Use of Training Subcarriers for Synchronization in Low Latency Uplink Communication with GFDM

Abstract

We consider low latency uplink communication where users transmit their signal using generalized frequency division multiplexing (GFDM) with K subcarriers and M subsymbols. The proposed approach for synchronization exploits both training subcarriers and training subsymbols embedded in a GFDM symbol. A frequency domain training sequence (FDTS) of length M is loaded on each training subcarrier, and at the receiver the corresponding time domain TS (TD-TS) of length N = KM is extracted by filtering the received signal. We employ FD-TSs having two identical halves of length M=2 so that the corresponding TD-TS has two identical halves of length N=2. The extracted TD-TS is used for coarse timing synchronization and carrier frequency offset (CFO) estimation. The training subsymbol of the proposed scheme is used only for fine timing synchronization. The synchronization approach with the proposed training structure is compared with the existing method exploiting only training subsymbols. The results demonstrate that the former outperforms the latter in CFO estimation, while requiring less TS overhead; both the approaches perform well in acquiring timing synchronization.