Abstract
In recent years, radio electromagnetic spectrum is considered as the most precious resource in wireless communication systems. More and more wireless systems co-exist in the same environment and sharing the bandwidth, consequently, they will interfere with each other. The condition is even worse as the wireless system is a wide-band system. In order to prevent interference, Cognitive Radio is an idea about sensing co-existence system, identifying the type of interference and negotiating between systems. In our work, we will introduce an algorithm called active interference cancellation to avoid interference at specific bandwidth by using AIC tones between interfering bands. We use the spirit of cognitive radio and construct a system to decrease the negative effect among users. Furthermore, we develop a multiple-input multiple-output (MIMO) system basing on this algorithm. By exploiting MIMO, we can transmit data by other transmitting antenna (except for AIC antenna) in the interfering band under the protection of one AIC antenna. This idea achieves decreasing improvidence and increasing bandwidth efficiency. Under MIMO system structure, it’s almost impossible to cause notch at specific band everywhere. The notch could be created at specific position or specific straight lines. We will further discuss the condition of channel between users which interfere with each other and, under this assumption; we find out that the method of direction of arrival (DOA) estimation is helpful to evaluate the channel, and benefit to our proposed MIMO active interference cancellation model.