Accurate detection of the number of arrival signals using pre-estimated signal subspace

This paper presents an accurate detector of the number of incident waves arriving at smart antenna. The array antenna and MIMO techniques are developing toward 4th generation mobile communication systems, and the accurate estimation of propagation environment becomes more important. This paper attracts attention to the accurate detection of the number of incident waves which is one of important characteristics in multidirectional communication. There are some recent papers on the accurate detection, but they still have problems of computational cost or estimation accuracy in severe environment like low SNR, small number of snapshots or adjacent waves. Thus AIC and MDL methods based on information theory are still often used. In this paper, we propose an accurate estimation method of the number of arrival signals using the orthogonality of sub-spaces derived from preliminary estimation of signal sub-space. The proposed method accurately estimates the number of signals especially in severe environments where AIC and MDL methods can hardly estimate.