Burst transmission symbol synchronization in the presence of cycle slip arising from different clock frequencies

Abstract

In digital communication systems, different clock frequencies of transmitter and receiver usually are translated into cycle slips. Receivers and transmitters may experience different sampling frequencies due to manufacturing imperfection, Doppler effect introduced by channel or having error in estimation of symbol rate. Timing synchronization in presence of cycle slip for a burst sequence of received information leads to severe degradation in system's performance. Therefore, the necessity of prior detection and elimination of cycle slip is obvious. Accordingly, the main idea introduced in this paper is to employ the Gardner detector (GaD) not only to recover a fixed timing offset, but also its output is processed such that timing drifts can be estimated and corrected. By deriving a two-step algorithm, first the cycle slips arising from symbol rate offset is eliminated, and then symbol's timing offset is synchronized in an iterative manner. GaD structure is used in a feedforward structure with the additional benefit that convergence and stability problems, which are typical challenges of the systems with feedback, are avoided. The proposed algorithm is able to compensate considerable symbol rate offsets at the receiver side. Results in terms of BER confirm the algorithm's proficiency.

Performance analysis of discrete wavelet transform for downlink non‐orthogonal multiple access in 5G networks

“…Hence, the received signal, after demodulation experiences phase distortion, ICI and amplitude reduction. As shown in previous works [51, 52], in an OFDM‐based system, the sub‐carriers may not be located at integer multiples due to the CFO. We analyse the impact of various levels of CFO on the BER performance of FFT–NOMA and W‐NOMA through simulation results.…”