A Survey of the Functional Splits Proposed for 5G Mobile Crosshaul Networks

Pacing the way toward 5G has lead researchers and industry in the direction of centralized processing known from Cloud-Radio Access Networks (C-RAN). In C-RAN research, a variety of different functional splits is presented by different names and focusing on different directions. The functional split...

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Bibliographic Details
Published in:IEEE Communications surveys and tutorials 2019, Vol.21 (1), p.146-172
Main Authors: Larsen, Line M. P., Checko, Aleksandra, Christiansen, Henrik L.
Format: Article
Language:English
Subjects:
3GPP
Antennas
Bit rate
C-RAN
Computer architecture
crosshaul
fronthaul
Functional split
Functionals
industry
Long Term Evolution
network architecture
Physical layer
Protocols
Standardization
Wireless networks
X-haul
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Summary:Pacing the way toward 5G has lead researchers and industry in the direction of centralized processing known from Cloud-Radio Access Networks (C-RAN). In C-RAN research, a variety of different functional splits is presented by different names and focusing on different directions. The functional split determines how many base station functions to leave locally, close to the user, with the benefit of relaxing fronthaul network bitrate and delay requirements, and how many functions to centralize with the possibility of achieving greater processing benefits. This paper presents for the first time a comprehensive overview systematizing the different work directions for both research and industry, while providing a detailed description of each functional split option and an assessment of the advantages and disadvantages. This paper gives an overview of where the most effort has been directed in terms of functional splits, and where there is room for further studies. The standardization currently taking place is also considered and mapped into the research directions. It is investigated how the fronthaul network will be affected by the choice of functional split, both in terms of bitrates and latency, and as the different functional splits provide different advantages and disadvantages, the option of flexible functional splits is also looked into.
ISSN:1553-877X
1553-877X
2373-745X
DOI:10.1109/COMST.2018.2868805