OVSF code allocation and two-stage combining method to reduce intercode interference in OFCDM system

In this paper, we propose an OVSF (Orthogonal Variable Spreading Factor) code allocation in OFCDM (Orthogonal Frequency and Code Division Multiplexing) system. In the proposed OVSF code allocation, codes which have a different ancestor code are allocated to users. When the proposed OVSF code allocation is used, a receiver can use a despreading which utilizes chips shorter than the spreading factor. Thus, symbols are generated. Furthermore, we propose a two-stage combining method. After first stage combining, by despreading, the symbols are multiplied by weights and combined in second stage combining. We show that the proposed scheme achieves better BER performance than the conventional scheme by computer simulations. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(9): 16– 24, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20381