Defining the standards for 5G transport

14 February 2019 | Natalie Bannerman

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With the imminent advent of 5G, networks will need wireless for backhaul as well as fibre. Nader Zein of ETSI tells Natalie Bannerman how wireless backhaul fits into the wider 5G picture

It seems obvious, doesn’t it? Increasingly connect mobile networks wirelessly and in the process improve performance and latency. Despite how simple it seems on the surface, a vast amount of research, planning and developing has to go into deploying such innovations in transport networks for 5G mobile services. 

Nader Zein is at the forefront of 5G developments at the European Telecommunications Standards Institute (ETSI). He is also chief engineer at NEC, but at ETSI he’s vice chair of the Millimetre Wave Transmission Industry Specification Group (mWT ISG). He talks me through the significance of wireless backhaul, “xhaul” in the 5G era – and how the industry at large is preparing for this new technology.

Mobile is accelerating rapidly towards 5G deployment. The aim is to develop new business opportunities related to enhanced mobile broadband, ultra-reliable and low latency communications and massive machine-type communications. New radio access network (RAN) architecture, aimed at delivering higher network efficiency and improved service delivery, also come within the scope of 5G. It is expected that 5G deployments will require increased network density, mainly via small cells.

The mWT ISG recently published a report, called GR mWT 012, which highlights the critical role of regulation, licensing and technologies to ease 5G wireless backhaul/xhaul deployments and addresses prominent 5G backhaul/xhaul scenarios.

According to the report, 5G will deliver higher capacity, lower latency, improved spectral efficiency, highly accurate synchronisation, advanced networking functionalities and network automation.

“Therefore in the medium to long-term, namely from 2020 and beyond, wireless backhaul applications will become even more relevant,” says Zein. The group also discussed innovations in microwave and millimetre wave (mm-wave) technologies, as well as regulation and licensing, he notes.

Key recommendations include the availability of more backhaul spectrum and bandwidth, plus band and carrier aggregation, as well as many other technological developments for 5G. From a regulatory standpoint, proposals included applying regulatory policies and costs in line with the requirements of likely 5G use cases.

Zein explains: “The report shows that microwave and millimetre wave transmission technologies are going to continue to play a pivotal role in the 5G era – as they will be fundamental pillars of service providers’ network development strategy to address the future 5G demands.”

ETSI is working on specifications for bands above 90GHz. In addition tech with integrated antennas – like those used for phased arrays and flat antennas – need the introduction of new radio requirements, another element ETSI is currently studying.

“New mm-wave technology, below and above 100GHz, coupled with the traditional microwave radios are vital for providing the increased capacity and reduced latency for the new 5G services,” says Zein.
ETSI isn’t the only standards organisation developing mm-wave requirements. The European Conference of Postal and Telecommunications Administrations has published its recommendations on the new bands, including the W-band around 100GHz and the D-band around 150GHz.

At the start of the year, Ericsson and Deutsche Telekom collaborated to demonstrate an mm-wave link with transmission speeds of 40Gbps – the first physical implementation of mWT ISG work that is a step towards future 100Gbps speeds beyond the existing 10Gbps.

The flexibility of 5G has led to increased interest in the functional split and virtualisation of the RAN – cloud RAN (C-RAN). This has introduced new types of interfaces and transport besides traditional backhaul – with the invention of terms such as “midhaul” and “fronthaul”, aka xhaul.

The idea is that wireless transport enables greater flexibility, in particular for sites where fibre is not readily available. Depending on the functional split in the RAN and the mix of services being delivered, various capacity and latency requirements are necessary and new transport architecture is needed.

“Many of us are discussing how to relax transport demands, in terms of capacity and latency, when compared to typical fronthaul like common public radio interface, while still managing performance and optimum use of radio access resources,” says Zein.

When it comes to transport for xhaul, Zein says that standards are needed for mapping of control and user planes into Ethernet frames for transportation. A number of standards organisations are already exploring this. One interesting claim from the ETSI report is that the current microwave and millimetre wave transmission technologies satisfy the 5G early-stage requirements and that the wireless xhaul technologies will address the 5G mature-stage requirements that will appear later.

Zein details early-stage 5G requirements as needing 5Gbps of tail-link capacity in urban and dense urban areas. Suburban and semi-rural areas will need approximately 3Gbps of tail-link capacity and rural areas will need 2Gbps.

By the time we get to the mature stage of 5G, urban and dense urban areas will need 5-10 Gbps; suburban and semi-rural areas will need 5Gbps while rural areas will need 3Gbps.

AI and IoT technologies

Zein sees xhaul as an enabler of internet of things (IoT) technology, “especially in IoT verticals where a high density of devices is installed”, he says.
Xhaul enables efficient and centralised management for dense clusters of devices, such as in factories. “C-RAN deployment, which uses xhaul transport for its realisation, is crucial for small cell and dense deployment of IoT devices and networks,” adds Zein.

The adoption of artificial intelligence (AI) into telecoms network management is emerging, especially with software-defined networking (SDN). It is used at the higher layers of the network where network nodes and large amounts of data traffic are generated and transported.

Zein predicts the biggest drivers of data in the 5G era will be gaming, social media, augmented reality and vertical services, which will occupy their own domains such as automotive and private networks.

“5G networks and systems are becoming hugely complex to manage in conventional network management systems – and it is becoming crucial that AI technology is used for efficient and reliable operation and delivery of diverse services,” adds Zein.