Sizing up spectrum: using transport the best way with new 5G assets

One of the major benefits of 5G is the improved user capacity it brings. Beside the optimization of the radio protocol stack, this improvement is enabled by the availability of multiple new frequency bands. Some 5G deployments increase the available capacity by 20 percent compared with 4G, while others provide up to 40 times more bandwidth.

Fluctuating figures

Ericsson has the privilege of observing many real mobile network deployments, which enables us to draw some general conclusions that apply to most networks.

On one hand, there is a great deal of variation in the figures relating to traffic in different parts of the network. The top 30 percent of sites – including high- and medium-capacity sites – in the network account for 75 percent of the total traffic, whereas the bottom 70 percent of sites carry only 25 percent of the total network traffic.

If we observe how networks evolve over time, we are able to deduce that both their rate of growth and traffic volumes vary from site to site. Growth is faster at high-traffic sites compared with low-traffic sites. The varying growth potential of these different kinds of sites will be further emphasized by the use of new 5G frequency bands.

There are three main frequency bands that can be used for the introduction of 5G:

• High-band or mmWave: a new band providing hotspot-like access with extreme high capacity and ultra-low latency. Spectrum assets up to 800MHz are available
• Mid-band: a new band that can be added in areas where high network capacity is required. Spectrum assets up to 100MHz are available
• Low-band: already used today for most 2G, 3G and 4G services, this band can be reused to achieve nationwide 5G coverage. Spectrum assets up to 20MHz are available

The higher the frequency band, the more air interface bandwidth is available, but the shorter the signal propagation becomes. The various network segments will utilize the available 5G spectrum assets in different ways, thus imposing different requirements on the transport network.

Backhaul options for low-capacity sites

Let us first consider the evolution of a typical low-capacity site to 5G over the next five-year period. The job of such a site is to provide wide coverage but not large capacity. To evolve the 4G network to meet capacity needs, we can enable better modulation or introduce more MIMO layers. And with 5G, we will usually switch on a low-band service by enabling Ericsson Spectrum Sharing: a straightforward software upgrade.

From a transport perspective, we can expect to grow the backhaul capacity required from about 100Mbps to roughly 500Mbps over the next few years. Most low-capacity sites are connected through microwave links, and this segment is home territory for traditional 6-42GHz band microwave solutions. With the MINI-LINK 6000, bringing about this evolution can be as simple as carrying out a software reconfiguration to cater to increased needs.

If such a site has a fiber connection, Ericsson recommends using a cell site router that has 10GE interfaces for future expansion. Even though the forecast site capacity does not require 10GE connectivity, low-latency applications could drive the migration to higher interface speeds.

Medium-capacity sites and mid-band spectrum

If we look at a typical medium-capacity site, we can expect multiple 4G spectrum assets as well as both low-band and mid-band 5G services to be turned on. One of the impacts on transport is that the backhaul capacity will need to grow sevenfold, increasing from 500Mbps to 3.5Gbps over the next few years. The most significant aspect of this is that the typical Gigabit Ethernet connection deployed today will not suffice in the future.

In the case of a site with microwave backhaul connectivity, we can choose to evolve the traditional 6-42GHz microwave solution to the required capacity, migrate to an E-band (70-80GHz) solution or use a multi-band option by combining the two technologies. The MINI-LINK portfolio offers both traditional and E-band solutions. Ericsson’s E-band solution can comfortably create capacity of up to 20Gbps using XPIC on a single carrier today, and we have already proven microwave connections of more than 100Gbps.

If such a medium-capacity site is connected to the backhaul with fiber, we recommend using a cell site router that is optimized for 10GE ports, but also offers 25GE and 100GE connections for future expansions.

High-capacity sites, high impact on traffic planning

Lastly, where high-capacity sites are concerned, we expect every 4G frequency band and all three 5G bands to be turned on at the same time in each location. This will impact transport planning in two significant ways.

First, the backhaul capacity requirement is expected to grow 10-fold from a typical 1.5Gbps level to more than 15Gbps.

The majority of these sites can be reached via a fiber connection today, and we recommend deploying a cell site router that offers 10GE, 25GE and 100GE interfaces so all current and future radio access products can be deployed.

When there is no fiber connection available, however, it can take several months to build out the last mile and reach new sites that have been planned. In these situations, Ericsson’s E-band microwave solution can facilitate the rapid launch of new 5G services while the details of fiber build are being worked out.

Second, there is a key consideration stemming from the multitude of frequency bands deployed on high-capacity sites. These sites provide an excellent opportunity to improve the user experience through radio coordination. These advanced functionalities can introduce substantial improvements such as increased capacity, a broader 5G coverage area or reduced user equipment power consumption.

Coordination, however, introduces new challenges, and places further requirements on the transport network. The radio protocol stack gets split – potentially even across multiple sites – and the transport therefore becomes the backplane of the disaggregated RAN solution.

In the next blog post in this series, we will take a closer look at how latency, quality of service, and synchronization in the backhaul affect RAN coordination, 5G coverage, and ultimately end-user quality of experience. Stay tuned!

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