Ericsson says microwave backhaul fits a high capacity, low latency future

Quick digest of Ericsson's Microwave Backhaul report.

Ericsson has released its latest Microwave Backhaul report, with some interesting predictions and proposals for microwave backhaul.

You can read the entire paper here, but if you are pressed for time TMN has extracted a few key points. (All the quotes below are directly lifted from the report – bold text is TMN’s own – click the images to see bigger versions).

Increasing capacities but at a few sites only

backhaul-capacity-requirements“In 2021, high capacity radio sites are expected to require backhaul in the 1 Gbps range, whereas low capacity is in the 100 Mbps range. The most extreme capacity sites are expected to target backhaul with fiber-like capacity. With the introduction of 5G the capacity evolves further, but will depend on radio access spectrum availability and local needs.”

“Towards 2025, high capacity radio sites are expected to require backhaul in the 5 Gbps range, with extreme capacity sites in the 10 Gbps range. However, the majority of radio sites will require less than 1 Gbps towards 2025.”

Increasing multiband

multiband-mw-ericsson“The attractiveness of the 70/80 GHz band is rapidly increasing. It offers very wide bandwidth, at a generally low spectrum fee, enabling capacities in the order of 10 Gbps or more over distances of a few kilometers.”

Multiband solutions , which enable enhanced data rates by combining resources in multiple frequency bands, already constitute an essential part of modern radio access systems and in the coming years will also be increasingly used in backhaul.

microwave backhaul bands trends(TMN precis: E-band will be driven by lower licensing costs, like in Poland where it fee is 4-10x lower than traditional bands.) “Operators can also now start to use the E-band spectrum to drastically lower their spectrum fees. This can be achieved by using channel widths in the same range as in traditional bands (62.5–125 MHz), and will accelerate the usage of E-band even further”

“Even though the main growth is in the higher bands, some of the lower bands are also growing in popularity (e.g. 6 and 11 GHz) due to local regulations, underutilization and good propagation properties in high rain rate regions. However, the band with the highest growth is E-band (70/80 GHz).”

5G demands on backhaul – low latency and high peak rates

5g-and-backhaul-spectrum“The IP-based interface between the virtualized RAN and the real-time radio processing functions has a characteristic similar to backhaul. It scales with user data and has a recommended latency of less than 5 milliseconds. The new fronthaul for 5G, eCPRI, is being standardized and will use ethernet over dedicated fiber connections. It will encompass increased bandwidth efficiency, increased capacities and lower latencies in order to meet the needs for 5G. The latency requirements are more stringent than today – less than 25 microseconds for eCPRI (dependent on 5G TTI) as compared to less than 150 microseconds today for CPRI.”

“The speeds at which signals can travel through the air and at which light can travel along a fiber are governed by fundamental laws of physics. The speed of light in fiber is roughly two-thirds the speed of signals in air. The lengths of deployed fiber are typically 1.5–2 times longer than the shortest distance through air. Thus, free space has 34–67 percent lower latency than fiber. This is the reason that microwave transport is extensively used in the most extreme low latency networks that exist today – high frequency stock trading networks”

Backhaul not a key SDN driver but can benefit from SDN introduction

“A number of microwave use cases have been proposed by the industry. It is important to remember that these types of use cases alone will not be sufficient to motivate SDN introduction in the networks. However, once an entire network is SDN capable, there are gains to be expected in the microwave domain as well.”

The elasticity of microwave links is a characteristic that could make SDN functions relevant. A microwave link’s capacity varies with propagation conditions and events; for example, rainfall causes fading that reduces capacity. This dynamic information can be used to optimize the overall network performance. The microwave bandwidth can be signaled to a router, using the ITU-T G.8013/Y.1731 bandwidth notification message (BNM) protocol, or signaled directly to an NMS/SDN system. Other areas that could drive SDN for microwave are usage of unlicensed spectrum and increased focus on energy efficiency.”

“The ultimate goal of software defined networking (SDN) is to obtain an end-to-end view of network conditions that span across multiple technologies and different vendors’ equipment. This to efficiently automate network provisioning and end-to-end services. As a result, unified management systems, along with open and standardized node interfaces, are vital pre-requisites. This drives the need for a microwave node interface standard that aligns with existing packet standards, which the industry is pursuing.”