Telecommunication System for Transmission of Adaptively Scaled Digital Images

The hardware and software of a telecommunication system designed for the transmission of adaptively scaled digital images has been developed. The system consists of transmission and reception subsystems. The hardware of the transmission subsystem includes a USB video camera, a microcomputer Raspberry Pi3 and a Raspberry Pi3 radio module. The hardware of the reception subsystem includes a radio module nRF24L01 # 2, a microcontroller Funduino Uno and a computer. The radio module Funduino Uno has a relatively low transmission speed, but provides low power consumption. The system software has been developed in Python and C++. In the transmission subsystem, the image from the video camera is read using the program cam2nrf, its scale is reduced by interpolation and the reduced image is transmitted via radio module # 1. In the reception subsystem, the reduced image is read via radio module # 2, its scale is increased by interpolation. Image scaling is performed using bilinear or bicubic interpolation. The program nrf_rx, which runs on the Funduino Uno microcontroller, is used to receive wireless data using the radio module nRF24L01. The program recv_img, which runs on the computer, reads the image from the microcontroller Funduino Uno, scales, visualizes and saves it. Scaling adaptability is ensured by choosing the image interpolation algorithm depending on its average spatial period TCR, which is calculated based on the Fourier power spectrum of the original image. For values TCR ​​< 4.5 pixels, bilinear interpolation is performed, and otherwise bicubic interpolation is performed. Testing of the telecommunication system for transmitting real images shows its operability. By reducing the image size by a factor of 2, the transmission time is reduced by a factor of 4 with a slight decrease in the visual quality of the resulting image. Such image scaling is especially effective when transmitting images over low-bandwidth channels. The developed hardware and software can be used in `Internet of Things systems for image transmission.