Multiple Primary Nodes for Robustness of Wireless Battery Management Systems

Abstract

The system (500) includes a first plurality of secondary devices (550), each secondary device (550) of the first plurality of secondary devices including a first wireless transmitter and a battery monitor integrated circuit (IC). The battery monitor IC is configured to acquire battery data from at least one battery cell, and the first wireless transmitter is configured to wirelessly transmit the battery data. The first primary device (502) has a second wireless transmitter wirelessly coupled to the first wireless transmitter of the first plurality of secondary devices via a first wireless network. The second primary device (506) has a second wireless transmitter. The second primary device (506) is configured to detect a fault with the first primary device and, in response to detecting the fault, establish a second wireless network with the first plurality of secondary devices.

Description

[Technical Field]

[0001] Battery packs are increasingly being integrated into systems not traditionally powered by batteries, such as cars, homes, and even portions of the power grid. In addition to becoming more common, battery packs are also becoming larger and more complex. For example, modern battery packs may contain hundreds or even thousands of battery cells. Monitoring the health and condition of individual cells within such battery packs helps to ensure the continued proper operation of systems powered by such battery packs. Summary of the Invention

[0002] A system includes a first plurality of secondary devices, each secondary device of the first plurality of secondary devices including a first wireless transmitter and a battery monitor integrated circuit (IC). The battery monitor IC is configured to acquire battery data from at least one battery cell, and the first wireless transmitter is configured to wirelessly transmit the battery data. A first primary device has a second wireless transmitter wirelessly coupled to the first wireless transmitter of the first plurality of secondary devices via a first wireless network. The second primary device has a second wireless transmitter. The second primary device is configured to detect a fault with the first primary device and, in response to detecting the fault, establish a second wireless network with the first plurality of secondary devices. [Brief explanation of the drawings]

[0003] For a detailed description of various examples, reference will now be made to the accompanying drawings.

[0004] [Figure 1] FIG. 1 is a block diagram illustrating a battery management system (WBMS) having a primary node and a secondary node, according to an example.

[0005] [Figure 2]FIG. 1 is another block diagram illustrating a WBMS, according to an example.

[0006] [Figure 3] 1 is a block diagram of a radio usable in a primary node and a secondary node of a WBMS according to an example.

[0007] [Figure 4] 1 is a diagram of a superframe for WBMS, according to an example.

[0008] [Figure 5] 1 is a block diagram of a WBMS system having a primary node, a backup primary node, and memory shared between the primary node and the backup primary node, according to an example.

[0009] [Figure 6] 1 is a block diagram of a WBMS system without shared memory and having a primary node and a backup primary node, according to an example.

[0010] [Figure 7] 1 is a block diagram of a WBMS system having a primary node and a backup primary node according to yet another example.

[0011] [Figure 8] 1 is a block diagram of a WBMS system having a primary node and a backup primary node according to another example.

[0012] In the drawings, the same reference numbers or other reference characters are used to denote identical or similar (in function and / or structure) features. DETAILED DESCRIPTION OF THE INVENTION

[0013] Some systems are battery-powered and include many battery cells. A subset of battery cells may be packaged together in a battery module. A group of interconnected battery modules represents a battery pack. Thus, a battery pack may have multiple battery cells, and in some cases, hundreds of battery cells or more. Electric vehicles (EVs) include rechargeable battery packs, for example, to operate the EV's electric motor and power various electronic components within the vehicle. In the context of an EV, the battery pack may provide 400V, 800V, or another voltage. Monitoring individual battery cells for information such as voltage, current, temperature, and register settings helps ensure the health and functionality of the entire battery pack. For example, battery cells may vary with respect to capacity and discharge (and / or charge) rate. Variations between cells may result in imbalances in the state of charge among the battery cells. Balancing techniques (e.g., passive cell balancing, active cell balancing) can be used to balance the load (and / or power) more evenly across all cells, which helps improve the usable capacity of the battery pack and increase its usable life. Passive cell balancing can dissipate excess charge in a given cell via a bleed resistor. Active cell balancing redistributes charge among individual cells during charge and discharge cycles. A battery management system may also be included to monitor and adjust the system's battery pack (e.g., cell balancing) as may be useful.

[0014] FIG. 1 is a block diagram illustrating a wireless battery management system (WBMS) 100 according to an aspect of the present disclosure. The WBMS 100 may function to power a system, such as an EV. In addition to the WBMS 100, the system includes a motor 118 (e.g., an electric motor for powering the EV) and an electric control unit (ECU) 124. The WBMS 100 includes battery modules 104A, 104B, . . . , 104N (collectively, battery modules 104) and a battery pack controller 114. The battery pack controller 114 wirelessly communicates with each of the battery monitors 104. Each battery monitor 104 monitors and controls a respective set of battery cells 102. Each instance of the battery cells 102 includes one or more cells (e.g., six cells, nine cells, eighteen cells, etc.), and the connected group of battery cells 102 represents a battery pack for the system (e.g., the EV). Each set of battery cells 102 is coupled to a battery module 104. In another embodiment, the battery cells 102 are included within and are part of a battery module 104. The number N of battery modules 104 depends on the number of individual battery cells 102 that each module can monitor. Sets of battery cells can be coupled in series to generate substantially high voltages (e.g., 400V, 800V, etc.). The battery pack controller 114 includes an interface (e.g., a controller area network (CAN) bus) to the ECU 124.

[0015] Each battery module 104 includes a battery monitor 106. Each battery monitor 106 includes an analog front end coupled to a corresponding battery cell 102 and may measure and collect information about the battery cell 102 (e.g., voltage, current, charge status, temperature, etc.). In this example, each battery monitor 106 is wirelessly coupled to a battery pack controller 114. A microcontroller 112 within the battery pack controller 114 may process and provide battery cell information for some or all of the cells 102 to the ECU 124.

[0016] Each battery monitor 106 collects and digitizes information about its respective battery cell 102 and wirelessly transmits the digital information to a battery pack controller 114 for receipt by the microcontroller 112. The microcontroller 114 may also be coupled to control the input of a switch 116 that couples the battery cells 102 to one or more motors 118 or other load devices. The microcontroller 112 may also be coupled to one or more other sensors, such as a current sensor 120, that may monitor the current being supplied by the battery pack to the motors 118. In this example, the battery pack controller 114 is powered by a battery 122 that is separate from the battery cells 102. The battery 122 may be a relatively low-voltage battery, such as a 12V battery, while the voltage generated by the series-connected set of battery cells 102 may be a higher voltage (e.g., 400V, 800V, etc.).

[0017] The battery monitor 104 wirelessly transmits their battery data to the battery pack controller 114. The battery pack controller 114 and / or the ECU 124 may monitor the status of the individual cells and may take various actions as necessary. For example, the ECU 124 may detect that the voltages of some of the cells 102 differ from one another and may respond by implementing a cell balancing procedure, such as a passive or active cell balancing process. If the battery pack controller 114 malfunctions or is unable to receive battery data from the battery monitor 104, the ability to monitor the battery cells of the battery pack and respond appropriately to the cell status may be unavailable.

[0018] The embodiments described herein are directed to the inclusion and use of a backup battery pack controller. Failure of the currently operating battery pack controller 114 can result in a failover process in which a backup battery pack controller takes over the functionality of the failed battery pack controller.

[0019] FIG. 2 is a block diagram illustrating an example of a WBMS 100 according to an aspect of the present disclosure. The WBMS 100 includes a primary node 202 that functions in a manner similar to the battery pack controller 114. The primary node 202 includes a microcontroller 204 that is coupled to the ECU 124, for example, via a CAN bus 203. The microcontroller 204 may operate in a manner substantially similar to the microcontroller 112. The microcontroller 204 is coupled to a radio 206 via a digital communication interface 207, such as a universal asynchronous receiver-transmitter (UART) interface, a serial peripheral interface (SPI), or shared memory. The radio 206 is wirelessly coupled to a secondary node 210. The secondary node 210 represents the battery module 104 of FIG. 1. Each secondary node 210 includes a radio 208 for communicating with the primary node's radio 206. Each secondary node 210 also includes one or more battery monitoring systems (BMS) 212 coupled to respective radios 208 via UART or other types of electrical interfaces. Although two BMSs 212 are shown in each battery module 210 in FIG. 2 , any suitable number of BMSs may be included in any given battery module (e.g., one or more). Radios 206 and 208 may transmit wirelessly via radio frequency (RF). Each secondary node 210 may be fabricated as a printed circuit board (PCB) onto which the BMSs 212 and radios 208 are mounted. In this configuration, each BMS 212 is fabricated as an integrated circuit (IC), and each radio 208 is also fabricated as an IC.

[0020] The BMS 212 may be similar to the battery monitor 106 and may include an analog front end coupled to the battery cells 204 to measure and collect information about the battery cells (e.g., voltage, current, etc.). This information may be sent to the radio 208 of each of the secondary nodes 210 via a digital communication interface. The radio 208 of each secondary node 210 then wirelessly transmits the information to the primary node 202. In some cases, this wireless transmission may be performed according to a wireless battery management protocol, such as the WBMS protocol.

[0021] A wireless battery management protocol may define a set of wireless channels along with a set of rules for how information can be wirelessly transmitted to monitor and manage the battery cells 102. In some cases, a wireless battery management protocol may utilize an unlicensed frequency band, such as 2.4 GHz, 5.8 GHz, or the like. Generally, a frequency band, such as the 2.4 GHz unlicensed frequency band, may be divided into a set of channels, each including a set of frequency resources within a set of frequencies. The number of channels and the size of the channels may be determined based on the protocol. For example, a WBMS protocol may divide the 2.4 GHz unlicensed frequency band into a set of 40 channels, each 2 MHz wide. As another example, an IEEE 802.11 wireless network may divide the same 2.4 GHz unlicensed frequency band into a set of 11 channels, each 20 MHz wide.

[0022] 3 is a block diagram of a radio 300 that may be used to implement either or both of the radio 206 of the secondary node 210 and the radio 208 of the primary node 202. In this example, the radio 300 includes an RF transceiver 302, a microcontroller 304, and a memory 306. The microcontroller 304 is coupled to the RF transceiver 302 and the memory 306. The memory 306 may store software 308 executable by the microcontroller 304. Creation of the mesh network in the examples described herein may be implemented by the microcontrollers 302 of the radios 206 and 208 upon executing the software 308. The software 308 provided on the radio 208 of the secondary node 210 may implement different functionality than the software provided on the radio 206 of the primary node 202.

[0023] The primary node 202 and the secondary nodes 210 exchange information according to a "superframe." FIG. 4 is a superframe diagram 400 of a WBMS superframe 450, during which the system on which WBMS is operating is ON, and therefore the battery pack controller 114 (primary node 202) is ON and may receive wireless battery data from the battery monitor 106 (secondary node 210). The left side of the superframe diagram 400 lists the primary node 402 and multiple secondary nodes 404A, 404B, . . . , 404N (collectively, secondary nodes 404). The primary node 402 may include or be the battery pack controller 114 of FIG. 1 or the primary node 202 of FIG. 2. The secondary node 404 may include or be the battery monitor 106 of FIG. 1 or the secondary node 210 of FIG. 2.

[0024] Along with the channel size, the WBMS protocol further defines how communication between nodes can occur. A WBMS network is directed by a primary node 402, which coordinates communication among a set of N secondary nodes 404. In one example, the primary node 402 coordinates communication for the WBMS network by defining communication intervals and allocating the intervals using a superframe 450 structure, as illustrated in the example of FIG. 4. The superframe 450 includes a downlink allocation 406 for the primary node 402 and uplink allocations 408A, 408B, ..., 408N (collectively, uplink allocations 408) for secondary nodes 404A, 404B, ..., 404N of the set of secondary nodes 404. In this example, the superframe 450 also includes a guard interval 416 before the downlink transmission 410, along with a switching interval 418 to provide time for the nodes to switch from a receive mode to a transmit mode or vice versa. The superframe interval 414 is the amount of time to complete all transmissions for a superframe 450, including the guard interval 416. The duration of the superframe interval 414 may vary from WBMS network to WBMS network based on the number of secondary nodes 404 in the WBMS network.

[0025] During the downlink allocation 406 to the secondary nodes 404, the primary node 402 transmits 410 allocation information regarding the uplink allocation 408 for the secondary nodes 404. The allocation information may include a set of channels (e.g., as indicated by a bitmap) that may be used for the WBMS network, along with a per-secondary node uplink allocation indicating when each secondary node 404A, 404B, ... 404N may transmit 412A, 412B, ... 412N to the primary node 402. In some cases, the allocation information may include additional information, such as an acknowledgment to an uplink transmission from a previous superframe, an indication of when the next superframe may begin, an adaptive frequency hopping countdown, etc. In some cases, each secondary node 404 wirelessly coupled to the primary node 402 is provided with an individualized uplink allocation 408 for transmitting information regarding the battery cells associated with the respective secondary node 404.

[0026] Each secondary node 404 collects information about its respective battery cells and wirelessly transmits 412 such information to the primary node 402 during the uplink interval 408 assigned to the secondary node. For example, secondary node 2 404B receives 420 downlink transmissions 410 from the primary node 402 during the downlink allocation 406. In some cases, the secondary node 404 may determine the downlink allocation 406 time based on an indicator from the previous superframe. Uplink transmissions 412 (and retransmissions, if any) by the secondary nodes 404 are completed within their respective uplink allocations 408, although the uplink transmissions may not occupy the entire uplink allocation 408.

[0027] After receiving the downlink transmission 410 from the primary node 403, each secondary node 404 may analyze the allocation information received from the primary node 402 to determine timing information for the secondary node's uplink allocation 408 allocated to the secondary node. In some cases, information may be exchanged during the WBMS network formation process on how to locate timing information associated with a particular secondary node.

[0028] 5 is a block diagram of a WBMS 500 that includes two primary nodes 502 and 506, a shared memory 510, and multiple secondary nodes 550. In this example, primary node 502 is designated as the "primary" primary node and therefore functions to exchange information with secondary node 550 according to the superframe structure described above. Primary node 506 may be an instance of the same primary node device as primary node 502, but functions in a backup role to primary node 502 (hence referred to as the "backup" primary node). If primary primary node 502 fails (e.g., if it is no longer able to send or receive packets to or from secondary node 550 or process packets received from secondary node 550), backup primary node 506 can assume the role of the primary primary node.

[0029] When operable to communicate with secondary nodes, the main primary node 502 and the backup primary node 506 function in a manner similar to the battery pack controller 114 described above. Each secondary node 550 may include a battery monitor (e.g., battery monitor 506) and may include multiple battery cells or may be coupled to one or more battery cells. The shared memory 510 may include volatile storage (e.g., random access memory) or non-volatile storage (e.g., programmable read-only memory).

[0030] While the primary node 502 is actively functioning to exchange packets with the secondary nodes 550, the primary node 502 stores network data in the shared memory 510. Such network data may include timing information such as scheduling downlink allocations (e.g., number of downlink slots), uplink allocations (e.g., number of uplink slots), frequency hopping tables, superframe configurations, security keys, encryption keys, device identifiers of devices for forming the network, etc.

[0031] The main primary node 502 includes fault detection capabilities. For example, a microcontroller in the main primary node may output a "heartbeat" signal to a fault detection circuit. The fault detection circuit may be configured to expect a heartbeat signal every n milliseconds (e.g., every 1 millisecond). Failure of the heartbeat signal to occur in a timely manner may indicate that the microcontroller is in an error state and may not function as intended. Regardless of the mechanism for detecting a fault in the main primary node 502, the main primary node (e.g., its fault detection circuit) outputs a fault line interrupt signal to the backup primary node 506 to indicate the occurrence of a fault condition in the main primary node 502.

[0032] Upon receiving the asserted fault line interrupt signal, the backup primary node 506 reads the network data from the shared memory 510 and uses the network data to assume the role of the primary node. To assume the role of the primary node, the backup primary node re-forms and synchronizes the network. For example, the backup primary node may initiate a network formation similar to what may occur in a power-on sequence.

[0033] FIG. 6 is a block diagram of a WBMS 500 including two primary nodes 602 and 606 and multiple secondary nodes 550. As described above, the primary node 602 is designated as the “primary” primary node and therefore functions to exchange information with the secondary nodes 550 according to the superframe structure described above. The primary node 606 may be an instance of the same primary node device as the primary node 602, but functions in a backup role to the primary node 602. If the primary primary node 602 fails (e.g., if it is no longer able to send or receive packets to or from the secondary nodes 550 or process packets received from the secondary nodes 550), the backup primary node 606 can assume the role of the primary primary node. When operable to communicate with the secondary nodes, the primary primary node 602 and the backup primary node 606 function in a manner similar to the battery pack controller 114 described above. This embodiment does not have the shared memory 510 described above.

[0034] As described above, the primary node 602 includes fault detection capability (e.g., fault detection circuitry) configured to expect a heartbeat signal every n milliseconds (e.g., every 1 millisecond) from the primary node's microprocessor. Failure of the heartbeat signal to occur in a timely manner may indicate that the microcontroller is in an error state and may not function as intended. As described above, the primary node 602 (e.g., its fault detection circuitry) outputs a fault line interrupt signal to the backup primary node 606 to indicate the occurrence of a fault condition with the primary node 602.

[0035] Due to the failure of the primary node 602, the secondary nodes 550 stop receiving downlink packets from the primary node. Each secondary node 550 has timing data previously provided by the primary node 602 that can determine when each such secondary node expects downlink packets from the primary node. Each secondary node 550 responds to the absence of expected downlink packets by transitioning to a scan mode in which the secondary node waits for a network creation packet from the primary node. The backup primary node 606 re-establishes the network with the secondary node 550 rather than using network data from shared memory. In one example, the network re-establishment process occurs through any of several different methods, which may include performing a re-joining act with encrypted key exchange packets to re-authenticate and establish the network.

[0036] The backup primary node 606 is currently operating as the primary node and may have the same failure detection capabilities as the previous primary node 602. The failed primary node 602 may be repaired or replaced in the WBMS 600 and may again assume the role of the primary node, for example, if the backup primary node 606 subsequently fails.

[0037] FIG. 7 is a block diagram of a WBMS 700 including two primary nodes 702 and 706 and multiple secondary nodes 550. As described above, the primary node 702 is designated as the “primary” primary node and therefore functions to exchange information with the secondary nodes 550 according to the superframe structure described above. The primary node 706 may be an instance of the same primary node device as the primary node 702, but functions in a backup role to the primary node 702. If the primary primary node 702 fails (e.g., if it is no longer able to send or receive packets to or from the secondary nodes 550 or process packets received from the secondary nodes 550), the backup primary node 706 can assume the role of the primary primary node. When operable to communicate with the secondary nodes, the primary primary node 702 and the backup primary node 706 function in a manner similar to the battery pack controller 114 described above. This embodiment does not have the shared memory 510 and fault line interrupt capabilities described above.

[0038] In this embodiment, the backup primary node independently determines to re-establish a network with the secondary node 550 based on the absence of packet transmissions exceeding a threshold time period. For example, the backup primary node 706 can synchronize to the primary primary node 702 in the configuration channel phase and continue to follow the primary primary node 702 in the connected mode. In this embodiment, the backup primary node can observe the network configuration in the configuration channel to determine the timing and size of the network. The backup primary node then tracks active network behavior in the connected mode to maintain synchronization with the primary primary node over time. After the initial synchronization, the backup primary node 706 can monitor the primary primary node 702 at periodic intervals (e.g., every 1 minute, every 5 minutes, etc.). The length of the periodic interval can be programmable in the backup primary node 706. If the backup primary node 706 is unable to receive packets from the primary primary node 702, the backup primary node 706 can determine that the primary primary node 702 has failed. In response to the cessation of packets from the primary node 702, the backup primary node 706 may begin the process to establish its own network with the secondary nodes 550. Additionally, the secondary nodes 550 that are not receiving packets from the primary node 702 participate in the network establishment process as described above.

[0039] FIG. 8 illustrates yet another embodiment of a WBMS 800 including two primary nodes 802 and 806, both of which actively communicate with secondary nodes. In this example, primary node 802 establishes a network with secondary node 850, and primary node 806 establishes a network with secondary node 860. The two networks operate simultaneously. The primary and secondary nodes may be implemented as described above. Each primary node 802, 806 is programmed with a unique identifier (e.g., address) of the secondary node for which each such primary node establishes its network. Thus, primary node 802 is programmed with the address of secondary node 850, and primary node 806 is programmed with the address of secondary node 860. Each primary node is also programmed with the address of the secondary node with which the other primary node has established a network for use if the other primary node fails. That is, each main primary node is programmed with the addresses of its own secondary nodes, as well as the secondary nodes in the network of other main primary nodes.

[0040] Each primary node 802 and 806 periodically (e.g., once every five minutes) scans for packets from the other primary nodes. If the primary node does not detect packets from the other primary nodes, it determines that the other primary nodes may have failed and implements a process to establish a network with all of the secondary nodes 850 and 860. A primary primary node 802 or 806 attempting to establish a network with all of the secondary nodes 850 and 860 may then extend the length of the superframe to include time slots for uplink allocations of more secondary nodes 850, 860. While the latency of each secondary node 850 and 860 transmitting its battery data to the surviving primary node may increase due to the greater number of secondary nodes accommodated by each superframe, the WBMS 800 has redundancy to handle failures of primary primary nodes.

[0041] In this description, the term "couple" may encompass a connection, communication, or signal path that enables a functional relationship consistent with this description. For example, if device A generates a signal that controls device B to perform a certain action, then (a) in a first example, device A is coupled to device B by a direct connection, or (b) in a second example, device A is coupled to device B via an intervening component C such that device B is controlled by device A via a control signal generated by device A, where intervening component C does not change the functional relationship between device A and device B.

[0042] A device that is "configured to" perform a certain task or function may be configured (e.g., programmed and / or hardwired) by a manufacturer at the time of manufacture to perform that function and / or may be configurable (or reconfigurable) by a user after manufacture to perform that function and / or other additional or alternative functions. Such configuration may be via firmware and / or software programming of the device, via the configuration and / or layout of hardware components, via the device's interconnections, or via a combination thereof.

[0043] Modifications may be made to the exemplary embodiments described, and other embodiments are possible, within the scope of the claims of the invention.

Claims

1. 1. A system comprising: a first plurality of secondary devices, each secondary device of the first plurality of secondary devices including a first wireless transmitter and a battery monitor integrated circuit (IC), the battery monitor IC configured to acquire battery data from at least one battery cell, and the first wireless transmitter configured to wirelessly transmit the battery data; a first primary device having a second wireless transmitter wirelessly coupled to the first wireless transmitters of the first plurality of secondary devices via a first wireless network; a second primary device having a second wireless transmitter; Including, the second primary device is configured to detect a failure with the first primary device and, in response to detecting the failure, establish a second wireless network with the first plurality of secondary devices. system.

2. 2. The system of claim 1, wherein the first primary device is configured to send an interrupt signal to the second primary device to indicate the failure of the first primary device.

3. 2. The system of claim 1, further comprising a shared memory accessible by the first primary device and the second primary device, wherein the first primary device is configured to store second data corresponding to the first wireless network in the shared memory, and the second primary device is configured to access the second data in the shared memory to establish the second wireless network.

4. 4. The system of claim 3, wherein the second data includes timing data for the first wireless network.

5. 2. The system of claim 1, wherein the second primary device is configured to periodically monitor transmissions from the first primary device and detect a failure with the first primary device in the absence of an expected transmission from the first primary device.

6. 10. The system of claim 1, further comprising a second plurality of secondary devices, wherein the second primary device is configured to be wirelessly coupled to the second plurality of secondary devices via a second wireless network, and wherein upon detection of the failure with the first primary device, the second primary device is configured to establish a third wireless network with the first and second plurality of secondary devices.

7. 7. The system of claim 6, wherein each secondary device in the first plurality of secondary devices and each secondary device in the second plurality of secondary devices includes a unique identifier, and wherein the second primary device includes the unique identifier of the secondary device of the first and second plurality of secondary devices.

8. 7. The system of claim 6, wherein, when establishing the third wireless network, the second primary device allocates an uplink allocation to each secondary device of the first and second plurality of secondary devices.

9. 1. A system comprising: a plurality of battery cells; a first plurality of secondary devices, each secondary device of the first plurality of secondary devices including a first wireless transmitter and a battery monitor integrated circuit (IC), the battery monitor IC coupled to a subset of the plurality of battery cells, the battery monitor IC configured to acquire battery data from each of the subset of the plurality of battery cells, the first wireless transmitter configured to wirelessly transmit the battery data, the battery data being at least one of voltage or current; a first primary device having a second wireless transmitter wirelessly coupled to the first wireless transmitters of the first plurality of secondary devices via a first wireless network; a second primary device having a second wireless transmitter, the second primary device configured to detect a failure with the first primary device and to establish a second wireless network with the first plurality of secondary devices in response to detecting the failure; Including, the system.

10. 10. The system of claim 9, wherein the first primary device is configured to send an interrupt signal to the second primary device to indicate the failure of the first primary device.

11. 10. The system of claim 9, further comprising a shared memory accessible by the first primary device and the second primary device, wherein the first primary device is configured to store network data corresponding to the first wireless network in the shared memory, and the second primary device is configured to access the network data in the shared memory to establish the second wireless network.

12. 12. The system of claim 11, wherein the network data includes timing data for the first wireless network.

13. 10. The system of claim 9, wherein the second primary device is configured to detect a failure with the first primary device in the absence of transmission from the first primary device.

14. 10. The system of claim 9, and a second plurality of secondary devices, the second primary device configured to be wirelessly coupled to the second plurality of secondary devices via a second wireless network; the second primary device is configured to establish a third wireless network with the first and second plurality of secondary devices upon detection of the failure with the first primary device.

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