1. Department of Electronics and Information Engineering; Huazhong University of Science and Technology; Wuhan 430074 China
2. Hubei Polytechnic University; Huangshi 435000 China
3. University of Southern California; Los Angeles CA 90089 U.S.A.
4. The LSI corporation; Milpitas 100080 U.S.A.
5. Division of Research; China Mobile Group Design Institute Co., Ltd.; Beijing 100080 China