Blind Symbol-Rate Estimation and Test Bed Implementation of Linearly Modulated Signals

Although several blind symbol-rate estimation methods have been proposed for linearly modulated signals, none of these methods are applicable to offset quadrature phase-shift keying (OQPSK)-modulated signals. The frequently used cyclic correlation (CC) methods are unable to estimate the symbol rate for OQPSK signals as the cyclic peak at the symbol-rate frequency disappears due to the presence of an offset between the in-phase (I) and quadrature (Q) components of OQPSK signals. In this paper, a blind symbol-rate estimation for linearly modulated signals has been proposed. The symbol rate of OQPSK signals has also been estimated with no knowledge of modulation schemes. The offset between I and Q components of the received signals is compensated for by using a set of approximate offsets in obtaining the cyclic peak at the symbol-rate frequency. The proposed estimation has a robust performance in the presence of unknown frequency offset, timing offset, and carrier phase. The algorithm is implemented on a test bed to provide experimental results.