The English full name of RSSI is received signal strength indication, which is the strength indication of received signal. It can measure the distance between the signal point and the receiving point by the strength of the received signal, and then carry out positioning calculation according to the corresponding data.
Overview of RSSI
RSSI has high requirements for communication channel parameters, and its ranging theory is based on the principle that the signal power decays with the propagation distance when the radio wave or sound wave is transmitted in the medium. According to the known signal transmission power and received signal power of beacon node, the distance between nodes can be calculated by the attenuation model between signal and distance. However, due to the influence of distance and obstacles in the process of signal propagation, the power intensity of the signal will be attenuated, which will indirectly affect the accuracy.
It should be understood that each ranging method has its own advantages and disadvantages.
Advantages of RSSI ranging method
The power consumption of RSSI ranging method is lower;
Low cost. Compared with TOF ranging, RSSI ranging requires less time system, and is not affected by transmission delay, antenna delay and other factors. Without additional hardware, RSSI can use the strength judgment of received wireless signal to push the distance between transceiver nodes, so the hardware cost, software cost and time cost are relatively low;
It is easy to use. Generally speaking, the calculation of received wireless signal strength is a function of commercial wireless transceiver chips. Generally speaking, it only needs to configure the relevant registers or call the relevant API.
Constraints of RSSI ranging mode
Environmental factors. Ranging accuracy is affected by obstacles, weather, non ranging signals and many other factors. For example, if there are obstacles (especially metal obstacles) between the transmitter and the receiver, the energy of electromagnetic wave will be attenuated;
Signal energy instability caused by multipath fading in wireless channel
The measurement accuracy is affected by antenna directivity, antenna gain and so on.
Generally speaking, RSSI ranging is suitable for the scene where the test environment is open and the environment interference is small. It can avoid being installed in the shaft or in the complex electromagnetic environment. Only in this way can the communication quality be improved and unpredictable interference phenomena such as background noise be reduced. In the actual environment, RSSI is mainly used in short distance ranging and indoor positioning.