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China Telecom deploys 5G-oriented C-RAN fronthaul network

Liaoning

© Flickr/cc-licence/Yoann Gauthier

  • Huawei’s Blade OTN solution deployed by China Telecom in Liaoning
  • Will improve LTE coverage and prepare for denser 5G cell requirements
  • Solution supports 15 channels of CPRI access
  • But is CPRI suitable for 5G C-RAN? How about PLS or ARoF?

China Telecom is building a 5G-oriented cloud radio access network (C-RAN) fronthaul network in the north-east Liaoning province, using Huawei’s Blade optical transport network (OTN) solution. The telco says this fronthaul network will enable Liaoning Telecom to effectively cope with the denser site deployment requirements of 5G, as well as further improving the existing LTE network coverage.

The deployment of small cells is now widely regarded as one of the key deployment architectures of 5G network, but this will add a significant load to current transport networks. Hence the need to evolve these transport networks alongside the evolution of the radio access network (RAN). This is where the concept of the centralised (or cloud, the two terms are currently interchangeable) Ran, or C-RAN, comes into play.

Liaoning Telecom has been gradually adopting C-RAN architecture to cope with difficulties in site acquisition and energy consumption. However, because C-RAN network architecture consumes a large amount of fibre resources at the access layer, there is a danger of a shortage of fibre resources when 5G deployments ramp up due to the requirement of denser site deployment. Liaoning Telecom has therefore investigated new solutions that will allow it to conserve fibre resources and quickly improve wireless network coverage.

Huawei says its Blade OTN solution – which is part of its broader and more comprehensive X-Haul architecture – is fronthaul-oriented and can effectively meet Liaoning Telecom's network deployment requirements. Blade OTN uses Huawei's Turbo WDM Technology to achieve 100G bandwidth using 10G optical components. It supports a maximum of 15 channels of CPRI (Common Public Radio Interface) access and implements aggregation of multiple service channels. Huawei believes that the resulting lower total cost of ownership will enable Liaoning Telecom to reduce core fibre requirements by over 90 per cent.

Huawei adds that its solution eliminates wavelength planning, automatically provisions services upon power-on, and remotely locates faults, meeting the rapid network deployment and automatic O&M requirements of C-RAN fronthaul networks. In addition, cascading should ensure a smooth network evolution towards 5G fronthaul networks. Expect to hear more about Huawei’s X-Haul strategy next month when the vendor hosts the Ultra-Broadband Forum in Hangzhou.

Cutting edge or bleeding edge?

C-RAN architectures are optimised for the small cell deployment model, but there are still issues regarding QoS, reliability and cost effectiveness for end-to-end networks. One of the major issues at the moment surrounds the fronthaul, and which technology is best suited. The traditional approach is to use CPRI (common public radio interface) and optical fibre-based transport – fibre is necessary because of the very high data rate requirements of CPRI. There are future alternatives, foremost being mmWave radio to provide a low cost and flexible alternative to fibre links.

But questions remain about CPRI’s suitability for 5G, as it uses data even when there is no traffic and also increases as the number of antennas increases (think Massive MIMO and you can start to see the problem).

There are alternatives to CPRI. The main ones are PLS (Physical Layer Split) and ARoF (Analogue Radio over Fibre), both of which may prove more cost-effective in the long-run. TelecomTV’s homework suggestion for this weekend is to read this recent presentation from the University of Melbourne on 5G C-RAN architectures and the accompanying research paper. Happy reading!

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