Resilient long-range and low-bandwidth mesh networking communications

Abstract

A radio configured to communicate in a wireless network comprises a physical layer subsystem that converts transmission baseband data into a transmission radio frequency (RF) signal and provides the RF signal to an antenna and accepts a received RF signal from the antenna and converts the received RF signal into received baseband data. The radio further comprises a data subsystem that provides the transmission baseband data to the physical layer subsystem for transmission and accepts received baseband data from the physical layer subsystem. The data subsystem utilizes a data packet structure that comprises a data field and a unified header, the unified header has aspects of at least two upper network layers into a single header. The unified header comprises aspects of a link header and a protocol header. The radio physical layer subsystem comprises a long range (LoRa) physical layer.

Description

Docket No. 5200.2428-001 (INV-25053)Resilient Long-Range and Low-Bandwidth Mesh Networking CommunicationsRELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 705,491, filed on October 9, 2024. The entire teachings of the above application(s) are incorporated herein by reference.BACKGROUND

[0002] Certain environments present difficulties for currently available radio systems. Challenging radio frequency (RF) propagation may exist, for example, in crowded urban scenarios, within structures such as office buildings, vessels, and factories, and in underground mining infrastructures. Some radio environments may present a high-failure rate topology that cause data packets to be partially or completely lost. Existing communication stack protocols tend to focus on compatibility with existing networks. Such protocols require significant overhead, which complicates operation in the above-mentioned challenging environments. When bare-minimum communications are necessary at all costs in any location, available systems are lacking.SUMMARY

[0003] The embodiments described herein are directed to a hybrid mesh radio network that utilizes a condensed protocol stack that merges aspects of two or more network layers.

[0004] In one aspect, the invention may be a radio configured to communicate in a wireless network, comprising a physical layer subsystem that (i) converts transmission baseband data into a transmission radio frequency (RF) signal and provides the RF signal to an antenna, and (ii) accepts a received RF signal from the antenna and converts the received RF signal into received baseband data. The radio may further comprise a data subsystem that provides the transmission baseband data to the physical layer subsystem for transmission and accepts received baseband data from the physical layer subsystem. The data subsystem may utilize a data packet structure that comprises a data field and a unified header. The unified header may have aspects of at least two upper network layers into a single header.

[0005] The unified header may comprise aspects of a link header and a protocol header. The physical layer subsystem may comprise a long range (LoRa) physical layer. The packet- 1 -4223147. vlDocket No. 5200.2428-001 (INV-25053) structure may further comprise a preamble for synchronizing a transmitter of the packet structure with a receiver of the packet structure. The unified header may facilitate a hybrid network topology that includes aspects of a tree network topology and a mesh network topology. The radio may use chirp spread spectrum modulation. The radio may use a data payload that is less than 255 bytes. The radio may use a modulation bandwidth between 7.8kHz and 500kHz.

[0006] In another aspect, the invention may be a method of communicating information in a wireless network, comprising providing transmission baseband data to a physical layer subsystem of a radio for transmission and accepting received baseband data from the physical layer subsystem, and utilizing a data packet structure that comprises a data field and a unified header, the unified header has aspects of at least two upper network layers into a single header. The method may further comprise converting the transmission baseband data into a transmission radio frequency (RF) signal and providing the transmission RF signal to an antenna. The method may also comprise accepting a received RF signal from the antenna and converting the received RF signal into received baseband data.

[0007] The method may further comprise forming the unified header with aspects of a link header and a protocol header. The method may further comprise implementing the physical layer subsystem with a long range (LoRa) physical layer. The method may further comprise augmenting the packet structure with a preamble for synchronizing a transmitter of the packet structure with a receiver of the packet structure. The method may further comprise using the unified header to facilitate a hybrid network topology that includes aspects of a tree network topology and a mesh network topology. The method may further comprise using chirp spread spectrum modulation. The method may further comprise using a data payload that is less than 255 bytes. The method may further comprise using a modulation bandwidth between 7.8kHz and 500kHz.

[0008] In another aspect, the invention may be a wireless network, comprising two or more radios, each of which (i) converts transmission baseband data into a transmission radio frequency (RF) signal and provides the RF signal to an antenna, (ii) accepts a received RF signal from the antenna and converts the received RF signal into received baseband data (iii) provides the transmission baseband data to a physical layer subsystem for transmission; (iv) accepts received baseband data from the physical layer subsystem, and (v) utilizes a data packet structure that comprises a data field and a unified header, the unified header has aspects of at least two upper network layers into a single header.- 2 -4223147. vlDocket No. 5200.2428-001 (INV-25053)

[0009] The packet structure may further comprise a preamble for synchronizing a transmitter of the packet structure with a receiver of the packet structure. The unified header may facilitate a hybrid network topology that includes aspects of a tree network topology and a mesh network topology. Each of the two or more radios may use chirp spread spectrum modulation.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The foregoing will be apparent from the following more particular description of example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments.

[0011] FIG. 1 shows an example of a tree (or star) network topology.

[0012] FIG. 2 shows an example of a traditional mesh network topology.

[0013] FIG. 3 shows a hybrid of a tree network topology and a traditional mesh network topology according to an embodiment of the invention.

[0014] FIG. 4A shows an example of the packet structure of a typical tree or mesh packet.

[0015] FIG. 4B shows an example of the packet structure of a hybrid network topology according to an embodiment of the invention.DETAILED DESCRIPTION

[0016] A description of example embodiments follows.

[0017] The described embodiments are directed to a hybrid mesh radio network that utilizes a condensed protocol stack that merges aspects of two or more network layers.

[0018] A tree (or star) network topology, an example of which is shown in FIG. 1, has sets of nodes that connect directly to a respective gateway. In the example of FIG. 1, nodes 102a, 102b, 102c each connects directly to gateway 104a, and nodes 102d, 102e each connects directly to gateway 104b. Multiple gateways (two gateways in this example) may be connected via an external network 106. Bidirectional communications occur between a node and a gateway, but nodes do not communicate directly to each other. Current implementations of tree network topologies are very general and support a broad range of data with substantial header overhead.- 3 -4223147. vlDocket No. 5200.2428-001 (INV-25053)

[0019] In a traditional mesh network, nodes are capable of bidirectional communication with other nodes. If one node cannot communicate with a particular other node directly, communication may occur through one or more other nodes. In the example shown in FIG. 2, node A 202a and node E 202e cannot communicate directly to one another, but node A 202a and node E 202e can communicate (i) through node B 202b, (ii) through node C 202c and node D 202d, (iii) through node B 202b and node C 202c, and (iv) through node B 202b and node D 202d and node C 202c. A traditional mesh network topology can be quite complicated, as optimization requires nodes knowing routes to each potential destination node to send messages. A gateway simply acts as another node in the traditional network topology.

[0020] The network topology of the described embodiments is a hybrid of the tree network topology and the traditional mesh, an example of which is shown in FIG. 3. Nodes operate in a tree structure, but also have branches. A node that does not communicate directly with a gateway can pass a message through another node or a series of nodes that do communicate with a gateway. The path to a gateway thus could be many nodes deep. Multiple gateways (two gateways in the FIG. 3 example) may be connected via an external network 106. As shown in FIG. 3, node B 302b does not communicate directly with node E 302e, but communication from node B 302b to node E 302e may be accomplished through node A 302a, gateway 304a, and gateway 304b. This hybrid topology greatly reduces the network optimization overhead, since each node only needs to learn and remember the route to its gateway instead of routes to all other nodes as in a tradition mesh network.

[0021] FIG. 4A illustrates an example of the packet structure of a typical tree or mesh packet. In general, the radio (or other network device) provides its own preamble header 402, the network has its own link header 404, and the packet data 406 being carried has its own protocol header 408. The link header 404 and the protocol header 408 are, in general, the minimum required in existing systems, although some systems may employ additional headers (represented by ellipsis between the link header 404 and the protocol header 408). The example embodiments utilize the physical preamble 402 because the physical preamble is a requirement of the physical Long Range (LoRa®) radios being used as described in more detail below. The preamble is used to synchronize the receiver with the transmitter and consists of eight symbols. The radio transmitter, however, may add another 4.25 symbols resulting in a final preamble length of 8 + 4.25 = 12.25 symbols.- 4 -4223147. vlDocket No. 5200.2428-001 (INV-25053)

[0022] The unified header 410 of the example embodiment, as shown in FIG. 4B, is specialized to a specific network structure and data being conveyed. The link header 404 and the protocol header 408 of the traditional network packet structure, along with any additional headers used / required by the system, are condensed into the unified packet 410. In one embodiment, the packet header being merged is based on the Message Queuing Telemetry Transport - Sensor Networks (MQTT-SN) specification (see, e.g., mqtt.org / mqtt- specification). The unified packet 410 may reduce the extra overhead from a traditional network packet structure through simplification and / or by eliminating redundancies, and facilitates the hybrid network topology described herein.

[0023] An example embodiment of the invention is a hybrid mesh network built on radios utilizing a LoRa® and FSK-based communications link. LoRa® radios are at the forefront of low bandwidth communications and are capable of a link budget with substantial link margin and considerable receiver sensitivity. This allows effective demodulation even when operating significantly below the noise floor. Building on top of the physical / data-link network provided by the LoRa® protocol, the mesh networking stack of the described embodiments can extend the effective link range and providing reliable data passing through the network. A characteristic of the LoRa® protocol is very low bandwidth capabilities, which is a result of, for example, chirp spread spectrum modulation, small data payloads (e.g., between about 50 and 255 bytes), and low modulation bandwidths (e.g., between about 125kHz and 500kHz). The networking stack of the described embodiment reduces the size of network packets and increases throughput. By focusing on providing very low bandwidth communications, the described embodiments operate and provide minimal communications capabilities in environments where other systems are incapable of operating.

[0024] What differentiates the described embodiments from existing network solutions is a resilient mesh network in a minimum-bandwidth situation. Existing network solutions are focused on higher bandwidth and operation within centralized networks, which limits range and resilience. The described embodiments focus on communication at all costs. When communicating a simple small message or small data packet is essential, the described embodiments provide a more resilient and capable network.

[0025] Example embodiment radios may include the STMICROELECTRONICS® STM32WLEx microcontroller unit (MCU), based on Arm® Cortex®-M4 and Cortex®-M0+ cores. The MCU incorporates a Semtech® SX126x sub-GHz radio on a single chip, and offers an open platform compatible with LoRa®, (G)FSK, (G)MSK and BPSK modulations. This- 5 -4223147. vlDocket No. 5200.2428-001 (INV-25053) dual-core design with an integrated radio facilitates the networking stack of the described embodiments to run on the dedicated low-power core and handle all the tasks that application developers would not need access to. The high-power Arm® Cortex®-M4 MCU can run applications running on this communications network, including multiple sensors reporting to another system on the network or interfacing with a computing device to allow users access to messages on the network.

[0026] On-chip radio specifications may comprise:• (G)FSK modulation o Bitrate: 0.6 to 300 Kbit / s o RX sensitivity: -123 dBm• Transmitter output power up to +22 dBm o Bitrate: 0.013 to 17.4 Kbit / s o RX sensitivity: -148 dBmMesh Network Layer

[0027] Significant portions of the described embodiments may be implemented on a mesh network layer. In an example embodiment, the LoRaMesher library (see, e.g., github.com / LoRaMesher) may be used to provide a baseline mesh network protocol stack. The LoRaMesher library implements a di stance- vector routing protocol for communicating messages among LoRa nodes. RadioLib, a versatile communication library that supports different LoRa series modules, is leveraged for the interaction with the LoRa radio chip. LoRaMesher is compatible with, and has been tested within, the SX1262 and the SX1268 radio modules. The LoRaMesher library includes an interface for the radio employed by the described embodiments. The LoRaMesher library supports a di stance- vector routing protocol along with broadcasting, ACK, and split packets. LoRaMesher itself implements a full mesh network. The described embodiments, on the other hand, employ a hybrid mesh and modify packet headers as described herein to simplify implementation. The described embodiments implement the LoRaMesher route discovery procedure.

[0028] Example embodiments may optimize packet overhead further and support different network topologies. Embodiments may employ novel routing optimization procedures. The mesh networking layer may run exclusively on the Arm® Cortex®-M0+ core on the radio and provide a documented API for interacting with the network from an application or user perspective. Simulation tools may be employed for testing protocol- 6 -4223147. vlDocket No. 5200.2428-001 (INV-25053) versions as well as development tools for visualizing what is happening in the network for debugging.

[0029] As the radios are capable of both LoRa® and (G)FSK modulation, the described embodiments may employ multi-modulation utilization and frequency-hopping spread spectrum for further network reliability and throughput optimizations. The radios are easily reconfigurable and will facilitate on-the-fly reconfiguration of the frequency or modulation being used in real-time.

[0030] If the use case for the radio network is compatible with a publish-subscribe paradigm, Message Queuing Telemetry Transport - Sensor Networks (MQTT-SN) protocol can be utilized as the transport and session layer, optimized for the publish-subscribe network paradigm. This implementation depends on one or more central gateways being present in the network. Multiple gateways could be utilized and share information to concurrently update message mailboxes. This would create more of a two-tiered mesh network where clients would first organize themselves in a star configuration and only mesh when the gateway is inaccessible to a client. The network could also intelligently select a client as the backhaul for a mesh of clients if the client has a significantly better connection to the gateway. Both network designs are shown below.Application Layer

[0031] The networking stack is configured to be self-contained on the Arm® Cortex®- M0+ core. APIs are exposed for both the on-chip Arm® Cortex® -M4 chip to use and through off-chip communication protocols. This enables development of applications on top of the networking stack including sensor networks or communications applications.

[0032] While example embodiments have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the embodiments encompassed by the appended claims.- 7 -4223147. vl

Claims

Docket No. 5200.2428-001 (INV-25053)CLAIMSWhat is claimed is:

1. A radio configured to communicate in a wireless network, comprising: a physical layer subsystem that (i) converts transmission baseband data into a transmission radio frequency (RF) signal and provides the RF signal to an antenna, and (ii) accepts a received RF signal from the antenna and converts the received RF signal into received baseband data; a data subsystem that provides the transmission baseband data to the physical layer subsystem for transmission and accepts received baseband data from the physical layer subsystem, the data subsystem utilizes a data packet structure that comprises a data field and a unified header, the unified header has aspects of at least two upper network layers into a single header.

2. The radio of claim 1, wherein the unified header comprises aspects of a link header and a protocol header.

3. The radio of claim 1, wherein the physical layer subsystem comprises a long range (LoRa) physical layer.

4. The radio of claim 1, wherein the packet structure further comprises a preamble for synchronizing a transmitter of the packet structure with a receiver of the packet structure.

5. The radio of claim 1, wherein the unified header facilitates a hybrid network topology that includes aspects of a tree network topology and a mesh network topology.

6. The radio of claim 1, wherein the radio uses chirp spread spectrum modulation.

7. The radio of claim 1, wherein the radio uses a data payload that is less than 255 bytes.

8. The radio of claim 1, wherein the radio uses a modulation bandwidth between 7.8kHz and 500kHz.- 8 -4223147. vlDocket No. 5200.2428-001 (INV-25053)9. A method of communicating information in a wireless network, comprising: providing transmission baseband data to a physical layer subsystem of a radio for transmission and accepting received baseband data from the physical layer subsystem, and utilizing a data packet structure that comprises a data field and a unified header, the unified header has aspects of at least two upper network layers into a single header; converting the transmission baseband data into a transmission radio frequency (RF) signal and providing the transmission RF signal to an antenna; accepting a received RF signal from the antenna and converting the received RF signal into received baseband data.

10. The method of claim 9, further comprising forming the unified header with aspects of a link header and a protocol header.

11. The method of claim 9, further comprising implementing the physical layer subsystem with a long range (LoRa) physical layer.

12. The method of claim 9, further comprising augmenting the packet structure with a preamble for synchronizing a transmitter of the packet structure with a receiver of the packet structure.

13. The method of claim 9, further comprising using the unified header to facilitate a hybrid network topology that includes aspects of a tree network topology and a mesh network topology.

14. The method of claim 9, further comprising using chirp spread spectrum modulation.

15. The method of claim 9, further comprising using a data payload that is less than 255 bytes.

16. The method of claim 9, further comprising using a modulation bandwidth between 7.8kHz and 500kHz.- 9 -4223147. vlDocket No. 5200.2428-001 (INV-25053)17. A wireless network, comprising: two or more radios, each of which: converts transmission baseband data into a transmission radio frequency (RF) signal and provides the RF signal to an antenna; accepts a received RF signal from the antenna and converts the received RF signal into received baseband data; provides the transmission baseband data to a physical layer subsystem for transmission; accepts received baseband data from the physical layer subsystem; and utilizes a data packet structure that comprises a data field and a unified header, the unified header has aspects of at least two upper network layers into a single header.

18. The wireless network of claim 17, wherein the packet structure further comprises a preamble for synchronizing a transmitter of the packet structure with a receiver of the packet structure.

19. The wireless network of claim 17, wherein the unified header facilitates a hybrid network topology that includes aspects of a tree network topology and a mesh network topology.

20. The wireless network of claim 17, wherein each of the two or more radios uses chirp spread spectrum modulation.- 10 -4223147. vl

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