Sensor networks play a key role in the need for rapid deployment, mobility, networking flexibility and a variety of possible applications, in many cases being the only cost-effective solution. One of the key tasks of functioning in the sensor network is to ensure reliable and efficient data transmission in conditions of limited resources.
Given the size of the sensor, the main requirement for sensor networks is to provide low power consumption and reliable reception. Their autonomy depends on the energy consumed by the nodes of the system.
The research contains the actual problem of increasing productivity in low-energy wireless communication channels. Unlike traditional wireless communication systems, a sensor network includes many devices that should transmit information to a base station. Sensor nodes can be placed permanently or be able to move in a certain space, so they must be autonomous, self-organized and do not require installation. The coverage area of such a network is extremely limited and can reach tens and hundreds of meters. The main task in building a sensor network is a reliable assessment of the energy characteristics of a wireless communication channel.
To solve the limitations of the communication channel, it is promising to search for new methods for transmitting information, choosing an effective type of modulation and error-correcting coding.
The basic tool for transmitting information is the signals of multi-position modulation. The choice of a combination of modulation type and error code rate provides the highest possible efficiency while providing adequate reliability to the communication channel. The multi-position modulation signals BPSK, QPSK and QAM16 were chosen as the considered signals. High-speed modulation types are not considered, since the sensor network does not involve the transmission of large amounts of information and has limited signal energy.
Broadband signals are one of the well-known methods for improving the noise immunity of a channel, but the properties of such signals under conditions of limited resources and signal energy have not been studied. To determine the most optimal method of signal transmission in low energy conditions, research on the properties of the narrowband signals was carried out based on models for assessing the quality of communication channels and comparing the noise immunity characteristic of wideband signals with equivalent signal energy.
To determine the maximum transmission performance in wireless low-energy communication channels, it is necessary to investigate the performance indicators of a given type of modulation signals and compare them with wideband signals with different values of the signal base B. It turned out that wideband signals do not provide better reliability compared to narrowband signals with the same transmission power and processing method.
The classical formulas for estimating the noise immunity of multi-position signals are accurate for high energy, but for h2 → 0 they are not accurate. Therefore, to determine the exact reliability for such conditions, it is proposed to use the vector-phase method. The vector-phase method helps to obtain accurate calculations for any energy, in contrast to the Prokis formulas, which can only be used for high energy.
The overall result of the research is performance evaluation of signal-code construction, that allows determining the efficiency of using a certain type of modulation and coding in a channel with given frequency and energy parameters according to the criterion of maximum approach to the Shannon bound, or the maximum of information efficiency for given signal reliability. Using this technique, it possible to evaluate the efficiency of using the resources of communication channels with multi-position modulation and error-correcting coding and calculate the costs of implementing measures to improve the reliability or performance of the proposed indicators.
Research contains the following new results:
1. The use of the vector-phase method for determining the noise immunity of multi-position signals under low energy conditions has been improved. The classic Prokis formulas are not accurate for low energy.
2. The method of signal synthesis has been improved, which makes it is possible to find the extremum of the communication channel performance and bring it closer to its capacity – the Shannon bounds.
3. The methodology for evaluating the effectiveness of the communication channel resources has been improved.
