Given the shortage of spectrum below 6GHz, millimeter wave (mmW) frequencies have played an important role in the emerging 5G networks and this trend is expected to continue in the next generations. Due to unfavorable propagation conditions and attenuation at high frequencies, mmW networks require the densification of base stations and radios equipped with a large number of antennas to compensate path loss via directional gain using narrow beams. The cost and power consumption of radios with antenna arrays present a significant challenge, and their architecture is of fundamental importance and influence on the entire networking stack. State-of-the-art approaches based on phased antenna array architecture are faced with several fundamental problems when radio bandwidth and the number of antennas increases including prohibitive latency in initial connectivity and link management, distortion in the directionality of the beams, reduced beamforming gain, and ability to suppress the interference in dense deployments. This project aims to develop and demonstrate a novel adaptive true-time-delay (TTD) based array for wideband mmW networks and overcome challenges of phased antenna arrays. The approach involves co-design and optimization of tunable radio frequency (RF) circuits, antenna array system, signal processing, and network protocols for low latency access, wideband beamforming gain, and interference management.
The research work will pursue four key thrusts: Thrust 1 will develop TTD array-based fast beam training and spatial interference detection and estimation for mmW networks with large modulated bandwidth. The objective is to reduce the overhead in initial access due to beam training by exploiting frequency-dependent antenna weight vectors in TTD arrays through signal processing and develop a low latency protocol design for simultaneous beam training and interference estimation in dense mmW networks. Thrust 2 will focus on the data communication design using TTD arrays to facilitate multiple-input multiple-output (MIMO) multiplexing and suppress interference from co-channel base stations and users. The main challenge is to achieve high beamforming gain over a wide modulated bandwidth together with effective nulling of wideband interferers. Thrust 3 will develop an experimental testbed for the evaluation of signal processing algorithms and protocols from Thrusts 1 and 2. It will involve the integration of widely reconfigurable delay compensating circuits and custom mmW front-end at 28GHz into a 16-element TTD antenna array. Thrust 4 will experimentally validate TTD array-based beam training, squint-free wideband beamforming and interference nulling, and wideband MIMO communications using the testbed developed in Thrust 3.
This project is supported by National Science Foundation award (#1955672/1955306). Lead PI on this project is Prof. Danijela Cabric (UCLA) with Profs. Subhanshu Gupta (WSU PI) and Deukhyoun Heo (WSU Co-PI). Partial support has been provided by the Center for Analog and Digital Integrated Circuits (CDADIC).
People – Faculty
- Danijela Cabric, University of California Los Angeles
- Subhanshu Gupta, Washington State University
- Deuk Heo, Washington State University
People – Current Students
- Aditya Wadaskar, Ph.D., University of California Los Angeles
- Chung-Ching Lin, Ph.D., Washington State University
- Mohammad Ali Mokri, Ph.D., Washington State University
- Mohammad Chahardori, Ph.D., Washington State University
- Soumen Mohapatra, Ph.D., Washington State University
- Veljko Boljanovic, Ph.D., University of California Los Angeles
People – Former Students
- Han Yan, Ph.D., University of California Los Angeles (now Design Engineer at Apple)
- Erfan Ghaderi, Ph.D. , Washington State University (now Design Engineer at Intel)
- Chase Puglisi, M.S., Washington State University (now Design Engineer at Texas Instruments)
The project goals are focused on novel designs of beam training and beam forming in wideband millimeter-wave networks by leveraging frequency-dependent beam steering/combining of true-time-delay arrays and recent advances in their implementation. Specifically, the project aims to address the high-latency beam training, wideband interference cancellation, and multiplexing of wideband signals with true time delay architectures. The work can be broadly divided into three parts: 1) system and algorithm design for all considered problems in true-time-delay based millimeter-wave networks; 2) design and implementation of a testbed with true-time-delay array architectures; 3) experimental demonstration and validation of proposed solutions.
- Veljko Boljanovic and Danijela Cabric, “Compressive Estimation of Wideband mmW Channel using Analog True-Time-Delay Array,” accepted to the IEEE International Workshop on Signal Processing Systems (SiPS), to be presented in Oct. 2021.
- Chung-Ching Lin, Chase Puglisi, Veljko Boljanovic, Soumen Mohapatra, Han Yan, Erfan Ghaderi, Deukhyoun Heo, Danijela Cabric, Subhanshu Gupta, “A 4-Element 800MHz-BW 29mW True-Time-Delay Spatial Signal Processor Enabling Fast Beam-Training with Data Communications,” accepted to the IEEE European Solid-State Circuits Conference (ESSCIRC), to be presented in Sept., 2021. (PDF)
- Veljko Boljanovic, Han Yan, Chung-Ching Lin, Soumen Mohapatra, Deuk Heo, Subhanshu Gupta, Danijela Cabric, “Fast Beam Training with True-Time-Delay Arrays in Wideband Millimeter-Wave Systems,” IEEE Transactions of Circuits and Systems – I: Regular Papers (TCAS-I), vol. 68, no. 4, pp. 1727-1739, April 2021. (PDF)
- Veljko Boljanovic, Han Yan, Erfan Ghaderi, Deuk Heo, Subhanshu Gupta, Danijela Cabric, “Design of Millimeter-Wave Single-Shot Beam Training for True-Time-Delay Array,” 20th IEEE Signal Processing Advances in Wireless Communications (SPAWC), May 19–23 2020, Atlanta, GA, pp. 1–6. (PDF)
- P. Agarwal, M. Chahardori, and D. Heo, “A New Boosted Active-Capacitor with Negative-Gm for Wide Tuning Range VCOs” , IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 68, no. 3, pp. 1080-1090, March 2021.
- Erfan Ghaderi, Ajith S. Ramani, Arya A. Rahimi, Deuk Heo, Sudip Shekhar and Subhanshu Gupta, “A 4-Element Wide Modulated Bandwidth MIMO Receiver with >35 dB Interference Cancellation,” IEEE Transactions of Microwave Theory and Techniques (TMTT), vol. 68, no. 9, pp. 3930-3941, Sept. 2020. (PDF)
- Han Yan, Veljko Boljanovic, and Danijela Cabric, “Wideband Millimeter-Wave Beam Training with True-Time-Delay Array Architecture,” Asilomar Conference on Signals, Systems, and Computers, Nov. 2019.
- New course modules have been introduced on discrete-time beamforming in advanced integrated circuit design (EE 596).
- PIs have disbursed research outcomes to semiconductor companies include Boeing Inc., Apple, Intel, Texas Instruments, Rohde & Schwarz, Analog Devices, Qualcomm, and Semiconductor Research Corporation.
- The PI has included course modules on millimeter wave communications and array architectures for spatial signal processing including the True Time Delay arrays in graduate course ECE 233 Wireless Communications System Design at UCLA and EE 596 at WSU.
Outreach and other broader impact outcomes