# Adaptive Antenna Array Control Algorithm in Radiocommunication Systems
## 2 Adaptive Antennas in Radio Communications
If there are no resources to service a connection, the connection is lost or there is a wait for the connection to become available, depending on the method used to handle such connection requests. Figure 1: Communication diagram between the base station and the mobile station. Figure 2: Land mobile radiocommunication network using base stations with adaptive antennas. When the mobile station ends the connection, the physical channel (time slot) it occupies is released and the slot is excluded from the adaptation process [13]. The algorithm for handling calls and ending calls is shown in Figure 3.  
The adaptive algorithm presented [14] in this work is based on the assumption that in subsequent time slots, the adaptive processor determines the parameters of the signal received by the antenna in a given time slot from a given mobile station and modifies the shape of the radiation characteristics of the adaptive array in such a way to adapt this characteristic to the new situation [15]. This is because while the base station serves other subscribers, the mobile station in question may change its position or the power radiated from the transmitter, or an additional signal may occur that will disturb the emission of the mobile station in question or the sector antenna. The power radiated towards the mobile station is also adjusted so that it ensures correct transmission in the radio link, but at the same time introduces the least possible interference to other base stations. We see that the radiation pattern of the sector antenna changes dynamically in relation to the observed changes in the surroundings of a given base station. The radiation characteristics of the adaptive antenna are the result of determining optimal characteristics for each mobile station separately. Its form is the sum of the component characteristics for mobile stations. In this way, a radiation pattern is formed that takes into account the location of all currently supported mobile stations as well as the directions of interference that affect the adaptive antenna. Minimizing the radiation characteristics in the direction of the interference source allows the use of lower radiation powers to and from the mobile station while maintaining the assumed connection quality (the ratio of the power of the useful signal to the power of the interfering signals). This introduces less interference to other base and mobile stations and reduces the power of interfering signals and noise occurring in the direction of the operated mobile station. Figure 3: Algorithm for handling calls and disconnections. Data transmission between the mobile station and the base station in a given _i-th_ slot and simultaneously from the base station to the mobile station in the slot (_i_ + 3) is carried out in parallel with the process of the adaptation of the radiation pattern by separate sets of the radio receiver and signal processor. Although adaptive antenna systems use antennas of various types and configurations, they can be classified into three basic classes:  
* Phase patterns;
* Multibeam antennas;
* And their combination. Each configuration has several ports in which \(x_{n}\) signals appear in response to signals from sources located in the antenna illumination field [16]. Therefore, the main problem in implementing the adaptation process is in determining the directions of arrival of signals [17]. A universal way to estimate the signal arrival angle is to use the covariance matrix. The problem comes down to estimating the angle of incidence of signals coming from the directions \(\Theta_{1}\), \(\Theta_{2}\ldots\Theta_{k}\) based on the received signals \(x_{1}\), \(x_{2}\)\(x_{m}\) (Figure 4).