the expected current to be measured. The expected current is directly linked to the operation mode of the DUT, and hence of the NB-IoT communication modem. During sleep phases the IoT device requires only a few lOOnA, during active radio transmissions the supply currents are of several 100mA and several 1mA during active radio reception or activities on application processor.

So, at the same time, the measurement setup must support maximum supply currents for active transmissions since test scenarios, e.g. DUT in live network operation, usually include phases with active radio transmissions. For high currents a small resistance is preferred while for low currents a higher (known) resistance should be selected. This is possible with the inventive apparatus.

The switching of the shunt resistors is performed in a synchronized fashion, where the status or operation mode of the DUT is at least partially known to the power measurement apparatus. This status or operation mode is either derived from the radio communication tester as part of the test environment or, if possible, queried directly from the DUT.

In a variant of the inventive apparatus, the measurement control unit comprises a look-up table for estimated current drawn by the DUT in each operation mode of the DUT.

Depending on the information about the operation mode of the DUT and e.g. a lookup table, the measurement control unit can estimate how much current the DUT is drawing. Based on this information the measurement control unit selects a shunt resistor that allows for current measurements with satisfactory accuracy while not harming the DUT

functionality .

The suggested solution increases the dynamic range of power consumption measurements for dynamic DUT operation while the system complexity stays rather low. It becomes possible to measure dynamically the amount of power and energy a NB-IoT communication modem is consuming for all DUT operation modes/states , from the high-power TX modes down to the different sleep and deep sleep states. The measurement control unit of the measurement setup can rather simply determines the status/operation mode of the DUT from querying the measurement equipment e.g. the radio communication tester and if possible, it can also query the DUT for its status/operation mode. Querying the status of the DUT may be done by polling status information via software through the regular communication interface of the DUT or by using the level of external status signals, depending on which features or interfaces the particular DUT provides.

Knowing the operation mode of the DUT is a main advantage also to plain gain control algorithms that would just change the shunt resistor value based on measured current values. A measurement system that does not know the DUT

state/operation mode would require much more complexity to guarantee that the voltage drop across the selected shunt resistor is not too high making the DUT not properly working anymore. Such a solution would require much more resistors and complexity. In a further variant of the inventive apparatus the

measurement control unit uses a trigger signal to select the shunt resistor to be used for power and energy measurement of the DUT.

The measurement control unit selects the shunt resistor based on information about the operation mode of the DUT to achieve enough sensitivity and not to harm the DUT

functionality by the voltage drop across the shunt resistor. This can be done e.g. by a trigger signal that switches between two different known shunt resistors. There can also be more than two shunt resistors that can be selected.

In a variant of the inventive apparatus, the power supply is a battery. This has the advantage to further reduce the noise impact on the measurement of the very low currents. Furthermore, a RF input transformer or an antenna and an optical-coupler for the needed control signals to reduce any ground loop current nor any impact from switching power supplies can be used.

In another variant of the inventive apparatus, the apparatus comprises more than two shunt resistors of different values. This has the advantage to increase accuracy over the

required dynamic range. The shunt resistor values are suitable to deal with current drawn from lOOnA up to 1A.

In another further variant of the inventive apparatus the radio communication tester communicates over RF signals with the DUT . This has the advantage to further reduce noise.

The invention will be explained in more detail using

exemplary embodiments.

The appended drawings show Fig. 1 Measurement setup according to the state-of-the- art ;

Fig. 2 Apparatus for precise power and energy consumption measurements of communication modems according to the invention; Fig. 3 Functional Block Diagram of the inventive

apparatus .

Figure 2 shows the inventive apparatus comprising a device under test (DUT) 1 configured to test power and energy consumption, a power supply 2 configured to power the DUT 1 and a measurement unit 3, which comprises means for

measuring a provided voltage to the DUT 1 by the power supply 2 and a current drawn by the DUT 1, whereas the current drawn is measured by a voltage drop over a selectable shunt resistor 4, 5. The apparatus further comprises a measurement control unit 6 configured to

dynamically select one shunt resistor 4, 5 out of at least two shunt resistors 4, 5 so that for high currents a small resistance is preferred while for low currents a higher (known) resistance should be selected.

The purpose of the apparatus with the DUT 1 is to run several communication scenarios and measure at the same time the energy (voltage, current) the DUT 1 is consuming. To achieve the required dynamic range of the current

consumption measurements, the value of the shunt resistor 4, 5 which is needed for current measurements is controlled by the measurement control unit 6.

Figure 3 shows the functional block diagram of the inventive apparatus. The measurement control unit 6 can estimate the current drawn by querying the DUT 1 status/operation mode either directly from the DUT 1 or indirectly either from the radio communication tester 7 or a base station of a live network to which the DUT 1 is connected to. The radio communication tester 7 communicates over RF signals 8 with the DUT 1 and is connected to the measurement control unit 6. The power supply 2 and the measurement unit 3 can be integrated into one unit or may be separated into two units.

The measurement control unit 6 selects the shunt resistor 4, 5 based on the information about the operation mode of the DUT 1 to achieve enough sensitivity and not to harm the DUT functionality by the voltage drop across the shunt resistor 4, 5. This can be done e.g. by a trigger signal that

switches between two or more different known shunt resistors 4, 5.

The setup of the inventive apparatus can be used with fully electrically isolation to eliminate any ground loops that may introduce additional noise. This would require battery operation, optical-coupler and an antenna or an RF

transformer for the modem RF port. Furthermore, the number of different shunt resistors 4, 5 may be increased beyond two to increase accuracy over the required dynamic range.

The suggested solution increases the dynamic range of power consumption measurements for dynamic DUT operation while the system complexity stays rather low. It becomes possible to measure dynamically the amount of power and energy a NB-IoT communication modem is consuming for all DUT operation modes/states from the high-power TX modes down to the different sleep and deep sleep states.

Knowing the state/operation mode of the DUT is a main advantage also to plain gain control algorithms that would just change the shunt resistor value based on measured current values. A measurement system that does not know the DUT state would require much more complexity to guarantee that the voltage drop across the selected shunt resistor is not too high making the DUT not properly working anymore. Such a solution would require much more resistors and complexity . The inventive apparatus and method are needed for device power consumption characterization as well as for firmware development. It helps to minimize the energy consumption of NB-IoT modems due to hardware and firmware improvements. Method and apparatus for precise power and energy consumption measurements of communication modems

List of Reference Signs 1 Device under test (DUT)

2 Power supply

3 Measurement unit

4 Shunt resistor

5 Shunt resistor

6 Measurement control unit

7 Radio communication tester

8 RF signal

-

Claims

1

Claims 1. A method for precise power and energy consumption

measurements of communication modems during operation, the method comprising the following steps:

querying information of an operation mode or a power and energy scenario of a device under test (1),DUT, either

directly from the DUT (1), or

indirectly either from a radio communication tester (7) , or

a base station, eNodeB, of a live network to which the DUT (1) is connected to, whereas

depending on the queried information a measurement control unit (6) of the communication modem

dynamically selects one shunt resistor (4, 5) of at least two shunt resistors (4, 5) for increasing a dynamic range of power consumption measurements for dynamic DUT operation.

2. The method according to claim 1, wherein the

measurement control unit (6) uses the queried

information and a look-up table for estimating how much current the DUT (1) is drawing and selecting the appropriate shunt resistor (4, 5) .

3. The method according to claim 1, wherein a measurement unit (3) measures a provided voltage to the DUT (1) by a power supply (2) and a current drawn by the DUT (1) . - 2

4. An apparatus for precise power and energy consumption measurements of communication modems during operation performing the test method according to claims 1 to 3, the apparatus comprising a device under test (1), DUT, to become configured and tested in various test

scenarios to measure its power and energy consumption, a power supply (2) configured to power the DUT (1), and a measurement unit (3) configured to measure a provided voltage to the DUT (1) by the power supply (2) and a current drawn by the DUT (1), wherein the apparatus further comprises a radio communication tester (7) configured to derive an operation mode of the DUT (1) or to create a desired power and energy scenario for the communication modem, and a measurement control unit (6) for dynamically selecting one shunt resistor (4, 5) of at least two shunt resistors (4, 5), whereas the selection of the shunt resistor (4, 5) is based on the estimation of the current drawn of the DUT (1) by querying the operation mode of the DUT (1) or the desired power and energy scenario either directly from the DUT (1) or indirectly either from the radio

communication tester (7) or a base station, eNodeB, of a live network to which the DUT (1) is connected to.

5. The apparatus according to claim 4, wherein the

measurement control unit (6) comprises a look-up table for estimated the current drawn by the DUT (1) in each operation mode of the DUT (1) .

6. The apparatus according to claim 4, wherein the

measurement control unit (6) uses a trigger signal to select the shunt resistor (4, 5) to be used for power and energy measurement of the DUT (1) . 3

7. The apparatus according to claim 4, wherein the power supply (2) is a battery.

8. The apparatus according to claim 4, wherein the

apparatus comprises more than two shunt resistors (4, 5) of different values.

9. The apparatus according to claim 4, wherein the radio communication tester (7) communicates over RF signals (8) with the DUT (1) .