Blind Carrier Frequency Offset Estimation Techniques for Next-Generation Multicarrier Communication Systems: Challenges, Comparative Analysis, and Future Prospects

Frequency synchronization is essential to achieving the intended performance for single and multicarrier wireless systems. Blind techniques, which don’t require prior channel knowledge or pilot symbols, are crucial for dynamic environments where self-adaptive synchronization is needed. A key objective of this paper is to provide the readers as well as the industry’s professionals with a comprehensive understanding of the carrier frequency offset (CFO) problem in multicarrier communication systems like orthogonal frequency division multiplexing (OFDM), single carrier-frequency division multiple access (SC-FDMA), multiple input multiple output (MIMO)-OFDM, and MIMO-SC-FDMA. These waveforms are used in today’s and future wireless communication systems such as wireless-fidelity (Wi-Fi), fifth-generation, and sixth-generation. Moreover, this paper also develops a taxonomy of the available solutions to address the CFO issue. We study blind techniques for CFO estimation presented in the recent literature and give potential future directions. We summarize various statistical methods and deep learning algorithms for CFO estimation and emphasize their advantages and limitations. We also incorporate the CFO impact on next-generation wireless systems such as orthogonal time frequency space and reconfigurable intelligent surface-assisted communication systems and provide a broader and deeper knowledge of the area. We provide simulation results of some existing estimators and their performance comparison in terms of mean square error for better understanding. Therefore, this paper is perfectly adapted to provide a comprehensive information source on blind CFO estimation techniques.

I. Introduction

Multicarrier modulation technique is extensively employed in many wireless and wireline high-speed communication environments because it enables high data rate transmissions with low complexity. Advanced techniques like orthogonal frequency division multiplexing (OFDM), single carrier-frequency division multiple access (SC-FDMA), multiple input multiple output (MIMO)-OFDM, MIMO-SC-FDMA, orthogonal time frequency space (OTFS), and reconfigurable intelligent surface (RIS)-assisted wireless communication systems are required to meet the growing demand for high data rates. OFDM has been deployed in several wireless communication standards and applications such as high-definition television terrestrial broadcasting, digital television video broadcasting-terrestrial [1], European digital audio broadcasting [2], [3], [4], [5], [6], and satellite-terrestrial interactive multi-service infrastructure in China. Multiband-OFDM has been adopted in ultra-wideband systems [7], [8], [9], [10], [11] like IEEE 802.15.3a, broadband wireless access like IEEE 802.16 [12], and mobile broadband wireless access like IEEE 802.20 [13]. SC-FDMA has similar standards and applications as that of an OFDMA system. In the downlink, long-term evolution (LTE) [14] uses OFDMA, which has a strong resemblance to worldwide interoperability for microwave access (WiMAX); however, SC-FDMA is employed in the uplink due to its low peak-to-average-power-ratio (PAPR) property, efficient resource utilization, low intersymbol interference (ISI), and low complexity receiver design. MIMO can utilize spatial resources and provide high capacity as well as diversity, whereas OFDM is immune to frequency selective fading. The synergistic integration of MIMO and OFDM is a highly promising technology for fifth-generation (5G), beyond 5G systems, and technology like new radio (NR), third-generation partnership projects (3GPP), various wireless standards, including IEEE 802.11 (e.g., 802.11a/g/n/ac/ax) [15].