In-Building Wireless Networks and the Emergence of Unlicensed Spectrum Solutions

9 March 2018 | Reading Time: 4 minutes

For enterprise spaces, in-building wireless (IBW) is an increasingly viable solution to ensure quality indoor connectivity. But as demand increases, so too does RF spectrum requirement.

As a result, we’re now seeing IBW solutions being driven onto unlicensed bands – which may come as some surprise in an industry as regulated as wireless communications.

It’s not only demand driving this move. Choosing to place part of your IBW solution on unlicensed bands can extend coverage quickly and economically. Yet there are still limitations and implications in using unlicensed bands; from dubious quality of service, to interference, to the need for roaming agreements (to connect with the licensed bands used by wireless operators) in a full IBW deployment.

So why adopt unlicensed frequencies? To understand we must first look at the emergence of unlicensed spectrum solutions.

Types of Unlicensed Spectrum Solution

Standard Wi-Fi and DAS solutions have co-existed in larger enterprise spaces for many years. Here, Wi-Fi serves data needs and the DAS typically supports voice communications. But as demand for IBW increased over time, it absorbed all the spectrum these solutions were designed to give. So, instead of operating on distinct frequencies, each solution converged, borrowing increasing amounts of unlicensed spectrum – resulting in conflict.

Common types of unlicensed solution include:

VoWi-FI: Voice over Wi-Fi (a.k.a Wi-Fi Calling) 

DAS solutions are used to move voice traffic on and off the core network and offer an advantage in their ability to interface with multiple operator networks, technologies (such as LTW, 3G and more), and are almost universally compatible with wireless devices. Voice over Wi-Fi (VoWiFi) offers an unlicensed alternative that uses the IP network to route voice calls with acceptable quality.

VoWiFi deployments are few, but slowly growing—powered by Next Generation Hotspot (Hotspot 2.0), which essentially, turns an indoor space into its own wireless operator. It can integrate with national wireless operators via a roaming agreement, just as national operators have with each other.

However while VoWiFi offers multi-operator support, it can suffer from limitations common to all WiFi applications:

• QoS can be unreliable. If VoWiFi traffic is not prioritized highly enough on the network, this can cause quality issues; particularly in high-traffic environments.
• Calls dropped at the door. While VoWiFi offers good connectivity within an enterprise space, it cannot smoothly hand off the call to the macro network when a caller leaves the covered space (or the reverse), causing the call to drop.
• Access points. As more access points are added to a Wi-Fi network (to support users), the amount of throughput at any given access point decreases. This introduces delays and jitters in voice calls.
• Lack of interference resolution. Unlicensed frequencies mean you’re on your own when it comes to interference. Shared spaces and multi-tenant buildings introduce the possibility of interference between neighboring Wi-Fi networks. While these can sometimes be resolved with informal agreements, no established legal or regulatory recourse is available in conflict cases.

For these reasons, VoWiFi is well suited to enterprises with tight control over use, where people spend most of their time indoors, and where one occupant fills the entire space.
Other unlicensed solutions may be best considered in other situations.

LTE-U and LAA 

Providing an LTE-style signal in the unlicensed 5 GHz band (the same band used by advanced Wi-Fi networks) to carry data and (to a lesser extent) voice traffic, LTE unlicensed bands (LTE-U) operate in a similar way to the ride-sharing service of wireless communications. However, as it shares frequencies with data traffic, this makes LTE-U prone to traffic jams and bottlenecks in voice or data (depending on the deployment).

In some cases, the LTE-U specification allows voice traffic to take control of the frequencies, regardless of other traffic that may be trying to cross the network at the same time.

LAA (licensed-assisted access) offers some standardisation here, as a formally standardized way for an operator to add data on unlicensed bands to an existing LTE band. LAA offers a way to aggregate licensed and unlicensed traffic in the channel – a listen before talk” scheme checks to see if the frequency is clear before proceeding to connect. This arrangement is fast becoming the standard and is already a regulatory requirement in some countries.

In either an LTE-U or LAA solution however, one particular type of traffic will be prioritised at the expense of another, so for IBW solutions, a local integration of LTE and Wi-Fi infrastructure is best, to carry data and voice over parallel systems, with similar speed and latency.

Enhancing IBW with Unlicensed Solutions, Not Replacing

Unlicensed solutions are an innovation that have emerged out of necessity; as a way to provide enhanced indoor connectivity. Affordable and easy to deploy, unlicensed-band IBW solutions like VoWiFi and LTE-U offer an effective way to economize, from both a financial and spectral perspective.

However it’s important to remember that operating in unlicensed bands alone, for most enterprise environments, will not be enough to provide the quality of service, reliability and performance required. Equally, for any unlicensed IBW solution, the enterprise must still integrate with the licensed bands used by wireless operators in order to connect with the outside world.

Ultimately most enterprise IBW deployments today can benefit from a combination of licensed-and-unlicensed-band networks. For infrastructure experts, maintaining up-to-date wireless training, to understand how both licensed and unlicensed solutions can combine to support IBW. Those who invest in training will be the ones to reap the benefits of a continually advancing and evolving wireless market – today and in future.