Endpoint clock frequency adjustment for narrowband and ultra-narrowband communication in mesh networks

Abstract

A system and method are disclosed for adjusting a clock frequency of an endpoint device in a mesh network for narrowband and ultra narrowband communication. The endpoint device receives a reference timing signal over a wireless network from a reference device in the network. The endpoint device determines a current value of the endpoint device's clock frequency and further determines a frequency difference between a reference frequency of the reference timing signal and the current value of the clock frequency. Based on the frequency difference, the endpoint generates a control signal and applies the control signal to a crystal oscillator of the endpoint device to adjust the frequency of the crystal oscillator. The endpoint device communicates with other devices in the network using the oscillation signal generated by the adjusted crystal oscillator.

Description

Technical Field

[0001] This disclosure generally relates to narrowband and ultra-narrowband communications in a wireless network, and more particularly to adjusting a clock frequency in an endpoint device of the network.

Background Art

[0002] Narrowband (NB) and ultra-narrowband (UNB) communications in a wireless network, such as an adaptive multi-rate (AMR) mesh network, are desirable in some cases where a longer range is required. An ultra-narrowband receiver is highly selective and can reject noise and interference that may cause the receiver to enter outside its narrow bandwidth, enabling a good signal-to-noise ratio (SNR) with relatively weak received signals.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, NB and UNB systems are particularly challenging because the channel bandwidth is small and thus a stable and accurate frequency reference is required between endpoints. These stable frequency references, such as a stratum 3 temperature-compensated crystal oscillator (TCXO) or an oven-controlled crystal oscillator (OCXO), typically require high power consumption, are bulky, and costly. Conventional frequency references (e.g., conventional TCXOs) are unreliable because their stability causes a frequency shift, thereby placing the information spectrum outside the intermediate frequency (IF) bandwidth of the transceiver and thus interfering with reliable communication.

Means for Solving the Problems

[0004] Embodiments and examples of apparatus and processes for adjusting the clock frequency of endpoint devices in a mesh network for narrowband and ultra-narrowband communication are disclosed. For example, a method performed by an endpoint device in a mesh network includes, while operating in initial communication mode, receiving a reference timing signal from a reference device in the mesh network via the mesh network; obtaining the current value of the frequency of the endpoint device's crystal oscillator; determining the frequency difference between the reference frequency of the reference timing signal and the current value of the frequency; generating a control signal based on the frequency difference; adjusting the frequency of the crystal oscillator according to the control signal; and determining that the error in the frequency of the crystal oscillator satisfies predetermined conditions. The method further includes switching to a narrowband or ultra-narrowband communication mode in response to determining that the error in the frequency of the crystal oscillator satisfies predetermined conditions. The data rate in the narrowband or ultra-narrowband communication mode is lower than the data rate in the initial communication mode. The method also includes, while operating in narrowband or ultra-narrowband communication mode, transmitting and receiving communication signals to and from other devices in the mesh network using the oscillation signal generated by the crystal oscillator.

[0005] In another embodiment, the system includes a reference device configured to transmit a reference timing signal to multiple endpoint devices in a mesh network, and a plurality of endpoint devices. Each of the plurality of endpoint devices is configured to receive the reference timing signal from the reference device via the mesh network while operating in initial communication mode, obtain the current value of the frequency of the endpoint device's crystal oscillator, determine the frequency difference between the reference frequency of the reference timing signal and the current value of the crystal oscillator's frequency, generate a control signal based on the frequency difference, adjust the frequency of the crystal oscillator by adjusting the crystal oscillator according to the control signal, and determine that the error in the crystal oscillator's frequency satisfies predetermined conditions. The endpoint device is further configured to switch to a narrowband or ultra-narrowband communication mode in response to determining that the error in the crystal oscillator's frequency satisfies predetermined conditions, and while operating in the narrowband or ultra-narrowband communication mode, communicate with the reference device or other devices in the mesh network using the oscillation signal generated by the crystal oscillator. The data rate in the narrowband or ultra-narrowband communication mode is lower than the data rate in the initial communication mode.

[0006] In yet another embodiment, the network endpoint device includes a crystal oscillator configured to generate an oscillating signal having a crystal oscillator frequency, a processor configured to execute computer-readable instructions, and memory configured to store computer-readable instructions that, when executed by the processor, cause the processor to perform an operation including: receiving a reference timing signal from a reference device in the network over the network while operating in initial communication mode, obtaining the current value of the crystal oscillator frequency, determining the frequency difference between the reference frequency of the reference timing signal and the current value of the crystal oscillator frequency, generating a control signal based on the frequency difference, adjusting the frequency of the crystal oscillator by applying the control signal to the crystal oscillator, and determining that the error in the frequency of the crystal oscillator satisfies predetermined conditions. The operation further includes switching the endpoint device to a narrowband or ultra-narrowband communication mode in response to determining that the error in the frequency of the crystal oscillator satisfies predetermined conditions. The data rate in the narrowband or ultra-narrowband communication mode is lower than the data rate in the initial communication mode. This operation also includes using an oscillation signal generated by a crystal oscillator to enable the endpoint device to communicate with other devices in the network while operating in a narrowband or ultra-narrowband communication mode.

[0007] These exemplary embodiments and features are mentioned not to limit or define the subject matter described herein, but to provide examples that aid in understanding the concepts described herein. Other embodiments, advantages, and features of the subject matter described herein will become apparent by reviewing the entire application. [Brief explanation of the drawing]

[0008] [Figure 1] Block diagram illustrating an exemplary operating environment for adjusting the clock frequency of endpoint devices in a mesh network for narrowband and ultra-narrowband communications, according to a predetermined aspect of the present disclosure. [Figure 2]This is a block diagram showing an embodiment of a frequency reference device and its associated endpoint device that receives a reference timing signal from the reference device, according to a predetermined aspect of the present disclosure. [Figure 3] This is a flowchart illustrating a process for adjusting the clock frequency of an endpoint device in a mesh network for narrowband and ultra-narrowband communications, relating to a predetermined aspect of this disclosure. [Figure 4] This is an embodiment of a block diagram of the endpoints of the networked system shown in Figure 1, relating to a predetermined aspect of this disclosure. [Modes for carrying out the invention]

[0009] These and other features, aspects, and advantages of this disclosure will be further understood when the following detailed description is read with reference to the accompanying drawings.

[0010] A system and method are provided for adjusting the clock frequency of endpoint devices in networked systems for narrowband and ultranarrowband communications. In a networked system such as a mesh network, an endpoint device (also called a “node”) may be a device in the networked system that can send and receive data to and from other endpoint devices or network devices. To provide appropriate adjustment for the clock frequency of endpoints in the network, the endpoint device communicates directly with a network device (referred to as a “reference device”) that has access to a reference timing signal, such as a gateway or router.

[0011] For example, the reference device may be a router in a network equipped with a receiver that receives a reference timing signal. The receiver may be, for example, a Global Positioning System (GPS) receiver that receives the reference timing signal at 1 pulse per second (pps) along with GPS information. The reference timing signal is generated by a device (e.g., a GPS clock) synchronized to a high-precision clock such as the NIST-7 cesium frequency standard. The reference device retransmits the reference timing signal to endpoint devices in the network. The endpoints receiving the reference timing signal can precisely adjust their clocks to the accuracy of the reference clock, thus enabling NB and UNB communication.

[0012] To adjust the clock frequency of the endpoint device for NB and UNB communication, the endpoint device may operate in a higher bandwidth communication mode at the start of an NB or UNB communication session to ensure that communication with the reference device does not fail. When a reference timing signal is received from the reference device, the endpoint device may adjust the frequency of the endpoint device's crystal clock oscillator. To do this, the endpoint device determines the current clock frequency of the endpoint device. The endpoint device further calculates the difference between the reference frequency of the reference timing signal and the current frequency. The frequency difference may then be used to generate a control signal that is supplied to the endpoint device's crystal clock oscillator to adjust its frequency.

[0013] The endpoint device further determines the frequency error between the tuned frequency and the reference frequency. If the error is within an acceptable range, the endpoint may switch to a narrowband or ultra-narrowband mode for communication. If the error is still too large, the endpoint continues to adjust the frequency of the crystal clock oscillator in the endpoint device by repeating the above process until the frequency error is within an acceptable range.

[0014] During NB or UNB communication, the endpoint device continuously receives a reference timing signal from the reference device. Therefore, the endpoint device may continuously adjust the frequency of its crystal clock oscillator based on the reference timing signal, as described above. In this way, the clock frequency of the endpoint device can be maintained at a high level of accuracy, thereby enabling reliable NB or UNB communication.

[0015] The technology described herein improves the feasibility and reliability of narrowband or ultra-narrowband communications. As described above, without the technology described herein, endpoint devices with a conventional frequency reference, such as a TCXO, cannot support reliable narrowband or ultra-narrowband communications due to the low stability of the conventional frequency reference (e.g., + / - 2 ppm). By adjusting the clock frequency of the endpoint device based on a reference timing signal received from a reference device, an endpoint device with a conventional frequency reference (e.g., a conventional crystal clock oscillator) can perform narrowband or ultra-narrowband communications.

[0016] Furthermore, continuously adjusting the clock frequency based on a continuously received reference timing signal prevents large frequency shifts and ensures that the information spectrum remains within the IF bandwidth of the transceiver, thereby enabling reliable communication. This eliminates the need to use a stable and accurate frequency reference, and therefore reduces power consumption and the size of the endpoint device. As a result, narrowband or ultra-narrowband communication can be performed in a variety of applications, including when power and space for the endpoint device are limited.

[0017] Figure 1 is a block diagram illustrating an exemplary operating environment for adjusting the clock frequency of endpoint devices in a mesh network for narrowband and ultranarrowband communications, according to a predetermined aspect of the present disclosure, in which a networked system 100 and a mesh network 102 provide a network infrastructure for smart devices (e.g., resource consumption meters including communication technology, vehicles, home appliances, etc.) to communicate over a network of multiple nodes (i.e., other smart devices), the Internet, and / or an intranet.

[0018] The networked system 100 includes a headend system 104, which may function as a central processing system receiving a stream of data from the network 120. The network 120 may be the Internet, an intranet, or any other data communication network. The mesh network 102 may include various endpoint devices or nodes 112A to 112H (which may be referred to hereby individually or collectively as endpoint devices, endpoints, or nodes 112). These endpoint devices 112 may include measurement nodes for collecting data from each location of the deployed nodes, processing nodes for processing the data available to the nodes, router nodes for forwarding data received from one node in the mesh network 102 to other nodes, or nodes configured to perform a combination of these functions.

[0019] In one embodiment, the mesh network 102 is associated with a resource distribution network and transmits measurement data or other data obtained in the resource distribution network. In this embodiment, the endpoint 112 may include meters deployed at various geographical locations within a customer premises via the resource distribution network, such as power meters, gas meters, water meters, and steam meters, and may be implemented to measure various operating characteristics of the resource distribution network. In the example of a power distribution network, exemplary characteristics include, but are not limited to, average or total power consumption, peak voltage of electrical signals, power surges, and load fluctuations. The endpoint 112 transmits the collected data via the mesh network 102 to root nodes 114A and 114B (which may be referred to as root node 114 individually or collectively in this application).

[0020] The root node 114 of the mesh network 102 may be configured to communicate with endpoints 112 to perform predetermined operations, such as managing endpoints 112, collecting data from endpoints 112, and forwarding data to the headend system 104. The root node 114 may also be configured to function as a node or endpoint device that measures and processes data itself. The root node 114 may be a personal area network (PAN) coordinator, gateway, router, or any other device capable of communicating with the headend system 104. The root node 114 ultimately transmits the generated and collected data to the headend system 104 via the network 120. Furthermore, the root node 114 may also receive network management messages from the headend system 104 and transmit network management messages to endpoints 112. Similarly, the root node 114 itself or endpoints 112 may also issue and transmit network management messages to other endpoints 112. The data and network management transmitted between nodes 114 and 112 may collectively be referred to as “communication data” in this application. These communication data are transmitted and routed via the data link 110 between nodes 114 and 112.

[0021] Communication data is typically routed between nodes and the headend system 104, or between nodes according to the node hierarchy of the mesh network 102. For example, a root node 114A that communicates directly with the headend system 104 via network 120 may generally be called a parent node due to its data links to endpoints 112A and 112B located in a lower node layer (e.g., layer 1) than root node 114A. During operation, endpoint 112 may allow all information to be collected by the root node 114 and ultimately by the headend system 104 via the node layer.

[0022] To communicate with other endpoints 112 or root nodes 114, each endpoint 112 and node 114 comprises a crystal clock oscillator, such as a voltage-controlled temperature-compensated crystal oscillator (VCTCXO), to generate signals within the range of communication bandwidth for communicating with other devices in the network 102. Due to temperature and aging, the crystal clock oscillator may have a frequency shift, thereby placing the information spectrum outside the communication bandwidth and resulting in unreliable communication. To address the frequency shift, each endpoint 112 or node 114 is configured to adjust its frequency based on a reference timing signal 118 received from a reference device within its communication range. The reference device may be a root node 114 or another endpoint 112 configured to have the ability to receive a reference timing signal from a reliable source. For example, the root node 114 may comprise a GPS receiver and thus may be a router that receives a 1pps timing signal along with GPS information. Since the GPS clock is synchronized to the NIST-7 cesium frequency standard, which is one of the most accurate clocks in the world, the 1pps timing signal received by the router may act as a reference timing signal for adjusting the clock frequency of the endpoints 112 in the mesh network 102. Additional details regarding the adjustment of the clock frequency of endpoint devices in a mesh network for narrowband or ultra-narrowband communication are provided below with respect to FIGS. 2 and 3.

[0023] During operation, a smaller or larger number of endpoints 112 may be included in the mesh network 102, and a larger number of root nodes 114 may be included in the networked system 100. Further, FIG. 1 shows a particular network topology (e.g., DODAG tree topology), but other network topologies are also possible (e.g., ring topology, mesh topology, star topology, etc.).

[0024] FIG. 2 is a block diagram showing an example of a reference device 201 according to a predetermined aspect of the present disclosure and an endpoint device 112 that receives a reference timing signal 118 from the reference device 201 for frequency adjustment. As described above with respect to FIG. 1, the reference device 201 may be a device in the mesh network 102 having a receiver that receives a reference timing signal, such as a GPS receiver that receives a 1 pps reference timing signal together with GPS information. The reference device 201 may be a root node 114, a router, a gateway, another endpoint device 112, or any other device in the mesh network.

[0025] The reference device 201 may retransmit the received reference timing signal 118 to the endpoint 112 that is directly communicating with the reference device 201 so that the endpoint devices 112 can adjust their respective clock frequencies based on the reference timing signal 118. In some embodiments, the reference device 201 retransmits the reference timing signal 118 to the endpoint 112 according to a mesh network protocol such as the IEEE 802.15.4g standard protocol. For example, the reference device 201 may retransmit the reference timing signal 118 via a common 50 kbps channel using frequency-shift keying (FSK) modulation according to the mesh network protocol.

[0026] The endpoint 112 receives a reference timing signal 118 and adjusts the frequency of its crystal clock oscillator 210 accordingly. To do this, the endpoint device 112 determines the difference between the frequency of the reference timing signal 118 (referred to as the "reference frequency") and the current frequency of the endpoint device 112's crystal clock oscillator 210. The current frequency of the endpoint 112 may be determined by a frequency counter 202, which processes the oscillation signal generated by the crystal clock oscillator 210 so that it is comparable to the reference frequency. In some embodiments, the frequency counter 202 may be implemented using a conventional temperature-compensated crystal oscillator (TCXO).

[0027] The frequency difference may be determined by inputting the frequency of the reference timing signal 118 and the current frequency of the endpoint device 112 into the frequency difference calculator 204. Based on the frequency difference, the control signal value calculator 206 determines the value of the control signal used to control the frequency of the crystal clock oscillator 210. In some embodiments, the control signal value calculator 206 maps the frequency difference to the control signal value according to a lookup table. Depending on the type of crystal clock oscillator 210, the control signal may be a voltage signal or another type of signal. In embodiments where the crystal clock oscillator 210 is a voltage-controlled oscillator, the control signal is a voltage signal, and the lookup table includes a mapping of various frequency differences to each voltage value for the control signal.

[0028] The determined control signal value may be converted into a control signal by a digital-to-analog converter (DAC) 208. In some embodiments, a precise and stable series voltage reference signal is used for the DAC 208. This voltage reference signal provides high precision and stability to the output frequency of the crystal clock oscillator 210. In embodiments where the crystal clock oscillator 210 is a VCTCXO, this voltage reference signal is directly proportional to or one-to-one mapped to the frequency stability of the VCTCXO. The DAC output voltage represents a linear mapping to the output frequency of the VCTCXO. As the voltage reference signal becomes more stable, the output frequency stability of the VCTCXO increases. Thus, by using a precise and stable series voltage reference signal, the DAC in the endpoint device 112 can accurately map the error between the received reference timing signal 118 and the oscillation signal arriving from the crystal clock oscillator 210. The control signal output by the DAC 208 is adjusted in proportion to the difference between the reference frequency of the reference timing signal 118 and the output frequency of the crystal clock oscillator 210. Next, a control signal is used to adjust the crystal clock oscillator 210 so that its frequency aligns with the frequency of the reference timing signal 118. In one embodiment, the crystal clock oscillator 210 is a VCTCXO. A VCTCXO, like a simple TCXO, has a high Q value (quality factor) and therefore low modulation sensitivity (kV) or tunability. Sensitivity is typically on the order of + / - 8 ppm / volt for a typical 39 MHz device. Low sensitivity ensures that the frequency remains stable over long periods of time without requiring constant updates from the DAC208.

[0029] The oscillation signal generated by the crystal clock oscillator 210 after adjustment is then provided to the frequency counter 202 for frequency calculation. Meanwhile, the endpoint device 112 continuously receives the reference timing signal 118 from the reference device 201. By repeating the adjustment process described above, the frequency accuracy of the crystal clock oscillator 210 can be maintained. This frequency adjustment can potentially achieve the same accuracy as the reference timing signal 118, thereby providing reliable narrowband or ultra-narrowband communication.

[0030] In Figure 2, the frequency difference calculator 204 and the control signal value calculator 206 may be implemented as software or hardware. Furthermore, although the frequency difference calculator 204 and the control signal value calculator 206 are described as separate components, they may be implemented in a single software or hardware component. In some embodiments, the frequency counter 202, frequency difference calculator 204, control signal value calculator 206, and digital-to-analog converter 208 may be implemented in the microcontroller of the endpoint device 112.

[0031] Figure 3 is a flowchart illustrating a process 300 for adjusting the clock frequency of an endpoint device in a mesh network for narrowband or ultra-narrowband communication, according to a predetermined aspect of this disclosure. One or more endpoints 112 of the network 102 perform the operation shown in Figure 3. For illustrative purposes, the process 300 will be described with reference to a predetermined embodiment shown in the drawings. However, other embodiments are also possible.

[0032] In block 301, process 300 includes the endpoint device 112 operating in initial communication mode. In initial communication mode, the endpoint device 112 communicates using a signal with a larger bandwidth or higher data rate (e.g., 50kbps) than the bandwidth or data rate (e.g., 100bps to 6.25kbps) of NB or UNB communication. The larger bandwidth and higher data rate in initial communication mode allow for larger frequency errors without communication failure. In other words, the endpoint device 112 can receive the reference timing signal 118 from the reference device 201 even if the frequency of the crystal clock oscillator 210 is significantly different from the reference frequency.

[0033] While operating in initial communication mode, the endpoint device 112 receives a reference timing signal 118 from the reference device 201 in block 302. In some embodiments, the reference device 201 transmits the reference timing signal 118 on multiple different frequency channels following a channel-hopping sequence. In this way, all endpoint devices 112 operating on multiple different channels can receive the reference timing signal 118. In block 304, the endpoint device 112 determines the current frequency of the crystal clock oscillator 210. The endpoint device 112 may use a frequency counter 202 to count the current frequency of the oscillation signal generated by the crystal clock oscillator 210.

[0034] In block 306, process 300 includes the endpoint device 112 calculating the difference between the reference frequency of the reference timing signal 118 and the current frequency of the crystal clock oscillator 210. The endpoint device 112 further maps the frequency difference to the value of the control signal, for example, via a lookup table. For example, if the crystal clock oscillator 210 is a VCTCXO, the control signal is a voltage control signal, and the endpoint device 112 maps the frequency difference to the voltage value of the control signal. In some embodiments, the mapping is linear in that the frequency difference is mapped proportionally to the voltage value of the control signal. The control signal is then generated using the control signal value, for example, via a digital-to-analog converter 208. In some embodiments, an accurate and stable series voltage reference signal is supplied to the DAC 208 so that the DAC can accurately map the frequency difference to the voltage control signal.

[0035] In block 308, process 300 includes the endpoint device 112 adjusting the frequency of the crystal clock oscillator 210 by providing a control signal to the crystal clock oscillator 210. In embodiments where the crystal clock oscillator 210 is a VCTCXO, a voltage control signal generated by the DAC 208 is provided to the VCTCXO so that the frequency of the oscillation signal generated by the VCTCXO is adjusted to be closer to a reference frequency.

[0036] In some scenarios, particularly when the initial difference between the reference frequency and the frequency of the crystal clock oscillator 210 is large, the operations related to blocks 302-308 need to be repeated multiple times to gradually change the frequency of the crystal clock oscillator 210 to match the reference frequency. After a predetermined number of adjustments or a predetermined time period, the endpoint device 112 determines in block 310 whether the frequency error is acceptable or whether the conditions for the frequency error are met. In one embodiment, the frequency error is determined to be a ratio of the frequency difference to the channel bandwidth. If the frequency error is less than a threshold, e.g., 10%, the frequency error is acceptable or the conditions are met. In this embodiment, the acceptable absolute frequency difference depends on the bandwidth. A larger bandwidth allows for a larger frequency deviation from the reference frequency, and vice versa. Note that the channel bandwidth used to determine the acceptable frequency error is the bandwidth of the intended NB or UNB communication, not the bandwidth of the initial communication mode.

[0037] In block 310, if it is determined that the frequency error is unacceptable, the endpoint device 112 continues to adjust the frequency of the crystal clock oscillator 210 by remaining in the initial communication mode. If the frequency error is within an acceptable range, the endpoint device 112 switches to the NB or UNB communication mode in block 312 to operate in the intended narrowband or ultranarrowband mode. While operating in the NB or UNB communication mode in block 313, the endpoint device 112 continues to adjust the frequency of the crystal clock oscillator 210 to match or approach the reference frequency. To do so, the endpoint device 112 continues to receive the reference timing signal 118 from the reference device 201 in a manner similar to block 302, but via the narrowband or ultranarrowband communication channel. Since the frequency of the crystal clock oscillator 210 has been adjusted to an acceptable range, the endpoint device 112 can reliably receive the reference timing signal 118 and other communication signals via the narrowband or ultranarrowband communication channel. The frequency adjustment performed while the endpoint device 112 is operating in NB or UNB communication mode ensures that the frequency of the endpoint device 112 does not shift excessively far from the reference frequency, thereby compromising the reliability of NB or UNB communication.

[0038] In block 316, the endpoint device 112 determines the current frequency of the crystal clock oscillator 210. In block 318, the endpoint device 112 calculates the frequency difference between the reference frequency and the current frequency of the crystal clock oscillator 210. Based on the difference, the endpoint device 112 generates a control signal. In block 320, the crystal clock oscillator 210 adjusts its frequency using the control signal. Blocks 314-320 are similar to blocks 302-308, respectively. In block 322, the endpoint device 112 communicates with other devices in the network using the signal generated by the crystal clock oscillator 210 via NB or UNB communication. As the endpoint device 112 continues to receive the reference timing signal 118 from the reference device 201, the endpoint device 112 ensures that the frequency of the crystal clock oscillator 210 is the same as or close to the reference frequency by repeating the adjustment operations in blocks 314-320.

[0039] Systems supporting reliable NB or UNB have a wide variety of applications in the Internet of Things (IoT). For example, NB or UNB systems may be used in low-power wide-area (LPWA) sensor / control networks for applications including smart cities, utilities, and infrastructure networks. Due to the high link budget of NB or UNB communications, thousands of widely scattered endpoints may be serviced by base stations (BS) acting as concentrators, with a low deployment density, such as one BS per 10 square kilometers.

[0040] Furthermore, while the above description focuses on adjusting the clock frequency of endpoint devices in a mesh network, the technology presented in this application is also applicable to other types of wireless networks that benefit from NB or UNB communications.

[0041] Exemplary node Figure 4 is an example block diagram of the components of endpoint 112 or node 114 of mesh network 102. Some or all of the components of node 400 may belong to one or more of endpoint 112 or node 114 in Figure 1. Node 400 includes a communication module 416. The functions of the communication module 416 include transmitting and receiving various signals to and from other nodes in mesh network 102, such as communication data, reference timing signals 118, and other network communication messages.

[0042] The communication module 416 may include a communication device 412, such as an antenna and a wireless device. Alternatively, the communication device 412 may be any device that enables wireless or wired communication. The communication device 412 may include a transceiver, such as an RF transceiver, that can transmit and receive RF communications from other nodes in the mesh network 102. The communication module 416 may also include a processor 413 and a memory 414. The processor 413 controls the functions performed by the communication module 416, such as one or more of the operations described above with respect to Figures 1 to 3. The memory 414 may be used to store data used by the processor 413 to perform its functions. The communication module 416 further includes a crystal clock oscillator 210 and other components not shown in Figure 4, such as a frequency counter 202 and a DAC 208.

[0043] In some embodiments, node 400 may optionally include a measurement module 418 connected to communication module 416 via a local or serial connection 430. The functions of the measurement module 418 include functions necessary for managing resources, in particular functions that enable access to resources and measure the resources being used. The measurement module 418 may include a processor 421, memory 422, and measurement circuitry 423. The measurement circuitry 423 handles the measurement of resources and may be used as a sensor for collecting sensor data. The processor 421 in the measurement module 418 controls the functions performed by the measurement module 418. The memory 422 stores the data required by the processor 421 to perform its functions. The measurement module 418 may also include a detection circuit, for example in the measurement circuitry 423, to detect characteristics of node 400 (e.g., power state). Communication module 416 and measurement module 418 communicate with each other via local connection 430 to provide data required by other modules, including power state data. Both the communication module 416 and the measurement module 418 may include computer-executable instructions stored in memory or another type of computer-readable medium, and one or more processors within the modules may execute instructions that provide the functions described herein.

[0044] Overall consideration Numerous specific details are described herein in order to provide a detailed understanding of the subject matter described in the claims. However, those skilled in the art will understand that the subject matter described in the claims may be carried out without these specific details. In other instances, methods, apparatus, or systems that would be known to those of the ordinary art are not described in detail so as not to obscure the subject matter described in the claims.

[0045] The features described herein are not limited to any particular hardware architecture or configuration. A computing device may include any suitable device consisting of components that provide results conditional on one or more inputs. A suitable computing device includes a computer system based on a multipurpose microprocessor that accesses stored software (i.e., computer-readable instructions stored in the memory of the computer system), which programs or configures the computing system to transform a general-purpose computing device into a special computing device that implements one or more aspects of the subject matter of this application. Any suitable programming, scripting, other types of languages, or combinations of languages ​​may be used in the software used to program or configure the computing device to implement the disclosures contained herein.

[0046] Embodiments of the methods disclosed herein may be performed in the operation of such a computing device. The order of the blocks presented in the above embodiments may be changed, for example, the blocks may be rearranged, combined, and / or divided into subblocks. A predetermined number of blocks or processes may be executed in parallel.

[0047] The use of “adapted to” or “configured to” in this application is intended to be open and inclusive terminology that does not exclude devices adapted or configured to perform additional tasks or steps. Furthermore, the use of “based on” is intended to be open and inclusive in that a process, step, calculation, or other operation “based on” one or more of the described conditions or values ​​may actually be based on additional conditions or values ​​beyond those described. The headings, lists, and numbers included in this application are for simplification purposes only and are not intended to limit the scope of the explanation.

[0048] While the subject matter of this application has been described in detail with respect to its particular aspects, those skilled in the art will recognize that, by understanding the foregoing, modifications, variations, and equivalents of such aspects can be readily created. Therefore, it should be understood that this disclosure is presented for illustrative purposes, not limitation, and does not exclude such modifications, variations, and / or additions to the subject matter of this application, as will be readily apparent to those skilled in the art.

Claims

1. A method for adjusting the frequency of a crystal oscillator of an endpoint device in a mesh network, performed by the endpoint device, The above method is used while operating in initial communication mode. Receiving a reference timing signal from a reference device in a mesh network via the mesh network, Obtain the current frequency value of the crystal oscillator in the above endpoint device, The frequency difference between the reference frequency of the above reference timing signal and the current value of the above frequency is determined, To generate a control signal based on the above frequency difference, The frequency of the crystal oscillator is adjusted according to the above control signal, This includes determining that the frequency error of the above crystal oscillator satisfies predetermined conditions, The above method, In response to determining that the frequency error of the above crystal oscillator satisfies the above predetermined conditions, the system switches to a narrowband or ultra-narrowband communication mode having a data rate lower than the data rate of the above initial communication mode. While operating in the above-mentioned narrowband or ultra-narrowband communication mode, the operation includes transmitting and receiving communication signals to and from other devices in the mesh network using the oscillation signal generated by the crystal oscillator. method.

2. The above control signal is a voltage control signal that has a voltage value proportional to the above frequency difference. The method according to claim 1.

3. The above voltage control signal is generated based on the voltage reference signal. The method according to claim 2.

4. While operating in the above narrowband or ultra-narrowband communication mode, Receiving a reference timing signal from the above reference device via the above mesh network, To obtain the updated current value of the frequency of the above crystal oscillator, The updated frequency difference between the above reference frequency and the updated current value of the above frequency is determined, A second control signal is generated based on the updated frequency difference described above. The frequency of the crystal oscillator is adjusted according to the second control signal described above. The further includes transmitting and receiving communication signals to and from the other devices using the oscillation signal generated by the crystal oscillator described above. The method according to claim 1.

5. The predetermined conditions are determined at least in part on the bandwidth of the narrowband or ultra-narrowband communication mode. The method according to claim 1.

6. The above crystal oscillator is a voltage-controlled and temperature-compensated crystal oscillator (VCTCXO). The method according to claim 1.

7. The above reference timing signal is transmitted from the reference device to the endpoint device in accordance with the IEEE 802.15.4g protocol. The method according to claim 1.

8. A system comprising a reference device configured to transmit a reference timing signal to multiple endpoint devices in a mesh network, and multiple endpoint devices, While each of the above-mentioned endpoint devices is operating in initial communication mode, The reference timing signal is received from the above reference device via the above mesh network. Obtain the current value of the frequency of the crystal oscillator in the above endpoint device. Determine the frequency difference between the reference frequency of the above reference timing signal and the current value of the frequency of the above crystal oscillator. Based on the above frequency difference, a control signal is generated. By adjusting the crystal oscillator according to the above control signal, the frequency of the crystal oscillator is adjusted. The above crystal oscillator is configured to determine when the frequency error satisfies predetermined conditions. Each of the above-mentioned endpoint devices is In response to determining that the frequency error of the above crystal oscillator satisfies the predetermined conditions, the system switches to a narrowband or ultra-narrowband communication mode having a data rate lower than the data rate of the initial communication mode. While operating in the above narrowband or ultra-narrowband communication mode, it is configured to communicate with the above reference device or other devices in the above mesh network using the oscillation signal generated by the above crystal oscillator. system.

9. The above reference device is further configured to receive the above reference timing signal from the Global Positioning System (GPS). The system according to claim 8.

10. The above control signal is a voltage control signal that has a voltage value proportional to the above frequency difference. The system according to claim 8.

11. The above voltage control signal is generated based on the voltage reference signal. The system according to claim 10.

12. While the above endpoint device is operating in the above narrowband or ultra-narrowband communication mode, The reference timing signal is received from the above reference device via the above mesh network. Obtain the updated current value of the frequency of the above crystal oscillator, Determine the updated frequency difference between the above reference frequency and the updated current value of the above frequency. A second control signal is generated based on the updated frequency difference described above. The frequency of the crystal oscillator is adjusted according to the second control signal described above. The system is further configured to transmit and receive communication signals to and from the reference device or other devices using the oscillation signal generated by the crystal oscillator described above. The system according to claim 8.

13. The predetermined conditions are determined at least in part on the bandwidth of the narrowband or ultra-narrowband communication mode. The system according to claim 8.

14. The above crystal oscillator is a voltage-controlled and temperature-compensated crystal oscillator (VCTCXO). The system according to claim 8.

15. A network endpoint device, A crystal oscillator configured to generate an oscillation signal having the frequency of the crystal oscillator, A processor configured to execute computer-readable instructions, The system comprises a memory configured to store the computer-readable instructions that, when executed by the above processor, cause the above processor to perform an operation including the following, The above operation is performed while operating in initial communication mode. Receiving a reference timing signal from a reference device in the above network via the above network, Obtain the current value of the frequency of the above crystal oscillator, The frequency difference between the reference frequency of the above reference timing signal and the current value of the frequency of the above crystal oscillator is determined, To generate a control signal based on the above frequency difference, The frequency of the crystal oscillator is adjusted by applying the above control signal to the crystal oscillator. This includes determining that the frequency error of the above crystal oscillator satisfies predetermined conditions, The above operation is, In response to determining that the frequency error of the crystal oscillator satisfies the predetermined conditions, the endpoint device is switched to a narrowband or ultra-narrowband communication mode having a data rate lower than the data rate of the initial communication mode. While operating in the above-mentioned narrowband or ultra-narrowband communication mode, the endpoint device is made to communicate with other devices in the network using the oscillation signal generated by the crystal oscillator. Endpoint device.

16. The above control signal is a voltage control signal that has a voltage value proportional to the above frequency difference. The endpoint device according to claim 15.

17. The above voltage control signal is generated based on the voltage reference signal. The endpoint device according to claim 16.

18. The above operation occurs while operating in the above narrowband or ultra-narrowband communication mode. Receiving a reference timing signal from the above reference device via the above network, To obtain the updated current value of the frequency of the above crystal oscillator, The updated frequency difference between the above reference frequency and the updated current value of the above frequency is determined, A second control signal is generated based on the updated frequency difference described above. The frequency of the crystal oscillator is adjusted by applying the second control signal to the crystal oscillator. The further includes using the oscillation signal generated by the crystal oscillator to cause the endpoint device to communicate with other devices in the network. The endpoint device according to claim 15.

19. The predetermined conditions are determined at least in part on the bandwidth of the narrowband or ultra-narrowband communication mode. The endpoint device according to claim 15.

20. The above crystal oscillator is a voltage-controlled and temperature-compensated crystal oscillator (VCTCXO). The endpoint device according to claim 15.

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