HK40105238A - Time division physical layer access for network communications - Google Patents

Description

Time-division physical layer access for network communication

Technical Field

This disclosure generally relates to communication between nodes in a network. More specifically, this disclosure relates to sending and receiving data packets via a network by time-division scheduling of sending and receiving nodes that support multiple physical (PHY) layer configurations in the network to switch to different communication modes.

Background Technology

In a network, infrastructure nodes (or simply "nodes"), such as endpoint devices, gateways, or routers, constantly communicate with each other to exchange messages or transmit data. However, different nodes can have different hardware and software configurations and therefore can support different communication modes. Furthermore, each node can support multiple communication modes. A communication mode can indicate a specific data rate, a specific coding scheme, a specific modulation scheme, or a combination thereof used for data transmission. For example, some nodes can be configured to support certain communication modes of Orthogonal Frequency Division Multiplexing ("OFDM"), while other nodes can be configured to support another set of OFDM communication modes. Some nodes can also be configured to support various communication modes based on Frequency Shift Keying ("FSK") instead of OFDM, or to support various communication modes based on Frequency Shift Keying ("FSK") in addition to OFDM. When transmitting data, the transmitting node can select a communication mode from the supported multiple communication modes to reliably and efficiently send data to the receiving node.

In order for the receiving node to correctly receive and decode the received data, the receiving node needs to identify the communication mode used to send the data and switch to the correct communication mode. A current mode switching mechanism relies on a mode switching header appended to the data packet to indicate the mode used by the sending node. Because the mode switching header is typically transmitted in the basic mode with a low data rate, sending the mode switching header significantly reduces transmission efficiency, especially for communication modes with high data rates.

Summary of the Invention

Aspects and examples of apparatus and processes for a network node to switch between different communication modes according to time-division scheduling to send and receive data packets are disclosed. In one example, a system includes a sending node and a receiving node. The sending node is configured to determine the communication mode of the upcoming time division according to time-division scheduling. Time-division scheduling includes multiple periods, each period including at least two time divisions and specifying a corresponding communication mode for the at least two time divisions. The sending node is further configured to: determine the communication mode of the upcoming time division and match it with a selected communication mode from a plurality of communication modes supported by both the sending node and the receiving node. The selected communication mode is determined based on the communication conditions of the sending node and the receiving node. The sending node is further configured to: generate data packets and send the data packets to the receiving node using the scheduled communication mode in response to determining that the upcoming time division has arrived and become the current time division. The receiving node is configured to operate in a communication mode of a schedule assigned to the current time segment by the time segmentation scheduler. When operating in the scheduled communication mode, it determines that a preamble of a data packet is detected in the current time segment, and in response to determining that a preamble of a data packet is detected, it receives and processes the remainder of the data packet in the scheduled communication mode.

In another example, a node in the network includes a processor configured to execute computer-readable instructions and a memory configured to store the computer-readable instructions, which, when executed by the processor, cause the processor to perform operations. The operations include operating in a communication mode of a first schedule specified by a time-division scheduling for the current time division. The time-division scheduling includes multiple cycles, each cycle including at least two time divisions and specifying a corresponding communication mode for each of the at least two time divisions. The first scheduled communication mode is one of multiple communication modes supported by the node. The operations also include: when operating in the first scheduled communication mode, determining whether a signal of a data packet transmitted by a sending node is detected in the current time division; receiving the remainder of the data packet in the first scheduled communication mode in response to determining that a signal of a data packet has been detected; and switching to a second scheduled communication mode specified by a time-division scheduling for a subsequent time division to receive data packets in response to determining that no data packets have been received during the current time division. The second scheduled communication mode differs from the first scheduled communication mode.

In another example, a method includes: determining, by a node of the network, a communication mode for an upcoming time segment based on time-segment scheduling, wherein the time-segment scheduling comprises multiple periods, each period comprising at least two time segments and specifying a corresponding communication mode for the at least two time segments. The method further includes matching the communication mode for the upcoming time segment's scheduling with a selected communication mode from a plurality of communication modes supported by both the node and the receiving node. The selected communication mode is determined based on communication conditions between the sending and receiving nodes. The method also includes: in response to determining that an upcoming time segment has arrived and become the current time segment, generating data packets and sending the data packets to the receiving node via the network using the scheduled communication mode.

These illustrative aspects and features are mentioned not to limit or restrict the subject matter currently described, but to provide examples to aid in understanding the concepts described in this application. Other aspects, advantages, and features of the subject matter currently described will become apparent upon review of the entire application.

Attached Figure Description

These and other features, aspects and advantages of this disclosure can be better understood when the following detailed description is read with reference to the accompanying drawings.

Figure 1 is a block diagram illustrating an illustrative operating environment for switching between different communication modes according to time-division scheduling to send and receive data packets, based on certain aspects of this disclosure.

Figure 2 is a diagram illustrating aspects of a sending node and a receiving node configured, according to certain aspects of this disclosure, to send and receive data packets separately by switching to different communication modes according to time-division scheduling.

Figure 3 is an example of a time-division scheduling for sending and receiving data packets followed by nodes in a network according to certain examples of this disclosure.

Figure 4A is a diagram illustrating an example of data packets received at the receiving node, the communication mode of the receiving node, and the operations performed by the receiving node according to the prior art mode switching mechanism.

Figure 4B is a diagram illustrating, according to certain aspects of this disclosure, data packets received at the receiving node, the communication mode of the receiving node, and an example of operations performed by the receiving node based on time-division scheduling.

Figure 4C is a diagram illustrating, according to certain aspects of this disclosure, data packets received at a receiving node, the communication mode of the receiving node, and an example of the operations performed by the receiving node when the communication mode specified by the time-division scheduling does not match the selected communication mode.

Figure 5 is an example of a process for receiving and processing data packets sent by a transmitting node, according to certain aspects of this disclosure.

Figure 6 is an example of a process for sending data packets by following a time-division scheduling, according to certain aspects of this disclosure.

Figure 7 is a block diagram illustrating an example of a computing system suitable for implementing various aspects of the technologies and processes presented herein.

Detailed Implementation

A system and method are provided for network nodes to switch between different communication modes for sending and receiving data packets according to time-division scheduling. Both the sending and receiving nodes switch to different communication modes according to time-division scheduling. Time-division scheduling comprises multiple cycles, and each cycle contains at least two time divisions, each indicating the communication mode for the corresponding time division. By following time-division scheduling, the sending and receiving nodes operate in the same communication mode at a given time. In this way, the communication modes of the sending and receiving nodes are matched to each other, thereby eliminating the need to add a mode-switching header to indicate the communication mode when sending data packets.

For example, the sending node selects a communication mode from a set of supported communication modes and generates data packets using the selected communication mode. If the selected communication mode matches the communication mode indicated by the current time division, the sending node directly uses the selected communication mode to send the data packets, instead of inserting a mode switching header into the data packets to indicate the selected communication mode. If the selected communication mode does not match the communication mode indicated by the current time division, the sending node waits until its communication mode matches the selected communication mode in the current time division, and then sends the data packets to the receiving node.

A receiving node operating in a time-division-based communication mode listens for traffic on the network. If the receiving node does not detect the preamble and header of a data packet in the current time division, it switches to the next communication mode specified by the time division scheduler for the next time division and listens for traffic in that new mode. If the receiving node detects the preamble and header of a data packet in the current time division, it continues to receive and process data packets. In some examples, at least one time division has a communication mode set as the basic communication mode, which is the mode with the longest communication range among a set of supported communication modes. One or more other time divisions may have a communication mode with a high data rate. In this way, the receiving node is able to detect traffic with the longest communication range for a period of time in each cycle and receive data at a higher data rate for the remaining time in that cycle.

The techniques described in this disclosure improve the efficiency of communication between nodes in a network. As mentioned above, due to the low data rate of the basic mode used to transmit the mode switching header, the mode switching header used in existing schemes may take longer to transmit than the payload. On the other hand, the time-division mode switching mechanism described in this disclosure allows data packets to be transmitted without using the mode switching header. As a result, transmission efficiency (e.g., the ratio between the effective data rate and the payload data rate) can be significantly improved.

Furthermore, the time-division mode switching mechanism described in this disclosure allows the receiving node to operate in the basic mode, which has the longest communication range, for at least a portion of each cycle. This enables the receiving node to communicate with distant sending nodes, thereby maximizing the node's communication range. During the remaining time period of each cycle, the node can be configured to operate at a much higher bit rate than in the basic mode. This further improves communication efficiency.

Figure 1 illustrates an illustrative network 100 according to certain aspects of this disclosure, wherein nodes are time-division scheduled to switch between different communication modes to send and receive data packets. The network 100 shown in Figure 1 includes multiple nodes 112A-112H (which may be referred to herein, individually, as node 112 or collectively, as node 112). Network 100 may be a radio frequency (RF) mesh network (such as an IEEE 802.15.4 network), a Wi-Fi network, a cellular network, Ethernet, a power line carrier network, or any other wired or wireless network. Accordingly, node 112 may be an RF radio, a computer, a mobile device, a power line network device, or another type of device that can communicate directly with other devices on network 100.

In an example where network 100 is a mesh network, node 112 may include a measurement node for collecting data from the respective deployment locations of the nodes, a processing node for processing the data available to the nodes, a router node for forwarding data received from one node in network 100 to another node, or a node configured to perform a combination of these functions. Nodes 112 are also configured to communicate with each other, enabling the exchange of messages or data between nodes 112.

In one example, network 100 may be associated with a resource distribution network (such as a utility network) to deliver measurement data obtained in the resource distribution network. In this example, node 112 may include meters such as electricity meters, gas meters, water meters, steam meters, etc., and is implemented to measure various operational characteristics of the resource distribution network and send the collected data through network 100 to, for example, root nodes 114A and 114B (which may be referred to herein as root node 114, respectively, or collectively as root node 114).

The root node 114 of network 100 can be configured to communicate with node 112 to perform operations such as managing node 112, collecting data from node 112, and forwarding data to headend system 104. Root node 114 can also be configured to act as a node for measuring and processing the data itself. Root node 114 can be a PAN coordinator, gateway, or any other device capable of communicating with headend system 104. Root node 114 ultimately sends the generated and collected data to headend system 104 via one or more additional networks (not shown in Figure 1). Headend system 104 can be used as a central processing system to receive data streams or message streams from root node 114. Headend system 104 can process the collected data or enable the collected data to be processed for various applications.

To enable communication between nodes in network 100, each node is configured to support one or more communication modes. For example, node 112 can be configured to support FSK at various data rates. Another node can be configured to support both OFDM and FSK at different modulation and coding scheme (MCS) levels. Because the different nodes in network 100 (including node 112 and root node 114) can be configured differently, their ability to support communication modes can differ. Thus, each node in the network is configured with a common basic communication mode.

In some examples, the base mode is determined by the deployment capabilities. For instance, a node deployment might include some older, less capable nodes and newer, more capable nodes. In this case, the network's base mode could be a mode that the older nodes can support, such as FSK modulation. Newer nodes with OFDM capabilities could use the FSK base mode for multicast messages and initiate mode switching operations. Furthermore, in this deployment, it can be assumed that nodes have the minimum capabilities required to join the network and support the base node until they receive positive confirmation from that node that it has enhanced capabilities. In one example, this information can be shared using information elements defined in the IEEE 802.15.4 standard. In another example, the base mode of node 112 is selected as a mode among the supported communication modes that has a longer communication range than most supported communication modes, such as the mode with the longest communication range.

To enable a pair of nodes to communicate with each other, the node sending data (also referred to herein as the "sending node") determines a communication mode such that data packets 122A, 122B, ..., or 122H can be successfully sent to the other node (also referred to herein as the "receiving node"). Data packets 122A-122H may be referred to herein separately as data packet 122 or collectively as data packet 122. According to some aspects of this disclosure, the receiving node may also use the selected communication mode to successfully send an acknowledgment packet back to the sending node to confirm that it has received data packet 122. In some examples, the receiving node is a diversity receiver, each supporting multiple physical layer configurations. To correctly receive and process data packet 122, the sending and receiving nodes switch between multiple supported communication modes according to the same time division schedule. As a result, when a transmission occurs, the sending and receiving nodes can communicate directly using the communication mode specified for the corresponding time division. Additional details regarding the use of communication modes for sending and receiving data packets according to time division scheduling are described below with reference to Figures 2-6.

It should be understood that communication of data packets based on the time-division scheduling described herein can be utilized by any node in network 100, including node 112, root node 114, or any other node in network 100 capable of communicating with other nodes in the network. Furthermore, while Figure 1 depicts a specific network topology (e.g., a DODAG tree), other network topologies are also possible (e.g., ring topology, mesh topology, star topology, etc.).

Referring now to Figure 2, Figure 2 illustrates aspects of a transmitting node and a receiving node configured, according to certain aspects of this disclosure, to transmit and receive data packets according to a Carrier Sense Multiple Access (CSMA) protocol and based on time-division scheduling. In the example shown in Figure 1, transmitting node 202 can be node 112, root node 114, or any other node in network 100 capable of communicating with another node in the network. Receiving node 212 is a neighbor of transmitting node 202, i.e., any node in network 100 with which transmitting node 202 can communicate directly.

The transmitting node 202 may include a mode selection module 204 configured to select a communication mode, enabling the transmitting node 202 to successfully communicate with the receiving node 212 using the selected communication mode. In some examples, the transmitting node 202 determines the communication mode based on the communication conditions between the transmitting node 202 and the receiving node 212. Various factors can be used to describe the communication conditions, including but not limited to the transmission power used to transmit data packets 122, path loss between the transmitting node 202 and the receiving node 212 (i.e., power attenuation of the transmitted signal as it propagates through the communication path), the SNR requirement at the receiving node 212, and the noise floor observed at the receiving node 212.

The transmitting node 202 also includes a data packet generation module 206, configured to generate data packets 122 using a selected communication mode for communication with the receiving node 212. The data packets 122 generated by the data packet generation module 206 may include preamble and synchronization data 222, a header 224, and payload data 226. The preamble and synchronization data 222 includes a preamble signal, followed by synchronization data that can be used by the receiving node 212 for purposes such as synchronization. The header 224 may include data such as data packet delimiters, a physical layer header describing the length of a data unit, etc. The payload data 226 includes the actual expected message.

To send data packet 122, sending node 202 and receiving node 212 follow a time-division scheduling 214 that specifies the communication mode for node 112 in network 100. Figure 3 shows an example of time-division scheduling 214. Time-division scheduling 214 includes multiple time divisions, and specifies a communication mode for node 112 for each time division, referred to herein as the “scheduled communication mode” for each time division. For example, during the first time division 302A (i.e., time 0 to 3 ms), node 112 in network 100 should use communication mode 2-FSK 10kbps. During the next time division 302B (i.e., time 3-5.5ms), node 112 in network 100 should use communication mode OFDM option 1, which supports data rates between 100kbps and 2.4Mbps. During the third time division 302C (i.e., time 5.5-8.5ms), the communication mode switches back to 2-FSK 10kbps. Subsequent time divisions repeat the same pattern. It should be understood that 2-FSK and OFDM option 1 are used as examples of communication modes that can be included in time-division scheduling 214, and should not be construed as restrictive. Other communication modes, such as IEEE 802.15.4 SUN O-QPSK, may also be used.

As shown in the example in Figure 3, the time-division scheduling 214 has multiple cycles, and each cycle includes two or more time divisions. Within each cycle, node 112 operates in different communication modes within different time divisions. The duration of time divisions within a cycle can be the same or different. In some examples, the duration of a time division is determined based on the communication mode specified for that time division. For example, the duration of a time division can be determined to be at least the sum of the time it takes for receiving node 212 to complete receiving the preamble, synchronizing data and headers, the time it takes for receiving node 212 to establish the communication mode, and the maximum time synchronization error.

According to this method, the duration of time partition 1 shown in Figure 3 can be determined as follows. If the time to receive the preamble using 2-FSK 10kbps is 1.6 milliseconds, the setup time of the 2-FSK 10kbps mode of receiving node 212 is 0.36 milliseconds, and the maximum time synchronization error is 1 millisecond, then the duration of time partition 1 is at least 1.6 + 0.36 + 1 ≈ 3 milliseconds. Similarly, for time partition 2, the time to receive the preamble, synchronization data, and header using OFDM option 1 is 1.08 milliseconds, the setup time of the OFDM mode of receiving node 212 is 0.29 milliseconds, and the maximum time synchronization error is again 1 millisecond, so the duration of time partition 2 is at least 1.08 + 0.29 + 1 ≈ 2.5 milliseconds. Although time partition scheduling 214 shows the duration of the time partition as the corresponding minimum duration, each time partition can have a duration longer than the corresponding minimum duration.

Referring back to Figure 2, the sending node 202 sends the generated data packet 122 to the receiving node 212 using the communication mode of the current time division. If the communication mode of the current time division does not match the selected communication mode determined by the mode selection module 204, the sending node 202 may, for example, wait until a future time division where its communication mode matches the selected communication mode. For example, if the communication mode selected by the mode selection module is OFDM Option 1 and the communication mode of the current time division is 2-FSK 10kbps, the sending node 202 may wait until the next time division where its communication mode is OFDM Option 1 in order to begin the transmission of data packet 122 under that communication mode.

As described above, receiving node 212 also switches between communication modes according to time division scheduling 214. At a given time, receiving node 212 operates in the communication mode of the current time division to listen for services in network 100. If receiving node 212 does not detect the preamble, synchronization data 222, and header 224 of data packet 122 within the current time division, receiving node 212 switches to the communication mode of the next time division and continues to listen for services on network 100. If, within the current time division, receiving node 212 detects the preamble, synchronization data 222, and header 224 of data packet 122, receiving node 212 continues to receive the remaining data in data packet 122, including payload data 226, using the current communication mode. When receiving node 212 finishes receiving data packet 122, data packet 122 determines the current time division based on time division scheduling 214 and switches to the communication mode specified for the current time division to listen for network services.

Referring now to Figures 4A and 4B, a comparison is made between the standard IEEE 802.15.4 mode switching mechanism and the time-division mode switching mechanism proposed herein. Figure 4A illustrates an example of data received at the receiving node, the receiving node's mode, and operations performed by the receiving node at different time periods according to the standard IEEE 802.15.4 mode switching communication mechanism. Figure 4B illustrates data received at the receiving node, the receiving node's mode, and operations performed by the receiving node based on time-division scheduling according to certain aspects of this disclosure.

The standard IEEE 802.15.4 mode switching mechanism shown in Figure 4A uses a mode switching header added to each data packet to transmit the communication mode selected by the sending node. Thus, during the overhead time period T0 for detecting the communication mode, the receiving node using the standard IEEE 802.15.4 mode switching mechanism receives the mode switching header by operating in basic mode, and then processes the header to determine the communication mode used by the sending node. After determining the communication mode, the receiving node switches to the determined communication mode to receive and process the preamble and synchronization data, header, and remaining data in the data packets. After this communication, the receiving node returns to basic mode.

In contrast, in the time-division mode switching mechanism presented in this paper, because the receiving node 212 operates on the same time-division schedule 214 as the sending node 202, the communication modes of the receiving node 212 and the sending node 202 are synchronized (the synchronization error between the receiving node 212 and the sending node 202 is omitted). Thus, when the sending node 202 sends data packet 122, the communication modes of the sending node 202 and the receiving node 212 are the same. As a result, the receiving node 212 can directly receive data packet 122 without pre-determining the communication mode of data packet 122. This eliminates the overhead time period T0 in the standard IEEE 802.15.4 mode switching mechanism. Therefore, the technique proposed in this paper can significantly improve communication efficiency.

However, in some cases, the communication mode selected by the transmitting node 202 may not match any of the communication modes specified in the time-division schedule 214. For example, the selected communication mode may be 2-FSK 100kbps, which is different from all the communication modes specified in the time-division schedule 214 shown in Figure 3. In this case, the transmitting node 202 can use a mode switching header mechanism to signal the selected communication mode to the receiving node 212. More specifically, when the transmitting node 202 is operating in a communication mode specified by the time-division schedule 214 of the current time division (such as the 2-FSK 10kbps mode), it can generate and send a mode switching header to indicate the selected communication mode. Afterward, the transmitting node 202 can switch to the selected communication mode and transmit the remainder of the data packet 122 in the selected communication mode.

When receiving node 212 operates in the communication mode scheduled for the current time division, it can receive a mode switching header and determine the selected communication mode for data packet 122. Once the selected communication mode is determined, receiving node 212 can switch to the selected communication mode to receive and process data packet 122. This scenario is illustrated in Figure 4C. Although the communication efficiency of the scenario in Figure 4C is similar to that of the standard IEEE 802.15.4 mode switching mechanism shown in Figure 4A, this scenario only occurs when the communication mode selected by sending node 202 does not match the communication mode specified in time division scheduling 214. Therefore, the overall communication efficiency of the proposed technique is still significantly higher than that of the standard IEEE 802.15.4 mode switching mechanism.

Figure 5 is an example of a process 500 for receiving and processing data packets by a receiving node, according to certain aspects of this disclosure. One or more nodes of network 100 (e.g., node 112 or root node 114) implement the operations depicted in Figure 5 by executing appropriate program code when operating as receiving nodes. Process 500 is described with reference to certain examples depicted in the accompanying drawings for illustrative purposes. However, other implementations are also possible.

At block 502, process 500 involves receiving node 212 listening for incoming traffic in the communication mode of the current time division (with division index i) according to time division scheduling 214. At block 504, process 500 involves receiving node 212 determining whether a packet signal has been detected. Depending on the communication mode, receiving node 212 may determine that a signal has been detected based on the detection of a preamble, synchronization data, and/or header. For example, if the current scheduled communication mode is FSK mode, receiving node 212 can determine that a signal has been detected when a preamble of a data packet is detected. If the current scheduled communication mode is OFDM mode, receiving node 212 can determine that a signal has been detected when a preamble, synchronization data, and header of a data packet are detected. In other examples, receiving node 212 can determine that a signal has been detected if a preamble or synchronization data of a data packet is detected when the current scheduled communication mode is OFDM mode. If receiving node 212 determines that no packet signal has been detected, process 500 proceeds to block 506 to determine whether the current time division i has expired. If the time slot has not expired, the sending node 202 continues to listen for incoming traffic in the scheduled communication mode. If, at box 506, the receiving node 212 determines that the current time slot has expired, process 500 involves switching to the scheduled communication mode for the next time slot and incrementing the time slot index i by 1. The receiving node 212 then continues to listen for incoming traffic using the new scheduled communication mode.

If receiving node 212 determines at box 504 that a packet signal has been detected, process 500 proceeds to box 510. At box 510, receiving node 212 continues to receive the remainder of data packet 122 in the currently scheduled communication mode. This reception process can span multiple time divisions. At box 512, process 500 involves receiving node 212 determining whether data reception is complete. If not, receiving node 212 continues to receive data packet 122 at box 510. If reception is complete, process 500 involves receiving node 212 determining the current time division according to time division scheduling 214 at box 514 and setting the time division index i accordingly. Then, process 500 involves receiving node 212 switching to the communication mode of the current time division scheduling at box 516 and using this mode to listen for incoming traffic at box 502.

Turning now to Figure 6, an example of a process 600 for sending data packets by following a time-division scheduling is presented. One or more nodes of network 100 (e.g., node 112 or root node 114) implement the operations depicted in Figure 6 by executing appropriate program code when operating as a sending node. For illustrative purposes, process 600 is described with reference to certain examples depicted in the accompanying drawings. However, other implementations are also possible.

In block 601, process 600 involves the sending node 202 receiving a request to send data. In block 602, process 600 involves the sending node 202 determining an upcoming time partition based on time partition scheduling 214. In block 604, process 600 involves the sending node 202 determining whether the communication mode scheduled for the upcoming time partition matches the selected communication mode for data packet 122. As described in detail above with respect to Figure 2, the sending node 202 can use the mode selection module 204 to determine the transmission mode of data packet 122 based on the communication conditions between the sending node 202 and the receiving node 212. If the scheduled communication mode does not match the selected communication mode, then in block 612, the sending node 202 waits for the next time partition and repeats the operation in block 602 to determine the communication mode scheduled for the upcoming time partition.

If, at block 604, transmitting node 202 determines that the scheduled upcoming communication mode matches the selected communication mode, process 600 involves transmitting node 202 performing pre-transmission operations at block 606. These operations include, for example, performing an idle channel assessment (CCA) to determine whether a channel is available for transmission. Pre-transmission operations may also include other operations that need to be performed by transmitting node 202 before starting to transmit data packets. At block 608, process 600 involves transmitting data using the scheduled communication mode when the upcoming time division has arrived (i.e., the time for entering the upcoming time division has arrived). Transmission may include establishing a transmission using the scheduled communication mode and waiting for a maximum time synchronization error period. Nodes 112 in network 100 synchronize their clocks from time to time. However, synchronization errors may occur, causing the clocks of nodes 112 to be offset from each other. The maximum time synchronization error period represents the maximum time period of synchronization error between nodes 112. Waiting for the maximum time synchronization error period allows receiving node 212 to be in the correct communication mode when data packet 122 is transmitted, even if there is a synchronization error between transmitting node 202 and receiving node 212. Then, sending node 202 sends data packet 122 in the communication mode of the current time division schedule.

Although Figure 6 illustrates that when the scheduled communication mode does not match the selected communication mode, the sending node 202 waits for the next time partition, in other examples, the sending node 202 can still use the scheduled communication mode for transmission even if the scheduled communication mode does not match the selected communication mode. For example, if both the sending and receiving nodes support the scheduled communication mode, the sending node can choose to transmit in the upcoming time partition instead of waiting for the next matching time partition (if doing so is faster). In this way, waiting time is avoided.

Note that the example process shown in Figure 6 can be used when the selected communication mode matches the communication mode of at least one of the time-division schedules 214. If the selected communication mode does not match the communication mode of any of the schedules in the time-division schedule 214, the sending node 202 can use the switching header as described above to indicate the selected communication mode.

It should be understood that the time-division scheduling 214 shown in Figure 3 is for illustrative purposes only and should not be construed as restrictive. Various other methods can be used to construct the time-division scheduling 214. For example, the time-division scheduling 214 may have more than two time divisions in one cycle. At least one communication mode in the time-division scheduling 214 is set to a basic mode or another long-range low data rate mode. At least one communication mode in the time-division scheduling 214 is set to a communication mode with one of the highest data rates. In some embodiments, the communication modes included in the time-division scheduling 214 can be determined based on the communication modes used by node 112 in network 100. For example, the time-division scheduling 214 may be configured to include communication modes frequently used by node 112 based on past communication. Furthermore, the time-division mode switching mechanism proposed herein can be implemented using the CSMA Media Access Control (MAC) protocol or other MAC protocols such as the Time Synchronization Channel Skip (TSCH) protocol.

In some scenarios, not all nodes 112 on network 100 implement the time-division mode switching mechanism described herein. In these scenarios, nodes 112 that do not implement the time-division mode switching mechanism (also known as incompatible nodes) may be unaware of the time-division schedule 214 and instead rely on the mode switching header to signal the selected communication mode to receiving nodes in network 100. This also includes scenarios where nodes implementing the time-division mode switching mechanism (also known as compatible nodes) initially join the network and have not yet acquired the time-division schedule 214. To enable compatible nodes 112 to communicate with incompatible nodes, the preamble of data packets 122 can be extended to a sufficient length to include the complete preamble detection period, regardless of where the receiving compatible node is operating within the period of the time-division schedule 214 when the preamble is sent. For example, the duration of the preamble can be determined as at least one period of the time-division schedule 214 plus the time period used to detect the preamble in basic mode. In this way, when receiving data packet 122 from a non-compatible node, the compatible node can detect the preamble and thus the mode switching header, and determine the selected communication mode for data packet 122. In another example, the length of the preamble can be configured to be close to but shorter than one cycle of the time-division schedule 214, such as 90%. This setting can be used in conjunction with the retry mechanism of the communication protocol to allow the receiving node to receive the preamble and determine the correct communication mode.

Exemplary node

Figure 7 illustrates an exemplary node 700, such as node 112 or root node 114, that can be used to implement the mode switching mechanism described herein. Node 700 may include a processor 702, a memory 704, and a transceiver device 720, each communicatively coupled via bus 710. The components of node 700 may be powered by an A/C power supply or a low-power source, such as a battery (not shown). Transceiver device 720 may include (or be communicatively coupled to) an antenna 708 for communicating with other nodes. In some examples, the transceiver device is a radio frequency (“RF”) transceiver for wirelessly transmitting and receiving signals.

The processor may include a microprocessor, an application-specific integrated circuit (“ASIC”), a state machine, a field-programmable gate array (“FPGA”), or other suitable computing device. The processor may include any number of computing devices and may be communicatively coupled to a computer-readable medium, such as memory 704. Processor 702 may execute computer-executable program instructions or access information stored in memory to perform operations, such as the time-division scheduling 214 described herein. Instructions may include processor-specific instructions generated by a compiler and/or interpreter from code written in any suitable computer programming language. When executed, these instructions may configure node 700 to perform any of the operations described herein. Although the processor, memory, bus, and transceiver devices are depicted as separate components communicating with each other in Figure 7, other implementations are possible. The systems and components discussed herein are not limited to any particular hardware architecture or configuration.

General considerations

This document sets forth numerous specific details to provide a thorough understanding of the claimed subject matter. However, those skilled in the art will understand that the claimed subject matter can be practiced without these specific details. In other instances, methods, apparatus, or systems known to those skilled in the art have not been described in detail to avoid obscuring the claimed subject matter.

The features discussed herein are not limited to any particular hardware architecture or configuration. A computing device can include any suitable arrangement of components that provide a result conditioned on one or more inputs. Suitable computing devices include multi-purpose microprocessor-based computer systems that access stored software (i.e., computer-readable instructions stored in the memory of the computer system) that programs or configures the computing system from a general-purpose computing device to a special-purpose computing device that implements one or more aspects of this subject. The teachings contained herein can be implemented in software using any suitable programming, scripting, or other type of language or combination of languages for programming or configuring the computing device.

The aspects of the methods disclosed herein can be executed in the operation of such a computing device. The order of the boxes presented in the above examples can be changed; for example, the boxes can be reordered, combined, and/or divided into sub-boxes. Some boxes or procedures can be executed in parallel.

The use of “suitable for” or “configured to” in this document is intended as an open and inclusive language, and does not exclude devices that are suitable for or configured to perform additional tasks or steps. Furthermore, the use of “based on” implies openness and inclusiveness, because processes, steps, calculations, or other actions “based on” one or more of the stated conditions or values may in practice be based on additional conditions or values beyond those stated. The headings, lists, and numbering included in this document are for ease of interpretation only and are not intended to be limiting.

While the subject matter has been described in detail with respect to specific aspects, it should be understood that those skilled in the art will readily make changes, variations, and equivalents to these aspects upon understanding the foregoing. Therefore, it should be understood that this disclosure is presented for illustrative purposes rather than for limitation, and does not exclude the inclusion of such modifications, variations, and/or additions to the subject matter, which will be apparent to those skilled in the art.

Claims (20)

1. A system comprising: The sending node is configured as follows: The communication mode for scheduling upcoming time partitions is determined based on time partition scheduling, wherein the time partition scheduling includes multiple cycles, each cycle includes at least two time partitions and specifies a corresponding scheduling communication mode for the at least two time partitions. The communication mode of the upcoming time division is determined to match a selected communication mode from a plurality of communication modes supported by both the sending node and the receiving node, the selected communication mode being determined based on the communication conditions of the sending node and the receiving node; and In response to determining that the upcoming time segment has arrived and becomes the current time segment, a data packet is generated and sent to the receiving node using the scheduled communication mode; and The receiving node is configured as follows: Operate in the communication mode of the schedule specified by the time division for the current time division; When operating in the communication mode of the schedule, it is determined that the preamble of the data packet was detected in the current time division; and The remaining portion of the data packet is received and processed in the scheduled communication mode, at least in part, based on the preamble that was detected in the data packet. 2. The system according to claim 1, wherein the receiving node is further configured to: Determine that no data packets were received during a given time interval; and Switch to the communication mode of the second schedule, which is specified by the time division schedule for subsequent time divisions, to detect data packets in the subsequent time divisions, wherein the communication mode of the second schedule is different from the communication mode of the first schedule. 3. The system of claim 1, wherein sending the data packet to the receiving node includes waiting for a time period determined according to the maximum time synchronization error period, and sending the data packet to the receiving node. 4. The system of claim 1, wherein the transmitting node is further configured to perform an idle channel assessment (CCA) before transmitting the data packet to the receiving node. 5. The system according to claim 1, wherein one of the scheduled communication modes is the basic mode of the receiving node, and the basic mode includes one of the supported multiple communication modes, the one communication mode having a longer communication range than most of the supported multiple communication modes. 6. The system according to claim 1, wherein the transmitting node is further configured to: Determine that the selected communication mode is different from the communication mode of any schedule in the time-division scheduling; and Generate and send a mode switching header in the communication mode of the schedule under the current time division to indicate the selected communication mode; and The data packets are sent in the selected communication mode. 7. The system according to claim 6, wherein the receiving node is further configured to: When operating in the scheduled communication mode, the mode switching header is detected to determine the selected communication mode; Switch to the selected communication mode; and The data packets are received and processed in the selected communication mode. 8. The system of claim 1, wherein the supported plurality of communication modes includes one or more Frequency Shift Keying (FSK) communication modes or one or more Orthogonal Frequency Division Multiplexing (OFDM) communication modes. 9. A node in a network, comprising: Processor, the processor being configured to execute computer-readable instructions; and Memory, configured to store the computer-readable instructions, which, when executed by the processor, cause the processor to perform operations, including: Operating under the communication mode of a first scheduling specified by a time-division scheduling for the current time division, wherein the time-division scheduling includes multiple cycles, each cycle includes at least two time divisions and specifies a corresponding scheduling communication mode for the at least two time divisions, and wherein the communication mode of the first scheduling is one of multiple supported communication modes of the node. When operating in the communication mode of the first scheduling, determine whether a signal of a data packet sent by the sending node is detected in the current time division; In response to the signal indicating that the data packet has been detected, the remaining portion of the data packet is received in the communication mode of the first scheduling; and In response to determining that no data packets are received during the current time division, the system switches to a communication mode of a second schedule, which is scheduled by the time division for subsequent time divisions, to receive data packets, wherein the communication mode of the second schedule is different from the communication mode of the first schedule. 10. The node of claim 9, wherein the data packet is sent by the sending node based on a selected communication mode for the data packet matching the communication mode of the first schedule specified by the time division for the current time division. 11. The node of claim 9, wherein one of the scheduled communication modes is the basic mode of the node, and the basic mode includes one of the plurality of supported communication modes, the one communication mode having a longer communication range than most of the plurality of supported communication modes. 12. The node of claim 9, wherein the signal determining that the data packet was detected includes determining that the data packet was detected by a preamble or determining that the data packet was detected by both the preamble and the header. 13. The node of claim 9, wherein the operation further comprises: When operating in the communication mode of the first schedule, the mode switching header of the data packet is detected to determine the selected communication mode; Switch to the selected communication mode; and The data packets are received and processed in the selected communication mode. 14. The node of claim 9, wherein the plurality of supported communication modes include one or more Frequency Shift Keying (FSK) communication modes or one or more Orthogonal Frequency Division Multiplexing (OFDM) communication modes. 15. A method comprising: The communication mode for scheduling an upcoming time partition is determined by network nodes based on time partition scheduling, wherein the time partition scheduling includes multiple cycles, each cycle includes at least two time partitions and specifies a corresponding scheduling communication mode for the at least two time partitions. The communication mode of the scheduled time division determined by the node is matched with a selected communication mode from a plurality of communication modes supported by both the node and the receiving node, the selected communication mode being determined based on the communication conditions of the sending node and the receiving node; and In response to determining that the upcoming time segment has arrived and become the current time segment, the node generates a data packet and sends the data packet to the receiving node through the network using the scheduled communication mode. 16. The method of claim 15, wherein sending the data packet to the receiving node includes waiting for a time period determined according to the maximum time synchronization error period, and sending the data packet to the receiving node. 17. The method of claim 15, further comprising: performing a free channel assessment (CCA) before sending the data packet to the receiving node. 18. The method of claim 15, wherein one of the scheduled communication modes is the basic mode of the receiving node, and the basic mode includes one of the supported plurality of communication modes, the one communication mode having a longer communication range than most of the supported plurality of communication modes. 19. The method of claim 15, further comprising: Determine that the selected communication mode is different from the communication mode of any schedule in the time-division scheduling; and Generate and send a mode switching header in the communication mode of the schedule under the current time division to indicate the selected communication mode; and The data packets are sent in the selected communication mode. 20. The method of claim 15, wherein the supported plurality of communication modes includes one or more Frequency Shift Keying (FSK) communication modes or one or more Orthogonal Frequency Division Multiplexing (OFDM) communication modes.