Browsing by Author "Liang, Di-Chun"

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A Generalized Analytical Framework for Coverage Evaluation in mmWave Heterogeneous Cellular Networks in Urban Areas
(2017-01-01)
Liu, Chun-Hung
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Liang, Di-Chun
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Yang, Jie-Ru
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Chen, Jie
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電機工程學系
In this paper, we introduce a generalized analytical framework to evaluate the coverage probability in an mmWave heterogeneous cellular network (HetNet) consisting of UHF macrocell base stations (BSs) and mmWave small cell BSs deployed in an urban area. A generalized user association scheme that can cover a few user association schemes is formulated and applied in the mmWave HetNet. Two important statistical properties of the associated BS under this scheme are derived for the general line-of-sight and non line-of-sight pathloss channel models and they can be largely simplified if the power-law channel model is applied. Using the two statistical properties, the coverage probability of a downlink multiple-input-single-output channel is found in a compact form, which reveals that the coverage probability in the mmWave HetNet can be significantly improved if compared with the cellular network consisting of a single tier of mmWave small cell BSs. Numerical results not only validate the correctness of the coverage probability derived but also indicate that the mmWave HetNet has the potential to achieve a high coverage probability in an urban area.
Coverage Analysis for Dense Heterogeneous Networks with Cooperative NOMA
(2017-01-01)
Liu, Chun-Hung
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Liang, Di-Chun
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Chen, Po-Chia
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Yang, Jie-Ru
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電機工程學系
In a heterogeneous cellular network (HetNet) consisting of M tiers of densely-deployed base stations (BSs), consider that each of the BSs in the HetNet that are associated with multiple users is able to simultaneously schedule and serve two users in a downlink time slot by performing the (power-domain) non-orthogonal multiple access (NOMA) scheme. This paper aims at the preliminary study on the downlink coverage performance of the HetNet with the non-cooperative and the proposed cooperative NOMA schemes. First, we study the coverage probability of the NOMA users for the non-cooperative NOMA scheme in which no BSs are coordinated to jointly transmit the NOMA signals for a particular cell and the coverage probabilities of the two NOMA users of the BSs in each tier are derived. We show that the coverage probabilities can be largely reduced if allocated transmit powers for the NOMA users are not satisfied with some constraints. Next, we study and derive the coverage probabilities for the proposed cooperative NOMA scheme in which the void BSs that are not tagged by any users are coordinated to enhance the far NOMA user in a particular cell. Our analyses show that cooperative NOMA can significantly improve the coverage of all NOMA users as long as the transmit powers for the NOMA users are properly allocated.
Heterogeneous Networks With Power-Domain NOMA: Coverage, Throughput, and Power Allocation Analysis
(2018-05-01)
Liu, Chun-Hung
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Liang, Di-Chun
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電信工程研究所
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Institute of Communications Engineering
In a heterogeneous cellular network (HetNet), consider that a base station in the HetNet is able to simultaneously schedule and serve K users in the downlink by performing the power-domain non-orthogonal multiple access (NOMA) scheme. This paper aims at the preliminary study on the downlink coverage and throughput performances of the HetNet with the non-coordinated NOMA and the proposed coordinated joint transmission NOMA (JT-NOMA) schemes. First, the coverage probability and link throughput of K users in each cell are studied and their accurate expressions are derived for the non-coordinated NOMA scheme in which no BSs are coordinated to jointly transmit the NOMA signals for a particular user. We show that the coverage and link throughput can be largely reduced if transmit power allocations among the K users do not satisfy the constraint derived. Next, we analyze the coverage and link throughput of K users for the coordinated JT-NOMA scheme in which the void BSs without users are coordinated to enhance the farthest NOMA user in a cell. The derived accurate results show that coordinated JT-NOMA can significantly improve the coverage and link throughput of all users. Finally, we show that there exist optimal power allocation schemes that maximize the average cell coverage and throughput under some derived power allocation constraints and numerical results validate our analytical findings.
Towards Accurate Throughput Analysis for Dense Heterogeneous Networks with Cooperative NOMA
(2017-01-01)
Liu, Chun-Hung
;
Liang, Di-Chun
;
電機工程學系
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Department of Electrical and Computer Engineering
In a heterogeneous cellular network (HetNet) consisting of M tiers of densely-deployed base stations (BSs), we consider that each BS in the HetNet associated with multiple users is able to simultaneously schedule and serve at most K users in a downlink time slot by performing the (power-domain) non-orthogonal multiple access (NOMA) scheme. This paper aims to provide accurate analyses for the link throughput of a (NOMA) user for the non-cooperative and the proposed cooperative NOMA schemes. The link throughput of the users is first studied for the non-cooperative NOMA scheme in which no BSs are coordinated to jointly transmit the NOMA signals for a particular BS and its tight and accurate lower bound is derived. We show that the link throughput performance can be largely degraded if allocated transmit powers for the users are not satisfied with certain constraints. To improve the link throughput of the users, we propose a cooperative NOMA scheme in which the void BSs that are not tagged by any users are coordinated to enhance the farthest user in a particular cell. The accurate approximated expression of the link throughput of a user is found for this cooperative NOMA scheme. We show that cooperative NOMA is able to significantly improve the link throughput of all users as long as the transmit powers are appropriately allocated among the users.