Frequency Estimation in OFDM Direct-Conversion Receivers Using a Repeated Preamble

Abstract

This paper investigates the problem of carrier frequency offset (CFO) recovery in an OFDM receiver affected by frequency-selective in-phase/quadrature (I/Q) imbalances. The analysis is based on maximum-likelihood (ML) methods and relies on the transmission of a training preamble with a repetitive structure in the time domain. After assessing the accuracy of the conventional ML (CML) scheme in a scenario characterized by I/Q impairments, we review the joint ML (JML) estimator of all unknown parameters and evaluate its theoretical performance. In order to improve the estimation accuracy, we also present a novel CFO recovery method that exploits some side-information about the signal-to-interference ratio. It turns out that both CML and JML can be derived from this scheme by properly adjusting the value of a design parameter. The accuracy of the investigated methods are compared with the relevant Cramer-Rao bound. Our results can be used to check whether conventional CFO recovery algorithms can work properly or not in the presence of I/Q imbalances and also to evaluate the potential gain attainable by more sophisticated schemes

Learning-Aided Physical Layer Authentication as an Intelligent Process

“…Such analog-domain attributes are inherently related to the unique imperfection of communicating devices and to the corresponding environment, which are hard to impersonate and predict. These physical layer attributes include the channel impulse response (CIR) [7], received signal strength indicator (RSSI) [8], carrier frequency offset (CFO) [9]- [11], in-phase-quadrature-phase imbalance (IQI) [11], and so on, which can also be used to generate more unique combinations of these attributes for authentication. These diverse physical layer attributes and their combinations provide new mechanisms in a multi-dimensional domain for the enhancement of physical layer authentication.…”

OFDM Signal Recovery in Deep Faded Erasure Channel

“…Several methods of OFDM symbol recovery and channel estimation have been proposed [8]- [11]. One approach is the data-aided framework, where pilot signals are uniformly interleaved among information symbols and used to estimate channel frequency response at pilot subcarriers [12]- [15].…”

Digital Pre-Distortion of Carrier Frequency Offset for Reliable Wi-Fi Enabled IoTs

“…The fundamental causes of the CFO are crystal inaccuracies and variations in the transmitter as well as the receiver side, and the Doppler effect when the mobile stations are moving. Frequency errors are typically corrected in the digital receiver side using the correlation properties of training sequences [15,16]. After the digital correction, very little frequency error exists.…”

“…Many studies have been done to provide reliable communication links to users in IEEE 802.11 standards [15][16][17][18]. In the conventional wireless devices, a CFO is estimated by a unit of a packet using a preamble located at a header of a data packet transmitted through a wireless channel in an OFDM wireless communication system [17,18].…”