Why Low-Band Spectrum Matters for 5G and 5G+ in Underground Locations

It’s infuriating to be underground in a car park, rail station or tunnel and suddenly lose your signal while you’re using mobile data. Underground spaces are a nightmare to service by mobile networks, and it’s a form factor cities that have decent 5G coverage still haven’t solved. Concrete, steel rebar, and the earth itself can decrease radio signals between transmitter and a device, while limited access to other cell sites can make things worse.

The 5G vs 5G+ difference is a little more important when you consider how such tough areas are handled by operators to boost coverage. In Singapore, 5G+ is a network-specific phrase for better network offerings, such as more spectrum and better network technologies. Low-band frequencies such as 700 MHz are very useful for extending signal coverage into buildings and basements and are therefore vital in broader 5G coverage plans.

Issues With Mobile Networks Underground

Radio signals carry mobile network data. Signals go from the cell sites to their associated devices, but can also be obstructed by physical impediments.

There can be a good amount of cell coverage problems with natural cave-ins and tunnels:

Dense Building Materials Block Signals

Concrete barriers, metal doors, dirt, and steel reinforcements can weaken radio signals. Some of these obstructions are present in underground trains and car parks and make it hard for external signals to reach customers.

Distance From Outdoor Cellular Towers

There can be underground levels that are many meters below the street. Outdoor coverage from a local cell tower may be robust, but if the service has to go further into levels, that coverage often is not there.

Population Density
Transport terminals, shopping complexes, subterranean pedestrian networks, etc. can attract huge crowds. Network bandwidth when multiple connections are made simultaneously is another issue.

For certain cases, operators need more than just exterior coverage. As such, they frequently must have a combination of the right frequency bands and specific indoor infrastructure.

Why Is Low-Band Spectrum So Special?

Conversely, a low-band spectrum refers to mobile frequencies below 1 GHz. In Singapore, low-band is already in use for 5G networks in portions of the 700 MHz band spectrum.

Compared to higher frequencies, lower frequency radio waves tend to travel further and are better able to penetrate various obstacles. This makes low-band spectrum valuable for expanding mobile coverage beyond the range of outdoor cell sites.

But low frequency does not equate to the fastest mobile data. Low-band spectrum tends to have better coverage but is not as high in capacity as some mid-band deployments.

Superior Signal Range

Sometimes, low-band signals might reach a broader area. This helps operators to cover areas that are difficult to reach with broadcasts from higher-frequency bands.

That would aid in sustaining the connection in underground scenarios along vents and entrances and the like when radio waves enter the space.

Enhanced Building Penetration

Many building materials attenuate lower frequencies less than higher frequencies. Thus, they can offer better indoor coverage than higher frequency options.

Depending on the building, this may be an advantage. Deep tunnels and underground facilities with deep shielding may nevertheless need distributed antenna systems or (dedicated) antennas.

Low-Band Spectrum and 5G/5G+

Low-band spectrum can boost other 5G frequencies. Operators can use it with mid-band spectrum to compensate for coverage and capacity.

Low-band frequencies can already be used by standard 5G. It’s not specific to 5G+ to support low-band. It is contingent upon what the operator does with its spectrum and what it’s adding to its upgraded service.

In Singapore, carriers have associated 5G+ with upgrades that include more 700 MHz spectrum and 5G Standalone technology. These improvements cater to a variety of network requirements:

Low-band spectrum: Provides coverage and building penetration.
Mid-band spectrum: Provides a tradeoff between coverage and capacity, and supports speedier data services in crowded regions.
5G Standalone: Dedicated 5G core for enhanced network capabilities and more adaptable traffic management.
Indoor system networks: Used for radio coverage underground, when signals cannot dependably reach from the outside.

Knowing these distinctions can help dispel a popular misconception: 5G+ doesn’t guarantee you’ll receive better signals everywhere below ground.

The Conditions for Underground Coverage Beyond Low Frequencies

While low-band spectrum can assist with coverage, it’s not a silver bullet for all underground connectivity problems. Often, operators need specialised infrastructure to carry signals via intricate structures.

Distributed Antenna Systems

A distributed antenna system (DAS) is a set of antennas connected to a common signal source. The antennas may be located on multiple floors, hallways, platforms, and below, to increase mobile coverage.

This helps to eliminate dead zones due to walls, corners, and long corridors.

Radio Equipment and Small Cells (Indoor)

Small cells are small-area access points. Operators can deploy them in larger buildings or underground for local coverage and capacity.

They shorten the distance from network equipment to users and can assist provide more uniform connectivity in dense areas.

Connectivity Backhaul

Indoor antennas and tiny cells must still connect into the main mobile network. Backhaul is the fibre or other appropriate backhaul infrastructure that transmits the data between the local network equipment and the operator’s core network.

Adding antennas without sufficient backhaul capacity may not provide the desired performance gains.

Why More 5G Coverage Underground Is a Benefit for Users

Having good underground coverage goes beyond browsing and leisure use. It enables underground commuters to connect to information, services, other users, and the mobile payment services as well as get crucial dispatches in transport means they utilise while on the move.

Businesses also benefit from reliable mobile access. Retailers in an underground shopping center might link point-of-sale, inventory, and customer apps. However, operators of the buildings can employ mobile connectivity in their maintenance, operator, and security systems.

Emergencies are also crucial. Mobile coverage is a backbone of communication and information access in catastrophes, however emergency services need separate systems that meet different safety/reliability standards.

How to Tell If Your Mobile Network Is 5G+ Underground

Seeing a 5G or 5G+ icon on a smartphone is great, but you need to start looking at real information of coverage.

Start with coverage information in the underground spaces you spend time in. Look for information on subways, basements, and indoor coverage.

Next, check if your phone supports the provider’s 5G frequency bands. For example, if the phone supports some 5G bands, but does not support a carrier’s 700 MHz rollout, the phone will not be allowed to use that frequency.

Also ensure your plan includes the provider’s higher-end 5G offering. As you weigh your Singapore mobile options, compare your features and plans with other providers and shop around to see if Giga can access networks as well as its equipment.

Test your connection across locations and hours for a better sense. The signal and data speeds will vary depending on congestion of the network, hardware of devices, and the particular infrastructure available at each location.

Low-Band Spectrum for Future Connectivity

Radio signals can easily get outdoors; one area where a little of network planning is required is indoor mobile coverage. This can be taken care of with low-band spectrum, which has higher propagation and can penetrate many building materials.

On 5G networks in Singapore, 700 MHz spectrum can supplement mid-band capacity in the outdoor macroenvironment, as well as dedicated infrastructure inside buildings. Some 5G+ services combine these resources with 5G Standalone capabilities to support a broader range of network requirements.

Ultimately, strong underground connectivity means a mix of technologies operating in concert. Low-band spectrum offers superior coverage, indoor antennas close coverage gaps, and sufficient backhaul helps backstop network capacity. Together these factors assist mobile operators to provide a better experience for those below ground working, on the move, and connecting with one another.