Hyperparameter-Free Receiver for Grant-Free NOMA Systems With MIMO-OFDM

Hara, Takanori; Iimori, Hiroki; Ishibashi, Koji

doi:10.1109/lwc.2020.3045159

Cited by 14 publications

(6 citation statements)

References 16 publications

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“…As described in [25], this granting procedure results in a latency of around 9.5 millisecond (ms), which hinders meeting the strict latency requirements of some IoT use cases [26]. Hence, grant-free access techniques such as 𝐾-repetition [27], variants of diversity slotted ALOHA [28][29][30] and code-domain GF-NOMA [25,[31][32][33][34] have been actively investigated to meet these low-latency re-quirements. Code-domain GF-NOMA can allow more users to transmit simultaneously without the BS's granting pro-cess and can theoretically achieve the most powerefficient communications [35].…”

Section: Grant-free Noma For Low-latency Massive Accessmentioning

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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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: Grant-free Noma For Low-latency Massive Accessmentioning

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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“…, (12) where p X (x n ; λ, β t ) is the prior distribution of x n given by p X (xn ; λ, β t ) = (1 − λ)δ 0 (xn ) + λCN(xn ; 0 M , β t,n I M ). ( 13)…”

Section: B Em-mmv-amp Algorithmmentioning

confidence: 99%

“…Moreover, a covariance-based approach was proposed in [11], [12], which reformulates AUD into a maximum likelihood estimation problem including a sample covariance matrix and solves it using the coordinate descent (CD) method. Although this approach can achieve superior performance without prior knowledge of the channels, its computational complexity grows quadratically with the pilot sequence length, inducing a prohibitive one in massive grant-free (GF) access.…”

Section: Introductionmentioning

confidence: 99%

Blind Multiple Measurement Vector AMP Based on Expectation Maximization for Grant-Free NOMA

Hara

Ishibashi

2022

IEEE Wireless Commun. Lett.

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We consider a new approach to perform active user detection and channel estimation in massive grant-free access without requiring prior knowledge of the wireless channels, such as information on large-scale fading coefficients. To this end, we propose a multiple measurement vector approximate message passing (MMV-AMP) with expectation-maximization (EM)-based hyperparameter update, i.e., EM-MMV-AMP. Moreover, we revisited the decision rule for active user detection for EM-MMV-AMP. The numerical results indicate that the performance of the proposed scheme is superior to those of conventional schemes.

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“…It hence is an attractive choice for 4G-LTE and 5G-NR [25]. Very recently, [26] and the early version of this work present OFDM-based grant-free access schemes for a wideband system under frequency-selective fading and propose ML estimation-based device activity detection methods for a single-cell network.…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, the authors in [26] ignore the relationship among multiple paths for each device for tractability and solve the maximization of an upper bound of the log-likelihood function under a specific frequency-selective fading model. On the contrary, in [1], we precisely characterize the relationship among multiple channel taps for each device and maximize the exact log-likelihood function under frequency-selective Rayleigh fading.…”

Section: Introductionmentioning

confidence: 99%

Statistical Device Activity Detection for OFDM-based Massive Grant-Free Access

Jia¹,

Cui²,

Jiang³

2021

Preprint

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Existing works on grant-free access, proposed to support massive machine-type communication (mMTC) for the Internet of things (IoT), mainly concentrate on narrow band systems under flat fading. However, little is known about massive grant-free access for wideband systems under frequency-selective fading. This paper investigates massive grant-free access in a wideband system under frequency-selective fading. First, we present an orthogonal frequency division multiplexing (OFDM)-based massive grantfree access scheme. Then, we propose two different but equivalent models for the received pilot signal, which are essential for designing various device activity detection and channel estimation methods for OFDM-based massive grant-free access. One directly models the received signal for actual devices, whereas the other can be interpreted as a signal model for virtual devices. Next, we investigate statistical device activity detection under frequency-selective Rayleigh fading based on the two signal models.We first model device activities as unknown deterministic quantities and propose three maximum likelihood (ML) estimation-based device activity detection methods with different detection accuracies and computation times. We also model device activities as random variables with a known joint distribution and propose three maximum a posterior probability (MAP) estimation-based device activity methods, which further enhance the accuracies of the corresponding ML estimation-based methods.Optimization techniques and matrix analysis are applied in designing and analyzing these methods.Finally, numerical results show that the proposed statistical device activity detection methods outperform existing state-of-the-art device activity detection methods under frequency-selective Rayleigh fading.

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Hyperparameter-Free Receiver for Grant-Free NOMA Systems With MIMO-OFDM

Cited by 14 publications

References 16 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

Blind Multiple Measurement Vector AMP Based on Expectation Maximization for Grant-Free NOMA

Statistical Device Activity Detection for OFDM-based Massive Grant-Free Access

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