An Efficient Frame Optimization Scheme for Low Power Wide Area Networks

Abstract

In order to support low power wide area networks (LPWANs) with a scarce pilot resource, we discuss the data framing and its corresponding optimization problem. In specific, we design a general pilot-symbol-assisted-modulation (G-PSAM) frame based on the standard PSAM (S-PSAM) frame and derive joint data-aided & non-data-aided Cramer-Rao bounds (DA&NDA CRBs) for carrier frequency offset (CFO), phase offset (PO), and time delay estimation, followed by an approximate DA&NDA CRB for the CFO. With the approximate DA&NDA CRB and the well-known control-variate method (CVM), we then provide an efficient G-PSAM frame optimization scheme, which is asymptotically optimal in terms of the mean-squared-error (MSE) performance. Simulation results show the superiority of the optimized G-PSAM frame over the S-PSAM frame for both the short-packet and long-packet transmissions. Meanwhile, we also present an example verification on the joint DA&NDA aided carrier synchronization (i.e., Turbo synchronization).