Codebook-Based Beam Tracking for Conformal ArrayEnabled UAV MmWave Networks
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Abstract:
Millimeter wave (mmWave) communications can potentially meet the high data-rate requirements of unmanned aerial vehicle (UAV) networks. However, as the prerequisite of mmWave communications, the narrow directional beam tracking is very challenging because of the three-dimensional (3D) mobility and attitude variation of UAVs. Aiming to address the beam tracking difficulties, we propose to integrate the conformal array (CA) with the surface of each UAV, which enables the full spatial coverage and the agile beam tracking in highly dynamic UAV mmWave networks. More specifically, the key contributions of our work are three-fold. 1) A new mmWave beam tracking framework is established for the CA-enabled UAV mmWave network. 2) A specialized hierarchical codebook is constructed to drive the directional radiating element (DRE)-covered cylindrical conformal array (CCA), which contains both the angular beam pattern and the subarray pattern to fully utilize the potential of the CA. 3) A codebook-based multiuser beam tracking scheme is proposed, where the Gaussian process machine learning enabled UAV position/attitude predication is developed to improve the beam tracking efficiency in conjunction with the tracking-error aware adaptive beamwidth control. Simulation results validate the effectiveness of the proposed codebook-based beam tracking scheme in the CA-enabled UAV mmWave network, and demonstrate the advantages of CA over the conventional planner array in terms of spectrum efficiency and outage probability in the highly dynamic scenarios.Keywords:
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Beam tracking can be utilized to compensate for beam misalignment and avoid performance degradation in millimeter wave (mmWave) systems. In order to reduce the training overhead, attitude information obtained from motion sensors has been proposed to assist beam tracking. In this letter, we extend attitude information aided beam tracking to the practical systems with codebook-based beamforming. Moreover, estimation errors of attitude information are inevitable in practical systems, and lead to a trade-off in codebook design: wider beams suffer more from insufficient power; narrower beams are more sensitive to the error. Therefore, it is necessary to design a codebook with appropriate beamwidth. We first derive the optimal beamwidth that maximizes the average transmission rate based on the sectored beam model. Further, we consider the codebook with overlapping beams, which can prevent misalignment. Then, both the optimal beamwidth and overlap ratio are derived. Finally, simulation results validate the performance of the proposed methods.
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Radiation characteristics of an artificial dielectric antenna excited by a line source are described. Analytical expressions for the half power beamwidth are obtained for odd and even modes. Results for beamwidth calculated from these expressions are in good agreement with the values of beamwidth obtained from the radiation pattern.
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Fan-beam antenna
Line (geometry)
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This paper discusses the algorithms of codebook generation in SCHMM based speech recognition system and their fundamental principle. Introducing the basic discipline of Stochastic Relaxation- Division (SR-D) algorithm, it introduces the general idea into the authors' initial codebook generation algorithm. The experiment results show that the new method significantly improves the system performance. With the modified initial codebook, the model is further trained with the criterion of Maximum Likelihood(ML),which leads the codebook and other parameters more consistent and compatible.The effect of codebook size to final performance is also discussed and relative experiment results are presented.
Linde–Buzo–Gray algorithm
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The codebook design which determines the quality of the encoded images is an important problem in the vector quantisation technique. The Linde–Buzo–Gray (LBG) technique is a widely used algorithm in the codebook design. However, LBG algorithm is very sensitive to the initial codebook and tends to trap to the local minimum. In this study, a high‐quality initial codebook design method is proposed. The proposed method utilises both the mean characteristic value and variance characteristic value of training vectors to divide the training vectors into groups. Then codewords are selected from each group to generate an initial codebook. The experimental results demonstrate that the authors proposed method has a better performance in the initial codebook than that of the related methods.
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Abstract Sparse code multiple access (SCMA) is an emerging technology developed to meet the requirements of 5G and 6G communications and improve the spectral efficiency of systems. The key behind SCMA technology is the design of its codebook method, particularly the design of the mother codebook method, which forms the basis of excellent user codebook design. Considering the limitations of existing mother codebook methods, a constellation evolution mother codebook design method is proposed here. Odd and even constellations are derived using the proposed method, and a multi-dimensional rotation angle is established. Then, the excellent mother constellations (mother codebook) are reconstructed. The proposed mother codebook design method demonstrates excellent performance in terms of the bit error rate and is found to be superior to existing codebook methods. It can provide a universal mother codebook for user codebooks, thus yielding excellent codebooks for efficient SCMA applications and establishing a technical basis for efficient 5G and 6G applications.
Linde–Buzo–Gray algorithm
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The design of focused transducers used to narrow the beamwidth over a finite distance in the nearfield region is outlined. A computer program was used to optimize the transducer's geometrical shape for beamwidth improvement, and off-axis computations for plane and focused transducers were programmed to check the improvement in beamwidth so obtained. The results of these computations show that a simple parameter can be used to describe and compare the degree of focusing of such transducers.
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Linde–Buzo–Gray algorithm
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A general and accurate formula for evaluating the single-sided beamwidth in one-dimensional unidirectional leaky-wave antennas has been recently proposed. The half-power beamwidth is then estimated by simply doubling the value of the single-sided beamwidth. However, this approximation may lead to inaccurate results as the beam approaches endfire; at that point, the left- and the right-sided beamwidth may considerably differ one another. This conference paper proposes and numerically validates a more general formula to solve this issue.
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Visual codebook has been popular in object classification as well as action analysis. However, its performance is often sensitive to the codebook size that is usually predefined. Moreover, the codebook generated by unsupervised methods, e.g., K-means, often suffers from the problem of ambiguity and weak efficiency. In other words, the visual codebook contains a lot of noisy and/or ambiguous words. In this paper, we propose a novel method to address these issues by constructing a compact but effective visual codebook using sparse reconstruction. Given a large codebook generated by K-means, we reformulate it in a sparse manner, and learn the weight of each word in the original visual codebook. Since the weights are sparse, they naturally introduce a new compact codebook. We apply this compact codebook to action recognition tasks and verify it on the widely used Weizmann action database. The experimental results show clearly the benefits of the proposed solution.
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In this paper, a general formula for the half-power beamwidth of one-dimensional leaky-wave antennas (1-D LWAs) is presented. With respect to previous beamwidth formulas found in the literature, the new formula allows for both arbitrary propagation wavenumber and length of the antenna. The pointing angle of the beam is allowed to be arbitrary, and may be near broadside or endfire, or any angle in between. The beamwidth is also allowed to be arbitrary, though a simpler approximate expression is obtained under the assumption of a narrow beam. Numerical results confirm the accuracy of the new beamwidth formula. Furthermore, it is shown that the previous existing formulas are approximate limiting cases of this more general result. This new formula will provide a very useful tool for obtaining more reliable results for the beamwidth of any type of 1-D LWA.
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