OFDM

The method of multiplexing of timer signal structures. based on OFDM technology was considered. This technology is used in many data transmission standards, both in wired channels — asymmetric digital subscriber line (ADSL), and in wireless networks — the standards of IEEE 802.11a and HiperLAN/2. OFDM is characterized by high spectral efficiency, resistance to radio frequency interference, low level of multi-path distortion.

In this paper considered the cognitive radio (CR) networks with the GSM network like primary network cooperation possibility. The cognitive radio system meant radio with a self-management mechanism with different levels of ability to adapt to the changing radio environment. The self-management mechanism is based on the principles of learning and artificial intelligence. In world practice, the frequency assigned to a particular entity in a certain area on a long term basis. However, most commonly frequency for this designated area not always used, and as necessary.

The implementation of beamforming and spatial diversity in Orthogonal Frequency Division Multiplexing (OFDM) systems reveals challenges in terms of complexity, feedback, and scenario dependencies. In this paper we discuss the differences and limitations of OFDM transmission over scenarios with different angular spread, which can viewed clearly from the base station antenna (BSA), signals departing to or arriving from the UE appear to be spread over a range of angle and evaluate the issues arising from the implementation of beam-forming and spatial diversity in OFDM systems.

The research findings in the sphere of mathematical modeling of modern broadband wireless access have been revealed in the article. Detailed description of algorithm program realized in multi- antenna channel has been provided. The distinctive feature of this algorithm is taking into account the digital signal processing correlation properties of multi-antenna channel.