| 1. |
- Li, Huafu, et al.
(författare)
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Air-to-Ground Channel Modeling and Performance Analysis for Cellular-Connected UAV Swarm
- 2023
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Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 27:8, s. 2172-2176
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we investigate the air-to-ground (A2G) channel model and transmission performance for a cellular-connected massive multiple-input multiple-output unmanned aerial vehicle (UAV) swarm system. First, we propose a spatially and temporally correlated A2G channel model that focuses on non-isotropic scattering, line-of-sight (LoS) propagation, and moving scatterers. Second, we derive a novel closed-form signal-to-interference-and-noise ratio expression for uplink transmission, taking into account the effect of channel aging with strong LoS. The results show that the frame length, pilot overhead, and UAV swarm scale can be pre-designed in a fine-grained manner depending on the propagation environment and transmission task. For example, for a low-speed scenario, a long frame can be configured due to the negligible channel aging effect. Moreover, more pilots may mitigate the damage of channel aging, but it is no better when a short frame is needed for transmission such as ultra-reliable and low-latency communications.
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| 2. |
- Li, Huafu, et al.
(författare)
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Impact of Channel Aging on Massive MIMO Vehicular Networks in Non-isotropic Scattering Scenarios
- 2021
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Ingår i: 2021 IEEE Global Communications Conference, GLOBECOM 2021 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- Massive multiple-input multiple-output (MIMO) relies on accurate channel estimation for precoding and receiving to achieve its claimed performance advantages. When serving vehicular users, the rapid channel aging effect greatly hinders its advantages, and a careful system design is required to ensure an efficient use of wireless resources. In this paper, we investigate this problem for the first time in a non-isotropic scattering scenario. The von Mises distribution is adopted for the angle of arrival (AoA), resulting in a tunable channel temporal correlation coefficient (TCC) model, which can adapt to different AoA spread conditions through the k parameter and incorporates the isotropic Jakes-Clarke model as a special case. The simulated results in a Manhattan grid-type multi-cell network clearly demonstrate the impact of channel aging on the uplink spectral efficiency (SE) performance and moreover, in order to maximize the area average SE, the size of the transmission block should be optimally selected according to some linear equations of k.
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| 3. |
- Li, Huafu, et al.
(författare)
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Performance Analysis and Transmission Block Size Optimization for Massive MIMO Vehicular Network with Spatially and Temporally Correlated Channels
- 2024
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Ingår i: IEEE Internet of Things Journal. - 2327-4662. ; 11:5, s. 8989-9003
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the effect of spatially and temporally correlated channels on the transmission performance of multi-cell multi-user massive multiple-input multiple-output (MIMO) vehicular networks in generic non-isotropic scattering environments. A new channel model is established to evaluate the harmfulness of the non-isotropic-scattered angle-of-departure/angle-of-arrival (AoD/AoA) spread and the high mobility of users on the uplink transmission. We derive the expressions of achievable spectral efficiency (SE), taking into account the effects of line-of-sight propagation, channel aging, and pilot contamination. Specifically, two novel receive combining schemes, namely the aging-aware maximum ratio combining and the aging-aware minimum mean square error combining, are presented to mitigate the SE decline caused by outdated channel state information. A low-complexity pilot assignment algorithm is proposed to suppress pilot contamination. We find that the quasi-static assumption of the channel may be unsafe for the system design of the vehicular networks even within a single transmission block period lasting from hundreds of microseconds to a few milliseconds. We observe that there exists an optimal block size Copt that maximizes area spectral efficiency. Especially, Copt can be expressed as a function of movement speed, AoD spread, and AoA spread. Numerical results are presented to validate the efficacy of the proposed schemes and highlight the importance of correct performance evaluation for practical massive MIMO system designs.
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