Patent Grant
10645628
The present invention relates generally to wireless networks and, more particularly, to interconnecting wireless field device networks that are separated either logically or physically from each other by a barrier to wireless communication.
A wireless field device network includes of a cloud of devices or nodes with a central controller or gateway. The nodes in the wireless network are able to both send and receive information. In a star network, exemplified by the popular Bluetooth® format, the reach of the network is limited by the transmission range of a master device. All communications from slave devices are routed through the master according to the master's communications schedule. The range of the wireless star network can be extended by allowing the slave devices to be members of different networks so that communications can be relayed from master to slave device through multiple networks in a scatternet fashion. Star networks can also create a genealogical relationship among interconnected networks; slave devices becoming master devices of child networks. The use of a star network topology imposes some inefficiency in the routing of communications as there is rigidity to the master-slave relationship that can force messages to take a sub-optimal path to the destination node.
Mesh networking is a more flexible network architecture that is becoming prevalent in industrial applications. A mesh network includes a cloud of nodes and a controller or gateway, but avoids many of the limitations of the star network topology by allowing neighboring nodes within the same network to communicate directly with each other, avoiding unnecessary routing of communications to the controller. Each node is assigned multiple communications pathways that are interchanged to compensate for bottlenecks and linkage failures. By allowing neighboring nodes to form communications relays directly to the target node, and by routing around failures or bottlenecks, network response time is improved while minimizing network power usage by minimizing the number of transmissions required to relay a message. Utilizing multiple communications pathways provides path diversity which improves network reliability. Mesh networks can also communicate with each other by sharing nodes. These shared nodes can keep the communications schedule of every network in which it is a part, using an algorithm to determine priority between networks when there is a conflict.
Wireless networks are independent when the wireless networks do not or cannot communicate with each other. A barrier to communication can range from physical obstacles, such as long distances to natural obstructions (such as hills or trees), or man made impediments (such as concrete construction), or to logical problems inherent to the networks, such as differences in network protocols. The lack of communication between networks is inefficient, and potentially dangerous. When control systems are unable to monitor subsystems located in different independent networks, the utility of a centrally located control system is dramatically reduced. The challenge of linking disparate independent networks is that the solution must be flexible, reliable, and effective while being inexpensive. Common methods of interconnecting independent wireless networks, such as using gateways connected by an intranet backbone or by a separate wireless backbone (e.g., Wi-Fi), or radio repeaters, or home run network cabling require large outlays for installation of expensive wiring and equipment. Another issue with these mechanisms is that they often require an external power source, not readily available or practicable in many areas that are serviced by wireless field device networks.
The term “field device” refers to any field-mounted device that performs a function in a control or process monitoring system or plant monitoring system, including all devices used in the measurement, control and monitoring of industrial plants, processes or process equipment, including plant environmental, health and safety devices. A field device typically includes a sensor or an actuator or both and may perform a control or alert function. In wireless network systems designed for sensor/actuator-based applications, many devices in the network must be locally-powered because power utilities, such as 120V AC utilities or powered data buses, are not located nearby or are not allowed into hazardous locations where instrumentation, sensors, and actuators and safety monitors or human interface devices must be located without incurring great installation expense. “Locally-powered” means powered by a local power source, such as a self-contained electrochemical source (e.g., long-life batteries or fuel cells) or by a low-power energy-scavenging power source (e.g., vibration, solar, or thermoelectric). A common characteristic of local power sources is their limited energy capacity or limited power capacity, either stored, as in the case of a long-life battery, or produced, as in the case of a solar panel. Often, the economic need for low installation cost drives the need for battery-powered devices communicating as part of a wireless field device network. Effective utilization of a limited power source, such as a primary cell battery which cannot be recharged, is vital for a well functioning wireless field device. Batteries are expected to last more than five years and preferably last as long as the life of the product.
In order to save power, some wireless network protocols limit the amount of traffic any node or device can handle during any period of time by only turning their transceivers ON for limited amounts of time to listen for messages. Thus, to reduce average power, the protocol may allow duty-cycling of the transceivers between ON and OFF states. Some wireless network protocols may use a global duty cycle to save power such that the entire network is ON and OFF at the same time. Other protocols (e.g., TDMA-based protocols) may use a local duty cycle where only the communicating pair of nodes that are linked together are scheduled to turn ON and OFF in a synchronized fashion at predetermined times. Typically, the link is predetermined by assigning the pair of nodes a specific time slot for communications, an RF frequency channel to be used by the transceivers, who is to be receiving, and who is to be transmitting at that moment in time (e.g., a TDMA with channel hopping protocol, such as WirelessHART®).
Wireless field device networks are used to control and monitor disparate processes and environments. For example, wireless field device networks may be used in oil fields. An oil field is composed of numerous discrete locations centered on well pads that are scattered over large areas. Communication between these isolated local areas is essential to the overall management of the field. The wireless field device network at a well pad monitors and controls everything from flow rates and fluid temperature to valve status and position and potential leaks. The resulting data is relayed through the network to controllers that analyze the data and actuate control mechanisms in order to manage production or prevent trouble. Home run cabling from each isolated well pad to a centrally monitored station may be impractically expensive, so often times a wireless Supervisory and Control Data Acquisition system (SCADA) is employed to connect the well pads together into a star network. However, SCADA systems are expensive to install and often require expensive solar panels with battery back-up to power them. The oil field environment can be extremely difficult for a wireless mesh network to operate reliably. Distances between well pads are often greater than the standard range of a wireless field device and there are often physical obstructions to wireless communication, such as earthen berms, tanks, processing equipment, rocker/rod pumps and sheds. Wireless links between networks are often blocked by natural vegetation, such as trees and bushes. Trees absorb 2.4 GHz spectrum radio emissions at ˜0.35 dB/m, rapidly consuming the link budget of low powered radios used in wireless networks. RF signal intensity is often insufficient with low level and low powered wireless field devices to cover the distances between well pads and overcome the obstacles required to communicate with other wireless field device networks. These well pad locations are typically remote, limiting ready access to convenient sources of electricity. This limits the power of the wireless transceiver that can be installed: without an external supply of electricity, a more powerful transceiver will drain stored energy rapidly and quickly run up replacement and maintenance costs while causing frequent interruptions of network interconnectivity.
One method for interconnecting scattered independent networks is to install a gateway or base station device within each network and link each network through a hardwired backbone or through a separate wireless backbone (e.g., Wi-Fi or a proprietary point-to-point RF network). There are two primary disadvantages to such devices: they are expensive and they are energy intensive devices. Remote locations may not have sufficient power sources available to operate the gateway or base station for long periods without frequent maintenance. There are also additional costs associated with the gateway or base station, which are typically expensive, and require large power sources. Placing cable runs throughout a network scattered over large areas is difficult and can be prohibitively expensive.
To avoid the difficulties of installing a separate communications backbone, network systems may use wireless repeaters to increase range or overcome obstructions. A repeater is a high powered device that functions by transmitting a received low powered signal at much higher power so that the signal will overcome obstructions and distant networks can detect it. Such repeaters require external power sources in order to provide the necessary amplification. Remote locations may not have sufficient power sources available to operate the repeater.
In applications where physical space constraints are a factor, one solution to overcoming an obstruction between two networks is to use a radio transceiver with two antennas. By placing a separate antenna in each area to be interconnected, a single radio transceiver can send and receive signals in both areas. External RF cables connect each of the two antennas to the radio through a powered or passive RF splitter. The use of external RF cables and an RF splitter imposes severe restraints on the length of cable used. For example, LMR-400 low loss RF cable will incur a signal loss of ˜0.22 dB/meter at 2.4 GHz and a passive RF splitter reduces the available RF signal strength at each output by half. Practically, this solution can only interconnect two networks, and these networks must be very close to each other before signal loss renders the device useless. Substituting an RF switch for the RF splitter and switching the RF signal between the two antenna's recovers some of the lost signal but adds considerable complexity to the wireless device and still leaves large losses associated with the extra RF antenna cable.
The present invention bridges a barrier to wireless communication between wireless field device networks using at least a pair of locally-powered wireless devices connected by a wired link spanning the barrier. At least one of the wireless devices in the at least pair is in wireless communication with each of the wireless networks intended to be interconnected. The wireless devices include a wireless transceiver and an antenna. Messages from one wireless field device network addressed to a member node of another wireless field device network are received by a wireless device on one side of the barrier and transmitted via the wired link to another wireless device on the other side of the barrier for routing to the member node of the other wireless field device network.
Another embodiment of the present invention includes a method for bridging a barrier to wireless communication between wireless field device networks. A message from a first wireless field device network addressed to a member node of second wireless field device network is received at a locally-powered wireless device in wireless communication with the first wireless field device network. The message is transmitted through the barrier over a wired link. A locally-powered wireless device in wireless communication with the second wireless field device network receives the message from the wired link and transmits the message into the second wireless field device network for routing to the member node.
The present invention will be discussed in terms of bridging barriers, whether logical or physical, to communication between wireless field device networks with at least partial mesh network topologies. A person skilled in the art will recognize that the invention is equally suited to other network topologies and is not limited to solely the embodiments described, but that the invention will include all embodiments falling within the scope of the appended claims.
The present invention comprises locally-powered wireless devices associated with each independent wireless field device network to be interconnected and a wired link connecting at least a pair of the wireless devices, the wired link penetrating any barrier to communication. With the present invention, the wireless devices are able to route received messages bi-directionally over the wired link, through the barrier, to other wireless devices associated with other field device networks. Responses to these messages follow a reverse path through the wired link into the originating network. This allows a controller or node in one of the interconnected wireless field device networks to access the nodes of any other interconnected field device network, creating a single unified field device network composed of all the separate parts of the wireless field device network. In a mesh network topology, this allows the unified wireless field device network to use only one Network Manager and one Access Point (or one Gateway) for the entire extended network. Further efficiencies in different embodiments of this invention can be had by using a bus data protocol on the wired link creating a wired data link and connecting several locally-powered wireless devices to the wired data link in an individually addressable, multi-drop, multi-point fashion. Multi-drop is an arrangement with one master or driver device, such as a data router, and multiple slave or receiver devices on a data bus. Multi-point is an arrangement with more than one master or driver device on a data bus. A field device lacking wireless communications capability can be integrated as part of a locally-powered wireless device in the bridging apparatus giving the field device wireless capability and linking it to the rest of the wireless field device network. Alternatively, the field device can be connected to the wired data link in the bridging apparatus, linking it to the rest of the wireless field device network. Further efficiencies can be had by allowing a locally powered field device on the wired link to provide power through the wired link to other devices on the wired link.
Interconnecting otherwise independent wireless field device networks to create a unified field device network increases efficiency by allowing nodes within a wireless network to query remote sensors and other nodes located in separate wireless field device networks directly. This increases the information immediately available throughout the unified field device network, allowing for more accurate and timely responses to changing events. The present invention provides a lower cost, lower loss, and lower power solution than current methods for routing inter-network communications around obstructions. Using a wired data link, instead of the standard method consisting of a single radio with an RF splitter or RF switch and external RF cable linking multiple antennas, reduces signal loss dramatically. By reducing RF loss, the wireless device's power requirements are reduced making a locally-powered apparatus feasible. The present invention is easy to install. The wired link needs be only long enough to span the obstruction, avoiding costly long wiring runs required of an internet backbone or homerun linkages. Because the wireless device is easily programmed to use any standard network protocol, there is ready interoperability with current hardware in existing networks. Using multiple wireless devices also allows the present invention to connect networks which use different network protocols, making it easier to manage, upgrade and expand existing field device networks.
The present invention interconnects wireless field device networks, especially wireless field device mesh networks, by bridging barriers to wireless communication. Every node of a wireless field device mesh network includes a wireless device used to communicate with its neighbors. A wireless device is a wireless transceiver, a wireless data router or a wireless field device. A wireless transceiver comprises a transceiver and an antenna integrated into a single device. A wireless data router comprises a wireless transceiver and a data router integrated into a single device. A wireless field device comprises a wireless data router and a field device integrated into a single device. A wireless transceiver is a device for transmitting and receiving RF-based communication data. A data router is a device that routes data packets received by the wireless transceiver, unpacking the communication payload for consumption by an attached field device (if that device's address matches the final destination address in the packet) or redirecting the communication payload back to the wireless transceiver to be relayed back into the network to the next destination in the logical path. The present invention bridges barriers to wireless communication by connecting a wired link between a plurality of locally-powered wireless devices associated with otherwise different field device networks and using the wired link to exchange messages between the locally-powered wireless devices in the different field device networks.
Network 12b is composed of a meshed cloud of wireless nodes 30a-30h . . . 30N. The nodes of network 12b are prevented from wirelessly communicating with the nodes of network 12a by barrier 16. As illustrated in
In order to integrate wireless field device mesh networks 12a and 12b into single wireless field device mesh network 10, wired link 32 is run between locally-powered wireless devices 34 and 36 and overcomes barrier 16. Wired link 32 is of any suitable type, for example, EIA/RS-485, Ethernet, or even a proprietary type. This arrangement allows wireless device 34 to transmit messages from network 12a over wired link 32 to wireless device 36 and into network 12b and allows wireless device 36 to transmit messages from network 12b over wired link 32 to wireless device 34 and into network 12a. For example, if host computer 26 requires information contained on node 30c, a message from host computer 26 is routed by gateway 18 into network 12a, where the message is relayed from node to node until it reaches wireless device 34. Wireless device 34 determines that the message is destined for node 30c within network 12b, and sends the message over wired link 32 to wireless device 36. The message is then transmitted into network 12b and is relayed to the destination node 30c. The response to the message follows the reverse path back to gateway 18 and host computer 26. If barrier 16 to wireless communication includes non-physical obstacles, such as different frequency bands or protocols, wireless devices 34 and 36 are able to convert the message into a common format for transmission over wired link 32 and reconvert the message into a format suitable for transmittal into networks 12a and 12b respectively. In addition, wireless devices 34 and 36 route standard wireless messages within their respective networks, 12a and 12b respectively, using standard ‘store and forward’ routing mechanisms associated with wireless networks. Functionally the two separate networks 12a and 12b become unified wireless field device mesh network 10 where each node can communicate with host computer 26 through gateway 18.
Local power sources 39 and 45 comprise at least one of self-contained electrochemical sources (e.g., long-life batteries or fuel cells) and low-power energy-scavenging power sources (e.g., vibration, solar, or thermoelectric). The local power sources 39 and 45 are integrated into their attached wireless devices, as shown. Alternatively, such local power sources are physically separate, but electrically connected to provide power to an attached wireless device. For example, a vibration generator attached to a nearby vibration source or a thermoelectric generator attached to a nearby heat source, such as a hot pipe, is electrically connected to a wireless device to supply power. In addition, low-power energy-scavenging power sources further comprise energy storage devices (e.g., rechargeable batteries or storage capacitors) when necessary to maintain power. For example, a solar power source requires an energy storage device, such as a rechargeable battery, to supply power at night.
In operation, a message for a node in network 12b is relayed through network 12a until it reaches wireless device 34a. Transceiver 46, through antenna 48, receives the message and passes it to data router 50. Data router 50 checks the address field of the message and formats the message for transmission by wireless transceiver 36c in communication with network 12b. Data router 50 sends the formatted message to transceiver 40 on the other side of barrier 16 via wired link 32a. Transceiver 40, through antenna 42, then broadcasts the message into network 12b to be relayed to the destination node. A return message follows the reverse path back. Data router 50 reformats messages received from either transceiver 40 or 46 into a format suitable for broadcasting by the other transceiver 46 or 40 to allow the apparatus to bridge a barrier in differing network protocols. Functionally the two separate networks 12a and 12b become unified wireless field device mesh network 10.
In operation, a message for a node in network 12b is relayed through network 12a until it reaches wireless device 34b. Transceiver 46, through antenna 48, receives the message and passes it to data router 50. Data router 50 checks the address field of the message, either unpacking it for field device 52 or formatting the message for transmission by wireless transceiver 36c in communication with network 12b. Data router 50 sends the formatted message to transceiver 40 on the other side of barrier 16 via wired link 32a. Wireless transceiver 40, through antenna 42, then broadcasts the message into network 12b to be relayed to the destination node. A return message follows the reverse path back. Functionally the two separate networks 12a and 12b become unified wireless field device mesh network 10.
Operation is as described for the embodiment shown in
While the embodiments illustrated in
In operation, a message for a node in network 12b is relayed through network 12a until it reaches wireless device 34a. Transceiver 46, through antenna 48, receives the message and passes it to data router 50. Data router 50 checks the address field of the message and formats the message for transmission over wired link 32b to wireless device 36a in communication with network 12b. Data router 50 sends the formatted message to data router 44 on the other side of barrier 16 via wired link 32b. Data router 44 checks the address field of the message and reformats the message for transmission by transceiver 40 in communication with network 12b. Transceiver 40, through antenna 42, then broadcasts the message into network 12b to be relayed to the destination node. A return message follows the reverse path back. Functionally the two separate networks 12a and 12b become unified wireless field device mesh network 10.
Operation is as described for the embodiment shown in
Operation is as described for the embodiment shown in
While the embodiments illustrated in
In operation, a message for a node in network 12b is relayed through network 12a until it reaches wireless device 34b. Transceiver 46, through antenna 48, receives the message and passes it to data router 50. Data router 50 checks the address field of the message and it either unpacks it for field device 52 or formats the message for transmission over wired link 32b to wireless device 36a in communication with network 12b. Data router 50 sends the formatted message to data router 44 on the other side of barrier 16 via wired link 32b. Data router 44 checks the address field of the message and reformats the message for transmission by transceiver 40 in communication with network 12b. Transceiver 40, through antenna 42, then broadcasts the message into network 12b to be relayed to the destination node. A return message follows the reverse path back. Functionally the two separate networks 12a and 12b become unified wireless field device mesh network 10.
In operation, a message for a node in network 12b is relayed through network 12a until it reaches wireless device 34b. Transceiver 46, through antenna 48, receives the message and passes it to data router 50. Data router 50 checks the address field of the message and it either unpacks it for field device 52 or formats the message for transmission over wired link 32c to wireless device 36a in communication with network 12b. In this embodiment, data router 50 sends the formatted message to field device 52, and field device 52 sends the message to data router 44 of wireless device 36a on the other side of barrier 16 via wired link 32c. Data router 44 checks the address field of the message and reformats the message for transmission by transceiver 40 in communication with network 12b. Transceiver 40, through antenna 42, then broadcasts the message into network 12b to be relayed to the destination node. A return message follows the reverse path back. Functionally the two separate networks 12a and 12b become unified wireless field device mesh network 10.
Operation is as described for the embodiment shown in
In operation, a message for a node in network 12b is relayed through network 12a until it reaches wireless device 34b. Transceiver 46, through antenna 48, receives the message and passes it to data router 50. Data router 50 checks the address field of the message and it either unpacks it for field device 52, formats it for transmission to field device 54 over wired link 56b, or formats the message for transmission by wireless device 36a in communication with network 12b. In this embodiment, data router 50 sends the formatted message for network 12b to field device 52, and field device 52 sends the message to data router 44 of wireless device 36a on the other side of barrier 16 via wired link 32c. Data router 44 checks the address field of the message and reformats the message for transmission by transceiver 40 in communication with network 12b. Transceiver 40, through antenna 42, then broadcasts the message into network 12b to be relayed to the destination node. A return message follows the reverse path back. Functionally the two separate networks 12a and 12b become unified wireless field device mesh network 10. Should the message be for field device 54, data router 50 sends the formatted message for field device 54 to field device 52, and field device 52 sends the message to field device 54 via wired link 56b. Field device 54, with no wireless capability of its own, is connected through wireless device 34b to unified wireless field device mesh network 10.
Operation is as described for the embodiment shown in
Operation is as described for the embodiment shown in
While the embodiments illustrated in
In operation, a message for a node in network 12b is relayed through network 12a until it reaches wireless device 34b. Transceiver 46, through antenna 48, receives the message and passes it to data router 50. Data router 50 checks the address field of the message and either unpacks it for field device 52 or formats the message for transmission over wired link 32b to wireless device 36b in communication with network 12b. Data router 50 sends the formatted message to data router 44 on the other side of barrier 16 via wired link 32b. Data router 44 checks the address field of the message and either unpacks it for field device 62 or reformats the message for transmission by transceiver 40 in communication with network 12b. Transceiver 40, through antenna 42, then broadcasts the message into network 12b to be relayed to the destination node. A return message follows the reverse path back. Functionally the two separate networks 12a and 12b become unified wireless field device mesh network 10.
In operation, a message for a node in network 12b is relayed through network 12a until it reaches wireless device 34b. Transceiver 46, through antenna 48, receives the message and passes it to data router 50. Data router 50 checks the address field of the message and it either unpacks it for field device 52 or formats the message for transmission over wired link 32c to wireless device 36b in communication with network 12b. In this embodiment, data router 50 sends the formatted message to field device 52, and field device 52 sends the message to data router 44 of wireless device 36b on the other side of barrier 16 via wired link 32c. Data router 44 checks the address field of the message and either unpacks it for field device 62 or reformats the message for transmission by transceiver 40 in communication with network 12b. Transceiver 40, through antenna 42, then broadcasts the message into network 12b to be relayed to the destination node. A return message follows the reverse path back. Functionally the two separate networks 12a and 12b become unified wireless field device mesh network 10.
In operation, a message for a node in network 12b is relayed through network 12a until it reaches wireless device 34b. Transceiver 46, through antenna 48, receives the message and passes it to data router 50. Data router 50 checks the address field of the message and it either unpacks it for field device 52 or formats the message for transmission over wired link 32d to wireless device 36b in communication with network 12b. In this embodiment, data router 50 sends the formatted message to field device 52, and field device 52 sends the message to field device 62 of wireless device 36b on the other side of barrier 16 via wired link 32d. Field device 62 passes the message to data router 44. Data router 44 checks the address field of the message and either unpacks it for field device 62 or reformats the message for transmission by transceiver 40 in communication with network 12b. Transceiver 40, through antenna 42, then broadcasts the message into network 12b to be relayed to the destination node. A return message follows the reverse path back. Functionally the two separate networks 12a and 12b become unified wireless field device mesh network 10.
Operation is as described for the embodiment shown in
Operation is as described for the embodiment shown in
Operation is as described for the embodiment shown in
Operation is as described for the embodiment shown in
Operation is as described for the embodiment shown in
Operation is as described for the embodiment shown in
Operation is as described for the embodiment shown in
While the embodiments illustrated in
In order to integrate wireless field device mesh networks 112a, 112b, and 112c into a unified mesh network, several of the embodiments of the bridging apparatuses shown above, employing two locally-powered wireless devices to interconnect two wireless mesh networks through a barrier using an external wired link between them, are illustrated. Wired link 170 overcomes barrier 162 and connects locally-powered wireless data router 172 and locally-powered wireless data router 174, interconnecting wireless networks 112a and 112b, respectively, employing an embodiment of the type illustrated above in
In operation, if Network Manager 122 requires information stored on node 140a located in network 112c, a request is generated and sent to gateway 118 where it is broadcast into and relayed through network 112a. The message is passed through network 112a until it is received by wireless field device 178. Wireless field device 178 determines that the destination for the message exists in network 112c and sends the message over wired link 176 to wireless field device 180. Wireless field device 180 receives the message, formats the message for wireless transmission, and broadcasts the message into network 112c to be relayed to the destination node 140a. The return message follows a reverse path back to gateway 118 and Network Manager 122. If the intended destination node is in network 112b then the process for sending and receiving the message is the same except that it is sent from wireless data router 172 to wireless data router 174 over wired link 170 and that it is wireless data router 174 that formats the message for wireless transmission, and broadcasts the message into network 112b rather than 112c. Wireless field device mesh networks 112a, 112b, and 112c become unified wireless field device mesh network 110 where each host system 126, 152, and 154 has access to all of the nodes in any of the other networks and can receive information from or send control signals to any node as needed.
Another advantage of the present invention is that wired links 170, 176, and 182 together provide redundancy for improved connection reliability. If in the previous example, where Network Manager 122 requires information stored on node 140a located in network 112c, wired link 176 were off line, a connection path would still exist. For example, as before, the request is generated and sent to gateway 118 where it is broadcast into and relayed through network 112a. The message is passed through network 112a until it is received by wireless data router 172. Wireless data router 172 sends the message over wired link 170 to wireless data router 174. Wireless data router 174 receives the message, formats the message for wireless transmission, and broadcasts the message into network 112b to be relayed to wireless field device 184. Wireless field device 184 sends the message over wired link 182 to wireless data router 186. Wireless data router 186 receives the message, formats the message for wireless transmission, and broadcasts the message into network 112c to be relayed to the destination node 140a. The return message follows a reverse path back to gateway 118 and Network Manager 122.
Typically, each locally-powered wireless device 192, 194, and 196 comprises its own local power source. However, like the embodiments illustrated in
If Network Manager 122 requires information stored on node 140a located in network 112c, a request is generated and sent to gateway 118 where it is broadcast into and relayed through network 112a. The message is passed through network 112a until it is received by wireless device 192. Wireless device 192 determines that the destination for the message exists in network 112c and sends the message over wired data link 190 to wireless device 196. Wireless device 196 receives the message, formats the message for wireless transmission, and broadcasts the message into network 112c to be relayed to the destination node 140a. The return message follows a reverse path back to gateway 118 and Network Manager 122. If the intended destination node is in network 112b then the process for sending and receiving the message is the same except that it is sent to wireless device 194 over wired data link 190 and that it is wireless device 194 that formats the message for wireless transmission, and broadcasts the message into network 112b rather than 112c. Wireless field device mesh networks 112a, 112b, and 112c become unified wireless field device mesh network 110 where each host system 126, 152, and 154 has access to all of the nodes in any of the other networks and can receive information from or send control signals to any node as needed.
Another feature of the embodiment illustrated in
According to one embodiment, local power source 239 comprises at least one of self-contained electrochemical sources (e.g., long-life batteries or fuel cells) and low-power energy-scavenging power sources (e.g., vibration, solar, or thermoelectric). Local power source 239 is integrated into its attached wireless device, as shown. Alternatively, such a local power source is physically separate, but electrically connected to provide power to the attached wireless device.
In operation, a message for a node in network 212b is relayed through network 212a until it reaches wireless device 234a. Transceiver 246, through antenna 248, receives the message and passes it to data router 250. Data router 250 checks the address field of the message and formats the message for transmission into network 212b. Data router 250 sends the formatted message to transceiver 240. Transceiver 240 then transmits the message via wired link 232 to antenna 242 and broadcasts the message into network 212b to be relayed to the destination node. A return message follows the reverse path back. Data router 250 reformats messages received from either transceiver 240 or 246 into a format suitable for broadcasting by the other transceiver 246 or 240 to allow the apparatus to bridge a barrier in differing network protocols. Functionally the two separate networks 212a and 212b become unified wireless field device mesh network 210.
Operation is as described for the embodiment shown in
The embodiments shown in
In all embodiments of the present invention, the wired link is powered solely by the connected locally-powered wireless devices. This is in contrast to prior art field device network buses where the bus itself is powered by an external source and may provide power to attached field devices. The present invention is ideally suited for locations where such external power is not readily available. To keep power low, the data rate of the wired link should be relatively high, at least on the same order as the data rate of the wireless protocol which it serves to connect. For example, with WirelessHART®, the wireless data rate is 250 Kbits/second, so the wired link data rate should be within approximately that same range of speed, for example, greater than 100 Kbits/second. Because the power efficiency of the wired link is much better than that for the wireless links, the wired link data rate can be somewhat lower than the wireless data rate without sacrificing too much of the available local power, such as battery life or energy scavenging output. Fast data rates allow the locally-powered wireless devices of the present invention to duty-cycle between ON, when they communicate quickly, and OFF, minimizing the ON time and reducing average power usage.
Interconnecting otherwise independent wireless field device networks to create a unified field device network increases efficiency by enabling a single Network Manager to manage and control the combined networks and by allowing nodes within a wireless network to query remote sensors and other nodes located in separate wireless field device networks directly. This increases the information immediately available throughout the unified field device network, allowing for more accurate and timely responses to changing events. The present invention provides a lower cost, lower loss, and lower power solution than current methods for routing inter-network communications around obstructions. Using a wired data link, instead of the current method consisting of a single radio with an RF splitter or RF switch and external RF cable linking multiple antennas, reduces signal loss dramatically. By reducing RF loss, the wireless device's power requirements are reduced making a locally-powered apparatus feasible. The present invention is easy to install. The wired link needs be only long enough to span the obstruction, avoiding costly long wiring runs required of an internet backbone or homerun linkages. Because the wireless device is easily programmed to use any standard network protocol, there is ready interoperability with current hardware in existing networks. Using multiple wireless devices also allows the present invention to connect networks which use different network protocols, making it easier to manage, upgrade and expand existing field device networks.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
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