IntroductionThe development of wireless personal networks and miniature wireless ECG sensors that do not require elec trical contact with the human body enables construction of a wireless system for monitoring human cardiovascular activity. Continuous monitoring requires storing and transmitting large amounts of data, which is inevitably reflected in the time of continuous operation of the sys tem. Bessmeltsev et al.[1] reviewed a monitoring system developed consisting of a heart rate sensor and contactless ECG sensors that transmit data via Bluetooth LE (BT LE) to a data acquisition and processing system (microserver) based on an STM 32 microcontroller with ultra low power consumption, which performs prelimi nary data processing. The microserver is paired wirelessly with a cell phone transmitting data to a remote medical server. The data received by the microserver are transmit ted to the cell phone via BT v. 3.0, with higher consump tion compared to a BLE channel. Reducing the amount of data transmitted to the cell phone lowers the load on the communication channel and increases the battery life of the complex. Most of the existing electrocardiographic signal (ECS) compression methods are focused on the use of stationary computing devices and require performing a large amount of computing operations [2 4]. However, there are effective ways of ECS compression that do not require a large amount of computational operations, based on the use of wavelet transformation and compres sion algorithms such as LZW and RLE [5]. This approach involves lossy compression, but allows the compression ratio to reach values in the range of 10 15 and may be rep resented as a set of the following steps:− normalization and wavelet transform of the source data;− zeroing of the portion of the obtained wavelet trans form coefficients whose absolute values are close to zero;− compression of the obtained coefficients. High values of the compression ratio (CR), in our opinion, are achieved through single character represen tation of data as ASCII code for storing wavelet coeffi cients on the computer hard disk using delimiters. This gives a higher redundancy than the "direct" byte repre sentation of the data in the mobile monitoring system. This article discusses a method of compressing the ECS which eliminates the need to use algorithms for compression of the wavelet transform coefficients. This method is based on changing the size and scale of the coefficients of the wavelet transform of the original data.
Obtaining the ECS and Preliminary ProcessingThe ECS is registered by wireless sensors having non contact capacitive sensors, similar to those described in [6]. The sensor has a built in analog filter, limiting the The article studies the problem of compression of data recorded by ECG sensors of mobile heart activity monitor ing systems. An ECG data compression algorithm is presented which is based on transformation of coefficients of a discrete wavelet transform implemented using a computing device with limited processing power and low...