5G backhaul will become the next growth point in the field of optical communications

According to industry insiders, 5G mobile services will not be officially launched until 2020, when 5G standards are established. Previous generations of mobile communications first brought data, then transmitted video to a voice-only platform. 5G will add support for traffic from the Internet of Things (IoT), greatly increasing the number of network terminals. Although 4G LTE can be seen as a substitute for wired broadband, 5G's powerful performance will be enough for some users to bypass Wi-Fi and use 5G services directly. Combined with new mobile IoT traffic, it will lead to a huge surge in mobile traffic.

This profound change in mobile service expectations with the rollout of 5G is bound to create new opportunities for optical networks. A new analysis published by CIR shows that 5G deployment will mean more fiber in mobile backhaul, especially PONs.

All of this leads to fiber being the best solution to the data rate and latency issues posed by 5G deployments, while also downplaying the fact that optical networks are typically the most expensive backhaul solution.

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More fiber optic investment

Overall investments in mobile backhaul are unlikely to increase over the next decade. However, CIR estimates that nearly 60% of global investments in mobile backhaul transport equipment will shift to optical links by 2022, compared to less than 50% in 2017.

(FSO stands for free space optical communication; mmWave stands for millimeter wave)

Given that the latest version of 4G LTE phones have an upload rate of 300 Mbps, 5G terminals will need to provide upload speeds of 10 Gbps. Similarly, 4G LTE can achieve 45 milliseconds of latency, while 5G latency is 1 millisecond. Not all 5G applications require this level of performance, but those 5G-specific advanced services such as self-driving cars, augmented reality and virtual reality will require 1 millisecond or lower latency.

In view of this, 5G backhaul is bound to bring new benefits to the optical network business in the next decade. CIR analysis shows that by 2026, the annual investment in 5G backhaul fiber infrastructure will reach 1.5 billion US dollars. Millimeter wave (mmWave) will also play an important role in providing impressive latency and significantly reduced costs. 80GHz millimeter wave provides extremely low latency and a data rate of 10Gbps, but the transmission distance is only 3 kilometers.

5G backhaul becomes a new development direction of PONs

Even with the technical advantages, expensive fiber remains an option, even though its installation costs can be cut by micro-tunneling. Passive optical networks (PONs) offer a more strategic solution to reduce costs and reduce the costs associated with fiber. Use cases in 5G backhaul Because PONs share fiber and use only passive components, they can meet the latency, data rate, and distance requirements of 5G with little cost difference to other non-fiber transmission technologies.

Currently, the most suitable PON technology for 5G backhaul is NG-PON2. NG-PON2 can support four independent full-duplex 10-Gbps feeds. This is what 5G backhaul requires, and each wavelength uses Ethernet to carry 5G packet information. Verizon has selected this technology for its future 5G backhaul. Cisco, Nokia, Huawei, Calix, ADTRAN, Ericsson, and Nokia are all actively involved in developing this 5G backhaul technology.

CIR expects investments in NG-PON2 and similar advanced PONs technologies to reach $890 million in 2022. Other investments in fiber backhaul will come from other PON technologies and other non-PON fibers.

The development direction of PON in data transmission rate and coverage will far exceed the requirements of fiber-to-the-home, making PON a powerful and potential technology choice for local loop and metropolitan area networks.

While the main factors shaping the optical link market in 5G backhaul are data rate, latency, and cost, we note that the differences between 5G backhaul architecture and 4G LTE and earlier technologies will be different. In particular, the boundary between fronthaul and backhaul will change, and this redesign of mobile infrastructure will also affect the use of optical fiber in backhaul.

Perhaps the most obvious way would be CPRI (Common Public Radio Interface), which is the current standard interface for connections between cell tower radios (Remote Radio Heads – RRHs) and the mobile network control backbone. CPRI was first defined in 2003 and was intended to be used as a fiber optic interface to replace the copper cables that were then connected to cell towers.

CPRI's data rates range from 614Mbps to 10Gbps, which seemed sufficient at the time, but may not be enough in the 5G era. In particular, equipment vendors have adopted multiple-input multiple-output (MIMO) technology for their 4G/5G equipment. MIMO uses multiple transmitters and receivers at the same time, thereby increasing data rate requirements. CPRI cannot adapt well to the demand for a larger number of antennas in the 5G era, mainly because of MIMO.

But CPRI is not going away anytime soon and will continue to be embedded in most centralized radio access network (C-RAN) architectures. However, there is growing discussion about whether CPRI supports the right data rates for 5G. There is some talk of reducing the pressure on CPRI by leveraging existing packet networks, but this is only a stopgap measure. In the long run, there must be a way to replace CPRI.

IEEE is currently addressing this issue through its Next Generation Fronthaul Interface Group (NGFI 1914.1 Working Group). This working group was formed to define the transport architecture for mobile fronthaul traffic. NGFI will be re-architected so that the fronthaul is a bandwidth-adaptive multipoint-to-multipoint (mostly fiber) network that responds to dynamic payload changes, supports high-gain coordination algorithms, and traffic decoupling for many antenna interfaces.

5G backhaul fiber: challenges and opportunities coexist

Other similar challenges will also emerge. For example, in the fronthaul domain, CPRI data transmission is achieved over short distances and includes standard optical parameter requirements such as jitter error, power loss and latency. However, as the emerging cloud RAN architecture extends to 25 kilometers, some optical performance parameters have become problematic; which is intended to show that while fiber is an important factor that will dominate 5G backhaul in the future, its deployment remains uncertain.