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Complex Scenarios, Big Benefits

Aug. 1, 2016
Evolving Backhaul Architectures for Next-Generation Networks “The ensuing data tsunami enabled by the introduction of small cells, remote radio heads, indoor and outdoor DAS, as well as C-RAN network architecture […]

Evolving Backhaul Architectures for Next-Generation Networks

The abundance of smart phones and bandwidth-heavy data applications continues to drive exponential traffic growth in wireless access networks. Many global wireless operators are still expanding their 4G LTE footprint to support the data surge and inevitable transition from circuit switched voice to Voice-over-LTE: VoLTE.

As smart phones and mobile data devices become more and more feature-rich, and prices for these devices decline, data services demand will continue to grow. So how do service providers address the impact of exponential traffic growth on their backhaul networks along with the intersection of new 5G technology?

This article traces the mobile network architecture evolution from 4G LTE through LTE-Advanced to 5G technology, and its impact on traditional backhaul.

C-RAN Architecture
Evolving RAN architecture from distributed to centralized and ultimately cloud RAN offers performance improvement and cost savings through centralization. In a typical configuration of the distributed RAN, base band units (BBU) and remote radio heads (RRH) are co-located at the macro tower location.

The first step in C-RAN is to centralize the BBU to a BBU hotel site within the latency budget of the radio system. This provides multiple advantages to the wireless service provider, offering spectral efficiency and enabling cell site aggregation where RAN traffic loads can be shared between multiple macro cell sites.

The benefits of C-RAN architecture yield up to 30% performance increase when compared to traditional distributed RAN, when instituting a centralized front-haul architecture. Higher spectral efficiency through the X2 interconnect at the BBU hotel yields load sharing and cell site aggregation, which provide capacity management for scheduled and unscheduled events.

Cell site aggregation allows multiple cell sites to simultaneously communicate with a single handset, providing more efficient capacity delivery. Without cell site aggregation, the one cell site closest to the handset provides capacity; if there is a concentration of in-use handsets close to a cell site, there will be a high instance of congestion resulting in decreased service performance.

The network architectural re-arrangement of C-RAN reduces operational and capital expenses through:
• Rent reduction of the macro cell site.
• Economies of scale for network elements.
• Simplified maintenance at Central Office.
• Capacity and spectral improvement.
• Energy efficiency at the Central Office.
• Overall power reduction due to BBU aggregation.

Presently, the distributed RAN backhauls about 150 Mbps to 250 Mbps of peak rate Carrier Ethernet traffic from the cell tower to the MSC. In a C-RAN architecture, backhaul requirements will escalate with the added access capacity and spectral efficiency realized through interconnecting BBUs. The backhaul demand under C-RAN architecture is expected to increase by at least a factor of 4.

5G Technology and X-haul Challenges
Now the industry attention is shifting from 4G LTE towards 5G mobile technology. The expected rapid access densification through millimeter/microwave spectrum and high data throughput promised by 5G — up to 20 Gbps speeds, extremely low latency connections of billions of new Internet of Things (IoT) devices, more advanced MIMO processing, adaptive beam-forming, and high data capacity of 1,000 times that of 4G data rates — will result in increased demand on existing backhaul infrastructure. But the challenge will not be limited only to increasing backhaul capacity; it will also be related to where and how the backhaul capacity is intelligently delivered.

An array of complex backhaul scenarios can be addressed with innovative wireline and wireless technologies such as point-to-point, point-to-multi-point, line-of-sight, non-line-of-sight distributed, and self-backhaul. The ensuing data tsunami enabled by the introduction of small cells, remote radio heads, indoor and outdoor DAS, as well as C-RAN network architecture variants, are just a few of the drivers for next-generation backhaul.

In other words, to handle excessive data traffic towards the core, the conventional backhaul is now being partitioned into x-haul: fronthaul, midhaul, and backhaul, to account for emerging mobile network architectures.

The expected higher backhaul traffic demand of 5G, albeit not trivial, will not be the only challenge faced by next-generation x-haul transport. The coexistence of 4G and 5G mobile access technologies brings an array of fronthaul, mid-haul, and backhaul scenarios to be considered. In addition to the traditional traffic backhauling from the macro base station, outdoor small cells deployment is expected to become a key part of the mobile network architectural shift in 5G. Data traffic from these small cells will have to be smartly aggregated, shaped, pruned, and transported to the Central Office.

End-to-end data traffic engineering that adaptively provisions and monitors the fronthaul, mid-haul, and backhaul transport network based on traffic demand through SDN and NFV will also be prominent going forward.

No Small Feat, But the Rewards Can Be Great
Although next-generation backhaul scenarios are expected to be complex, mobile operators will be looking for new data transport architectures that are agile, deliver services faster, and help to reduce cost, while simplifying their networks for future expansion. The introduction and integration of advanced x-haul technology solutions to meet increased traffic demand from the access will not be a small feat, but the rewards — more efficient network performance and faster service delivery — can be great.

About the Authors:
Dr. Femi Adeyemi is the Lead LTE Solutions Architect at Fujitsu Network Communications. He has more than 20 years of experience in wireless technology and product strategy. For more information, please email [email protected].

Joseph Mocerino is a Principal Solutions Architect at Fujitsu Network Communications. He has more than 30 years of experience in engineering and product line management. For more information, please email [email protected].

About the Author

Femi Adeyemi

Dr. Femi Adeyemi is the Lead LTE Solutions Architect at Fujitsu Network Communications. He has more than 20 years of experience in wireless technology and product strategy. For more information, please email [email protected].