SYSTEM AND METHOD FOR PROVIDING COMMUNICATIONS WITH AN IMPROVED NETWORK FRAME STRUCTURE ARCHITECTURE IN A WIRELESS SENSOR NETWORK - Patent application

Abstract

To provide systems and methods for providing communications with an improved network frame structure within wireless sensor networks.SOLUTION: In a wireless sensor network, a system includes: a hub having one or more processing units and RF circuitry for transmitting and receiving communications in a wireless network architecture of a wireless network; and a plurality of sensor nodes each including a wireless device equipped with a transmitter and a receiver that enable two-way communications with the hub in the wireless network architecture. A method for operating sensor nodes in an energy efficient manner by the one or more processing units of the hub in a wireless sensor network includes executing instructions to cause a change from a first power mode of a receiver of a sensor node to a second power mode upon transmitting notifications to the sensor node during a repeated hub broadcasting time slot.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] Related Applications This application claims the benefit of U.S. Patent Application No. 15 / 684,894, filed August 23, 2017, the entire contents of which are incorporated herein by reference.

[0002] SUMMARY OF THE INVENTION Embodiments of the present invention relate to systems and methods for providing communication with an improved network frame structure architecture in a wireless sensor network. [Background technology]

[0003] Wireless sensor networks have been researched for many years in the consumer electronics and computer industries. In a typical wireless sensor network, one or more sensors are implemented in combination with radios, enabling wireless collection of data from one or more sensor nodes deployed within the network. Each sensor node can contain one or more sensors and includes a radio and a power source to power its operation. In conventional wireless systems, it is difficult to simultaneously achieve low power and low latency in networks with a large number of sensor nodes. Providing each sensor node with a dedicated time slot results in excessively long wait times for the next slot. Providing random access to each sensor node results in collisions when many sensor nodes transmit simultaneously. Summary of the Invention [Problem to be solved by the invention]

[0004] In one embodiment of the present invention, a system and method for providing communications within a wireless sensor network for an improved network frame structure for sensor nodes are disclosed herein. In one embodiment, the system includes a hub having one or more processing units and RF circuitry for transmitting and receiving communications within a radio network architecture of the wireless network. The system also includes a plurality of sensor nodes, each having a radio device with a transmitter and a receiver that enables bidirectional communication with the hub within the radio network architecture. The one or more processing units of the hub are configured to execute instructions to cause a change in a receiver of the sensor node from a first power mode to a second power mode upon sending a notification to the sensor node during a recurring hub broadcast time slot.

[0005] In one example, a sensor node for a wireless network architecture includes at least one sensor, a memory for storing instructions, and processing logic coupled to the memory and the at least one sensor. The processing logic processes data received from the at least one sensor and executes instructions for processing communications of the sensor node. Radio frequency (RF) circuitry is coupled to the processing logic. The RF circuitry includes transmitter and receiver functionality for sending communications to a hub and receiving communications from the hub within the wireless network architecture. The processing logic is configured to execute instructions to change a first low power mode of the receiver functionality to a second low power mode upon receiving a communication having control or alarm information from the hub during a recurrence of a hub broadcast time slot with control or alarm information originating from the hub or from a group of sensor nodes.

[0006] Other features and advantages of embodiments of the present invention will become apparent from the accompanying drawings and from the following detailed description.

[0007] Embodiments of the present invention are illustrated by way of example, and not limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements and in which: [Brief explanation of the drawings]

[0008] [Figure 1] 1 illustrates an exemplary system of wireless nodes having time slots of different lengths for different types of communications for an improved network frame structure, according to one embodiment. [Figure 2] 1 illustrates a system having primarily a tree network architecture capable of mesh network functionality where sensor nodes may have time slots of different lengths for different types of communication and suppression of notifications, suitable for an improved network frame structure according to one embodiment. [Figure 3] 1 illustrates a system with an asymmetric tree and mesh network architecture with multiple hubs where each group of sensor nodes is assigned a time slot based on a pseudo-random algorithm for communication, according to one embodiment. [Figure 4] 1 illustrates a timeline having time slots of different lengths for different types of communication of wireless nodes in a wireless network architecture, according to one embodiment. [Figure 5] 1 illustrates a method for identifying time slots of different lengths for different types of communication and suppression of notifications, as appropriate for an improved network frame structure of wireless sensor nodes in a wireless sensor network, according to one embodiment. [Figure 6] 1 illustrates a method for scalable and energy-efficient downlink alarm distribution according to a wireless sensor node in a wireless sensor network, according to one embodiment. [Figure 7] 1 illustrates a timeline with a scalable and energy-efficient method of downlink alarm delivery for wireless nodes in a wireless network architecture, according to one embodiment. [Figure 8] 1 illustrates a method for operating sensor nodes in an energy-efficient manner in a wireless sensor network, according to one embodiment. [Figure 9A] 15 illustrates an exemplary embodiment of a hub implemented as an overlay 1500 for a power outlet, according to one embodiment. [Figure 9B] 15 illustrates an exemplary embodiment of an exploded view of a block diagram of a hub 1520 implemented as an overlay for a power outlet, according to one embodiment. [Figure 10A] 1 illustrates an exemplary embodiment of a hub implemented as a card for deployment in a computer system, appliance, or communications hub, according to one embodiment. [Figure 10B] 16 illustrates an exemplary embodiment of a block diagram of a hub 1664 implemented as a card for deployment in a computer system, device, or communications hub, according to one embodiment. [Figure 10C] 1 illustrates an exemplary embodiment of a hub implemented within a device (e.g., a smart washing machine, a smart refrigerator, a smart thermostat, other smart appliances, etc.) according to one embodiment. [Figure 10D] 16 illustrates an exemplary embodiment of an exploded view of a block diagram of a hub 1684 implemented within a device (e.g., a smart washing machine, a smart refrigerator, a smart thermostat, other smart devices, etc.) according to one embodiment. [Figure 11] FIG. 1 shows a block diagram of a sensor node according to an embodiment. [Figure 12] 18 shows a block diagram of a system or device 1800 having a hub, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Disclosed herein are systems and methods for providing communications within a wireless sensor network with an improved network frame structure architecture. In one embodiment, the system includes a hub having one or more processing units and RF circuitry for transmitting and receiving communications within a wireless network architecture of the wireless network. The system also includes a plurality of sensor nodes, each having a wireless device with transmitter and receiver functionality enabling bidirectional communication with the hub within the wireless network architecture. The one or more processing units of the hub are configured to execute instructions to change the receiver functionality of the sensor node from a first power mode to a second power mode upon sending a notification to the sensor node during a recurrence of a hub broadcast time slot with a notification originating from the hub or a different sensor node.

[0010] In one example, the notification originates from a hub or another sensor node.

[0011] The hub may include RF circuitry operable during relevant time periods for transmitting and receiving communications to sensor nodes in the wireless network, particularly in indoor environments, which for this purpose are assumed to include near-indoor environments such as the surrounding areas of buildings and other structures where similar issues (e.g., the presence of nearby walls) may exist.

[0012] A wireless network includes a hub and devices that belong to one or more device groups (e.g., sensor nodes). The hub is constantly listening for notifications from the devices, while the devices are primarily asleep to conserve power. Devices may need to send notifications to the hub and other devices in their group. Notifications usually occur in bursts. Some devices are more likely to receive notifications simultaneously than others. If random access were allowed during a burst, the number of devices would be large enough to congest the wireless connection. Devices with random access would eventually cause collisions if many devices transmit simultaneously. The number of devices is also large enough that low latency cannot be guaranteed, since each device's dedicated time slot requires a long time between two slots.

[0013] In networks with a large number of devices (e.g., at least five devices, at least ten devices), it is difficult to achieve both low power and low latency simultaneously. Slotted frame structures such as 802.15.4 TSCH have long slot lengths, which are only efficient for data transfer. Small control packets use only a small fraction of the slots, so applications that mix a lot of control information with large data packets will have very low network throughput.

[0014] The current design targets applications where it is beneficial for a device to be able to communicate with a specific subset of devices or wake up from a low-power mode whenever necessary.

[0015] The current design includes the following key improvements: 1) Combination of short uplink control slots, downlink transfer slots, and long data slots; 2) Control signal suppression enabled by device grouping.

[0016] In one embodiment, the asymmetry of power supply can be exploited to provide long-range communication within a wireless asymmetric network architecture while maintaining long battery life for nodes powered by battery sources. In one exemplary embodiment, a communication range of 20 meters between communicating nodes can be achieved while simultaneously providing long battery life (e.g., approximately 10 years, at least 10 years) for battery-powered nodes. This can be achieved by implementing an energy-aware networking protocol according to embodiments of the present invention. Specifically, when long-life battery-powered nodes are used at the ends of the tree, a tree-like network architecture with mesh-based functionality can be used.

[0017] Exemplary tree-like network architectures are described in U.S. patent application Ser. No. 14 / 607,045, filed Jan. 29, 2015, U.S. patent application Ser. No. 14 / 607,047, filed Jan. 29, 2015, U.S. patent application Ser. No. 14 / 607,048, filed Jan. 29, 2015, and U.S. patent application Ser. No. 14 / 607,050, filed Jan. 29, 2015, which are incorporated by reference herein in their entireties.

[0018] The wireless sensor network is described for use in indoor environments, including homes, apartments, offices, and commercial buildings, as well as nearby exterior locations such as parking lots, sidewalks, and gardens. The wireless sensor network can also be used in any type of building, structure, enclosure, vehicle, boat, etc., with a power source. The sensor system provides good battery life for the sensor nodes while maintaining a long communication range.

[0019] 1 illustrates an exemplary system of wireless nodes having time slots of different lengths for different types of communications for an improved network frame structure, according to one embodiment. System 100 has a primarily tree network architecture capable of mesh-like network functionality, according to one embodiment. System 100 has a tree network architecture primarily for standard communications (e.g., node identification information, notifications, sensor data, node status information, synchronization information, location information, other such information for wireless sensor networks, time-of-flight (TOF) communications, etc.). System 100 includes hub 110 with wireless control device 111, sensor node 120 with wireless device 121, sensor node 124 with wireless device 125, sensor node 128 with wireless device 129, sensor node 130 with wireless device 131, and sensor node 132 with wireless device 133. Additional hubs, not shown, can communicate with hub 110 or other hubs. Each hub communicates bidirectionally with sensor nodes 120, 124, 128, 130, and 132. The hubs are also designed to communicate bidirectionally with other devices (e.g., client devices, mobile devices, tablet devices, computing devices, smart appliances, smart TVs, etc.).

[0020] In one embodiment, the control device 111 of the hub 110 is configured to execute instructions to specify different length time slots for different types of communication between the hub and the sensor nodes (e.g., nodes 120, 124, 128, 130, 132). For example, the control device 111 may be configured to specify shorter uplink control time slots, downlink transfer time slots, and longer data time slots. The hub or sensor nodes may also be configured to suppress notifications as needed due to grouping of sensor nodes.

[0021] A sensor node is an end node if it only has upstream communication with a higher-level hub or node and no downstream communication with another hub or node. Each wireless device contains RF circuitry with a transmitter and receiver (or transceiver) to enable bidirectional communication with hubs or other sensor nodes.

[0022] FIG. 2 illustrates a system primarily having a tree network architecture capable of mesh network functionality, where sensor nodes may have different length time slots for different types of communication and notification suppression, suitable for an improved network frame structure according to one embodiment. System 250 may establish a mesh network architecture for locating sensor nodes based on triggered threshold criteria (e.g., movement of at least one node by a specific distance, change in path length between a node and a hub by a specific distance). System 250 includes hub 210, a first group 295 of nodes 220, 224, 228, 230, and 232, and a second group 296 of nodes 270, 280, and 290. Sensor nodes can be assigned to different groups. In another example, group 296 is divided into a first subgroup of nodes 220 and 224 and a second subgroup of nodes 228, 230, and 232. In one example, each group (or subgroup) is assigned a pseudo-random time slot for communicating with other nodes or the hub.

[0023] Hub 210 includes wireless device 211, sensor node 220 includes wireless device 221, sensor node 224 includes wireless device 225, sensor node 228 includes wireless device 229, sensor node 230 includes wireless device 231, sensor node 232 includes wireless device 233, sensor node 270 includes wireless device 271, sensor node 280 includes wireless device 281, and sensor node 290 includes wireless device 291. Additional hubs not shown can communicate with hub 210 or other hubs. Hub 210 communicates bidirectionally with the sensor nodes.

[0024] These communications include bidirectional communications 240-244, 272, 282, and 292 within a wireless asymmetric network architecture. Sensor nodes communicate bidirectionally with each other based on communications 261-266, 273, and 283, providing mesh-like functionality for different applications including locating hubs and sensor nodes.

[0025] In one embodiment, the control device 211 of the hub 210 is configured to execute instructions to specify different length time slots for different types of communication between the hub and the sensor nodes. For example, the control device 211 may be configured to specify shorter uplink control time slots, downlink transfer time slots, and longer data time slots. The hub or sensor nodes may also be configured to suppress notifications as needed depending on the grouping of sensor nodes.

[0026] FIG. 3 illustrates a system with an asymmetric tree and mesh network architecture having multiple hubs, with each group of sensor nodes assigned a time slot based on a pseudo-random algorithm for communication, according to one embodiment. System 700 includes additional hubs, including a central hub 710 with a wireless control device 711, a hub 720 with a wireless control device 721, a hub 782 with a wireless control device 783, and a hub n with a wireless control device n. The additional hubs, not shown, may communicate with central hub 710, other hubs, or may be additional central hubs. Each hub communicates bidirectionally with the other hubs and one or more sensor nodes. The hubs are also designed to communicate bidirectionally with other devices, including devices 780 (client devices, mobile devices, tablet devices, computing devices, smart appliances, smart TVs, etc.).

[0027] Sensor nodes 730, 740, 750, 760, 770, 788, 792, n, and n+1 (or end nodes) include wireless devices 731, 741, 751, 761, 771, 789, 793, 758, and 753, respectively. A sensor node is an end node if it has only upstream communication with a higher-level hub or node and no downstream communication with another hub or node. Each wireless device includes RF circuitry with a transmitter and receiver (or transceiver) to enable bidirectional communication with hubs or other sensor nodes.

[0028] In one embodiment, central hub 710 communicates with hubs 720, 782, hub n, device 780, and nodes 760 and 770. These communications include communications 722, 724, 774, 772, 764, 762, 781, 784, 786, 714, and 712 in the wireless asymmetric network architecture. The central hub with wireless control device 711 is configured to send communications to the other hubs and receive communications from the other hubs to control and monitor the wireless asymmetric network architecture, including assigning groups of nodes and allocating time slots based on a pseudo-random algorithm that uses time slots of different lengths for different types of communications.

[0029] Hub 720 communicates with central hub 710 and also with sensor nodes 730, 740, and 750. Communications with these sensor nodes include communications 732, 734, 742, 744, 752, and 754. For example, from the perspective of hub 720, communication 732 is received by the hub and communication 734 is sent to the sensor node. From the perspective of sensor node 730, communication 732 is sent to hub 720 and communication 734 is received from the hub.

[0030] In one embodiment, a central hub (or other hub) assigns nodes 760 and 770 to group 716, nodes 730, 740, and 750 to group 715, nodes 788 and 792 to group 717, and nodes n and n+1 to group n. In another example, groups 716 and 715 are combined into a single group.

[0031] The wireless control device of the central hub, alone or in combination with other hubs, is configured to execute instructions to specify time slots of different lengths for different types of communication between the hub(s) and the sensor nodes. For example, the hub may be configured to specify shorter uplink control time slots, downlink transfer time slots, and longer data time slots. The hub or sensor node may also be configured to suppress notifications when appropriate (e.g., when certain notifications are not needed or desired).

[0032] 1-3, nodes requiring long battery life can minimize the energy expended in communications, while higher-level nodes in the tree hierarchy can be implemented using available energy sources or alternatively use batteries offering higher capacity or shorter battery life. To facilitate achieving long battery life in battery-operated end nodes, communications between those nodes and their higher-level counterparts (hereafter referred to as lowest-level hubs) can be established such that minimal send and receive traffic occurs between the lowest-level hubs and the end nodes.

[0033] In one embodiment, a node spends most of its time (e.g., more than 90% of the time, more than 95% of the time, about 98% or more than 99% of the time) in a low-energy, non-communicating state. When a node wakes up and enters a communicating state, it is operable to transmit data to the lowest level hub. This data includes node identification information, sensor data, node status information, synchronization information, location information, and other such information related to the wireless sensor network.

[0034] In one example, to conserve power, sensor nodes configured in a low-power mode (e.g., sleep state) wake up only in a high-power mode and check for communication signals in downlink transmission slots. Typically, a hub receiving uplink traffic uses this slot to forward received short group messages. The group identifier in the message tells the receiving sensor nodes which group is expected to respond or be awake after receiving this message. Sensor nodes that need to transmit a group message use one of the uplink slots in a randomly determined manner. The random slot can be calculated to ensure there is little (or no) chance of collisions within a group. This is beneficial in applications where groups can be formed from sensor nodes that are likely to transmit control information at the same time. For example, a network that detects space occupancy includes groups of sensor nodes. Each sensor node in the first group is likely to transmit control information at approximately the same time that the occupancy is detected, as opposed to sensor nodes in the second group that are not currently detecting the occupancy.

[0035] In applications where the primary purpose of a control message is to wake up a group of devices and the group is likely to have several devices waking up simultaneously, sending a wake-up command is not required for all devices (e.g., sensor nodes). This design includes the concept of signal suppression to reduce congestion in the wireless network. When several devices in a group attempt to transmit control information, they use pseudo-randomly assigned time slots. While waiting for a transmission time slot, these devices have an operational receive mode to detect other transmissions from the same group. If a transmission from another device in the group is detected, the device cancels its own future transmissions to reduce network congestion in the wireless network. When a notification control packet is eventually transmitted by one of the devices in the group, confirmation of successful reception of this control packet or another control packet from a device in this group can be detected in the subsequent downlink broadcast slot. If confirmation is detected, all devices in the group that receive the confirmation suppress further transmissions. Otherwise, the devices continue to transmit repeatedly using control packets until confirmation of at least one transmission is detected.

[0036] FIG. 4 illustrates a timeline with different length time slots for different types of communication for wireless nodes in a wireless network architecture, according to one embodiment. Broadcast beacon signals 402-406 are periodically repeated on timeline 450. A broadcast beacon signal may include a one-byte field x that indicates to other systems that this is a beacon frame, followed by field y, which may include frame-related information 441 and 442 that can be found in beacon information 440. Frames such as 422 are time slots during which hubs and nodes can communicate without other systems interfering. Data, acknowledgements, notifications, beacons, or MAC command packets may be transmitted during the frame.

[0037] The beacon defines a frame using a known protocol at the beginning of the beacon before its own content to prevent other systems from transmitting during the guaranteed time slot. In one example, other systems (e.g., IEEE 802.15.4 systems) do not transmit during period 422 (or other similar periodic period) based on including frame information 441 and 442 at the beginning of every beacon. Frame order field 442 contains information about the length of the frame, and beacon order field 441 contains information about the time between two frames.

[0038] Additional details of the network frame architecture are described in U.S. Patent Application No. 14 / 925,889, filed October 28, 2015, which is incorporated herein by reference in its entirety.

[0039] In one example, the hub utilizes a pseudo-random algorithm to identify time slots 411-420 for the first group of sensor nodes. The pseudo-random algorithm can define time slots of different lengths for different types of communications. In one example, devices (e.g., sensor nodes) in the first group have transmitters operable to transmit notifications (e.g., control information, alarm information) during time slot signals 411, 412, and 415-420. Devices (e.g., sensor nodes) in the first group have transmitters operable to transmit data communications during longer time slot signals 413-414. Each time slot signal can be divided into shorter time slots for multiple sensor nodes.

[0040] 5 illustrates a method for identifying different length time slots for suppression of different types of communications and notifications, as appropriate for an improved network frame structure for wireless sensor nodes in a wireless sensor network, according to one embodiment. The operations of method 500 may be performed by a wireless device, a hub wireless control device (e.g., apparatus), or a system that includes processing circuitry or processing logic. The processing logic may include hardware (e.g., circuitry, dedicated logic), software (e.g., running on a general-purpose computer system or dedicated machine or device), or a combination of both. In one embodiment, an anchor node, a hub, or a wireless device performs the operations of method 500.

[0041] A wireless network architecture having a plurality of wireless nodes and at least one hub is initialized in operation 501. The initialization may include locating each of the plurality of wireless nodes.

[0042] At operation 502, processing logic of the hub identifies groups of wireless sensor nodes, a group identifier for each group, a first device identifier for each sensor node, and a second shortened or reduced device identifier for each sensor node. At operation 504, processing logic of the hub identifies time slots of a first length (e.g., 30 units, approximately 300 microseconds, less than 500 microseconds, etc.) for notifications in the wireless network and time slots of a second, different length (e.g., 1000 units, approximately 10 milliseconds, at least 1 millisecond, etc.) for data communications. In one example, the wireless network is optimized for notifications having time slots of a first length (e.g., 30 units, approximately 300 microseconds, less than 500 microseconds, etc.) for a first time period and time slots of a second, different length (e.g., 1000 units, approximately 10 milliseconds, at least 1 millisecond, etc.) for data communications for a second time period. The hub can switch between the first and second lengths of time slots depending on the particular application of the wireless sensor network.

[0043] In operation 506, processing logic at the hub identifies a hash function for each sensor node based on the second device identifier of each sensor node. The hub can assign shortened device identifiers such that a hash function based on the short device identifiers can effectively spread uplink packets across all available time slots.

[0044] In operation 508, the processing logic of the hub executes a pseudo-random algorithm to randomly assign a time slot to each sensor node based on at least the hash function, the second device identifier, the time, and the group identifier, where the pseudo-random time slot is designed based on the fact that sensor nodes within a group are less likely to have the same time slot compared to other sensor nodes within the same group, and that sensor nodes in different groups are more likely to occupy the same time slot.

[0045] In one example, a trigger event detected by a wireless sensor network generates an alarm signal, which must be reliably delivered, thus requiring a retransmission mechanism. Alarm signals can be transmitted simultaneously from multiple sensor nodes, necessitating a large number of uplink alarm micro-timeslots. A retransmission mechanism that relies on unicast can result in a large micro-timeslot size, which limits the number of uplink alarm micro-timeslots.

[0046] In one example, the alarm signal is a control packet for each constellation (e.g., each group). As the number of constellations increases, the TDMA system requires more downlink alarm time slots, which is not scalable. Furthermore, multiple downlink alarm time slots force the sensor node into active receive mode for more time slots to receive alarm packets, which causes an increase in the active period of the RF module of the sensor node.

[0047] Thus, the present design provides a scalable and energy-efficient method of downlink alarm delivery. FIG. 6 illustrates a method for scalable and energy-efficient downlink alarm delivery according to a wireless sensor node in a wireless sensor network, according to one embodiment. The operations of method 600 may be performed by a wireless device, a hub wireless control device (e.g., apparatus), or a system that includes processing circuitry or processing logic. The processing logic may include hardware (such as circuitry, dedicated logic), software (such as running on a general-purpose computer system or a dedicated machine or device), or a combination of both. In one embodiment, a node, a hub, or a wireless device performs the operations of method 600.

[0048] In operation 602, the hub receives communications with alarm information from at least one group of sensor nodes. In operation 604, the hub provides a target alarm delay by waiting to receive additional communications with alarm information (e.g., uplink alarms) from additional sensor nodes and potentially from different groups of sensor nodes during a specified period of time.

[0049] Next, in operation 606, the hub identifies unique alarms from groups (e.g., constellations) of sensor nodes and combines multiple alarm information of different groups (e.g., constellations) of sensor nodes into a communication comprising an alarm packet. In one example, a first group of sensor nodes transmits first alarm information to the hub, and a second group of sensor nodes transmits second alarm information to the hub. In operation 608, the hub assigns downlink alarm time slots that each sensor node must receive during active receive mode. The hub can assign downlink alarm time slots to sensor nodes by using a hash function (e.g., y = f(constellation ID)).

[0050] In operation 610, the hub is configured to execute instructions that, upon sending a notification to at least one sensor node during a recurrence of the hub broadcast time slot with control or alarm information originating from the hub or a group of sensor nodes, cause a change in a receiver of the at least one sensor node from a first power mode to a second power mode, where the second power mode (e.g., active receive mode) may be required for the sensor node.

[0051] FIG. 7 illustrates a timeline showing a scalable, energy-efficient method for downlink alarm distribution for wireless nodes in a wireless network architecture, according to one embodiment. A broadcast beacon signal 702 is periodically repeated on the timeline 700. The broadcast beacon signal may include a one-byte field that indicates to other systems that this is a beacon frame, followed by other fields that may contain other information. An aggregated alarm signal 704 may include alarm information from multiple sensor nodes and multiple groups of sensors. The hub removes the device identifier from the alarm information and adds the group information to the alarm information. The sensor node can monitor the alarm information in the aggregated alarm information to identify the group identifier associated with a particular sensor node. The signal 706 may include additional aggregated alarm information for different group identifiers, or the signal 706 may be a different type of control packet. For example, the aggregation of multiple pieces of information may be used for other control packets, such as capturing an image using a sensor node, retrieving the image, and deleting the image.

[0052] In one example, aggregated alarm signal 704 includes alarm information for groups 1-4, and aggregated alarm signal 706 includes alarm information for groups 5-8.

[0053] This design provides an alarm retransmission mechanism by utilizing the detected forwarded alarm signal as an acknowledgment. After transmitting a broadcast alarm signal, the sensor node transmitting the alarm signal waits for the next alarm slot to confirm whether the transmitted alarm signal has been forwarded (e.g., forwarded by the hub). If the sensor node can receive the forwarded alarm signal, this indicates that the hub has received the alarm signal, and this does not trigger a retransmission of the alarm signal. Otherwise, the sensor node retransmits the alarm signal for cases such as no alarm delivery from the sensor node to the hub.

[0054] In one example, a sensor node detects a trigger event that causes the sensor node to generate and transmit an alarm signal during the next randomly identified time slot. The hub receives the alarm signal and identifies an action based on receiving the alarm signal (e.g., repeating the alarm signal to wake up all nodes, sending the alarm signal to the homeowner, police department, fire department, ambulance, etc.). Upon waking up other sensor nodes, the hub may receive additional communications from other sensors. The hub can then identify appropriate actions based on the additional communications. For example, all sensors after receiving a wake-up signal from the hub can capture images and transmit the images to the hub for analysis.

[0055] In one example, retransmission of data is based on whether an acknowledgement communication is detected. To shorten the length of a time slot, carrier sensing and backoff slots within the time slot are not appropriate.

[0056] Therefore, the current design reduces the chance of collisions during uplink packet transmission from multiple nodes by distributing the uplink packets from the sensor nodes to the hub(s) across all available time slots. The current design uses randomness in the selection of time slots.

[0057] 8 illustrates a method for operating a sensor node in an energy-efficient manner within a wireless sensor network, according to one embodiment. The operations of method 800 may be performed by a wireless device, a hub (e.g., appliance) wireless control device, or system that includes processing circuitry or processing logic. The processing logic may include hardware (e.g., circuitry, dedicated logic), software (e.g., running on a general-purpose computer system or dedicated machine or device), or a combination of both. In one embodiment, the sensor node or wireless device performs the operations of method 800.

[0058] In operation 802, processing logic of the sensor node is configured to change a first low power mode of a receiver function of the sensor node to a second power mode upon receiving a communication having control or alarm information from the hub during a repetition of a hub broadcast time slot with control or alarm information originating from the hub or a group of sensor nodes, wherein the receiver function of the sensor node is configured with a minimum level of power to listen for broadcast messages during the first power mode (e.g., only an operational receiver function) and is operable during the second power mode at a level above the minimum power level, including having an operational transmitter function.

[0059] At operation 808, processing logic of the sensor node is configured to execute instructions to identify a group identifier of the received communication, identify a group identifier of the sensor node, and cancel transmission of the communication from the sensor node if the group identifier of the received communication matches the group identifier of the sensor node, thereby alleviating congestion in the wireless network.

[0060] In one example, groups of sensor nodes are formed to increase the likelihood that the groups of sensor nodes will transmit communications at approximately the same time or close in time.

[0061] At operation 810, processing logic of the sensor node is configured to execute instructions to send a communication, confirm successful receipt of the notification for the node group by checking the next hub broadcast slot for notification forwarding, and resend the communication with at least one modified parameter of the pseudo-random function if successful receipt is not confirmed.

[0062] Communication between the hub and nodes described herein can be achieved using a variety of means, including, but not limited to, direct wireless communication using radio frequencies; power line communication achieved by modulating signals onto electrical wiring within a home, apartment, commercial building, etc.; WiFi communication using standard WiFi communication protocols such as 802.11a, 802.11b, 802.11n, 802.11ac, and other such WiFi communication protocols apparent to those skilled in the art; cellular communication such as GPRS, EDGE, 3G, HSPDA, LTE, and other cellular communication protocols apparent to those skilled in the art; Bluetooth communication; communication using well-known wireless sensor network protocols such as Zigbee, and other wire-based or wireless communication schemes apparent to those skilled in the art.

[0063] Radio frequency communication between the end nodes and the hub can be implemented in a variety of ways, including narrowband, channel overlapping, channel stepping, multi-channel wideband, and ultra-wideband communication.

[0064] A hub may be physically implemented in many ways according to embodiments of the present invention. Figure 9A shows an exemplary embodiment of a hub implemented as an overlay 1500 for a power outlet according to one embodiment. The overlay 1500 (e.g., a faceplate) includes a hub 1510 and connections 1512 (e.g., communication links, signal lines, electrical connections, etc.) that couple the hub to the outlet 1502. Alternatively (or additionally), the hub is coupled to the outlet 1504. The overlay 1500 covers or surrounds the outlets 1502 and 1504 for safety and aesthetic purposes.

[0065] 9B shows an exemplary embodiment of an exploded view of a block diagram of a hub 1520 implemented as an overlay for a power outlet, according to one embodiment. The hub 1520 includes a power rectifier 1530 that converts alternating current (AC), which periodically reverses direction, into direct current (DC), which flows in only one direction. The power rectifier 1530 receives AC from the outlet 1502 via connection 1512 (e.g., a communication link, signal line, electrical connection, etc.), converts the AC to DC, and provides power to the controller circuit 1540 via connection 1532 (e.g., a communication link, signal line, electrical connection, etc.) and to the RF circuit 1550 via connection 1534 (e.g., a communication link, signal line, electrical connection, etc.). The controller circuit 1540 includes a memory 1542 or is coupled to a memory that stores instructions executed by processing logic 1544 (e.g., one or more processing units) of the controller circuit 1540 to control the operation of the hub to form, monitor, and perform localization of a wireless asymmetric network as described herein. The RF circuitry 1550 may include a transceiver or separate transmitter 1554 and receiver 1556 functionality for sending and receiving bidirectional communications to and from wireless sensor nodes via antenna(s) 1552. The RF circuitry 1550 communicates bidirectionally with the controller circuitry 1540 via a connection 1534 (e.g., a communication link, a signal line, an electrical connection, etc.). The hub 1520 may be a wireless control device 1520, or the combination of the controller circuitry 1540, RF circuitry 1550, and antenna(s) 1552 may form a wireless control device as described herein.

[0066] 10A shows an exemplary embodiment of a hub implemented as a card for deployment in a computer system, device, or communications hub, according to one embodiment. Card 1662 can be inserted into system 1660 (e.g., a computer system, device, or communications hub), as indicated by arrow 1663.

[0067] 10B shows an exemplary embodiment of a block diagram of a hub 1664 implemented as a card for deployment in a computer system, device, or communications hub, according to one embodiment. The hub 1664 includes a power supply 1666 that provides power (e.g., DC power) to a controller circuit 1668 via connection 1674 (e.g., a communications link, signal line, electrical connection, etc.) and power to an RF circuit 1670 via connection 1676 (e.g., a communications link, signal line, electrical connection, etc.). The controller circuit 1668 includes a memory 1661 or is coupled to a memory that stores instructions executed by the processing logic 1663 (e.g., one or more processing units) of the controller circuit 1668 that control the operation of the hub to form, monitor, and communicate within a wireless asymmetric network as described herein. The RF circuit 1670 can include a transceiver or separate transmitter 1675 and receiver 1677 functionality for transmitting and receiving bidirectional communications to and from wireless sensor nodes via antenna(s) 1678. The RF circuitry 1670 communicates bidirectionally with the controller circuitry 1668 via a connection 1672 (e.g., a communication link, a signal line, an electrical connection, etc.). The hub 1664 can be a wireless control device 1664, or the controller circuitry 1668, the RF circuitry 1670, and the antenna(s) 1678 can combine to form a wireless control device as described herein.

[0068] 10C shows an example embodiment of a hub implemented in an appliance (e.g., a smart washing machine, a smart refrigerator, a smart thermostat, other smart appliances, etc.) according to one embodiment. Appliance 1680 (e.g., a smart washing machine) includes hub 1682.

[0069] 10D shows an exemplary embodiment of an exploded view of a block diagram of a hub 1684 implemented within a device (e.g., a smart washing machine, a smart refrigerator, a smart thermostat, other smart appliance, etc.), according to one embodiment. The hub includes a power supply 1686 that provides power (e.g., DC power) to a controller circuit 1690 via connection 1696 (e.g., a communication link, a signal line, an electrical connection, etc.) and powers an RF circuit 1692 via connection 1698 (e.g., a communication link, a signal line, an electrical connection, etc.). The controller circuit 1690 includes a memory 1691 or is coupled to a memory that stores instructions executed by the processing logic 1688 (e.g., one or more processing units) of the controller circuit 1690 to control the operation of the hub to form, monitor, and perform localization of a wireless asymmetric network as described herein. The RF circuit 1692 can include a transceiver or separate transmitter 1694 and receiver 1695 functionality for transmitting and receiving bidirectional communications with wireless sensor nodes via antenna(s) 1699. The RF circuitry 1692 communicates bidirectionally with the controller circuitry 1690 via a connection 1689 (e.g., a communication link, a signal line, an electrical connection, etc.). The hub 1684 may be a wireless control device 1684, or the controller circuitry 1690, the RF circuitry 1692, and the antenna(s) 1699 may combine to form a wireless control device as described herein.

[0070] In one embodiment, an apparatus (e.g., a hub) for providing a wireless asymmetric network architecture includes memory for storing instructions, processing logic (e.g., one or more processing units, processing logic 1544, processing logic 1663, processing logic 1688, processing logic 1763, processing logic 1888) of the hub for executing the instructions for establishing and controlling communications within the wireless asymmetric network architecture, and radio frequency (RF) circuitry (e.g., RF circuitry 1550, RF circuitry 1670, RF circuitry 1692, RF circuitry 1890) including multiple antennas (e.g., antenna(s) 1552, antenna(s) 1678, antenna(s) 1699, antenna(s) 1311, 1312, 1313, etc.) for transmitting and receiving communications within the wireless asymmetric network architecture. The RF circuitry and multiple antennas transmit communications to multiple sensor nodes (e.g., Node 1, Node 2), each having a wireless device with a transmitter and receiver (or the transmitter and receiver functionality of a transceiver) that enables bidirectional communication with the RF circuitry of an apparatus in the wireless asymmetric network architecture. The one or more processing units are configured to execute instructions to provide a target alarm delay by receiving at least one communication with alarm information from sensor nodes of at least one group of sensor nodes and waiting for a specified period of time to receive additional communications with alarm information from additional sensor nodes and potentially from sensor nodes of different groups.

[0071] In one example, one or more processing units of the device are configured to execute instructions for identifying a unique alarm from at least one communication received from at least one group of sensor nodes.

[0072] In another example, one or more processing units of the device are configured to execute instructions for combining multiple alarm information of unique alarms of sensor nodes of different groups into a communication comprising an alarm packet.

[0073] In another example, one or more processing units of the apparatus are configured to execute instructions to receive a first plurality of communications having first alarm information from a first group of sensor nodes and a second plurality of communications having second alarm information from a second group of sensor nodes.

[0074] In another example, one or more processing units of the apparatus are configured to execute instructions for allocating downlink alarm time slots for alarm packets sent to the sensor nodes by using a hash function.

[0075] In another example, the one or more processing units of the device are configured to execute instructions to change a receiver of the sensor node from a first power mode to a second power mode upon transmitting an alarm packet having alarm information to the sensor node during a recurring hub broadcast time slot.

[0076] A variety of batteries can be used in wireless sensor nodes, including lithium-based chemistries such as lithium-ion, lithium-thionyl chloride, lithium manganese oxide, lithium polymer, lithium phosphate, and other chemistries that will be apparent to one skilled in the art. Additional chemistries that can be used include nickel-metal hydride, standard alkaline battery chemistries, silver-zinc and zinc-air battery chemistries, standard carbon-zinc battery chemistries, lead-acid battery chemistries, or other chemistries that will be apparent to one skilled in the art.

[0077] The present invention also relates to apparatus for performing the operations described herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored within the computer. Such a computer program may be stored on a computer-readable storage medium, such as, but not limited to, a floppy disk, an optical disk, a CD-ROM, and a magneto-optical disk, read-only memory (ROM), random-access memory (RAM), EPROM, EEPROM, a magnetic or optical card, or any type of disk, including any type of medium suitable for storing electronic instructions.

[0078] The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method operations.

[0079] 11 shows a block diagram of a sensor node according to one embodiment. The sensor node 1700 includes a power supply 1710 (e.g., an energy source, a battery source, a primary cell, a rechargeable cell, etc.) that provides power (e.g., a DC power source) to a controller circuit 1720 via connection 1774 (e.g., a communication link, a signal line, an electrical connection, etc.), provides power to the RF circuit 1770 via connection 1776 (e.g., a communication link, a signal line, an electrical connection, etc.), and provides power to the sensing circuit 1740 via connection 1746 (e.g., a communication link, a signal line, an electrical connection, etc.). The controller circuit 1720 includes a memory 1761 or is coupled to a memory that stores instructions executed by processing logic 1763 (e.g., one or more processing units) of the controller circuit 1720 to control the operation of the sensor node to form and monitor a wireless asymmetric network as described herein. The RF circuitry 1770 (e.g., communications circuitry) may include a transceiver or separate transmitter 1775 and receiver 1777 functionality for sending and receiving bidirectional communications via antenna(s) 1778 with the hub(s) and optional wireless sensor nodes. The RF circuitry 1770 communicates bidirectionally with the controller circuitry 1720 via connection 1772 (e.g., electrical connection). The sensing circuitry 1740 may include various types of sensing circuits and (or) sensors, including image sensor(s) and circuit(s) 1742, moisture sensor(s) and circuit(s) 1743, temperature sensor(s) and circuit(s), humidity sensor(s) and circuit(s), air quality sensor(s) and circuit(s), light sensor(s) and circuit(s), motion sensor(s) and circuit(s) 1744, sound sensor(s) and circuit(s) 1745, magnetic sensor(s) and circuit(s), and sensor(s) and circuit(s). The sensor includes one or more sensors.

[0080] In one embodiment, a sensor node in a wireless network architecture includes at least one sensor, a memory that stores instructions, and processing logic coupled to the memory and the at least one sensor. The processing logic processes data received from the at least one sensor and executes instructions for processing communications of the sensor node. The sensor node includes radio frequency (RF) circuitry coupled to the processing logic. The RF circuitry includes transmitter and receiver functionality for sending communications to a hub and receiving communications from the hub within the wireless network architecture. The processing logic is configured to execute instructions to change a first low power mode of the receiver functionality to a second low power mode upon receiving a communication having control or alarm information from the hub during a repeating hub broadcast time slot using control or alarm information originating from the hub or a group of sensor nodes.

[0081] In one example, control or alarm information originates from a hub or group of sensor nodes.

[0082] In another example, the receiver functionality of the sensor node is configured to be at a minimum level of power (e.g., have only an operational receiver functionality) to listen for broadcast messages during a first power mode, and to be operable during a second power mode at any power level above the minimum, including having an operational transmitter functionality.

[0083] In another example, the processing logic is configured to execute instructions to identify a group identifier of the received notification, identify a group identifier of the sensor node, and cancel transmission of the communication from the sensor node if the group identifier of the received notification matches the group identifier of the sensor node, thereby alleviating congestion in the wireless network.

[0084] In another example, groups of sensor nodes are formed to increase the likelihood that the groups of sensor nodes will send communications at approximately the same time or close in time.

[0085] In another example, the sensor node operates from a battery source.

[0086] In another example, the processing logic is configured to execute instructions to send a communication, confirm successful receipt of the communication by checking the next hub broadcast slot for notification forwarding, and resend the communication with at least one modified parameter of the pseudo-random function if successful receipt is not confirmed.

[0087] In one example, the sensor node is configured to execute instructions to detect at least one of the energy of the transmission and the preamble of the transmission to verify the transmission without consuming power to process the data of the transmission.

[0088] 12 shows a block diagram of a system 1800 having a hub according to one embodiment. The system 1800 includes or is integrated with a hub 1882 or central hub of a wireless asymmetric network architecture. The system 1800 (e.g., a computing device, a smart TV, a smart appliance, a communication system, etc.) can communicate with any type of wireless device (e.g., a mobile phone, a wireless telephone, a tablet, a computing device, a smart TV, a smart appliance, etc.) for transmitting and receiving wireless communications. The system 1800 includes a processing system 1810 including a controller 1820 and a processing unit 1814. The processing system 1810 communicates with a hub 1882, an input / output (I / O) unit 1830, radio frequency (RF) circuitry 1870, audio circuitry 1860, an optical device 1880 for capturing one or more images or videos, an optional motion unit 1844 (e.g., accelerometer, gyroscope, etc.) for determining motion data (e.g., three-dimensional) for the system 1800, a power management system 1840, and a machine-accessible non-transitory medium 1850 via one or more bidirectional communication links or signal lines 1898, 1818, 1815, 1816, 1817, 1813, 1819, 1811, respectively.

[0089] Hub 1882 includes a power source 1891 that provides power (e.g., DC power) to controller circuit 1884 via connection 1885 (e.g., a communication link, a signal line, an electrical connection, etc.) and provides power to RF circuit 1890 via connection 1887 (e.g., a communication link, a signal line, an electrical connection, etc.). Controller circuit 1884 includes a memory 1886 or is coupled to a memory that stores instructions executed by processing logic 1888 (e.g., one or more processing units) of controller circuit 1884 for controlling the operation of the hub to form and monitor a wireless asymmetric network as described herein. RF circuit 1890 may include a transceiver or separate transmitter (TX) 1892 and receiver (RX) 1894 functionality for sending and receiving bidirectional communications via antenna(s) 1896 with wireless sensor nodes or other hubs. RF circuit 1890 communicates bidirectionally with controller circuit 1884 via connection 1889 (e.g., a communication link, a signal line, an electrical connection, etc.). The hub 1882 may be a wireless control device 1884 or controller circuitry 1884, RF circuitry 1890, and antenna(s) 1896, which may combine to form a wireless control device as described herein.

[0090] The system's RF circuitry 1870 and antenna(s) 1871 or the hub's 1882's RF circuitry 1890 and antenna(s) 1896 are used to transmit and receive information to one or more other wireless devices of the hub or sensor node described herein via a wireless link or network. The audio circuitry 1860 is coupled to an audio speaker 1862 and a microphone 1864 and includes known circuitry for processing audio signals. The one or more processing units 1814 communicate with one or more machine-accessible, non-transitory media 1850 (e.g., computer-readable media) via the controller 1820. The media 1850 may be any device or medium (e.g., storage device, storage medium) capable of storing code and / or data used by the one or more processing units 1814. The media 1850 may include a memory hierarchy, including, but not limited to, a cache, a main memory, and a secondary memory.

[0091] The medium 1850 or memory 1886 stores one or more instruction sets (or software) that implement any one or more of the methodologies or functions described herein. The software may include an operating system 1852, network services software 1856 for establishing, monitoring, and controlling a wireless asymmetric network architecture, a communications module 1854, and applications 1858 (e.g., home or building security applications, home or building integrity applications, developer applications, etc.). Software may also reside, completely or at least partially, within the medium 1850, memory 1886, processing logic 1888, or processing unit 1814 during its execution by the device 1800. The components shown in FIG. 18 may be implemented in hardware, software, firmware, or any combination thereof, including one or more signal processing and / or application-specific integrated circuits.

[0092] The communication module 1854 enables communication with other devices. The I / O unit 1830 communicates with different types of input / output (I / O) devices 1834 (e.g., displays, liquid crystal displays (LCDs), plasma displays, cathode ray tubes (CRTs), touch display devices or touch screens for receiving user input and displaying output, and optional alphanumeric input devices).

[0093] In one embodiment, a system includes a hub having one or more processing units and RF circuitry for transmitting and receiving communications within a radio network architecture of a radio network, and a plurality of sensor nodes, each having a radio device with transmitter and receiver capabilities that enable bidirectional communication with the hub within the radio network architecture, wherein the one or more processing units of the hub are configured to execute instructions to cause a change in a receiver of the sensor node from a first power mode to a second power mode upon sending a notification to the sensor node during a recurring hub broadcast time slot.

[0094] In one example, the notification originates from a hub or another sensor node. The receiver functionality of the sensor node is configured at a minimum power level to listen for broadcast messages during the first power mode and is operable during the second power mode at any power level above the minimum power level, including having an operable transmitter functionality.

[0095] In another example, the sensor node is configured to execute instructions to identify a group identifier of a received notification, identify a group identifier of the sensor node, and cancel transmission of a communication from the sensor node if the group identifier of the received notification matches the group identifier of the sensor node, thereby alleviating congestion in the wireless network.

[0096] In another example, the sensor node is configured to execute instructions to send a notification, confirm successful receipt of the notification for a group of nodes by checking the next hub broadcast slot for notification forwarding, and resend the notification with at least one modified parameter of the pseudo-random function if successful receipt is not confirmed.

[0097] In another example, the one or more processing units of the hub are configured to execute instructions to identify transmission time slots for the plurality of sensor nodes using pseudo-random slot locations based on sensor nodes within a group being less likely to have the same time slot compared to other sensor nodes within the group, while sensor nodes within different groups are more likely to occupy the same time slot.

[0098] In another example, one or more processing units of the hub are configured to execute instructions to identify time slots of a first length for notifications and time slots of a second length for data communications in the wireless network.

[0099] In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be apparent that various modifications and changes can be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.

Claims

1. In the system, a hub having a set of processing units and radio frequency circuitry; a set of sensor nodes; each sensor node of the set of sensor nodes comprises a wireless device having a transmitter and a receiver configured to enable bidirectional communication with the hub in a wireless network; the set of sensor nodes comprises a first sensor node configured to execute instructions; The first sensor node executes the instruction, transitioning a receiver of the first sensor node from a first power mode to a second power mode in response to receiving a set of communications from a hub during a repeating hub broadcast time slot, the set of communications including alarm information from the hub; receiving a second communication from a second sensor node; determining a second group identifier for the second communication; determining a first group identifier for the first sensor node; and canceling transmission of the communication from the first sensor node in response to the second group identifier of the second communication matching the first group identifier of the first sensor node, thereby reducing congestion in the wireless network.

2. 10. The system of claim 1, the set of sensor nodes comprises the second sensor node configured to execute instructions; The second sensor node executes the instruction, a second communication including the alarm information originating from the hub and received by the second sensor node, to the first sensor node during a first hub broadcast time slot.

3. 3. The system of claim 2, The second sensor node executes the instruction, transmitting the second communication during the first hub broadcast time slot; confirming successful receipt of the second communication at the hub based on a third communication received from the hub during a second hub broadcast time slot subsequent to the first hub broadcast time slot; and retransmitting the second communication in response to a failure to receive a third communication from the hub during the second hub broadcast time slot.

4. 4. The system of claim 3, The set of processing units executes instructions to defining a first length of the first hub broadcast time slot for the second communication; defining a second length of the second hub broadcast time slot for the third communication, the second length being different from the first length.

5. 10. The system of claim 1, a receiver and a transmitter of the first sensor node; detecting a first communication transmitted from the hub at a first power level in the first power mode; responsive to the second group identifier of the second sensor node being different from the first group identifier of the first sensor node, transmitting a third communication at a second power level in the second power mode.

6. 10. The system of claim 1, the set of processing units of the hub are configured to randomly assign broadcast time slots to the first sensor node based on a hash function, the first group identifier of the first sensor node, the current time, and the second group identifier of the second communication.

7. In the sensor node, A set of sensors, a memory for storing instructions; processing logic coupled to the memory and the set of sensors, processing data received from said set of sensors; processing logic that executes instructions for processing communications for the sensor node; a radio frequency circuit coupled to the processing logic, the radio frequency circuit including a transmitter and a receiver for sending communications to and receiving communications from a hub in a wireless network architecture; The processing logic executes instructions to: changing the receiver from a first power mode to a second power mode in response to receiving a set of communications from the hub during a recurring hub broadcast time slot, the set of communications including alarm information from the hub; receiving a second communication from a second sensor node; determining a second group identifier for the second communication; determining a first group identifier for the set of sensor nodes; 1. A sensor node configured to cancel transmission of a communication from the sensor node to reduce congestion in the wireless network if the second group identifier of the second communication matches the first group identifier of the set of sensor nodes.

8. The sensor node according to claim 7, The sensor node, wherein the transmitter and the receiver are configured to receive broadcast messages in the first power mode and to receive and transmit broadcast messages in the second power mode.

9. The sensor node according to claim 7, The sensor node is configured to be supplied with power from a battery.

10. The sensor node according to claim 7, The processing logic executes instructions to: Transmitting a third communication during the first broadcast time slot; in response to receiving a third communication transmitted during a second broadcast time slot from the hub, confirming successful receipt of the third communication by the hub; and configured to retransmit a third communication forwarded from the hub during the second broadcast time slot in response to a failure to receive the third communication.

11. In the system, a hub having a set of processing units and radio frequency circuitry for transmitting and receiving communications in a wireless network; a set of sensor nodes, each sensor node of the set comprising a wireless device having a transmitter and a receiver configured to enable bidirectional communication with the hub in the wireless network; A set of processing units of the hub are configured to receive instructions, configured to execute instructions to, in response to a first communication including alarm information being transmitted to a first sensor node of the set of sensor nodes during a first broadcast time slot, cause a receiver and a transmitter of the first sensor node to change from a first power mode to a second power mode; each sensor node in the set of sensor nodes is configured to send communications to and receive communications from the hub; The first sensor node of the set of sensor nodes executes an instruction to determining a second group identifier for a second communication from the hub; determining a first group identifier for the first sensor node; and canceling transmission of the communication from the first sensor node in response to the second group identifier of the second communication matching the first group identifier of the first sensor node.

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