Effect of Wideband Beam Squint on Codebook Design in Phased-Array Wireless Systems

Cai, Mingming; Gao, Kang; Nie, Ding; Hochwald, Bertrand M.; Laneman, J. Nicholas; Huang, Huang; Liu, Kunpeng

doi:10.1109/glocom.2016.7841766

Cited by 83 publications

(76 citation statements)

References 12 publications

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“…The algorithms in [29], [32] partly compensate for beam squint in analog phased arrays by increasing the codebook size in beamforming. Based on the massive MIMO-OFDM channel model considering the spatial-wideband effect, we have developed the fast Fourier transform-based channel estimation approach [23], which can address the beam squint issue in wideband communications but encounters error floors at high SNR regions.…”

Section: Introductionmentioning

confidence: 99%

Beam Squint and Channel Estimation for Wideband mmWave Massive MIMO-OFDM Systems

Wang

Jian

Gao

et al. 2019

IEEE Trans. Signal Process.

140

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With the increasing scale of antenna arrays in wideband millimeter-wave (mmWave) communications, the physical propagation delays of electromagnetic waves traveling across the whole array will become large and comparable to the time-domain sample period, which is known as the spatial-wideband effect. In this case, different subcarriers in an orthogonal frequency division multiplexing (OFDM) system will "see" distinct angles of arrival (AoAs) for the same path. This effect is known as beam squint, resulting from the spatial-wideband effect, and makes the approaches based on the conventional multipleinput multiple-output (MIMO) model, such as channel estimation and precoding, inapplicable. After discussing the relationship between beam squint and the spatial-wideband effect, we propose a channel estimation scheme for frequency-division duplex (FDD) mmWave massive MIMO-OFDM systems with hybrid analog/digital precoding, which takes the beam squint effect into consideration. A super-resolution compressed sensing approach is developed to extract the frequency-insensitive parameters of each uplink channel path, i.e., the AoA and the time delay, and the frequency-sensitive parameter, i.e., the complex channel gain. With the help of the reciprocity of these frequency-insensitive parameters in FDD systems, the downlink channel estimation can be greatly simplified, where only limited pilots are needed to obtain downlink complex gains and reconstruct downlink channels. Furthermore, the uplink and downlink 2 channel covariance matrices can be constructed from these frequency-insensitive channel parameters rather than through a long-term average, which enables the minimum mean-squared error (MMSE) channel estimation to further enhance performance. Numerical results demonstrate the superiority of the proposed scheme over the conventional methods under general system configurations in mmWave communications.

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Section: Introductionmentioning

confidence: 99%

Beam Squint and Channel Estimation for Wideband mmWave Massive MIMO-OFDM Systems

Wang

Jian

Gao

et al. 2019

IEEE Trans. Signal Process.

140

View full text Add to dashboard Cite

show abstract

“…In this section, we evaluate the performance of the proposed transmission scheme and consider the fine beam as the baseline [9]. Due to the symmetry of each beam pattern, we only show the performance of half the beam focus range θ 0 ∈ (0, 1).…”

Section: Numerical Resultsmentioning

confidence: 99%

“…However, such approaches have these defects, such as high implementation cost, large size, or excessive power consumption, which make them unattractive to mobile wireless communication. In [9], the authors have proposed a denser codebook design algorithm to compensate for beam squint. In addition, multiple noncontiguous band can be aggregated to increase the bandwidth, but at the same time, it introduces significant beam squint issues [10].…”

Section: Introductionmentioning

confidence: 99%

Space-Time Block Coding-Based Beamforming for Beam Squint Compensation

Liu

Qiao

2019

IEEE Wireless Commun. Lett.

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In this paper, the beam squint problem, which causes significant variations in radiated beam gain over frequencies in millimeter wave communication system, is investigated. A constant modulus beamformer design, which is formulated to maximize the expected average beam gain within the bandwidth with limited variation over frequencies within the bandwidth, is proposed. A semidefinite relaxation (SDR) method is developed to solve the optimization problem under the constant modulus constraints. Depending on the eigenvalues of the optimal solution, either direct beamforming or transmit diversity based beamforming is employed for data transmissions. Through numerical results, the proposed transmission scheme can compensate for beam squint effectively and improve system throughput. Overall, a transmission scheme for beam squint compensation in wideband wireless communication systems is provided. Index TermsMillimeter Wave, Beamforming, Space-time Block Coding, beam squint, Throughput.The authors are with the

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“…It observed that the AoA/AoD changes with the signal frequency, which is also called beam squint [31,32] as shown in Fig. 2.…”

Section: Wideband Mmwave Channel Modelmentioning

confidence: 92%

Rotman lens-based two-tier hybrid beamforming for wideband mmWave MIMO-OFDM system with beam squint

Liu

Zhu

2018

J Wireless Com Network

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In this paper, we study the hybrid beamforming for the wideband mmWave multiuser MIMO-OFDM system. We characterize the frequency-dependent beam angle problem, i.e., beam squint effect. Firstly, we extend the mmWave channel model from the Saleh-Valenzuela representation with the consideration of beam squint. Secondly, a two-tier hybrid beamforming is proposed to achieve the maximum spectral efficiency in wideband mmWave multiuser MIMO-OFDM system. In the first tier, the Rotman lens array is adopted as the analog precoder to provide true-time-delay (TTD) and reduce the beam squint impairment. Moreover, the first-tier baseband precoder is designed based on block diagonalization (BD) to cancel inter-user interference. We further consider the finite spatial resolution and power leakage problem of the lens array. The second-tier hybrid precoder is proposed to collect the leak power with the phase shifter array. The optimal second-tier hybrid precoder design is formulated as the matrix factorization problem, and the two-tier hybrid precoding algorithm is based on the alternative minimization. It is found that both the beam squint and frequency-selective effect should be considered in the wideband mmWave system. Simulation results show that the proposed two-tier hybrid precoder could reduce beam squint impairment and inter-user interference, and could approximate to the optimal full-digital precoder with much fewer RF chains.

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Effect of Wideband Beam Squint on Codebook Design in Phased-Array Wireless Systems

Cited by 83 publications

References 12 publications

Beam Squint and Channel Estimation for Wideband mmWave Massive MIMO-OFDM Systems

Beam Squint and Channel Estimation for Wideband mmWave Massive MIMO-OFDM Systems

Space-Time Block Coding-Based Beamforming for Beam Squint Compensation

Rotman lens-based two-tier hybrid beamforming for wideband mmWave MIMO-OFDM system with beam squint

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