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Beam Discovery and Tracking for Mobile MIMO

Abdelrazek, Mohamed Naguib Hussein
http://orcid.org/0000-0001-5731-3153
http://rave.ohiolink.edu/etdc/view?acc_num=osu1669934800384059

Abstract Details

2022, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
The real-time applications and the IoT promote the need for a newer idle spectrum to support the required high traffic. This pushes toward the emergence of the millimeter-wave (mmWave) and the sub-Terahertz (sub-THz) bands in wireless communication. Albeit these higher frequency bands offer wide spectrum help improving the spectral efficiency, it comes with the challenge of alleviating the severe attenuation. MmWave transceivers use large antenna arrays to form high-directional beams and overcome severe attenuation. A large array size leads to a costly beam alignment process if no prior information about beam directions is available. Beam alignment has two phases: beam discovery, and beam tracking. Beam discovery is finding the beam direction by consuming several pilot symbols to find the optimum direction. Moreover, beam tracking is a common approach to keep the discovered beams tightly coupled without frequent beam discovery to eliminate the overhead associated with realignment. Both phases become more difficult as the beams get narrower since slight mismatches lead to significant degradation in SNR as the beam coherence times are short. As a result, beams may lose alignment before they can be readjusted periodically with the aid of pilot signals. In this thesis, we introduce two complementary proposals. The first proposal is for the issue of beam tracking, and the second proposal is for the issue of beam discovery. In the first part of the thesis, we propose a model where the receiver adjusts beam direction continuously over each physical-layer sample according to a carefully calculated estimate of the continuous variation of the beams. Our approach contrasts the classical methods, which fix the beams in the same direction between pilots. In our approach, the change of direction is configured using the estimate of variation rate via two different methods; a Continuous-Discrete Kalman filter and an MMSE of a first-order approximation of the variation. Our method incurs no additional overhead in pilots, yet, the performance of beam tracking and the resulting effective SNR are improved significantly. In addition, we propose a low-complexity discrete beam tracking algorithm that only requires a single pilot symbol with an angle of arrival (AoA) that lies in the main lobe of the beamforming. In typical situations, we achieve up to 4 dB enhancement in SNR and can reach 7 dB for large array sizes. This gain is associated with our algorithm's average Mean Squared Error (MSE) reduction by up to 99.5%. Furthermore, we introduce an analytical method of choosing the Pilot Period to sustain reliable tracking for a desirable Link Reestablishment Time based on two definitions: (1) beam coherence and (2) outage probability. The numerical results reveal that the Continuous-Discrete algorithms reduce the pilot overhead by 60% and up to 87% while supporting 95% of the maximum achievable rate. In the second part of the thesis, we present a novel beam direction discovery approach that utilizes beam pattern amplitudes and combines it with the phase information available for a quick estimate of the beam direction. The proposed approach surpasses the traditional approaches, which exhaustively search all possible directions or follow hierarchical beam-sweeping architecture by dividing the angular space into sectors. Our approach minimizes the signaling overhead by estimating the beam direction in a single measurement in most instances instead of a number of measurements proportional to the array size as in traditional beam discovery approaches. Numerical results reveal a significant reduction of the pilot overhead by 42% and up to 62% compared to the state-of-the-art.
C. Emre Koksal (Advisor)
Eylem Ekici (Committee Member)
Abhishek Gupta (Committee Member)
123 p.
Computer Science; Electrical Engineering; Information Science
Beam Discovery; Beam Tracking; Millimeter-Wave; Measurement Lower Bound; Probability of Detection; MIMO; Outage Capacity; Beam Coherence Time; Large-Scale Arrays; Pilot Period

Recommended Citations

Citations

  • Abdelrazek, M. N. H. (2022). Beam Discovery and Tracking for Mobile MIMO [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1669934800384059

    APA Style (7th edition)

  • Abdelrazek, Mohamed. Beam Discovery and Tracking for Mobile MIMO. 2022. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1669934800384059.

    MLA Style (8th edition)

  • Abdelrazek, Mohamed. "Beam Discovery and Tracking for Mobile MIMO." Doctoral dissertation, Ohio State University, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=osu1669934800384059

    Chicago Manual of Style (17th edition)

osu1669934800384059
100
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This open access ETD is published by The Ohio State University and OhioLINK.