433MHz is an open carrier frequency band, so far there is no wireless ad hoc network scheme provided by an international large manufacturer in this frequency band. Due to the inherent electromagnetic wave characteristics of this frequency band—strong penetration, the adaptability to the environment is strong. Many domestic manufacturers have verified the weak penetrability of ZigBee, and have considered re-selecting the carrier frequency band as a carrier for wireless communications. The application of 433MHz wireless communication is very extensive. It is equipped with a mature ad hoc network and TCP protocol and can cover almost all wireless communication fields. Such as wireless power meter reading, wireless industrial automation, modern agriculture, coal mines, catering wireless a la carte, wireless temperature measurement, wireless voice transmission, wireless remote control electric vehicles, game console billing and so on.
At present, many of the 433MHz wireless modules in China do not show any superiority in performance. There are several reasons for this:
Most of the products or applications integrated in the 433MHz wireless transmission module do not have a protocol stack. The direct data transmission on the RF chip is the low bandwidth of the 433MHz passthrough module and the system delay is relatively large. The user's single chip cannot directly pass the SPI (12M bps ) The bus controls the RF chip, but controls the RF chip 433MHz transparent transmission module through the serial port (115.2Kbps). If there is no protocol support, it is impossible to build a large wireless network. The serial port usually transmits transparent data streams. The transmission instruction controls the radio frequency chip and realizes the radio frequency communication proprietary operations such as channel switching and frequency calibration; the 433 MHz transmission module cannot dynamically change the receiving gain and the transmitting power, resulting in the inability to dynamically sense the distance of the peer communication node, and thus cannot simultaneously Cover a very long distance (below the threshold) and a close distance (saturation block) The RF chip of the 433MHz pass-through module, due to differences in the semiconductor process, often requires the use of a PLL phase locked loop for frequency calibration during operation. Frequency drift occurs, communication will lose sight and lead to quality degradation or even transmission failure. With the 3MHz pass-through module, all work must be addressed to the user application layer. The verification level is greatly delayed, resulting in low data transmission rate and no guarantee of network security. The 433MHz wireless module introduced by Micronet's WiMi-net overcomes the deficiencies of the above 433MHz wireless module and fully exploits the advantage of the open-carrier frequency band of 433MHz - strong penetration, combined with the self-developed WiMi-net wireless ad hoc network protocol and The TCP protocol has achieved obvious advantages in terms of wireless network size, transmission distance, wireless speed, stability, reliability, signal quality, low power consumption, and network security. In practical applications, large-scale WANs can be set up. The maximum size of the network is 65,535 nodes, and the depth of network relays is 64; the transmission of large-scale data traffic (such as pictures) is realized; no packet-breaking occurs within the signal coverage; Bidirectional symmetrical data transmission; applicable to open areas, but also applicable to complex buildings, strong adaptability to the environment, in modern agriculture, intelligent buildings, intelligent transportation, smart power, intelligent ordering, etc. Applications.