Massive Grant-Free OFDMA With Timing and Frequency Offsets

Sun, Gangle; Li, Yining; Yi, Xinping; Wang, Wenjin; Gao, Xiqi; Wang, Lei; Wei, Fan; Chen, Yan

doi:10.1109/twc.2021.3121066

Cited by 13 publications

(12 citation statements)

References 40 publications

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“…• Time and frequency synchronization among RUs and UEs: In GF-NOMA, the carrier frequency offset (CFO) and the timing offset cause performance degradation [52]. In addition, precise time and frequency synchronization are necessary for robust CoMP [49].…”

Section: Discussionmentioning

confidence: 99%

“…In addition, precise time and frequency synchronization are necessary for robust CoMP [49]. These synchronization issues have already been reported in the literature [52,53] but have not been fully addressed. • Efficient resource allocation for different requests: The proposed flexible RAN has to accommodate a massive number of completely different types of user requirements, such that highly efficient resource allocation is essential.…”

Section: Discussionmentioning

confidence: 99%

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User-Centric Design of Millimeter Wave Communications for Beyond 5G and 6G

Ishibashi

Hara

Uchimura

et al. 2022

IEICE Trans. Commun.

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In this paper, we propose new radio access network (RAN) architecture for reliable millimeter-wave (mmWave) communications, which has the flexibility to meet users' diverse and fluctuating requirements in terms of communication quality. This architecture is composed of multiple radio units (RUs) connected to a common distributed unit (DU) via fronthaul links to virtually enlarge its coverage. We further present grant-free non-orthogonal multiple access (GF-NOMA) for lowlatency uplink communications with a massive number of users and robust coordinated multi-point (CoMP) transmission using blockage prediction for uplink/downlink communications with a high data rate and a guaranteed minimum data rate as the technical pillars of the proposed RAN. The numerical results indicate that our proposed architecture can meet completely different user requirements and realize a user-centric design of the RAN for beyond 5G/6G.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

User-Centric Design of Millimeter Wave Communications for Beyond 5G and 6G

Ishibashi

Hara

Uchimura

et al. 2022

IEICE Trans. Commun.

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“…For the frequency asynchronous case, [23] deals with joint device activity detection and channel estimation using norm approximation, and [24] and [25] handle device activity detection using MLE-based methods. For the time and frequency asynchronous case, [26] investigates joint device activity detection and channel estimation for an orthogonal frequency division multiplexing (OFDM) system using an AMP-based method. The optimization problems in [21]- [25] are solved using the majorizationminimization method [23], CD method [24], and block coordinate descent (BCD) method [21], [22], [25].…”

Section: Introductionmentioning

confidence: 99%

“…The optimization problems in [21]- [25] are solved using the majorizationminimization method [23], CD method [24], and block coordinate descent (BCD) method [21], [22], [25]. Notice that most existing works [21], [23], [24], [26] incur much higher computational June 13, 2023 DRAFT complexities than those for the synchronous case, especially at a large range of offset values. To address this issue, our early work [25] proposes a low-complexity algorithm to solve the MLE problem for the frequency asynchronous case under Raleigh fading using the BCD method and fast Fourier transform (FFT).…”

Section: Introductionmentioning

confidence: 99%

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MLE-based Device Activity Detection for Grant-free Massive Access under Rician Fading

Liu

Cui

Yang

et al. 2022

2022 IEEE 23rd International Workshop on Signal Processing Advances in Wireless Communication (SPAWC)

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Most existing studies on massive grant-free access, proposed to support massive machine-type communications (mMTC) for the Internet of things (IoT), assume Rayleigh fading and perfect synchronization for simplicity. However, in practice, line-of-sight (LoS) components generally exist, and time and frequency synchronization are usually imperfect. This paper systematically investigates maximum likelihood estimation (MLE)-based device activity detection under Rician fading for massive grant-free access with perfect and imperfect synchronization. Specifically, we formulate device activity detection in the synchronous case and joint device activity and offset detection in three asynchronous cases (i.e., time, frequency, and time and frequency asynchronous cases) as MLE problems. In the synchronous case, we propose an iterative algorithm to obtain a stationary point of the MLE problem. In each asynchronous case, we propose two iterative algorithms with identical detection performance but different computational complexities. In particular, one is computationally efficient for small ranges of offsets, whereas the other one, relying on fast Fourier transform (FFT) and inverse FFT, is computationally efficient for large ranges of offsets. The proposed algorithms generalize the existing MLE-based methods for Rayleigh fading and perfect synchronization. Numerical results show the notable gains of the proposed algorithms over existing methods in detection accuracy and computation time.

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Hybrid Beamforming for Ergodic Rate Maximization of mmWave Massive Grant-Free Systems

Sun

Wang

et al. 2022

GLOBECOM 2022 - 2022 IEEE Global Communications Conference

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Massive Grant-Free OFDMA With Timing and Frequency Offsets

Cited by 13 publications

References 40 publications

User-Centric Design of Millimeter Wave Communications for Beyond 5G and 6G

User-Centric Design of Millimeter Wave Communications for Beyond 5G and 6G

MLE-based Device Activity Detection for Grant-free Massive Access under Rician Fading

Hybrid Beamforming for Ergodic Rate Maximization of mmWave Massive Grant-Free Systems

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