A Low Complexity ICFO Estimator and Compensator for IEEE 802.15.4g MR-OFDM PHY: Algorithm Proposal and Hardware Implementation

Abstract

This work proposes a novel algorithm and a hardware implementation for frequency-domain Integer Carrier Frequency Offset (ICFO) estimation and compensation, targeting the Multi-Rate and Multi-Regional Orthogonal Frequency Division Multiplexing (MR-OFDM) physical layer (PHY) of IEEE 802.15.4g, which is an amendment to IEEE 802.15.4 standard for supporting Smart Metering Utility Networks (SUN). The paper derives a simple closed-form for both ICFO estimation and compensation processes, by considering not only the shift in subcarrier indices as an effect of the ICFO, which is commonly seen in the literature, but also a phase accumulation resulting from the combined effect of the ICFO and the presence of a Cyclic Prefix (CP). We present an estimation method robust to both multipath channel and time offset, as well as a simple compensation scheme in the frequency domain, which makes uses only of shift and sign operations. We also detail the implemented architecture and present results of performance simulation and RTL synthesis. The simulation results show the algorithm is robust to symbol boundary error and to channel with exponential power delay profile, with good performance under low SNR, achieving a failure rate of 0.1% at -3dB for one of the studied cases. The synthesis targeting Altera Cyclone IV GX FPGA resulted in 8% of resource usage. This ICFO estimator/compensator is part of a project that aims to implement in ASIC the three PHYs defined in the standard and integrate them to build a system fully compliant to IEEE 802.15.4g.