In-depth discussion on the positioning function and Implementation of the wireless ZigBee network

The positioning function is a major feature of the wireless ZigBee network. The wireless ZigBee network technology based on IEEE 802.15.4 is not subject to interference. The positioning function is added. For details, see the following. Hope to help you.

Positioning

Positioning data can significantly increase the value of exchanged information in many applications. For patient monitoring, asset tracking, inventory control, preservation, warehousing, manufacturing logistics, and highly sensitive service and billing applications, the positioning function is driving the development of wireless sensor networks. The node or sensor location information also facilitates the transmission and adjustment of wireless networks. For example, a wireless node can use an existing system such as a global positioning system (GPS) to obtain location information. However, GPS-type systems may be expensive and may consume too much power and complexity for low-cost and wide-range simple network applications. In addition, GPS can effectively and precisely implement the positioning function in the outdoor environment, but not in the room.

In many wireless personal LAN (WPAN) applications, for networks with positioning functions, the attraction lies in low-cost sensor devices, and automatic operation with low power consumption to achieve a longer service life of the device. Due to the diversity of wireless ZigBee sensor networks and the expected future popularity, regional positioning is likely to become one of the most exciting features of such wireless systems. The concept is to add positioning functions to a large number of wireless ZigBee networks in a simple and cost-effective way to add positioning functions to sensor node silicon chip devices, this only slightly increases complexity and costs. If this type of Position Module is integrated into the chip and an existing signal indicator is used in wireless signal processing to estimate the position, for example, the received signal strength pointer (SNR ), you can minimize the complexity of the increase in size, power consumption, and location estimation. Radio frequency positioning is a complex process. Through distributed methods (algorithms), the entire process can be divided into multiple manageable work projects, which not only reduces the amount of resources required by nodes, compared with the centralized method, this method can significantly reduce the network traffic related to location.

ZigBee SoC with built-in positioning Engine

For most ZigBee wireless applications, to reduce the cost and complexity of the application system, without compromising the functions of IEEE 802.15.4/wireless Zigbee network technology, it is critical to have a single-chip system with optimal design. A single-chip system solution is used to integrate all operating functions, such as wireless RF transceiver, Data Processing Unit, memory, and user application functions, into one silicon chip, to achieve high performance, low cost, and fast listing. The reason why Low Power Consumption can achieve high performance is that the built-in Special Functions of the chip interact closely, greatly reducing the consumption of resources. Through the minimum system BOM, smaller size and fewer components, easier assembly and testing, and simple and reliable design, its manufacturing costs are reduced and the time to market can be accelerated.

Figure 1 is a representative CC2431 in Commercial silicon chip solutions. It is a real Single-Chip CMOS system that not only achieves high performance, it also meets the low-cost and low-power requirements of IEEE 802.15.4/ZigBee wireless standards operating in the 2.4 GHz ISM band. As the 2.4 GHz ISM band has the largest bandwidth and is universal worldwide, it can promote the development of the global market and the elasticity of application design. The IEEE 802.15.4 standard 2.4 GHz PHY has considerable potential. CC2431 combines high-performance 2-4 GHz Direct Sequence frequency show (DSSS) Wireless RF Transceiver with industry-recognized high-efficiency 8051 microcontroller, 8 kB RAM, kb embedded flash memory, and other practical support functions. One of them is the powerful HTTP positioning engine, which is suitable for low-power ZigBee wireless sensor network applications, such as asset tracking, patient monitoring, inventory control, preservation and trial network. A major function of the built-in positioning engine of the chip is the distribution algorithm, for example, location computing on each node. Because only the computing location is transmitted during the process, rather than the data used for calculation, the location computing on the node can reduce the network traffic and communication latency caused by the centralized calculation method.

Figure 1 ZigBee SoC device with positioning function

Distributed Localization)

The CC2431 positioning engine is a digital hardware block that enables wireless nodes to quickly and effectively determine their plane coordinates in IEEE 802.15.4 or ZigBee networks. The signal values received by multiple reference nodes of the same engine or other dynamic neighboring nodes can be used to calculate, calculate, and estimate the most possible positions to locate wireless nodes.

The positioning engine module is designed for ease of use and integration with the chip's built-in microcontroller. This independent module features low power consumption and fast operation, so it can be used continuously without consuming the computing resources of the device.

In the network, a node with a known location is called a reference node, and a node with an unknown location that needs to be computed is called a node to be tested (blind node ). Based on the information received by the nearest reference node, CC2431 can use the distributed positioning function to locate the node to be tested.

The network traffic is only limited to the nodes covered by the communication scope of the (to be tested) node, rather than expanding to the central node that may be far away from each other. This distributed method can process a large number of nodes to be tested on the same network, while the network traffic of the centralized method will increase sharply because there are too many nodes to be tested. The required information exchanged between the reference node and the node to be tested is the X and Y coordinates of the reference node. The received information of the reference node contains the measured HTTP and HTTPS values. The positioning engine calculates its own (X, Y) according to the reference (X, Y) coordinates and the obtained HTTP and HTTPS values) coordinates.

The difference between the two radio frequencies is greatly affected by the Environment (Change). To supplement this change, the CC2431 positioning engine collects ~ Data of 16 reference nodes for location calculation. If the received data comes from more than 16 nodes, the received reference node is sorted and 16 of the most powerful reference nodes are used.

The actual indoor measurement of the wireless ZigBee network using CC2431 is shown in figure 2.

Figure 2 distributed location of CC2431

Conclusion

In addition to considerable business opportunities, applications of low-power wireless networks can also improve the security, comfort and efficiency of daily life. ZigBee, which adopts the High-stability IEEE 802.15.4 standard, has technical quality and industry support, and can promote the popularization of wireless sensor solutions.

The positioning Engine Integrated with CC2431 can use the existing ZigBee infrastructure to provide positioning functions, and can perform distributed location estimation with the 'indoor smart' precision of sensor nodes in the wireless ZigBee network, this not only saves a lot of energy, but also greatly reduces the cost for communication. Important location information can be used for location-sensitive services, tracking and monitoring, and navigation purposes.