5G Millimeter-Wave Communications

5G and future cellular technology rely on millimeter-wave (mmW) communications to achieve extreme data rates, introducing new algorithm and hardware challenges. Efficient beam alignment is one challenge, due to the narrow beams from large phased arrays required by these high frequency mmW systems. Traditional designs use an exhaustive beam sweep, testing each possible pair of beams, to choose the best pointing direction. User association and resource allocation for future cellular systems require improved algorithms to reduce computational complexity and improve performance under realistic network scenarios.  Additionally, transceiver hardware architectures must be optimized for mmW communications. The optimization is constrained by power and circuit impairments due to an order of magnitude higher carrier frequency, processing bandwidth, and number of antenna elements.

Our research addresses these problems through both model-based approaches using signal processing and model-free approaches using machine learning. We have developed novel algorithms that combine compressed sensing and machine learning techniques that use pseudorandom beam designs to estimate angle of arrival information from fewer measurements [1]. Using donated Terragraph 60 GHz channel sounders from Facebook, we have verified our mmW algorithms experimentally [2]. We have comprehensively analyzed the performance of physical layer procedures including initial access, transceiver synchronization, channel tracking, beamforming and multiplexing under hardware impairments and quantified their impact on the power consumption of mmW radios [3]. Recently, we have proposed novel array architecture based on true-time-delay (TTD) arrays as an alternative to phased antenna arrays due to their large delay-bandwidth products. We have shown that TTD arrays can accelerate beam training using frequency-dependent probing beams and achieve high resolution accuracy using a single training pilot [4], [5]. These results hold a great potential and have attracted significant interest and funding from federal agencies and industry.

Our mmW research has been supported by



Q. Xu et al., "A Switching-Less True-Time-Delay-Based Beam Probing Approach for Ultra-Low Latency Wireless Communications: System Analysis and Demonstration," in IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 69, no. 10, pp. 4113-4117, Oct. 2022, doi: 10.1109/TCSII.2022.3178716.
Veljko Boljanovic and Danijela Cabric, "Compressive Estimation of Wideband mmW Channel using Analog True-Time-Delay Array," in IEEE International Workshop on Signal Processing Systems (SiPS), Oct. 2021
V. Boljanovic, H. Yan, E. Ghaderi, D. Heo, S. Gupta, and D. Cabric, "Design of Millimeter-Wave Single-Shot Beam Training for True-Time-Delay Array," in IEEE 21st International Workshop on Signal Processing Advances in Wireless Comm. (SPAWC), May 2020
H. Yan and D. Cabric, "Digital predistortion for hybrid precoding architecture in millimeter-wave massive MIMO systems," in IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Mar. 2017
H. Yan and D. Cabric, "DSP Linearization for Millimeter-Wave All-Digital Receiver Array with Low-Resolution ADCs," in IEEE 20th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), July 2019
B. W. Domae, C. Chen, D. Cabric, "Energy Efficiency Tradeoffs for Sub-THz Multi-User MIMO Base Station Receivers," in 2022 55th IEEE International Symposium on Circuits and Systems (ISCAS), May 2022
D. Zhao, I. Pehlivan, A. Wadaskar and D. Cabric, “Fast Frequency-Direction Mapping Design for Data Communication With True-Time-Delay Array Architecture, ” 2024 International Conference on Computing, Networking and Communications: Signal Processing for Communications (ICNC’24 SPC)
V. Boljanovic, D. Cabric, "Joint Millimeter-Wave AoD and AoA Estimation Using one OFDM Symbol and Frequency-Dependent Beams," in the 2023 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), June 2023