V. N. Bondarenko - Dr.Sc. (Eng.), Professor, Department of Radio Electronic Systems, Institute of Engineering Physics and Radio Electronics, Siberian Federal University. E-mail: vbondarenko@sfu-kras.ru
R. G. Galeev - Ph.D. (Eng.), General Director, JSC «SPP «Radiosvyaz?»
V. F. Garifullin - Postgraduate Student, Department of Radio Electronic Systems, Institute of Engineering Physics and Radio Electronics, Siberian Federal University. E-mail: vadimgar@mail.ru
T. V. Krasnov - Engineer, Assistant, Department of Radio Electronic Systems, Institute of Engineering Physics and Radio Electronics, Siberian Federal University. E-mail: KrasnovTV@ngs.ru

In the article there is a quasi-optimal double-level search algorithm for the spread spectrum signal (SSS) with minimal frequency shift keying of MSK-BOC format due to delay time. On the first level there is search on the envelope line of code (without subcarrier frequency) with cell size equal to meander chip duration. The search algorithm for MSK-BOC signal, which is invariant to subcarrier frequency is based on considering of every quadrature signal component as two components on «high» and «low» frequencies. On the second level the additional search of main peak of MSK-BOC signal is produced. For this case the traditional parallel procedure of searching with the cell size equal to a half of meander chip duration and with three channels is used. The immunity analysis of considered search algorithm is produced with using a probability of abnormal errors exceeding a half of additional searching step as criterion. The analysis results show that the loss in immunity of quasi-optimal searching algorithm in comparison with the optimal searching algorithm is less than 1,5 dB and it is entirely repaid by the benefits of practical implementation.