Improved subspace intersection based on signed URV decomposition

Asynchronous co-channel interference mitigation is a tough problem for cellular systems, which greatly degrades the performance of multi-user receiver algorithms, especially blind source separation (BSS) algorithms when the interferences partially present in the time slot. Although “codes” (or training data) based algorithms can more or less solve this problem, they require unique “codes” for each user and fail when the “codes” are corrupted by unknown effects, such as Doppler shift. In this paper, based on the fact that signals always present in observations but interferences not, we propose an improved subspace intersection (SI) based on the signed URV decomposition to find the interference-free subspace. By using the proposed SI, we propose a new preprocessing method for BSS algorithms. This method takes subspace intersections on the divided received data matrices and finds the desired subspace. Simulations show that our proposed method significantly improves the performance of BSS algorithms under asynchronous interferences.