Estimaton of the number of signals based on orthogonal projection of  forward-backward covariance matrix
MU Jianchao1,2，GAO Meiguo1，JIANG Changyong1
Journal of Systems Engineering and Electronics . 2010, (10): 2036 -2040 .  DOI: 10.3969/j.issn.1001-506X.2010.10.04