In this paper, a blind symbol timing offset (STO) estimation method is proposed for offset quadrature phase‐shift keying (OQPSK) modulated signals, which also works for other linearly modulated signals (LMS) such as binary‐PSK, QPSK, π/4‐QPSK, and minimum‐shift keying. There are various methods available for blind STO estimation of LMS; however, none work in the case of OQPSK modulated signals. The popular cyclic correlation method fails to estimate STO for OQPSK signals, as the offset present between the in‐phase (I) and quadrature (Q) components causes the cyclic peak to disappear at the symbol rate frequency. In the proposed method, a set of close and approximate offsets is used to compensate the offset between the I and Q components of the received OQPSK signal. The STO in the time domain is represented as a phase in the cyclic frequency domain. The STO is therefore calculated by obtaining the phase of the cyclic peak at the symbol rate frequency. The method is validated through extensive theoretical study, simulation, and testbed implementation. The proposed estimation method exhibits robust performance in the presence of unknown carrier phase offset and frequency offset.

中文翻译：

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偏移量QPSK调制信号的盲符号定时偏移量估计

本文提出了一种针对偏移正交相移键控（OQPSK）调制信号的盲符号定时偏移（STO）估计方法，该方法也适用于其他线性调制信号（LMS），例如二进制PSK，QPSK，π/ 4-QPSK和最小移位键控。有多种方法可以用于LMS的盲STO估计；但是，在OQPSK调制信号的情况下无效。流行的循环相关方法无法估计OQPSK信号的STO，因为同相（I）和正交（Q）分量之间存在的偏移会导致循环峰值在符号率频率下消失。在提出的方法中，使用一组接近和近似的偏移量来补偿接收到的OQPSK信号的I和Q分量之间的偏移量。时域中的STO表示为循环频域中的相位。因此，通过获得符号速率频率下的循环峰值的相位来计算STO。该方法已通过广泛的理论研究，仿真和测试平台实施得到了验证。