TECHNICAL FIELD The present disclosure relates to a prepaid metering adaptor, in particular an adaptor connectable to a Virtual Token Carrier (VTC) port of a prepaid metering device. The present disclosure further relates to a method for controlling a prepaid metering device.

BACKGROUND

The prepaid billing model for electricity is widely spread in several countries of Africa and Asia. There is a large consumer base utilizing a prepaid charging model. The leading standard for prepaid metering is the Standard Transfer Specification (STS). Common STS prepaid metering devices use a standardized VTC interface that relies on a RS232 serial interface which is basically meant for maintenance purposes. This interface is the only open interface that is provided by STS meters.

There is a need for integration of STS meters into a modern Smart Metering System with backend based prepaid functionality.

SUMMARY

It is the object of the invention to provide a concept for integration of prepaid metering devices into a smart metering system.

This object is achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

In order to describe the invention in detail, the following terms, abbreviations and notations will be used:

AES Advanced Encryption Standard

FAC Frequent Access Cycle: See En-137575 wMBus Specification

HAN Home Area Network

HES Head End System LMN Local Metrological Network

MUC: Multi Utility Controller or Communicator

OMS: Open Metering Standard

PRISM: Platform for international Smart Metering

RSA: Republic of South Africa

STS: Standard Transfer Specification

VTC: Virtual Token Carrier

MBus: Meter Bus

wMBus: Wireless M-Bus

According to a first aspect, the invention relates to a prepaid metering adaptor, comprising: a first interface connectable to a prepaid metering device; a second interface connectable to a server; and a processor configured to retrieve consumption values indicating a consumption of a physical quantity from the prepaid metering device via the first interface and to transmit the retrieved consumption values to the server via the second interface, and to upload a credit token via the first interface to the prepaid metering device responsive to a credit token upload request received from the server via the second interface, wherein the credit token is indicative of an amount of consumption value credit to be available on the prepaid metering device for consuming the physical quantity. The physical quantity may be for example an amount of electricity, gas, water or others.

Such a prepaid metering adaptor has the advantage that the first interface can be used for communicating with the prepaid metering device and the second interface can an interface that is adapted for communicating with a server of a smart metering system. Therefore, the prepaid metering device can be easily integrated into a smart metering system. In an implementation form of the prepaid metering adaptor the first interface is a wired serial interface and the second interface is a wireless bus interface.

When the first interface is a wired serial interface any common prepaid metering device can be connected to the server by the first interface. When the second interface is a wireless bus interface, the adaptor can connect to a wireless communication system such as a smart metering system. This has the advantage that the prepaid metering device can be maintained and controlled from the outside.

In an implementation form of the prepaid metering adaptor the first interface is connectable to the prepaid metering device according to the Standard Transfer

Specification, STS.

This has the advantage that by using such STS interface, the prepaid metering adaptor can communicate with all legacy STS meters.

In an implementation form of the prepaid metering adaptor the first interface is an RS232 interface, in particular an RS232 to TTL interface.

This has the advantage that by using an RS232 interface, the prepaid metering adaptor can connect to all legacy STS meters.

In an implementation form of the prepaid metering adaptor the first interface is connectable to a Virtual Token Carrier, VTC port of the prepaid metering device. This has the advantage that the prepaid metering adaptor can connect to a VTC port that is available in legacy STS meters.

In an implementation form of the prepaid metering adaptor the second interface is a wireless Meter-Bus, M-Bus interface.

This has the advantage that by using such M-Bus interface, the prepaid metering adaptor can communicate with smart metering systems over a radio interface.

In an implementation form of the prepaid metering adaptor the second interface is a telegram-based interface, in particular a telegram-based interface according the Open Meter System, OMS standard.

This has the advantage that by using a telegram-based interface, the prepaid metering adaptor is compatible with telegram-based standards for smart metering, in particular with the OMS standard. In an implementation form of the prepaid metering adaptor the processor is configured to automatically retrieve the consumption values periodically from the prepaid metering device when connected to the first interface.

This has the advantage that the prepaid metering adaptor needs no trigger signal from the outside, i.e. it can operate as an autonomous and autarkic entity.

In an implementation form of the prepaid metering adaptor the processor is configured to pack the retrieved consumption values into a telegram and to send the telegram via the second interface to the server.

This has the advantage that a periodically transmitted telegram with the consumption values does not put a high load on the smart metering system. Hence, system resources can be saved by using such adapter device.

In an implementation form of the prepaid metering adaptor the processor is configured to retrieve a status of the uploading of the credit token from the prepaid metering device via the first interface; and the processor is configured to retrieve static metering data, in particular a meter specific maximum power limit or a firmware release number of the prepaid metering device via the first interface.

This has the advantage that an error can be detected and uploading can be performed again when the retrieved status of the uploading indicates no success. By reading meter specific data remote diagnostics of the prepaid meter device can be performed.

In an implementation form the prepaid metering adaptor comprises an external housing having a back side and a front side, wherein the back side of the external housing mechanically fits onto a Common Base Plate accommodating the prepaid metering device, and wherein the front side of the external housing mechanically and electrically fits onto a back side of the prepaid metering device which backside of the prepaid metering device is to be mounted onto the Common Base Plate.

This has the advantage that the prepaid metering adaptor can be applied with common prepaid metering devices by simply plugging the prepaid metering adaptor through meter device and common base plate. Existing prepaid meter devices can be still be used without changing their housing.

In an implementation form of the prepaid metering adaptor the external housing of the prepaid metering adaptor is formed as a sandwich box configured to be mounted between the Common Base Plate and the prepaid metering device.

This has the advantage that the sandwich box can be easily installed in the field together with existing prepaid meter devices.

In an implementation form of the prepaid metering adaptor the external housing of the prepaid metering adaptor comprises at least one clamp mounted on the back side of the external housing, the at least on clamp fitting into at least one clamp opening on the Common Base Plate; and the external housing of the prepaid metering adaptor comprises at least one clamp opening mounted on the front side of the external housing, the at least one clamp opening fitting into at least one clamp on the back side of the prepaid metering device.

This has the advantage that the clamp solution provides an easy way to put the prepaid metering adaptor between the meter device and the common base plate.

In an implementation form the prepaid metering adaptor comprises: a printed circuit board mounted inside the external housing of the prepaid metering adaptor, the printed circuit board carrying the processor and the first and the second interface; and an integrated power supply mounted inside the external housing of the prepaid metering adaptor, wherein the integrated power supply is connected to the printed circuit board for providing power to the printed circuit board, and wherein the integrated power supply is connected to the clamp holes of the external housing for providing the internal power supply with a ground connection.

This has the advantage that the prepaid metering adaptor can operate in an autarkic manner. The clamps can be used for both, fixing the prepaid metering adaptor between the meter device and the common base plate and for providing a ground potential to the prepaid metering adaptor. According to a second aspect, the invention relates to a prepaid metering system, comprising: a metering utility server; at least one prepaid metering adaptor, comprising: a first interface connected to a prepaid metering device; a second interface connected to the metering utility server; and a processor configured: to retrieve consumption values indicating a consumption of a physical quantity from the prepaid metering device via the wired serial interface and to transmit the retrieved consumption values to the metering utility server via the wireless bus interface, and to upload a credit token via the wired serial interface to the prepaid metering device responsive to a credit token upload request received from the metering utility server via the wireless bus interface, wherein the credit token is indicative of an amount of credit to be available on the prepaid metering device for consuming the physical quantity.

Such a prepaid metering system has the advantage that a lot of metering devices with their associated metering adapters can be connected to one metering utility server thereby saving system resources. That means, the prepaid metering adaptor can be easily and efficiently integrated into the prepaid metering system.

In an implementation form of the prepaid metering system, the first interface is a wired serial interface and the second interface is a wireless bus interface.

When the first interface is a wired serial interface any common prepaid metering device can be connected to the server by the first interface. When the second interface is a wireless bus interface, the adaptor can connect to a wireless communication system such as a smart metering system. This has the advantage that the prepaid metering device can be maintained and controlled from the outside.

According to a third aspect, the invention relates to a method for controlling a prepaid metering device, the method comprising: retrieving consumption values indicating a consumption of a physical quantity from the prepaid metering device via a first interface and transmitting the retrieved consumption values to a server via a second interface; and uploading a credit token via the first interface to the prepaid metering device responsive to a credit token upload request received from the server via the second interface, wherein the credit token is indicative of an amount of credit to be available on the prepaid metering device for consuming the physical quantity. By such method prepaid metering devices such as legacy STS meters can be easily integrated into a smart metering system.

In an implementation form of the method, the first interface is a wired serial interface and the second interface is a wireless bus interface.

When the first interface is a wired serial interface any common prepaid metering device can be connected to the server by the first interface. When the second interface is a wireless bus interface, the adaptor can connect to a wireless communication system such as a smart metering system. This has the advantage that by using the method the prepaid metering device can be maintained and controlled from the outside.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the invention will be described with respect to the following figures, in which:

Fig. 1 shows a schematic diagram illustrating a prepaid metering adaptor 100 according to an implementation form;

Fig. 2 shows a schematic diagram illustrating a smart metering system 200 according to an implementation form; Fig. 3 shows a schematic diagram illustrating a smart metering system 300 according to an implementation form;

Fig. 4 shows a schematic diagram illustrating a first message flow 400 of a smart metering system according to an implementation form;

Fig. 5 shows a schematic diagram illustrating a second message flow 500 of a smart metering system according to an implementation form;

Fig. 6 shows a drawing of a common base plate 600 of a prepaid metering device according to an implementation form; Fig. 7 shows a picture of the front side of a prepaid metering device 700 according to an implementation form; Fig. 8 shows a picture of the back side of the prepaid metering device 700 depicted in Fig. 7;

Fig. 9 shows a picture of the front side 900 of a stand-alone prepaid metering device according to an implementation form;

Fig. 10 shows a picture of the rear side 1000 of the prepaid metering device depicted in Fig. 9;

Fig. 1 1 shows a schematic diagram illustrating a sandwich box 1 100 for a prepaid metering adaptor 1 107 according to an implementation form;

Fig. 12 shows a view 1200 onto the sandwich box 1 100 depicted in Fig. 1 1 ;

Fig. 13 shows a picture 1300 of the rear side of the sandwich box 1 100 depicted in Fig. 1 1 ;

Fig. 14 shows a view 1400 onto the front side of the sandwich housing depicted in Fig. 1 1 with a meter connected to it; Fig. 15 shows a view 1500 into the opened sandwich box depicted in Fig. 1 1 ;

Fig. 16 shows a schematic diagram illustrating a smart metering system 1600 according to an implementation form; and Fig. 17 shows a schematic diagram illustrating a method 1700 for controlling a prepaid metering device according to an implementation form;

DETAILED DESCRIPTION OF EMBODIMENTS In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

It is understood that comments made in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

The devices and methods described herein may be applied with smart meters and used in smart metering systems. A smart meter or smart metering device is an electronic device that records consumption of electric energy or other consumer items in some time intervals and communicates that information (e.g. on a daily basis) back to the utility for monitoring and billing purposes. Smart meters enable two-way communication between the meter and the central system. Unlike home energy monitors, smart meters can gather data for remote reporting. Such an advanced metering infrastructure differs from traditional automatic meter reading in that it enables two-way communications with the meter.

In the following description methods and devices using prepaid metering devices are described. A prepaid metering device, also referred to as a prepayment meter allows for paying energy on demand. Prepayment meters work similar to a pay as you go mobile phone - the customer has to top-up with credit to get his gas and/or electricity, e.g. at recognized PayPoint or Payzone shops or at The Post Office. Payment may be done by using a credit token also simply referred to as a token, a key or a smart card which may be charged up at local stores. If the token, key or card is not recharged no energy is supplied. The main types of prepayment meters are: key meters, smart card meters and token or card meters. Key meters have electronically coded keys which are specific to the meter and contain tariff information which is updated when the card is charged. Smart card meters download information about energy usage onto the card to send back to the supplier when topping up. Token or card meters may be required to be adjusted manually whenever the tariff changes. The meter records the amount of gas, electricity, water or consumable supplies used.

The devices and methods described herein may use VTC interfaces and may be applied with STS metering devices. The Standard Transport Specification (STS) Suite defines a set of standards and technology for prepaid smart metering. STS itself is defined by the STS organization (http://www.sts.org.za/) and it is backed by a number of international IEC norms, such as for example [IEC62055-31] "Electricity metering - Payment systems Part 31 : Particular requirements - Static payment meters for active energy (classes 1 and 2) 2005", [IEC62055-41] "Electricity Metering - Payment Systems - Part 41 : Standard Transfer Specification (STS) - Application layer protocol for one-way token carrier systems July 2013", [IEC62055-51] "Electricity metering - Payment systems - Part 51 : Standard transfer specification (STS) - Physical layer protocol for one-way numeric and magnetic card token carriers. July 2007", [IEC62055-52] "Electricity metering - Payment systems - Part 52: Standard transfer Specification - Physical Layer Protocol for a two- way virtual token carrier for direct local connection July 2006". The core notion of STS is prepayment metering supported by a robust and easy to use meter device for the end consumer. Energy is purchased in form of an electronic code called "Token". Once purchased, the end consumer needs to enter the token using the keypad of the meter. This activates the token and the corresponding amount of energy can now be consumed. STS compliant meters are modern electronic meter devices, however they provide insufficient communication capabilities for Smart Metering

Applications. The standard only dictates the presence of the VTC interface described in [DISSCAAA9] "PARTICULAR REQUIREMENTS PREPAYMENT METERS August 2005" which is primarily meant for maintenance purposes. However there is no support for standard Smart Metering interface like e.g. IEC 62056-21 or wireless M-Bus. Accordingly STS meters are rather stand-alone devices and as such not directly eligible for the integration into a Smart Metering System.

The devices and methods described herein may be applied with multi utility controllers (MUC). A multi utility controller or a multi utility server may be defined as a server according to the OMS specification [OMSVOI1] "Open Metering System Specification, Volume 1 , General Part, Issue 1 .4.0 / 201 1 -01 -31 , www.oms-group.org".

The devices and methods described herein may be applied for integration of STS meters in a smart metering system. STS meters only provide the VTC-interface for a machine to machine communication. This interface also provides a full set of operations needed to control the meter remotely. The interface is based on the physical RS232 with TTL voltage levels. Hence only a one to one ratio is possible between a concentrator (MUC) unit and a STS meter. A one to one ratio is unacceptable for economic and reasons of technical complexity. The meter model and version specific behavior on the VTC Interface introduces additional complexity for the meter integration with respect to meter model and version specific register addressing, meter model and version specific data format and meter model and version specific behavior on the physical RS232 interface. STS meters do not support any standard Smart Metering Protocol. Accordingly a standard MUC controller (concentrator) can only be employed when using a prepaid metering adaptor or a method for controlling a prepaid metering device according to the disclosure. Without using the devices and methods as described in this disclosure, STS meters are not eligible for the integration into a Smart Metering System. The devices and methods described herein may be applied for integration of STS meters in a smart metering system by using the Open Meter System (OMS) and the wireless M- Bus. In the world of smart metering infrastructures and specifically in the area of LMN (Local Metrological Network), there exists a variety of meters with different transport technologies and protocols. One of these many is Wireless M-Bus according to OMS (Open Meter System). For the integration of utility meters (e.g. electricity, gas, water) with pulse output or wired M-Bus interface in an Open Meter System (OMS) compliant Wireless M-BUS network, e.g. according to [EN 137574] "Communication systems for meters and remote reading of meters, Part 4: Wireless meter readout (Radio meter reading for operation in the 868 MHz to 870 MHz SRD band); 201 1 ", a wireless M-Bus interface or adapter may be used. Wireless M-BUS interfaces are the ideal cable replacement and provide a quick, inexpensive and non-critical cabling in a Wireless M- Bus / OMS radio network. After commissioning of the Wireless M-BUS interface, the connected and configured meters may be read automatically. The data content may be packed into a wM-Bus-compliant radio telegram and sent. The VTC- adaptor devices according to the disclosure may be employed to extend a STS meter with VTC interface with an OMS compliant wireless M-Bus interface on 868 MHz.

The described devices and systems may include integrated circuits and/or passives and may be manufactured according to various technologies. For example, the circuits may include logic integrated circuits, analog integrated circuits, mixed signal integrated circuits, optical circuits, memory circuits and/or integrated passives.

Fig. 1 shows a schematic diagram illustrating a prepaid metering adaptor 100 according to an implementation form. The prepaid metering adaptor 100 includes a first interface 101 connectable to a prepaid metering device. The first interface 101 may be a wired serial interface. The prepaid metering adaptor 100 includes a second interface 103 connectable to a server. The second interface 103 may be a wireless bus interface. The prepaid metering adaptor 100 includes a processor 105 that is configured to retrieve consumption values indicating a consumption of a physical quantity from the prepaid metering device via the first interface 101 and to transmit the retrieved consumption values to the server via the second interface 103. The processor 105 is further configured to upload a credit token via the first interface 101 to the prepaid metering device responsive to a credit token upload request received from the server via the second interface 103. The credit token is indicative of an amount of credit to be available on the prepaid metering device for consuming the physical quantity.

The first interface 101 may be connectable to the prepaid metering device according to the Standard Transfer Specification, STS. The first interface 101 may be an RS232 interface, in particular an RS232 to TTL interface. The first interface 101 may be connectable to a Virtual Token Carrier, VTC port of the prepaid metering device. The second interface 103 may be a wireless Meter-Bus, M-Bus interface. The second interface 103 may be a telegram-based interface, in particular a telegram-based interface according the Open Meter System, OMS standard. The processor 105 may be configured to automatically retrieve the consumption values periodically from the prepaid metering device when connected to the first interface 101. The processor 105 may pack the retrieved consumption values into a telegram and send the telegram via the second interface 103 to the server. The processor 105 may retrieve a status of the uploading of the token from the prepaid metering device via the first interface 101 . The processor 105 may retrieve static metering data, in particular a meter specific maximum power limit or a firmware release number of the prepaid metering device via the first interface 101 .

The prepaid metering adaptor 100 may include an external housing as described below with respect to Figs. 1 1 -15. The prepaid metering adaptor 100 may be applied in a smart metering system 200, 300 as described below with respect to Figs. 2 and 3.

Fig. 2 shows a schematic diagram illustrating a smart metering system 200 according to an implementation form. The prepaid metering system 200 includes a metering utility server 209 and at least one prepaid metering adaptor 207. The prepaid metering adaptor 207 includes a first interface 202, e.g. a wired serial interface connected to a prepaid metering device 205 and a second interface 204, e.g. a wireless bus interface connected to the metering utility server 209. The prepaid metering adaptor 207 further includes a processor. The processor is configured to retrieve consumption values indicating a consumption of a physical quantity from the prepaid metering device 205 via the first 202 and to transmit the retrieved consumption values to the metering utility server 209 via the second interface 204. The processor is further configured to upload a credit token via the first interface 202 to the prepaid metering device 205 responsive to a credit token upload request received from the metering utility server 209 via the second interface 204. The credit token is indicative of an amount of credit to be available on the prepaid metering device 205 for consuming the physical quantity.

The first interface 202 may be connected to the prepaid metering device 205 according to the Standard Transfer Specification, STS. The first interface 202 may be an RS232 interface, in particular an RS232 to TTL interface. The first interface 202 may be connected to a Virtual Token Carrier, VTC port of the prepaid metering device 205. The second interface 204 may be a wireless Meter-Bus, M-Bus interface. The second interface 204 may be a telegram-based interface, in particular a telegram-based interface according the Open Meter System, OMS standard. The processor may be configured to

automatically retrieve the consumption values periodically from the prepaid metering device 205. The processor may pack the retrieved consumption values into a telegram and send the telegram via the second interface 204 to the metering utility server 209. The processor may retrieve a status of the uploading of the credit token from the prepaid metering device 205 via the first interface 202. The processor may retrieve static metering data, in particular a meter specific maximum power limit or a firmware release number of the prepaid metering device 205 via the first interface 202 and may send that data to the metering utility server 209.

The prepaid metering adaptor 207 may include an external housing as described below with respect to Figs. 1 1 -15. Such a prepaid metering adaptor 207 being connected to a VTC port of the prepaid metering device 205 may also be referred to as VTC-Adaptor or VTC-Adaptor device in the following. The prepaid metering adaptor 207 may correspond to the prepaid metering adaptor 100 as described above with respect to Fig. 1 . The VTC-Adaptor device enables the integration of current STS meters into a Smart Metering System with support for meter readout, alarming and token upload. A meter model and version independent interface may be exposed by the VTC-Adaptor via the standard Smart Metering Technology (protocol) wireless M-Bus. The interface may be bidirectional and may support the above mentioned core operations. A concentrator device like a MUC controller thus does not need to have any knowledge of the specifics of a connected STS meter. Furthermore a concentrator device can still rely on Smart Metering standard protocols like wireless M-Bus. The wireless M-Bus interface exposed by the VTC-Adaptor may be compliant to the OMS standard and the wireless M-Bus standard. Interoperability is thus facilitated by the VTC-Adaptor.

Fig. 2 shows the system context for the integration of a STS meter into a standard Smart Metering System. The VTC-Adaptor 207 may operate as an autonomous integration component between STS meter 205 and MUC controller or concentrator 209. It may expose a standard compliant wireless M-Bus radio interface 204 to the MUC 209 and may connect to the STS meter 205 via the VTC-lnterface 202 over RS232 TTL. The MUC controller 209 can be connected to multiple VTC-Adaptor / STS meter 205 pairs thus achieving a one to N ratio as depicted by the sign "1 " at MUC side and at VTC- Adaptor side. The MUC 209 may function as a data concentrator and integration component supporting the central Head End System (HES) 221 in the Data center 203.

The VTC-Adaptor device 207 may operate event and time driven. ^ Periodic wireless M- Bus telegrams for meter consumption and status data may be automatically created and sent onto the wireless M-Bus channel 204. The VTC-Adaptor device 207 may

automatically use VTC interface communication 202 to the meter 205 to collect this data. Alarm and error conditions on the meter 205 and/or VTC-lnterface 202 may be recognized and an alarm condition may be signaled to the MUC 209. Token operations like token upload may be exposed via the wireless M-Bus interface 204 of the VTC-Adaptor 207. These operations may be available to the MUC controller 209 for various token management operations. Ad hoc query operations may be exposed on the wireless M-Bus interface 204. The wireless M-Bus interface 204 may be compliant to the OMS

specification and the wireless M-Bus standard. The interface 204 may be independent of the connected STS meter model or version. A STS meter 205 may become a standard compliant OMS wireless M-Bus meter once operated with the VTC-Adaptor 207. The VTC-Adaptor device 207 may automatically recogize the specific meter 205 it is connected to via VTC interface commands. The information thus gained may be used to activate the matching meter profile so that the specifics of the meter 205 may be handled properly. If the connected meter 205 is not recognized an alarm telegram may be sent out via wireless M-Bus 204.

The VTC-Adaptor Device 207 is designed to be energy efficient. It is available with a power supply unit and as a battery driven version.

The VTC Adaptor provides for an integration of STS meters into a modern Smart Metering System with backend based prepaid functionality. The VTC-adaptor connects to the VTC port of an STS meter and extends it with an OMS compliant wireless M-Bus interface.

This interface may be bidirectional in order to also support the uploading of STS tokens onto the meter. Futhermore the VTC-Adaptor may automatically push meter readout data periodically. It is thus similar to a wireless M-Bus impulse gateway used for water and gas meters. The wireless M-Bus interface of the VTC-Adaptor is designed to be open and it thus supports interoperability. However the process of a token upload is not fully covered by a standard like OMS. Still the VTC-Aadptor follows a OMS compliant sequence of processing.

Fig. 3 shows a schematic diagram illustrating a smart metering system 300 according to an implementation form. The prepaid metering system 300 includes a metering utility controller or server 309 and at least one prepaid metering adaptor 307. The prepaid metering adaptor 307 includes a wired serial interface 302 connected to a prepaid metering device 305 and a wireless bus interface 304 connected to the metering utility controller 309. The prepaid metering adaptor 307 further includes a processor. The processor is configured to retrieve consumption values from the prepaid metering device 305 via the wired serial interface 302 and to transmit the retrieved consumption values to the metering utility controller 309 via the wireless bus interface 304. The processor is further configured to upload a token via the wired serial interface 302 to the prepaid metering device 305 responsive to a token upload request received from the metering utility controller 309 via the wireless bus interface 304. The token is indicative of an amount of credit to be available on the prepaid metering device 305. The wired serial interface 302 may be connected to the prepaid metering device 305 according to the Standard Transfer Specification, STS. The wired serial interface 302 may be an RS232 interface, in particular an RS232 to TTL interface. The wired serial interface 302 may be connected to a Virtual Token Carrier, VTC port of the prepaid metering device 305. The wireless bus interface 304 may be a wireless Meter-Bus, M-Bus interface. The wireless bus interface 304 may be a telegram-based interface, in particular a telegram- based interface according the Open Meter System, OMS standard. The processor may be configured to automatically retrieve the consumption values periodically from the prepaid metering device 305. The processor may pack the retrieved consumption values into a telegram and send the telegram via the wireless bus interface 304 to the metering utility controller 309. The processor may retrieve a status of the uploading of the token from the prepaid metering device 305 via the wired serial interface 302. The processor may retrieve static metering data, in particular a meter specific maximum power limit or a firmware release number of the prepaid metering device 305 via the wired serial interface 202 and may send that data to the metering utility controller 309.

The prepaid metering adaptor 307 may include an external housing as described below with respect to Figs. 1 1 -15. Such a prepaid metering adaptor 307 being connected to a VTC port of the prepaid metering device 305 may also be referred to as VTC-Adaptor or VTC-Adaptor device in the following. The prepaid metering adaptor 307 may correspond to the prepaid metering adaptor 207 described above with respect to Fig. 2 or to the prepaid metering adaptor 100 described above with respect to Fig. 1.

Fig. 3 describes the overall system context of the VTC-Adapter component 307. A locally installed MUC device 309 may be connected through wireless M-Bus 304 to multiple legacy prepaid devices 305 that may be extended by the VTC-Adapter component 307. The MUC device 309 itself may be connected to the GPRS service of the mobile network 331 that may be connected to the backend smart metering platform 321 through a VPN connection 308. All legacy prepaid meters 305 provide a RS-232 interface that may be used to connect to the VTC Adapter 307. Through that serial interface302 the meter device 305 can be controlled by the VTC protocol.

The smart metering system 300 depicted in Fig. 3 may serve the following core functions: Collection of consumption values, Transmission of STS tokens, Retrieval of STS token upload status and Collection of various other meter parameters. Consumption values may be retrieved from the prepaid meter device 305 and may be transmitted to the backend platform 321 , e.g. a PRISM backend platform. STS tokens that may be created though backend business processes may be transmitted from the smart metering backend 321 via the MUC device 309 to the prepaid meter 305. There are different business processes that may create prepaid tokens to be applied. The main process may be the acquisition of prepaid energy through the end consumer. The processing of uploaded STS tokens on the meter device 305 can fail for various reasons. The retrieval of the token upload status will allow determining the outcome of the upload operation. Various other meter parameters may be collected, for example the meter specific maximum power limit or a software version of the meter 305.

The VTC-Adaptor device 307 may provide the following core functionality: Collection and transmission of various dynamic meter data, Collection and transmission of various static meter data, Upload of STS tokens onto the meter 305, Collection and transmission of various static meter data and Upload of STS tokens onto the meter 305. Dynamic meter data, like for example the available credit, may be periodically read out from the meter 305 and may be transmitted via wireless M-Bus 304. This may be a unidirectional

communication where data may be actually pushed. The data items listed above may be periodically collected from the meter 305 by the VTC-Adaptor 307 and then transmitted to the MUC 309 by a SND-NR message. Static data, like for example the firmware version or the STS meter number, may also periodically read out and transmitted via wireless M-Bus 304. This may also be a unidirectional communication. The VTC-Adaptor 307 may offer a service for the uploading of STS tokens via the wireless M-Bus Interface 304. This may happen by a bidirectional communication and the Token reception may be acknowledged on the VTC-adaptor 307. The upload process may happen during a wireless M-Bus FAC cycle and may not be started at an arbitrary point in time. It may only be initiated shortly after the VTC-Adaptor 307 has sent his period telegram. Static data, like for example the firmware version or the STS meter number, may also be periodically read out and transmitted via wireless M-Bus 304. This may also be a unidirectional communication. Fig. 4 shows a schematic diagram illustrating a first message flow 400 of a smart metering system according to an implementation form.

The message flow 400 includes a first message "Query variable meter data()" 401 from VTC adaptor 307 to meter device 305 to query variable meter data. In a second message 402 from meter device 305 to VTC adaptor 307, the meter device 305 provides the VTC adaptor 307 with the queried meter data. In a third message 403 "SND-NR()" the VTC adaptor 307 transmits the received meter data to the MUC device 309. The data items listed above may be periodically collected from the meter 305 by the VTC-Adaptor 307 and then transmitted to the MUC 309 by a SND-NR message 403. The message flow 400 may be used by the VTC-Adaptor device 307 to provide the above described core functionality of collection and transmission of various dynamic meter data.

Fig. 5 shows a schematic diagram illustrating a second message flow 500 of a smart metering system according to an implementation form. The token upload may be performed within an OMS frequent access cycle (FAC). The FAC may be initiated by the MUC 309 after reception of a periodic SND-NR message 503. The initiation may happen by the immediate sending of the SND-UD message 504 to the VTC-Adaptor 307. In compliance to OMS a reply interval 507 of 5 seconds may be employed. This means that the ACK 508 may be send approximately 5 seconds after the reception of the SND-UD 504. The same may apply to the REQ-UD2 / RSP-UD interaction 509, 514. The delay may be used to allocate enough time for the meter device 305 to process the token and update the token uploads status register. During the FAC cycle two telegram exchanges may be performed to upload the token and thereafter query the status of the token upload process. A first telegram exchange with respect to SND-UD / ACK messages 504, 508 may be used to transmit the actual token from the MUC 309 to the VTC adaptor 307 for upload. A second telegram exchange with respect to REQ-UD2 / RSP-UD 509, 514 may be needed to query the token upload status.

The actual token may be send to the VTC-adaptor 307 using a SND-UD message 504. The VTC adaptor 307 may write 505 the token to the meter's 305 token upload registers and may receive the acknowledgement 506. Then it may send the ACK telegram 508 to the MUC 308 acknowledging the reception of the SND-UD message 504.

The first three messages 501 , 502, 503 may correspond to the message flow 400 as described above with respect to Fig. 4.

The following sequence description may be used for the message flow 500:

(1 ) Initialization of FAC

The VTC-adaptor 307 sends its periodic SND-UD message 504 to the MUC 309.

Immediately after sending the message the VTC-adaptor 307 opens its reception window. The MUC 309 receives the periodic SND-NR telegram 503 and has a new token available for upload.

(2) Sending of Token

The MUS prepares a SND-UD telegram 504 that carries the token and sends it to the VTC-adaptor 307.

(3) Processing of token on VTC-adaptor

The VTC-adaptor 307 extracts the token from the SND-UD message 504 and writes 505 it to the meter's token upload register. The meter acknowledges 506 the VTC write command 505.

(4) Wait T1

The VTC-adaptor 307 waits 507 time T1 before it sends the ACK telegram 508 to the MUC 309. T1 is determined so that there is a time interval of 5 seconds between the arrival of the SND-UD message 504 and the sending of the ACK response 508.

(5) MUC receives ACK telegram 508

(6) Request Token upload Status

The MUC 309 prepares and sends a REQ-UD2 telegram 509 to query the token upload status.

(7) Receive Token Upload Status Request

The VTC-adaptor 307 receives the REQ-UD2 telegram 509 and is thus informed that the token upload status is requested.

(8) Wait T2

The VTC-adaptor 307 waits 4 seconds 510.

(9) Query Token Upload Status

The VTC-adaptor 307 reads 51 1 the token upload status register of the meter 305. Then it prepares a RSP-UD telegram 514 that encodes the token upload status byte. (10) Wait T3

The VTC-adaptor 307 waits 513 a time T3 before is sends the RSP-UD telegram 514. T3 is determined so that there is a 5 second interval between the reception of the REQUD2 message 512 and the sending of the reply RSP-UD 514.

(1 1 ) Receive Token Upload Status

The telegram RSP-UD 514 with the token upload status is received by the MUC 309.

(12) End FAC

The FAC cycle is terminated by the MUC 309 through sending a SND-NKE telegram 515 to the VTC adaptor 307.

Fig. 6 shows a drawing of a common base plate 600 of a prepaid metering device according to an implementation form. The VTC- adaptor device as described above with respect to Figures 1 to 5 may be employed to extend a STS meter with VTC interface with an OMS compliant wireless M-Bus interface on 868 MHz. The VTC-Adaptor device may be available with the following two housing solutions: In a first housing solution the device may be used in a stand-alone fashion. This VTC-adaptor may be available as a battery driven version and as version with an external power supply. This first solution is shown below in Figures 7-10. In a second housing solution the VTC-Adaptor device may be fully integrated with a power supply into the housing. That solution may be targeted for the field deployment and will be explained in detail below with respect to Figures 1 1 -15.

All legacy prepaid meters are designed to be mounted on a common base plate 600 as shown in Fig. 6. The meter housing has approximately the size of Width x Height x Depth = 140 x 252 x 80 mm. In Fig. 6 the common base plate can be seen in a front view 601 , a top view 602, a bottom view 603, a right side view 604, a sectional view BB 605 and a sectional view AA 606. The common base plate 600 includes mounting holes 61 1 a neutral earth (ground) link 612 and clamps 613 for connection with a meter device.

Fig. 7 shows a picture of the front side of a prepaid metering device 700 according to an implementation form. The prepaid metering device 700 may correspond to one of the prepaid metering devices 100 or STS meters 205, 305 as described above with respect to Figures 1 to 3. Fig. 8 shows a picture of the back side of the prepaid metering device 700 depicted in Fig. 7. Fig. 9 shows a picture of the front side of a stand-alone prepaid metering device 900 according to an implementation form. The prepaid metering device 900 may correspond to one of the prepaid metering devices 100 or STS meters 205, 305 as described above with respect to Figures 1 to 3. On the right of the front side, the external power supply can be seen. The stand-alone prepaid metering device 900 may be provided as a battery driven version and as a version with external power supply. The battery driven version comes with a small plastic housing with Sub-D plug and a copper rod as antenna. The Sub-D plug may serve multiple purposes, for example connection to the meters VTC port or for providing the configuration interface. The antenna is a copper rod on the rear side that is bendable. It is typically brought to a vertical position for normal operation. The stand-alone device with external power supply is derived from the battery driven stand-alone device. However it uses an external standard power supply and is ready for DIN rail mounting. Fig. 10 shows a picture of the rear side 1000 of the prepaid metering device 900 depicted in Fig. 9. In the picture, braces for DIN rail mounting can be seen.

Fig. 1 1 shows a schematic diagram illustrating a sandwich box 1 100 for a prepaid metering adaptor 1 107 according to an implementation form. The prepaid metering adaptor 1 107 may correspond to the prepaid metering adaptors 307, 207 as described above with respect to Figs. 2 and 3 or to the prepaid metering adaptor 100 described above with respect to Fig. 1.

The prepaid metering adaptor 1 107 includes an external housing 1 101 having a back side and a front side. The back side of the external housing 1 101 mechanically fits onto a Common Base Plate 1 103, .e.g. as shown above in Fig. 6 accommodating the prepaid metering device 1 109. The front side of the external housing 1 101 mechanically and electrically fits onto a back side of the prepaid metering device 1 109 which backside of the prepaid metering device 1 109 is to be mounted onto the Common Base Plate 1 103. The prepaid metering device 1 109 may correspond to the prepaid metering devices or STS meters 205, 305 as described above with respect to Figs. 2 and 3.

The external housing 1 101 of the prepaid metering adaptor 1 107 may be formed as a sandwich box configured to be mounted between the Common Base Plate 1 103 and the prepaid metering device 1 109. The external housing 1 101 of the prepaid metering adaptor 1 107 may include one or more clamps 1 1 13a mounted on the back side of the external housing 1 101 . The clamps 1 1 13a are designed to fit into clamp openings 1 1 13b on the Common Base Plate 1 103. The external housing 1 101 of the prepaid metering adaptor 1 107 may include one or more clamp openings 1 1 1 1 b mounted on the front side of the external housing 1 101 . The clamp openings 1 1 1 1 b may be designed to fit into clamps 1 1 1 1 a on the back side of the prepaid metering device 1 109. The prepaid metering adaptor 1 107 may include a printed circuit board and an integrated power supply as described below with respect to Fig. 15.

The sandwich box 1 100 solution depicted in Fig.1 1 may be applied for field application. It provides a clean and field applicable solution for housing the VTC-Adaptor module. This solution is robust and easily mountable. The sandwich box may provide an external housing for the VTC adaptor device with its antenna. The sandwich box provides the following advantages: The sandwich box 1 100 fits mechanically onto the wall mounted Common Base Plate mounted as the original STS meter. It has an integrated power supply unit that may be used for the VTC-adaptor device. It provides the same electrical and mechanical interface to a meter on its front side. The meter can be mounted onto the sandwich box like it can be mounted onto the standardized Common Base Plate.

Fig. 12 shows a view 1200 onto the sandwich box 1 100 depicted in Fig. 1 1 with Common Base Plate 1 103 and meter device 1 109. Fig. 13 shows a picture 1300 of the rear side of the sandwich box 1 100 depicted in Fig. 1 1 with Common Base Plate 1 103, VTC adaptor device housing 1 101 and meter device 1 109. The rear side of sandwich box includes clamps to connect into the common base plate 1 103. Fig. 14 shows a view 1400 onto the front side of the sandwich housing 1 101 depicted in Fig. 1 1 with a meter 1 109 connected to it.

Fig. 15 shows a view 1500 into the opened sandwich box depicted in Fig. 1 1 . The prepaid metering adaptor 1500 includes a printed circuit board 1501 and an integrated power supply 1503. The printed circuit board 1501 may be mounted inside the external housing 1 101 of the prepaid metering adaptor 1500. The printed circuit board 1501 may carry the processor 105 and the first 101 and the second 103 interface as described above with respect to Fig. 1 . The integrated power supply 1503 may be mounted inside the external housing 1 101 of the prepaid metering adaptor 1500. The integrated power supply 1503 may be connected to the printed circuit board 1501 for providing power to the printed circuit board 1501 . The integrated power supply 1503 may be connected to the clamp holes 1505 of the external housing 1 101 for providing the internal power supply 1503 with a ground connection.

In a mass rollout scenario with millions of legacy STS meters, the extention of the STS Meter with the VTC Adaptors can be performed quick, secure and with no complexity. The VTC Adaptor housing solution, also called "Sandwich-Box", meets these requirements. In order to integrate an STS meter into a Wireless M-BUS / OMS compliant radio network, a field technician may perform just the following steps: Unplug the STS meter from the common base plate; Plug the Sandwich Box onto the common base plate; Connect the VTC-Adapter with the STS Meter using the meters VTC serial interface; and Plug the STS meter onto the Sanwich Box. Afterwards a simple prepaid STS meter becomes a fully Wireless M-BUS / OMS compliant meter, enabling the integration into a Smart Metering Infrastructure. Fig. 16 shows a schematic diagram illustrating a smart metering system 1600 according to an implementation form. The smart metering system 1600 may include a development center 1601 , a first customer location 1606 including multiple VTC adaptors 1623 and metering devices 1625 coupled to a wM-Bus 1621 , e.g. as described above with respect to Figures 2 and 3, a first service center 1603, a second service center 1609 that may communicate through an IP-Sec secured VPN network 1619.

A second customer location 161 1 including a VTC adaptor 1633 and a metering device 1635 coupled to a wM-Bus 1631 , e.g. as described above with respect to Figures 2 and 3, may be connected to the first service center 1603 by a radio network 1615, e.g. a GPRS network. The customer of a third customer location 1613 with a prepaid meter device without VTC adaptor is not electronically connected to the smart metering system 1600. Instead, he must go to a shop 1617 to buy some credit for his prepaid meter device. The shop may be electronically connected to the second service center 1609. Fig. 17 shows a schematic diagram illustrating a method 1700 for controlling a prepaid metering device according to an implementation form. The method 1700 may be applied on a processor 105 of a prepaid metering adaptor 100 as described above with respect to Fig. 1 . The method 1700 may be applied on a prepaid metering system 200, 300 as described above with respect to Figs. 2 and 3. The method 1700 may include retrieving 1701 consumption values indicating a consumption of a physical quantity from the prepaid metering device via a first interface and transmitting the retrieved consumption values to a server via a second interface. The method 1700 may include uploading 1702 a credit token via the first interface to the prepaid metering device responsive to a credit token upload request received from the server via the second interface, wherein the credit token is indicative of an amount of credit to be available on the prepaid metering device for consuming the physical quantity. The first interface may be a wired serial interface and the second interface may be a wireless bus interface. In an implementation form, the method 1700 may include only retrieving 1701 without uploading 1702 or only uploading 1702 without retrieving 1701 .

The methods, systems and devices described herein may be implemented as electrical and/or optical circuit within a chip or an integrated circuit or an application specific integrated circuit (ASIC). The invention can be implemented in digital and/or analogue electronic and optical circuitry.

While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms "coupled" and "connected", along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other. Although specific aspects have been illustrated and described herein, it will be

appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein. Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present invention has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described herein.