海南世电科技有限公司 - 【室内定位技术】—

summarize

ZigBee, also known as Purple Bee (based on the way bees connect with each other, bees fly through the Zig-Zag to notify the location of food found, distance and direction and other information), is a low-speed, short-range transmission of wireless network protocols, the bottom is the use of the IEEE 802.15.4 standard specification of the media access layer and the physical layer. The main features are low speed, low power consumption, low cost, support for a large number of network nodes, support for a variety of network topologies, low complexity, reliability and security.

Developed by the ZigBee Alliance, a group of Honeywell companies, it has been in development since 1998, and in 2001 was introduced to theInstitute of Electrical and Electronic Engineers (IEEE)proposal into the IEEE 802.15.4 standard specification.IEEE802.15.4The agreement isIEEE802.15.4The Working Group for Low-Rate Wireless Personal Area Network (WPAN: Wireless Personal Area Network) was formed in December 2002 to define an inexpensive, low-complexity, low-cost, low-power, low-rate wireless connectivity technology for fixed, portable, or mobile devices, and in December 2003 it The first 802.15.4 standard was adopted. With the development of wireless sensor network technology, wireless sensor network standards have also been rapid development. 802.15.4 standard defines the way in the personal area network through the radio frequency mode in the interconnection between the device and the protocol, the standard uses to avoid the conflict of the carrier listening to the multi-access access to the way as a media access mechanism, and at the same time to support the star and peer-to-peer type topology.

Two physical frequency bands and Direct Sequence Spread Spectrum (DSSS) physical layer bands are specified in the 802.15.4 standard: 868/915 MHz and 2.4 GHz.The 2.4 GHz physical layer supports a rate of 250 kilobits per second (kb/s) over the air, whereas the 868/915 MHz physical layer supports transmission rates of 20 kb/s and 40 kb/s over the air. The actual data throughput will be less than the specified bit rate due to packet overhead and processing delays. As a protocol standard to support low-rate, low-power, and short-range wireless communications, 802.15.4 specifies the radio frequency and data rate, data transmission model, device type, network operating mode, and security. And the protocol model is divided into two sub-layers, the physical layer and the media access control layer for implementation

ZigBee Operating Frequency Bands

Channel 0: 868 MHz (Europe)
Channels 1-10: 915 MHz (United States and Australia)
Channels 11-26: 2.4 GHz (worldwide)

ZigBee Network Topology

star topology
grid topology
tree topology

ZigBee Network Architecture

Zigbee architecture is a combination of 6 layers, which are application layer (belongs to the user level program), application interface layer, security layer, network layer, access control layer, and physical layer; in which the application layer is the user's program, the application interface, security layer, and network layer Zigbee Alliance's are used for storing the data, the access control layer and the physical layer is the IEEE 802.15.4; which is the hardware protocol for the physical layer.

Features of the ZigBee standard

It is inIEEE 802.15.4Developed under.
The frequency range supported by Zigbee is mostly 2.4 GHz worldwide.
It also uses BPSK and QPSK modulation techniques such as UWB.
zigbee supports small and large networks with over sixty-five thousand (65,000) cell nodes.
There are 16 RF channels in zigbee.
Zigbee also requires low bandwidth, but most of the time it is greater than Bluetooth's bandwidth.
The radio signal range of zigbee is 10 to 100 meters.
Low data rate (20-250 kbps)
low power consumption
Join network time (approx. 30 ms)
Low product cost and low implementation cost (open source protocols)
Operating frequency band (only one channel is selected for use in the network)

ZigBee Application Areas

According to its characteristics, ZigBee is aimed at applications such as industrial, home automation, telemetry, e.g. light automation, wireless data acquisition and monitoring of sensors, oilfield, power, mining and logistics management.

WorldTech ZigBee'slocalizationprinciple

Various positioning techniquesThe focus is different, and the areas and markets involved are also different. In specific scenarios, it is necessary to consider various aspects to decide to use that kind of program to carry out, the general practical considerations are positioning accuracy, positioning range, positioning number, number of users, privacy, equipment installation, update frequency, power consumption, scalability, compatibility with other systems, the format of the output data, and most importantly, the cost.

Positioning principle

Measurement of the wireless signal field strength of the tag to calculate the distance between the tag and the antenna, distance and wireless signal strength for the exponential curve relationship between

There are 3 values that we need to measure and calibrate over and over again

1, L0: the signal strength when the distance between the tag and the reader is 0 cm, the measured value is -8dBm.
2、 L1: The signal strength when the distance between the tag and the reader is 40 centimeters, the measured value is -20dBm.
3, L2: label and reader distance of 100 cm when the signal strength, measured value of -30dBm

Based on these three values, the derived equation is as follows.

In the warehouse, the workshop's surroundings installs the good localization base station (reads the card) to be able to measure the label's approximate position. In the effective range of each base station will get the electronic label and their own distance, according to the 2 ~ 3 closest to the electronic label of the base station's test value, may get the electronic label in the space of the approximate position. Positioning accuracy 1~3 meters

application block diagram

Device Access Method

Access to 16 wireless card readers

Personnel positioning connection method

Access to 32 485 readers

Features of Zigbee products

motion detection

Motion Detection Improves Label Life

Selects "the movement detects" the working mode electronic label, the label long time does not have the movement (the default 10 minutes), the label automatically stops working. This can effectively save power, greatly prolongs the label to use the time. When the label is used as the personnel, the vehicle localization, the recommendation chooses "the movement detects" the electronic label which the working mode. Tag from the motion state to the stationary state of the detection time default for ten minutes (can be customized to 1 ~ 60 minutes). Stationary state tag default does not work (can be customized to work slowly, 1 ~ 60 seconds to send a). Need to customize and our customer serviceContact to place an orderThe

Sound and light labels

Zigbee tags from Seiden Technology combine audible alerts, motor vibration, and flashing LEDs to alert users when they are looking for a tag, and with the app on the cell phone, it's easy to find the tagged product.

Without a locator system installed, it is still possible to find a tag using only the handheld. Directly in the handheld enter the label ID, or use inventory software to send the label ID of the item to the handheld, the handheld to start looking for, you can confirm that the label is in the vicinity of the label to confirm the initial location of the label, so that the handheld to send commands to activate the label, through the sound and light reminder can be easily find the label. Methods are as follows:
Turn on the handheld, enter the "Find" page, enter the corresponding label code, click the "Start" button, you can find whether the label is nearby. If you find the label in the vicinity, the handheld will display the actual distance between the label and the handheld, you can judge the distance value of the label near and far, to quickly determine the label in which area, to improve the efficiency of the search for items.

The found tag glows (blinks continuously) to remind the user of the tag's location. If you still can't find it, you can click the horn button at the bottom right, the tag will beep, beep, beep, beep, beep, beep, beep to make you find the tag more conveniently.

SMS Labeling

The use of SMS tags need to deploy positioning system, using free client software can view any one of the electronic tag on the map real-time location, positioning system can also be tag location coordinates data sent to third-party platforms, to facilitate the development of third-party platforms to develop their own a variety of positioning applications. Provide open protocol and source code reference for SMS call, convenient for users to develop their own SMS sending platform.
The SMS tag can standby for more than three months on a single charge, with real-time power display. The tag can store up to 500 text messages with cyclic storage.1.54" high brightness OLED display, text messages are clearly readable in sunlight.

Solar Labeling

Charged by solar energy, the charging current can be up to 60mA on sunny days.Built-in 120mAH power small battery, after fully charged, it can continue to work for 120 hours in a dark environment. After the battery is undervoltage (less than 20%), it can be restored to full charge in 2 hours of sunshine on a sunny day.
The electronic label periodically broadcasts the label ID information to the outside world every second, the transmitting power is 100mW, and the transmitting distance can reach 300 meters in the open.
The tags are widely used in systems such as bus stop announcements, dump truck counting, go-karting lap keeping, and real-time registration of yachts docking at marinas.