Blind Time-Synchronization of CCSK Short Frames

Kassem SAIED – Post-Doc IMT-Atlantique présentera ses travaux au grand amphi de l'IMT-Atlantique.

Abstract :

The efficient transmission of short frames is a prerequisite for the effectiveness of a wireless Internet of Things (IoT) network. In classical systems, each message is preceded by a preamble to help in detecting the arrival of the frame and simplify the demodulation operations. To avoid the bandwidth loss introduced by this preamble, we propose to study a new type of frame called Quasi-Cyclic Short Packet (QCSP). The whole QCSP frame can be considered first as a preamble to simply perform the detection and synchronization functions, then as an encoded codeword to correct the transmission errors. A QCSP frame is based on the association of a Cyclic Code Shift Keying (CCSK) modulation with a non-binary error correction code.

Those studies the QCSP frame reception problem by combining theoretical aspects with the definition and evaluation of algorithms. We first studied a detection algorithm adapted to QCSP frames. A theoretical model, validated by Monte-Carlo simulation, allows us to fully characterize the proposed algorithm. Then, we develop different time, frequency and phase synchronization algorithms. In particular, we propose to add an over-modulation of CCSK symbols to remove the time synchronization ambiguity at the symbol level. In addition, the non-binary code structure is also used to help the time and phase synchronizations. We formalized the QCSP frame parameter optimization problem as a trade-off between detection, synchronization and decoding performance. Finally, Software Defined Radio (SDR) modules allow us to experimentally validate the theoretical contributions of the thesis. It is thus possible to transmit 360 bits of information at a very low signal-to-noise ratio (-12 dB) with a transmission time reduced by 23% compared to the use of a classical frame.