# Adaptive Antenna Array Control Algorithm in Radiocommunication Systems
## 2 Adaptive Antennas in Radio Communications  
Mobile radiocommunication is a dynamically developing field of radio communications. Its main task is to ensure communication between mobile subscribers and enable access to the fixed telecommunications network. The area covered by the wireless network is divided into appropriately small sub-areas called cells, within which mobile subscribers move. Each cell is equipped with a base station responsible for collecting and updating user data and intermediating the user's connection with a selected subscriber of the same network, another network, or a fixed-line network [4]. Dividing the area into cells allows you to reduce the power of transmitters and allows for multiple use of the same frequency range. The following assumptions apply to the radiocommunication system-mobile telephony, in which the analyzed adaptive antenna control algorithm can be implemented:  
* The system works on two frequency ranges [5; 6];
* Upstream channels (from mobile station to base station);
* Down channels (from base station to mobile station). This is a two-way transmission carried out in the frequency domain; depending on the operating frequency, a different bandwidth is used. With the development of mobile radio communication systems and the increasing density of users of these systems, the issue of radio interference generated by base stations and mobile stations becomes more important [7; 8]. In the antenna aspect, this refers to the shape of the radiation pattern of the base station antenna. When considering base stations with classic antennas with omnidirectional radiation characteristics or sector characteristics, the harmful impact of co-channel and adjacent-channel interference generated by the assumed evenly distributed electromagnetic field from the base station antennas and the fields generated by mobile stations should be taken into account (Figure 1). One of the effective ways to reduce the level of the interference field is to use antennas with directional radiation characteristics in base stations, in particular adaptive antennas with a moving main beam that follows the mobile station in real time. In a similar period, work was carried out independently by Widrow, which was based on the use of the Least Mean Square Algorithm (LMS) to eliminate strong radio interference generated by sources located in close proximity to the received useful stations [9]. The original concept of controlling the zeroing band of the receiving antenna was replaced by a solution of forming a multi-beam radiation pattern of the base station antenna, in which each of the created characteristic lobes is responsible for maintaining communication and tracking a selected mobile station or group of mobile stations (Figure 2) (beam forming) [10,11]. Currently, and in the future, a more effective solution is to combine the method of zeroing the antenna pattern, which eliminates interference, with the simultaneous use of the same antenna as a system with multi-beam radiation characteristics. Mobile stations located in the area served by a given sector antenna are assigned to a given antenna. This takes place when the area covered by one sector antenna is transferred to another sector. In the new sector, the mobile station receives an identifier that determines its location in the mobile network [12]. When a mobile station requests service, it sends a service request signal on a specific, fixed frequency. The base station checks whether it has free resources to service this mobile station. If so, it allocates a time slot called a physical channel on the appropriate frequency. A similar situation occurs when the base station receives a request from the exchange to establish a connection to the mobile station. From now on, the mobile station will be operated by an algorithm controlling the radiation pattern of the sector antenna.