A recent series of experimental measurements over atmospheric channels using an optical receiver with tilt-tip control revealed that the first order statistics were well described by a log-normal probability density function under some conditions. The second order statistics in the form of the covariance function for the natural logarithm of the normalized optical intensity were observed to be well described by a double exponential decay. This paper presents a model for the channel in terms of a pair of stochastic differential equations which can be numerically evolved in time to produce time records of faded normalized optical intensities. The first and second order statistics of the faded intensity can be matched to those actually observed in the real channel. These simulated records can then be used to design free-space optical receivers that employ packet retransmission and or forward error corrective coding architectures.

In order to solve the problem of low accuracy in indoor positioning, a system based on ultra‐wideband and optimized time difference of arrival (TDOA) is designed. The optimized algorithm of TDOA is adopted to solve the problem of synchronization between anchors and improve the positioning accuracy. The use of LoRa technology for wireless data transmission between anchors improves the flexibility of anchor layout. According to the test, the system can work stably in corridors, rooms, warehouses and other scenarios, and the positioning error is controlled at about 13 cm. The positioning accuracy is 10 times that of the positioning system using WiFi and Bluetooth technology, which can meet the requirements of accurate mobile positioning in complex indoor environment. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

In order to solve the problem of liquid leakage due to high injection pressure and fast injection speed in the current medical high pressure injector, a set of intelligent anti-leakage diversion alarm system for high pressure injector was designed by using TI microcontroller MSP430F4619, precision electronic FS2050 pressure sensor and Nordic company’s NRF24L01+ wireless transmission chip. The system can monitor the process of high pressure injection in real time. Once the leakage of drug solution is detected, wireless acousto-optic alarm will be given immediately and diversion switch will be made quickly. This system not only overcomes the disadvantage of the previous mechanical design scheme which is easy to be loosened, but also increases the function of diversion switch which can effectively reduce the pain of patients. The results of animal experiments show that the intelligent diversion alarm system is stable, reliable and highly sensitive, which can effectively reduce the leakage of drug solution in high pressure injector.