WO2016016432A2

WO2016016432A2 - System and method for the dynamic assignment and operation of wireless networks in an automated plant

Info

Publication number: WO2016016432A2
Application number: PCT/EP2015/067676
Authority: WO
Inventors: Dirk Schulz; Markus Ruppert
Original assignee: Abb Technology Ag
Priority date: 2014-08-01
Filing date: 2015-07-31
Publication date: 2016-02-04
Also published as: WO2016016432A3

Abstract

The invention relates to a system and corresponding method for a dynamic assignment and operation of wireless sensor networks in an automated plant or process automation facility, and in particular in automation technology and/or plant automation processes. The inventive system comprises a data processing device, a data storage and communication interface for the dynamic assignment of wireless devices into one particular network out of a plurality of available networks, wherein it is provided means based on a raw wireless KPIs (Key Performance Indicators). The KPIs gather and process ongoing wireless site survey data for given and/or predefined tasks without actually performing a "classic/manual" (one-time) site survey.

Description

System and method for the dynamic assignment and operation of wireless networks in an automated plant

Description

The invention relates to a system and corresponding method for a dynamic assignment and operation of wireless sensor networks in an automated plant or process automation facility, and in particular in automation technology and/or plant automation processes.

While the location of wireless devices in the field is determined by the 10 points of the process, the number process, the number and placement of gateways and repeaters must is constrained by the applied communication technology, needed latency and bandwidth, and the radio properties of the site. A wireless layout must place gateways and repeaters considering obstructions, interferences, and bandwidth limits so that the QoS (Quality of Service) needs of the respective applications are met.

An efficient and accurate offline planning of all wireless networks in an industrial plant comes with high effort. While the networks, gateways, devices, and QoS requirements may be known beforehand, in particular the wireless properties of the site are hard to assess and/or determine. Even if CAD data are available to the wireless planning and layout, radio propagation and interferences are eventually complex to calculate and/or to determine. In addition, details may change until or after the plant is operational, making a one-time planning unfeasible. It is to be expected that a certain number of devices are assigned to a network with sub- optimal QoS properties - especially "edge" devices located at equal distance between gateways.

Wireless site surveys seem to be a very practical approach to the problem.

Moreover, detailed wireless site survey information is very valuable for various tasks during the engineering and operation of wireless automation networks. Detailed wireless site survey information enables a simplified engineering process followed by operation-time optimization of the networks. It supports troubleshooting at operation time by giving detailed information about the possible root causes of communication problems.

Ideally, the devices of the operational network may be used instead of additional "survey devices" that would have to be carried around in the plant.

However, state-of-the-art wireless communication protocols do not support site survey functionality to the desirable extent. For example in WirelessHART, only a fraction or share of the useful and/or valuable information is collected within the devices and made available through commands, in particular standardized commands.

Wireless network co-existence and physical obstructions count among the main challenges for the planning and operating of wireless networks. They must be considered during engineering and the actual behavior of the networks must be observed during operation.

Already during commissioning, the quality of the initial engineering impacts the ease with which the networks can be started up; during their remaining life-time, in everyday operation, the initial engineering determines the contingency bandwidth that is available to counter temporary strains or permanent changes/additions to the networks. Both, wireless network co-existence and physical obstructions are challenges that mostly target the physical network layer. In addition to the monitoring of the basic device health and its energy source, the quality of the physical and link layer for

^■ ongoing engineering (adding wireless devices)

^■ wireless mesh monitoring

^■ wireless mesh optimization

^■ wireless troubleshooting,

have to be determined.

Existing standardized protocols have insufficient support for this. WirelessHART, for example provide some information on the health of a device or a neighbor, but aggregates too much of this information to pinpoint a root cause. In addition, WirelessHART focuses on a single network and in particular on optimizing the mesh of a single network, while our interest is in an overall survey of the entire site including all of its networks.

Accordingly, the object of the invention is to provide a possibility for a better and more efficient setup and operation of wireless networks in plant automation or in automation industry, in particular acquisition and allocation of ongoing site survey data with minimized effort.

This object may be solved by a system for the dynamic assignment and operation of wireless networks according to the features of claim 1 . Further embodiments and refinements of the invention as well as a corresponding method are disclosed in further claims and the following description.

According to the disclosure of said application, a solution is proposed presuming the availability of some and/or specific site survey functions within the applied and provided field devices themselves. Such devices are assigned to networks using only basic constraints such as required bandwidth or distance to the gateways, wherein the consideration of wireless co-existence is rather independent. This is done by leaving a defined slack of free bandwidth in each network. During commissioning of said network, the site-survey functionality within the devices or mobile tools is used for example by a FDI (Field Device Integration) device management system (DMS) to identify sub-optimal assignments and move devices to the networks with the best QoS.

The system according to the invention provides ongoing site survey data for given and/or predefined tasks without actually performing a "classic/manual" (one-time) site survey; and is for example based on an advanced HART7 standard and a FDI device management system (DMS). The DMS comprises means and is equipped to assess the localized network health and rate the likelihood of root causes for troubleshooting and network optimization with high quality and/or lead to better/faster support and human decisions. Furthermore, it allows a more efficient engineering/layout approach.

Essentially, site survey information is constructed and/or generated and/or determined from periodically collected suitable health indicators, in particular new suitable health indicators, of the wireless network.

Thus, the system according to the invention comprises a device side arrangement, comprising accessing means, which make available via standardized or proprietary HART commands information that can be gathered directly or through additional processing from the communication stack of a field device. Furthermore, in one embodiment devices themselves are allowed to choose their network and/or change their network dynamically, which improves their reachability in case of network problems during regular network operation, and which ensures a more dynamic and efficient operation of the wireless network and/or using site survey functions to optimize the wireless engineering and commissioning process but also the operational processes.

In general, in particular, in a plant and/or process automation facility or in process automation, the radio area covered by all gateways has to include all devices and the devices belonging to a network must not exceed the bandwidth, which is available by a gateway.

The coverage area of a gateway is determined depending on the environment where it is used, which mostly relates to the level of obstruction and co-existing networks.

Its diameter should reflect the expected communication range of a gateway and the number of acceptable hops. The distance of each such hop naturally varies with the level of obstruction, transmission power, and the number of hops depends on application and safety requirements.

Since the real plant does not perfectly match up with a typical one, planning is required to leave a certain amount of slack on the communication load of each network. A cell contains an area where communication is expected to always work as required, wherein this area is called the core area, and an area where it sometimes may not, wherein this area is called the slack area.

The size of the slack area is varied with the obstruction level of the environment. As a result, each network is designed with free bandwidth for additional devices. Layout is performed with an overlap of slack areas. The resulting layout allows and/or discloses devices that are more distant from a gateway to have at least one alternative network to connect to if needed.

Neighboring cells with few devices may be merged if the application allows additional hops, which in particular were expected to be introduced by every cell, and if blacklisting permits it. This cell aggregation reduces the number of gateways but still allows planning with slack areas.

To reduce the amount of reserved but unused and/or wasted bandwidth, in a further embodiment of the invention the probability for the transfer and/or switch of a "slack device" to a neighboring network is used, wherein neighbors only have to reserve bandwidth for the expected total number of moved devices then.

In a further refinement, the plant or the individual floor plans are covered with individually sized and/or shaped coverage areas per gateway.

Furthermore each floor may be divided into a number of regularly shaped, adjoining cells and the gateways may be placed in centers of these cells, wherein due to the radial shape of the wireless signals in particular a hexagonal cell shape as planning area for a network is used and/or applied.

In another embodiment neighboring cells, comprising only a few devices each, may be merged if the respective application allows additional hops and/or if blacklisting permits it.

Furthermore, by using the number of devices per cell and the expected communication load, in particular including WiFi if known, the planning tool gives and/or provides feedback on at least one of coverage, reliability, and energy constraints.

Moreover, in a further system embodiment a layout unit with a layout tool is provided, wherein the layout unit and/or tool may determine and/or count the number of devices in the respective core and slack areas and performs a validity check of the planning, in particular checking whether all devices are covered, if all slack-devices have alternative networks, and in particular available alternative networks, if networks are overloaded from a bandwidth perspective and the like. In a further embodiment an assessment unit is provided, wherein by using said assessment unit a quality assessment of the network is performed and/or provided, including the maximum and minimum, in particular if it must take all slack-devices, free bandwidth per network, reserved and/or potentially wasted bandwidth.

Furthermore, devices, dedicated repeaters, and gateways may be installed and commissioned.

In a further embodiment a site survey is performed by the FDI DMS as a central wireless authority, using site-survey support built into the devices and/or provided by the devices, wherein for each device in the vicinity of a network "edge", the DMS may perform join trials or test joins.

In a further refinement said trials or test joins comprises steps of moving the device to a network and establishing test communication tailored to obtain survey data, which in particular causes no disruption of operative traffic during commissioning.

Furthermore, it has to be denoted, that the procedure benefits from a high advertising frequency as the device has more liberty to choose a good join partner.

Alternatively, in another embodiment these trials could be implemented within the device itself, wherein this could be standardized.

In a further, refinement security credentials would be received for all potential networks and/or during the join process it gets to listen to advertisements from all "audible" networks anyway.

In a further refinement, to have or to obtain a better control of this behavior, a dedicated trial mode flag may be implemented, wherein only if this flag is set, a device attempts to perform join trials on its own. In another refinement, a part of the FDI DMS dedicated to WirelessHART identifies suboptimal network assignments in the border regions between overlapping networks and then moves such devices into the best available network, considering the impact of this shift.

This procedure allows for a layout that is "off" by the specified slack, wherein this may be insufficient if for example a considerable number of WiFi networks have not been taken into account

In a further embodiment of the invention during the test joins, it is conceivable that a device is asked to join a network that is actually not reachable, wherein in consequence, the device itself would become inaccessible wirelessly, too.

In order to prevent such a severed device, in a further embodiment, the device remembers the last working communication configuration and/or a list of them and/or reverts to it upon a defined timeout.

Furthermore, to have better control of this behavior, the trial mode flag proposed above may be used, wherein only during join trials a device will revert to the last working configuration and wherein during regular operation, the device will attempt to rejoin its assigned network.

In a further refinement, a configurable timeout may be implemented to be set from the DMS.

In a further embodiment, the DMS establishes the maximum amount and/or update rate of bust commands from the respective device, wherein this benchmarks the typical operational traffic for wireless sensor networks, transmitting for example primary, secondary, tertiary, and quaternary process values to the gateway and in particular the gateway master. Essentially, this tests how well a device communicates to its neighbors. In another embodiment, the DMS performs a permanent download to the device, wherein in particular valid data such as engineered device parameters are preferably used.

Furthermore, in order to maximize the communication strain for the benchmarks, a dedicated burst command may be introduced which requires a full frame length, wherein standard commands may be shorter and release the medium earlier.

Moreover, the described layout and commissioning approach may be continued during network operation.

In a further embodiment, the QoS is monitored, in particular as part of mesh monitoring, and/or site-survey information is or are updated periodically, which allows the DMS to propose and/or execute network changes.

In another embodiment, if devices carry credentials for all networks in their vicinity, they may be configured to try to switch to another network in case that they lose connection, wherein this behavior may be configured in various ways, which for example comprise enabled/disabled, number of credentials, timeout after which to switch and/or how the stored credentials are ranked among each other.

Moreover, when adding new devices or entire networks a combination of the previous approaches may be applied.

In particular, one (or more) new gateway(s) may be proposed within the weakest area(s) of the plant, wherein weakest meaning worst coverage or worst QoS.

In a further embodiment of the system as well as of the corresponding method in order to achieve a full coverage during site survey, including the quality of all available networks, at least one of the following approaches may be used as such or in combination:

^■ the DMS performs join trials with each device

^■ a mobile tool including sniffer functionality compares the quality of all available networks by listening to regular traffic, survey traffic, or advertisement messages

^■ the devices themselves are provisioned with network IDs and join keys for all potential networks and rate advertising devices across all these networks before they decide where to join, wherein the standard only defines that this is done for a single network.

In a further embodiment the system determines and/or keeps statistics per channel (not in standard) and directionally per neighbor (directional)

^■ successful transmits

^■ failed transmits, in particular transmits without acknowledge

^■ failed receptions, in particular receptions with CRC errors and/or new for channels and neighbors.

Furthermore, the local transmit signal strength (standardized) and/or the receive signal level per neighbor (new) may be recorded.

Advantageously, no complex processing is required to determine this information within a device.

In a further refinement, the system comprises a system side arrangement, wherein the provided (FDI) device management system (DMS) comprises means, which gather the information previously described from each device that has joined the network with a configurable and/or predeterminable periodicity. Since most quality indicators are volatile within the devices and are lost following a reset or a re-join, the device management system may cache their values and use the full history data for its calculations. The corresponding commands are part of the FDI EDDs (Field Device Integration Electronic Device Description) for gateways and field devices.

The FDI DMS (Field Device Integration Device Management System) calculates the localized interference level for each communication channel across all wireless field networks; it also calculates the local obstruction level. This essentially constitutes a full, built-in, ongoing wireless site survey that comes as a native part of such a wireless system.

In a further refinement, this site survey can be further improved by taking into account already available data like send and receive signal strength.

Furthermore, if the distance between devices is known, then the DMS may be put into perspective to send and receive signal level to determine obstructions.

In a further embodiment taking into account the obstructions, the quality of the physical layer can be rated with very high precision.

In a further refinement life-cycle integration means are provided by which the DMS supports setting of life-cycle phase, in particular commissioning/survey, operational, wherein during commissioning, specific defined test traffic is generated to gather condition indicators.

Moreover, in a further embodiment means to provide and/or perform wireless mesh monitoring are provided, wherein mesh monitoring includes site survey information to detect and predict QoS (Quality of Service) problems within the wireless networks. Detailed site-survey information allows a very precise pin-pointing of the "asset" which has or will have a problem. It allows distinguishing between interference on a single frequency band or a local obstruction.

Prediction is generally possible by observing the trends of any health indicator in the site survey information.

In another refinement, troubleshooting means are provided, wherein the troubleshooting process includes the processing of site survey information to determine the possible root causes or at least rate the likelihood of the possible root causes for a detected problem. An essential part of troubleshooting is the elimination of possible root causes. The number of conceivable root causes is limited, but eliminating each can incur considerable effort, in particular the manual handling of installed devices in the operative plant, re-engineering, etc..

Precise site information helps to improve the precision with which root causes are rated and thus reduces the effort of finding the root cause.

Accordingly, in a further embodiment of the invention a new, smart statistics of basic quality indicators from within all wireless field devices and gateways are used to create and/or generate a detailed site survey "out of the box".

Furthermore, additional already existing indicators can be added to increase the rating quality. No dedicated site survey tool or "sniffer" or actually going into the field for an on-site funding or analysis is needed.

In a further embodiment site survey information is generated and/or created based on new suitable health indicators of the wireless network.

Implementing some of the following features may require access to the wireless stack.

In a further embodiment they might be fed into standardization and might be implemented in processing unit or device like a chip and/or an integrated circuit.

per device

Source Description Layer

#798 Output Power in dBm PHY

#779, 840 Percent Availability since last join (from all peer devices). DLL

#779, 840 Percent Availability (from all peer devices) for the lifetime DLL of device MIC failures, CRC errors, NONCE counters are only the sums over all neighbors/ channels. Latency and number of generated/terminated packets (APP) are not used for survey. er channel

In a further embodiment, during wireless site survey, the radio properties of a number of defined locations are determined. These properties may influence the QoS of the wireless communication and are and/or have to be considered during wireless network layout.

Furthermore, an essential aspect of any site survey is thus the knowledge of site layout and the position of the surveyed locations. If the location information is not obtained or lost, the radio properties have no frame of reference. According to the invention, using the field devices themselves as sources for site survey information has the advantage that the survey information is always in the context of a, in particular traceable, device tag. Some exemplary commands with the same data are available both as a network manager (#8xx) and a device (#7xx).

779 Report Device Health / 840 Read Device Statistics - performance statistics; at best for detecting an issue, but not for "shooting" it; the following information is given for the device, but in particular should be given per channel and per neighbor:

^■ Number of Data-Link Layer MIC failures detected,

^■ Number of Network Layer (Session) MIC failures detected,

^■ Number of CRC Errors detected, and

^■ Number of Unicast Nonce Counter Values not received.

798 Read Radio Output Power - required

787 Report Neighbor Signal Levels - included in 780 and 833

780 Report Neighbor Health List / 833 Read Device's Neighbor Health,

wherein the following information is determinable

^■ RSL of communication received at this device from neighbor,

^■ Packets transmitted to the neighbor,

^■ Failed transmits to the neighbor (number of packets expecting an ACK and none was received), and

^■ Packets received from neighbor

In a further embodiment, both the "regular" transmissions and the acknowledges (ACK, sent in the same time-slot) are secured by a CRC (cyclic redundancy check); thus send/receive counters to increase evenly during error-free transmission are provided; furthermore the probability for a lost ACK (acknowledgement) to be low as in case of transmission problems is considered and the original packet is much more prone to errors.

Furthermore, failed transmits and sent/received packets in 780 include retries, which may make sense because the neighbor may change for each retry; thus send/receive counters to be entirely on the DLL are provided.

Proposed Site-Survey Commands according 7/8xx Read Channel Statistics

To achieve a full coverage during site survey, including the quality of all available networks, the system and method for the dynamic assignment and operation of wire- less networks provide several options and/or embodiments, wherein

^■ the DMS performs join trials with each device, and/or

^■ a mobile tool including sniffer functionality compares the quality of all available networks by listening to regular traffic, survey traffic, or advertisement messages, and/or

^■ the devices themselves are provisioned with network IDs and join keys for all potential networks and rate advertising devices across all these networks before they decide where to join (the standard only defines that this is done for a single network)

The invention as well as further embodiments and refinements are furthermore disclosed and presented according to some drawings and illustrative examples.

The figures

Figure 1 Illustration of Sequence and Error Counters for Device D and

Neighbor N,

Figure 1 a exemplary system according to the invention,

Figure 1 b exemplary system device arrangement,

Figure 1 c exemplary system indicators,

Figure 1 d exemplary method chart according to the invention,

Figure 1 Network Coverage/Interference Areas (D6 different protocol on sameband),

Figure 2 Survey Area of D3,

Figure 3 Survey Communication D3,D4 and Impact from D6 on D3,

Figure 4 Principle of Channel-Related Indicators,

Figure 5 Principle of Directional Indicators,

Figure 6 Combining Channel and Directional Statistics,

Figure 8 Cell-Based Network Layout with Access Points (AP),

Figure 9a Cell Overlap (using a regular, squarish cell shape as one example) and aggregation of (sparsely populated) squarisch cells,

Figure 9 Cell Overlap (using a regular, hexagonal cell shape as one example), and

Figure 10 Aggregation of (sparsely populated) cells.

In Fig. 1 an illustration of sequence and error counters for device D and neighbor N within an exemplary system in a WirelessHART network according to the invention (see Fig. 1 a) is presented, wherein said system

System and method for the dynamic assignment and operation of wireless networks in an automated plant ongoing site survey data for given and/or predefined tasks without actually performing a "classic/manual" (one-time) site survey based on an advanced HART standard and in cooperation with an FDI device management system (DMS).

According to fig. 1 b the above mentioned functionalities like

Furthermore, the system assesses the localized network health and rates the likelihood of root causes for troubleshooting and network optimization with high quality and/or leads to better/faster support and human decisions. The system comprises means which construct and/or generate site survey information from periodically collected (new) suitable health indicators (see fig. 1 c) of the wireless network and wherein a device side arrangement is provided, comprising accessing means, which make available via standardized or proprietary HART commands information that can be gathered directly or through additional processing from the communication stack of a field device. An essential part of troubleshooting is the elimination of possible root causes. The number of conceivable root causes is limited, but eliminating each can incur considerable effort, in particular the manual handling of installed devices in the operative plant, re-engineering, etc.. Thus, precise site information helps to improve the precision with which root causes are rated and thus reduces the effort of finding the root cause. Furthermore, a new, smart statistics of basic quality indicators (see fig. 1 c) from within all wireless field devices and gateways are used to create and/or generate a detailed site survey "out of the box", wherein already existing indicators can be added to increase the rating quality.

Moreover, the site survey information may be generated and/or created based on new suitable health indicators of the wireless network.

The following information is given for the device, but in particular should be given per channel and per neighbor:

^■ Number of Data-Link Layer MIC failures detected,

^■ Number of Network Layer (Session) MIC failures detected,

^■ Number of CRC Errors detected, and

^■ Number of Unicast Nonce Counter Values not received.

^■ RSL of communication received at this device from neighbor,

^■ Packets transmitted to the neighbor,

^■ Packets received from neighbor

Both the "regular" transmissions and the acknowledges (ACK, sent in the same time- slot) are secured by a CRC (cyclic redundancy check); thus send/receive counters to increase evenly during error-free transmission are provided; furthermore the probability for a lost ACK (acknowledgement) to be low as in case of transmission problems is considered and the original packet is much more prone to errors.

Furthermore, failed transmits and sent/received packets include retries, which may make sense because the neighbor may change for each retry; thus send/receive counters to be entirely on the DLL are provided.

MIC failures, CRC errors, NONCE counters represent the sums over all neighbors/ channels. Latency and number of generated/terminated packets (APP) are not used for survey.

In Fig 1 d an illustration of an exemplary embodiment of the method according to the invention is presented, which provides ongoing site survey data for given and/or predefined tasks without actually performing a "classic/manual" (one-time) site survey; and is based on an advanced HART standard and a FDI device management system (DMS). The DMS comprises means and is equipped to assess the localized network health and rate the likelihood of root causes for troubleshooting and network optimization with high quality and/or lead to better/faster support and human decisions. Furthermore, it allows a more efficient engineering/layout approach.

Essentially, site survey information is constructed generated from periodically collected (new) suitable health indicators of the wireless network.

Means are provided which make available via standardized or proprietary HART commands information that can be gathered directly or through additional processing from the communication stack of a field device. Furthermore, devices themselves are allowed to choose their network, which improves their reachability in case of network problems during regular network operation and which ensures a more dynamic and efficient operation of the wireless network and/or using site survey functions to optimize the wireless engineering and commissioning process but also the operational processes.

Site survey is performed by the FDI DMS as a central wireless authority, using site- survey support built into the devices, wherein for each device in the vicinity of a network "edge", the DMS may perform join trials or test joins. In a further refinement said trials or test joins comprises steps of moving the device to a network and establishing test communication tailored to obtain survey data, which in particular causes no disruption of operative traffic during commissioning. Furthermore, it has to be denoted, that the procedure benefits from a high advertising frequency as the device has more liberty to choose a good join partner. Alternatively, in another embodiment these trials could be implemented within the device itself, wherein this could be standardized.

Security credentials would be received for all potential networks and/or during the join process it gets to listen to advertisements from all "audible" networks anyway. To have or obtain a better control of this behavior, a dedicated trial mode flag may be implemented, wherein only if this flag is set, a device attempts to perform join trials on its own.

A part of the FDI DMS may be dedicated to WirelessHART identifies suboptimal network assignments in the border regions between overlapping networks and then moves such devices into the best available network, considering the impact of this shift. This procedure allows for a layout that is "off" by the specified slack, wherein this may be insufficient if for example a considerable number of WiFi networks have not been taken into account

Furthermore, during the test joins, it is conceivable that a device is asked to join a network that is actually not reachable, wherein in consequence; the device itself would become inaccessible wirelessly, too. In order to prevent such a severed device, in a further embodiment, the device remembers the last working communication configuration and/or a list of them and/or reverts to it upon a defined timeout.

Moreover, the maximum amount and/or update rate of bust commands from the respective device is established, wherein this benchmarks the typical operational traffic for wireless sensor networks, transmitting for example primary, secondary, tertiary, and quaternary process values to the gateway and in particular the gateway master.

Essentially, this tests how well a device communicates to its neighbors. Furthermore, a permanent download to the device, wherein in particular valid data such as engineered device parameters are preferably used, is performed.

In order to maximize the communication strain for the benchmarks, a dedicated burst command may be introduced which requires a full frame length, wherein standard commands may be shorter and release the medium earlier.

The QoS is monitored, in particular as part of mesh monitoring, and/or site-survey information is updated periodically, which allows the DMS to propose and/or execute network changes.

If devices carry credentials for all networks in their vicinity, they may be configured to try to switch to another network in case that they lose connection, wherein this behavior may be configured in various ways, which for example comprise enabled/disabled, number of credentials, timeout after which to switch and/or how the stored credentials are ranked among each other.

In particular, one (or more) new gateway(s) may be proposed within the weakest ar- ea(s) of the plant, wherein weakest meaning worst coverage or worst QoS.

Moreover according to the presented method means are provided which gather the information previously described from each device that has joined the network with a configurable and/or predeterminable periodicity. Since most quality indicators are volatile within the devices and are lost following a reset or a re-join, the device management system may cache their values and use the full history data for its calculations. The corresponding commands are part of the FDI EDDs (Field Device Integration Electronic Device Description) for gateways and field devices. The localized interference level for each communication channel across all wireless field networks is calculated; it also calculates the local obstruction level. This essentially constitutes a full, built-in, ongoing wireless site survey that comes as a native part of such a wireless system.

The site survey can be further improved by taking into account already available data like send and receive signal strength.

Moreover, in a further embodiment means to provide and/or perform wireless mesh monitoring are provided, wherein mesh monitoring includes site survey information to detect and predict QoS (Quality of Service) problems within the wireless networks.

Detailed site-survey information allows a very precise pin-pointing of the "asset" which has or will have a problem. It allows distinguishing between interference on a single frequency band or a local obstruction.

Prediction is generally possible by observing the trends of any health indicators in the site survey information.

In another refinement troubleshooting means are provided, wherein the troubleshooting process includes the processing of site survey information to determine (or at least rate the likelihood) of the possible root causes for a detected problem. An essential part of troubleshooting is the elimination of possible root causes. The number of conceivable root causes is limited, but eliminating each can incur considerable effort, in particular the manual handling of installed devices in the operative plant, re-engineering, etc.

In a further embodiment site survey information is generated and/or created based on new suitable health indicators of the wireless network. Implementing some of the following features may require access to the wireless stack.

In an exemplary embodiment three radio entities (gateways, repeaters, devices) D3, D4, D5 are provided using one radio protocol and D6 using another radio protocol within the same frequency band.

Figure 2 shows the radio coverage areas of D3, D4, and D6 assuming ideal signal antennae and signal propagation. Fehler! Verweisquelle konnte nicht gefunden werden. illustrates which devices can be surveyed from the perspective of D3, namely D4 and D6. Figure 4 illustrates dedicated survey communication between D3 and D4 if they are in the same network; this leads to a higher amount of survey data compared to D6, which even uses another protocol and survey is only possible indirectly.

Interference issued from the point of a wireless node do not depend on the directions it communicates to. Since obstruction and interference are basically independent from each other, it is thus not required to collect quality indicators per channel and direction as shown in Figure 7.

While the location of wireless devices in the field is determined by the 10 points of the process, the number and placement of gateways and repeaters must is constrained by the communication technology, needed latency and bandwidth, and the radio properties of the site. A wireless layout must place gateways and repeaters considering obstructions, interferences, and bandwidth limits so that the QoS needs of the applications are met.

A perfect offline planning of all wireless networks in an industrial plant comes with high effort. While the networks, gateways, devices, and QoS requirements may be known beforehand, the wireless properties of the site are hard to determine. Even if CAD data are available to the wireless planning and layout, radio propagation and interference are eventually complex to calculate. In addition, details may change until or after the plant is operational, making a perfect one-time planning unfeasible. It is to be expected that a certain number of devices is assigned to a network with sub- optimal QoS properties - especially "edge" devices located at equal distance between gateways. Wireless site surveys are a very practical approach to the problem, but they are time consuming, require tool support, can naturally only take place once the plant has already been constructed, and know nothing of wireless interference.

A solution is proposed presuming the availability of some site survey functions within the field devices themselves. Devices are assigned to networks using only basic constraints such as required bandwidth or distance to the gateways (the consideration of wireless co-existence is rather independent). This is done leaving a defined slack of free bandwidth in each network. During commissioning, the site-survey functionality within the devices or mobile tools is used by the FDI device management system (DMS) to identify sub-optimal assignments and move devices to the networks with the best QoS.

Another option is to allow devices themselves to choose their network, which improves their reachability in case of network problems during regular network operation.

With classical fieldbuses, the execution hosts for the applications application (controllers for closed-loop control, PCs for mesh or device monitoring) determine to which communication master a field device must be connected.

With field-mounted wireless gateways connected to a common backbone, the assignment of a field device to a gateway can/should be done mostly with regard to communication aspects; the execution host of the wireless applications is secondary if it can access the common backbone.

This means that the wireless coverage area of the gateways plays an important role; it is a selection criterion for assigning the network IDs to a device.

While security credentials can be shared (e.g. shared join keys in WirelessHART), the network ID as part of the addressing scheme must be unique.

Since a gateway or access point typically only provides one network, a field device must be provisioned with the correct unique network ID to be able to communicate. It cannot simply connect to any network that promises good QoS (e.g. signal strength). In particular, even with a device eventually connected to a "sub-optimal" network, there are no standard mechanisms to automatically move it to a better available network.

This results in the challenge to determine and distribute the network assignments to gateways and devices. It is a particular problem to derive the network assignments from offline engineering in order to reliably distribute them to the field devices. For this, it may not even be desirable to have to perform a perfect assignment during offline engineering if this comes with high engineering effort; rather, it would be desirable to use survey information from the actual site. Since such information may also be tedious to collect - or even impossible because the site does not exist yet - the most preferable solutions should allow some flexibility for network assignment during the actual commissioning process. In this case, a method is required to also update the previous (sub- optimal) offline engineering. This is required not only to generate "as built" information but also to actually allow the network to operate (since the gateways have to the information about the different network assignment).

Generally, the radio area covered by all gateways must include all devices (see Fig. 1 a) and the devices belonging to a network must not exceed the bandwidth which is available by a gateway.

The coverage area of a gateway is determined depending on the environment where it is used (which mostly relates to the level of obstruction and co-existing networks).

Since the real plant does not perfectly match up with a typical, planning is required to leave a certain amount of slack on the communication load of each network. As shown in Figure 8, a cell contains an area where we expect communication to always work as required {core area) and an area where it sometimes may not {slack area).

The size of the slack area is varied with the obstruction level of the environment.

As a result, each network is designed with free bandwidth for additional devices. Layout is performed with an overlap of slack areas (see Figure 9, 9a). The resulting layout allows devices that are more distant from a gateway to have at least one alternative network to connect to if needed.

Neighboring cells with few devices may be merged (seeFigurel O, 9a) if the application allows additional hops (which we expect every cell to introduce) and if blacklisting permits it. This cell aggregation reduces the number of gateways but still allows planning with slack areas.

To reduce the amount of reserved but unused (i.e. wasted) bandwidth, the probability for the transfer of a "slack device" to a neighboring network is used and/or processed. Neighbors must only reserve bandwidth for the expected total number of moved devices then.

In one embodiment the plant or the individual floor plans are covered with individually sized/shaped coverage areas per gateway.

Regarding workflow execution, another more efficient approach is to divide each floor into a number of regularly shaped, adjoining cells and place the gateways in centers of these cells. Due to the radial shape of the wireless signals, the use of a hexagonal cell shape as planning area for a network is preferred.

Neighboring cells with few devices may be merged if the application allows additional hops and if blacklisting permits it.

Using and/or processing the number of devices per cell and the expected communication load, in particular including WiFi if known, the planning unit and/or tool gives feedback on coverage, reliability, and energy constraints:

The layout unit and/or tool counts the number of devices in the core and slack areas and performs a validity check of the planning, (are all devices covered, do all slack- devices have alternative networks, are networks overloaded from a bandwidth perspective). Additionally, it may provide a quality assessment of the network, including the maximum and minimum (if it must take all slack-devices) free bandwidth per network, reserved (potentially wasted) bandwidth.

Furthermore, according to the invention devices, dedicated repeaters, and gateways, in particular in a plant or in a process automation facility, are installed and commissioned, as disclosed in Fig. 1 a.

A site survey is performed by the FDI DMS as a central wireless authority, using site- survey support built into the devices. The corresponding method or process is presented according to fig. 1 d. For each device in the vicinity of a network "edge", the DMS performs join trials or test joins: It moves the device to a network and establishes test communication tailored to obtain survey data; this causes no disruption of operative traffic during commissioning. The procedure benefits from a high advertising frequency as the device has more liberty to choose a good join partner.

Alternatively, these trials could be implemented within the device itself, see fig. 1 b, and/or this could be standardized; it would receive security credentials for all potential networks. During the join process, it gets to listen to advertisements from all "audible" networks anyway.

To have better control of this behavior, a dedicated trial mode flag may be implemented. Only if this flag is set, a device attempts to perform join trials on its own.

A part of the FDI DMS dedicated to WirelessHART identifies suboptimal network assignments in the border regions between overlapping networks. It then moves such devices into the best available network, considering the impact of this shift.

This approach allows for a layout that is "off" by the specified slack. This may be insufficient if e.g. a considerable number of WiFi networks have not been taken into account

During the test joins, it is conceivable that a device is asked to join a network that is actually not reachable; in consequence, the device itself would become inaccessible wirelessly, too. To prevent such a severed device, it remembers the last working communication configuration (or a list of them) and reverts to it upon a defined timeout.

To have better control of this behavior, the trial mode flag proposed above is used. Only during join trials, a device will revert to the last working configuration. During regular operation, it will attempt to rejoin its assigned network.

In addition, a configurable timeout may be implemented to be set from the DMS.

Survey data are provided by means of the system according to the invention, wherein the DMS establishes the maximum amount and update rate of bust commands from the device. This benchmarks the typical operational traffic for wireless sensor networks, transmitting e.g. primary, secondary, tertiary, and quaternary process values to the gateway (master). Essentially, this tests how well a device communicates to its neighbors.

Optionally, the DMS performs a permanent download to the device (preferably using valid data such as engineered device parameters).

To maximize the communication strain for the benchmarks, a dedicated burst command may be introduced which requires a full frame length. Standard commands may be shorter and release the medium earlier.

Regarding troubleshooting, the described layout and commissioning approach is continued during network operation.

The QoS is monitored (e.g. as part of mesh monitoring) and site-survey information is updated periodically; this allows the DMS to propose (or execute) network changes. Regarding runtime stability if devices carry credentials for all networks in their vicinity, they may be configured to try to switch to another network in case that they lose connection. This behavior may be configured in various ways (enabled/disabled, number of credentials, timeout after which to switch, how the stored credentials are ranked among each other).

When adding new devices or entire networks a combination of the previous approaches is applied.

In particular, one (or more) new gateway(s) are proposed within the weakest area(s) of the plant; weakest meaning worst coverage or worst QoS.

Claims

1.

2. System and method for the dynamic assignment and operation of wireless networks in an automated plant a data processing device, a data storage and communication interface for the dynamic assignment of wireless devices into one particular network out of a plurality of available networks, wherein it is provided means based on a raw wireless KPIs, which gather and process ongoing wireless site survey data for given and/or predefined tasks without actually performing a "classic/manual" (one-time) site survey.

3. System and method for the dynamic assignment and operation of wireless networks in an automated plant ongoing wireless site survey data for given and/or predefined tasks without actually performing a "classic/manual" (onetime) site survey based on raw wireless KPIs according to the HART standard and in cooperation with an FDI device management system (DMS).

4. System according to claim 1 or 2, characterized in that means are provided to assess the localized network health and rate the likelihood of each possible root cause for degraded or failed network service quality from a predefined list of such root causes for troubleshooting and network optimization tasks with high quality and/or lead to better/faster support and human decisions.

5. System according to one of the preceding claims, characterized in that means are provided which construct and/or generate, particular wireless, site survey information from periodically collected (new) suitable health indicators of the wireless network.

6. System according to one of the claims 2 - 4, characterized in that a device side arrangement is provided, comprising accessing means, which make available via standardized or proprietary HART commands information that can be gathered directly or through additional processing from the communication stack of a field device.

7. System according to one of the preceding claims, characterized in that the provided system comprises means which gather the information previously described from each device that has joined the network with a configurable and/or predeterminable periodicity, wherein since most quality indicators are volatile within the devices and are lost following a reset or a re-join, the device management system may cache their values and use the full history data for its calculations and/or determinations.

8. System according to claim 6, characterized in that the provided FDI device management system (DMS) comprises means which gather the information previously described from each device that has joined the network with a configurable and/or predeterminable periodicity, wherein since most quality indicators are volatile within the devices and are lost following a reset or a re-join, the device management system may cache their values and use the full history data for its calculations and/or determinations.

9. System according to one of the preceding claims, characterized in that means are provided which determine the localized interference level for each communication channel across all wireless field networks and/or which calculates the local obstruction level.

10. System according to claim 8, characterized in that already available data like send and receive signal strength are taken into account and/or are processed.

1 1 . System according to one of the preceding claims, characterized in that wireless mesh monitoring is provided and/or performed, wherein mesh monitoring includes site survey information to detect and predict QoS (Quality of Service) problems within the wireless networks.

12. System according to one of the preceding claims, characterized in that means are provided which process site survey information to determine/identify or at least rate the likelihood of the defined possible root causes for a detected problem.

13. System according to one of the preceding claims, characterized in that smart statistics of basic quality indicators from within all wireless field devices and gateways and/or suitable health indicators of the wireless network are used to create and/or generate a detailed site survey.

14. System according to one of the preceding claims characterized in that to reduce the amount of reserved but unused, in particular in the operational net- work wasted, bandwidth in the network, the calculated probability for the transfer of a "slack device" to a neighboring network is used, wherein neighbors only have to reserve spare ("slack") bandwidth for the expected total number of moved devices then.

15. System according to one of the preceding claims, characterized in that each network floor or level, in particular of the plant or process automation facility, may be divided into a number of regularly shaped, adjoining cells and the gateways may be placed in centers of these cells, wherein due to the radial shape of the wireless signals in particular a hexagonal cell shape as planning area for a network is used and/or applied.

16. System according to claim 12, characterized in that neighboring cells comprising only a few devices each may be merged into one network if the respective application allows additional hops and/or if blacklisting permits it regarding wireless interference and/or wherein a planning unit is provided which, by using the number of devices per cell and the expected communication load, in particular including co-existing WiFi netwroks if known, gives and/or provides feedback on at least one of coverage, reliability, and energy constraints.

17. System according to one of the preceding claims 12 tor 13, characterized in that an assessment unit is provided executing and/or performing a quality assessment of the network, including at least one of the maximum in particular if it must take all slack-devices, minimum, median, or average, free bandwidth per network, compared to the reserved and thus potentially wasted bandwidth.

18. Method for the operation of wireless networks in an automated plant or process automation facility to dynamically assign wireless devices into one particular network according to predefined performance criteria, wherein ongoing site survey data is gathered and/or determined for given and/or predefined tasks without actually performing a "classic/manual" (one-time) site survey; and by using raw wireless KPI from the HART standard and a device management system (DMS), and wherein the localized network health and performance is assessed and the likelihood of root causes for troubleshooting and network optimization is rated with high quality to provide and allow an more efficient network assignment of wireless devices in engineering and commis- sioning for a more effective network design with regard to network performance and service quality.