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Robust beamforming design for ultra-dense user-centric C-RAN in the face of realistic pilot contamination and limited feedback

Robust beamforming design for ultra-dense user-centric C-RAN in the face of realistic pilot contamination and limited feedback
Robust beamforming design for ultra-dense user-centric C-RAN in the face of realistic pilot contamination and limited feedback
The ultra-dense cloud radio access network (UD-CRAN), in which remote radio heads (RRHs) are densely deployed in the network, is considered. To reduce the channel estimation overhead, we focus on the design of robust transmit beamforming for user-centric frequency division duplex (FDD) UD-CRANs, where only limited channel state information (CSI) is available. Specifically, we conceive a complete procedure for acquiring the CSI that includes two key steps: channel estimation and channel quantization. The phase ambiguity (PA) is also quantized for coherent cooperative transmission. Based on the imperfect CSI, we aim for optimizing the beamforming vectors in order to minimize the total transmit power subject to users’ rate requirements and fronthaul capacity constraints. We derive the closed- form expression of the achievable data rate by exploiting the statistical properties of multiple uncertain terms. Then, we propose a low-complexity iterative algorithm for solving this problem based on the successive convex approximation technique. In each iteration, the Lagrange dual decomposition method is employed for obtaining the optimal beamforming vector. Furthermore, a pair of low-complexity user selection algorithms are provided to guarantee the feasibility of the problem. Simulation results confirm the accuracy of our robust algorithm in terms of meeting the rate requirements. Finally, our simulation results verify that using a single bit for quantizing the PA is capable of achieving good performance.
1536-1276
Pan, Cunhua
9ee3d968-c5c2-42ba-8041-d54667205d5b
Ren, Hong
70f95b41-d967-4036-948d-6a58b8fcd27f
Elkashlan, Maged
27c756ff-bfd3-4844-8769-ace5ad28c840
Nallanathan, Arumugam
8accfa88-3b13-4cda-b080-0d247c6058e9
Hanzo, Lajos
66e7266f-3066-4fc0-8391-e000acce71a1
Pan, Cunhua
9ee3d968-c5c2-42ba-8041-d54667205d5b
Ren, Hong
70f95b41-d967-4036-948d-6a58b8fcd27f
Elkashlan, Maged
27c756ff-bfd3-4844-8769-ace5ad28c840
Nallanathan, Arumugam
8accfa88-3b13-4cda-b080-0d247c6058e9
Hanzo, Lajos
66e7266f-3066-4fc0-8391-e000acce71a1

Pan, Cunhua, Ren, Hong, Elkashlan, Maged, Nallanathan, Arumugam and Hanzo, Lajos (2018) Robust beamforming design for ultra-dense user-centric C-RAN in the face of realistic pilot contamination and limited feedback. IEEE Transactions on Wireless Communications. (doi:10.1109/TWC.2018.2882442).

Record type: Article

Abstract

The ultra-dense cloud radio access network (UD-CRAN), in which remote radio heads (RRHs) are densely deployed in the network, is considered. To reduce the channel estimation overhead, we focus on the design of robust transmit beamforming for user-centric frequency division duplex (FDD) UD-CRANs, where only limited channel state information (CSI) is available. Specifically, we conceive a complete procedure for acquiring the CSI that includes two key steps: channel estimation and channel quantization. The phase ambiguity (PA) is also quantized for coherent cooperative transmission. Based on the imperfect CSI, we aim for optimizing the beamforming vectors in order to minimize the total transmit power subject to users’ rate requirements and fronthaul capacity constraints. We derive the closed- form expression of the achievable data rate by exploiting the statistical properties of multiple uncertain terms. Then, we propose a low-complexity iterative algorithm for solving this problem based on the successive convex approximation technique. In each iteration, the Lagrange dual decomposition method is employed for obtaining the optimal beamforming vector. Furthermore, a pair of low-complexity user selection algorithms are provided to guarantee the feasibility of the problem. Simulation results confirm the accuracy of our robust algorithm in terms of meeting the rate requirements. Finally, our simulation results verify that using a single bit for quantizing the PA is capable of achieving good performance.

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Accepted/In Press date: 16 November 2018
e-pub ahead of print date: 17 December 2018

Identifiers

Local EPrints ID: 426234
URI: http://eprints.soton.ac.uk/id/eprint/426234
ISSN: 1536-1276
PURE UUID: ac19fd74-d27e-4eaf-9067-70e555ec16a2
ORCID for Lajos Hanzo: ORCID iD orcid.org/0000-0002-2636-5214

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Date deposited: 20 Nov 2018 17:30
Last modified: 18 Mar 2024 02:36

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Contributors

Author: Cunhua Pan
Author: Hong Ren
Author: Maged Elkashlan
Author: Arumugam Nallanathan
Author: Lajos Hanzo ORCID iD

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