Bluetooth dynamic multi-protocol technology

ZigBee Bluetooth dynamic multi-protocol technology

1. Introduction to dynamic multi-protocol technology

ZigBee/Bluetooth dynamic multi-protocol technology is a technology proposed by Silicon Labs that can run two different protocols of low-power Bluetooth and ZigBee concurrently on a single system chip. This technology combines the main advantages of the two protocols, can complete the main functions of the two protocol stacks, and does not increase the structural complexity and cost of the hardware. Compared with the dual-chip structure with the same function, the dynamic multi-protocol reduces the chip area and cost by nearly 40% by sharing the radio frequency module. In a chip that supports dynamic multi-protocol technology, the software system kernel running in it runs ZigBee tasks and Bluetooth tasks in time based on priority, and quickly modifies the configuration parameters of the radio frequency module when switching tasks, so as to reliably support different protocol stacks. The system also listens to all system-related tasks and inter-task communications while running each task. Therefore, an efficient dynamic multiprotocol system requires a radio scheduler capable of supporting task switching, resource sharing, and managing time slicing, in addition to having a common code infrastructure, sufficient memory, and a common radio interface.

2. The principle of dynamic multi-protocol technology

2.1 Dynamic multi-protocol system framework

(1) Hardware architecture: The hardware framework of the dynamic multi-protocol system is shown in Figure 3-10. RAIL (Radio Abstraction Interface Layer, wireless abstraction interface layer) provides an intuitive and easy-to-configure radio interface and application programming interface (API) to support Various wireless protocols.

RAIL includes a public radio configuration interface and radio scheduler, supporting dynamic multi-protocol operation. The radio scheduler assigns default priorities to the different radio operations in each protocol based on importance and time sensitivity to make decisions when radio usage conflicts. The difference in the characteristics of the two protocols can be utilized in dynamic multi-protocol design. The radio usage schedule in the Bluetooth Low Energy mission is very strict and predictable, with both advertisements and connections occurring at predetermined times. In contrast, ZigBee tasks are more flexible in the timing of processing message events, and CSMA-CA in ZigBee has a random dodging mechanism that can delay ZigBee events for several milliseconds. The data packets of Bluetooth beacons are very short, no more than 30 bytes, and only take up about 1ms of radio time when sending. The time between beacons is typically no shorter than 100ms, so Bluetooth only has about a 1% duty cycle in radio use, which means the radio can be used for the main ZigBee network the other 99% of the time. Therefore, it can be ensured that ZigBee can be used to reliably send and receive data while using Bluetooth low energy normally.

(2) Software architecture: As shown in Figure 3-11, in the dynamic multi-protocol system, each stack uses the Micrium OS kernel to run a separate RTOS task to provide task switching, and the tasks are equivalent to threads in other operating systems. These tasks use inter-process communication (IPC) mechanisms such as message queues and semaphores to coordinate mutual communication and realize data sharing.

2.2 Dynamic Multiprotocol Radio Scheduling

Since two different protocols cannot rely on a single radio transceiver to send and receive data at the same time, in order to achieve dual protocols, the two protocols can only share the use of radio transceivers. In order not to impact the functionality of either protocol, they must be able to take the radio out of use intermittently without significant performance degradation or loss of data. In different cases, the different radio operations in the two protocols are not as important or time-sensitive, which requires the use of radio scheduling to plan radio usage.

The radio scheduler is a software program that intelligently responds to stack requests to perform radio operations, maximizing reliability and minimizing latency. Each event is broken down into radio operations in the scheduler, corresponding to the radio configuration and priority. If the scheduler receives a higher-priority operation that conflicts in time, it will interrupt the current operation and execute the higher-priority operation, and lower-priority operations that cannot run according to the schedule will fail and be retried by the stack. Once the scheduler starts performing a radio operation, the stack can continue to use the radio until the operation completes or the scheduler receives a higher priority radio operation. BLE radio operations will almost always have higher priority than ZigBee radio operations.

Each stack can request the radio scheduler to perform three radio operations: (1) background receive: receive data continuously unless interrupted by other tasks; (2) timed receive: receive data at a future point in time with the shortest possible time; ( 3) Timing sending: send data in the shortest time at a certain point in the future.

Each operation has a start time, reserve time, processing time, and priority. Among them, the start time indicates when the radio operation will take place, the reserved time indicates the time when the operation uses the radio and can be accepted by the stack, and the processing time indicates the approximate time required to complete the operation. A send operation usually has a definite processing time, while a receive operation usually has an unknown processing time, which is used by the radio scheduler to determine whether to allow the operation.

3. Advantages of dynamic multi-protocol technology

Dynamic multi-protocol technology switches and runs different protocols through time multiplexing, and the way of sharing radio transceivers simplifies system design and reduces material costs. By combining the two protocols, Dynamic Multi-Protocol has the key advantages of ZigBee and Bluetooth.

Compared with ZigBee technology, dynamic multi-protocol technology has the following advantages: (1) supports direct configuration and control based on smartphones; (2) provides diagnostic functions, and can check the health status of devices through smartphones; (3) can pass Bluetooth performs high-speed OTA upgrade of firmware; (4) supports positioning function.

Compared with Bluetooth technology, dynamic multi-protocol technology has the following advantages: (1) ZigBee-side networking is more flexible and simple; (2) ZigBee mesh network with routing method has larger capacity, while BLE Mesh adopts large data flow Flooding, greater network load and poorer scalability; (3) ZigBee devices that comply with the specification have excellent interoperability, while Bluetooth interoperability requires manual modification of the Bluetooth connection settings.

Compared with the traditional dual-chip supported dual-protocol (such as ZigBee/Bluetooth gateway), dynamic multi-protocol has the following advantages: (1) By sharing the RF module, the size and material cost are reduced by nearly 40% and the wireless subsystem design is simplified; (2) Dynamic multi-protocol uses time-division multiplexing to reduce signal interference between Bluetooth and ZigBee working in the same frequency band. To sum up, it can be seen that dynamic multi-protocol has obvious advantages over single protocol and dual-chip supported dual-protocol. It not only makes full use of the respective strengths of Bluetooth and ZigBee, but also saves costs and enhances scalability. Therefore, this paper uses dynamic multi-protocol technology at the control center, and uses ZigBee technology as the main communication method between system nodes.

This article discusses ZigBee/Bluetooth dynamic multi-protocol technology, explains its working principle, and analyzes the advantages of dynamic multi-protocol technology compared to single protocol and traditional dual-chip dual-protocol.