Abstract
In mobile communications, radio-frequency receivers are mainly implemented using the direct-conversion architecture. A critical aspect in the design of this receiver type is the matching between the analog in-phase (I) and quadrature (Q) paths. Any gain or phase imbalance generates image components in the baseband, which distort the desired receive signal. Many digital solutions for online compensation of this effect have been proposed in the literature. A common statistical measure that is used by non-data-aided algorithms is the so-called propriety of the receive signal. This concept is suitable for most communication signals, but fails, for instance, in case of the real-valued binary phase-shift keying (BPSK) modulation. In this work, we provide a thorough statistical analysis of Long-Term Evolution (LTE) and New Radio (NR) up- and downlink sequences, which allows us to extend a propriety-based estimator to improper alphabets. This algorithm employs the method of moments. We show that the observed signal statistics can be altered by omitting a predefined set of samples. In a second step, we prove that this concept substantially enhances the imbalance compensation also for proper quadrature amplitude modulation (QAM) alphabets. All theoretical results are supported by simulations to evaluate the actual performance gains in practical scenarios. Depending on the resource block allocation and the noise levels, we obtain double-digit improvements of the image rejection ratio, while reducing the computational effort by about 6.6% compared to the standard moment-based I/Q imbalance estimator.
Highlights
T HE direct-conversion or homodyne receiver architecture is very popular in state-of-the-art radio frequency (RF) transceivers, because it allows for high integration with only a few external components required [1], [2]
We provide two novel results compared to [8], [16], [17]: First, we show that a modified momentbased estimator features substantial performance improvements for improper Long-Term Evolution (LTE)/New Radio (NR) sequences
The method of moments is a standard approach in statistics, where certain moments of the true distribution of a random variables (RVs) are expressed as analytic functions in one or several unknown parameters [31]
Summary
T HE direct-conversion or homodyne receiver architecture is very popular in state-of-the-art radio frequency (RF) transceivers, because it allows for high integration with only a few external components required [1], [2]. Any non-idealities in the analog components lead to amplitude and/or phase mismatches between the I and the Q signal components, known as I/Q imbalance Due to this effect, the complex conjugate of the receive (Rx) signal. The I/Q imbalance problem is extensively covered in literature, where various algorithms have been published ranging from very low [3]–[8] to comparably high hardware complexity [9]–[14] Some of these approaches target a frequency-dependent I/Q imbalance, while others assume a frequency-independent effect. We focus on a specific propriety-based approach, which employs the method of moments [16] In detail, this concept utilizes the variance and pseudo-covariance of the receive signal with I/Q imbalance.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
