How much spectrum does a user need for 1 Gbps Wi-Fi® coverage?

The need for 1 Gbps coverage

The Wi-Fi^® industry innovation engine is currently focused on improving performance of Wi-Fi networks in dense environments. Early development work is underway in Wi-Fi Alliance^® for a program based on the IEEE 802.11ax MAC/PHY technology, which will launch into a marketplace where 1 Gbps networking performance targets are increasingly becoming the norm.

Some examples:

• Service providers (e.g. cable companies) are expressing ‘whole home 1 Gbps coverage’ as a requirement
• 1 Gbps access networks are being rolled out in various countries
• 1 Gbps coverage is listed as a target for 5G cellular discussions

The central question

A research team at Qualcomm Technologies, Inc., a subsidiary of Qualcomm Incorporated, conducted a top down, engineering driven analysis to identify the amount of wireless spectrum required to achieve sustained 1 Gbps throughput throughout coverage areas, under various networking topologies in dense residential and enterprise deployment scenarios*. A whitepaper describing the methodology and more detailed findings can be found here.

Spectrum required for 1 Gbps Wi-Fi coverage

The analysis shows that in dense environments that primarily rely on Wi-Fi networking, a total amount of approximately 1280 MHz of spectrum centered around the 5 GHz band is required. This will accommodate four antenna clients in residential settings where the Wi-Fi APs in each room are meshed together using Wi-Fi for mesh backhaul, as well as enterprise settings with two antenna clients. The analysis shows that in the case that Wi-Fi mesh networking is deployed inside dwellings accommodating one AP for each of the four rooms, two antenna clients can be supported in 960 MHz of spectrum.

This amount of required spectrum is significantly higher than the amount of 5 GHz spectrum that is currently available for unlicensed technologies today. Currently, 580 MHz is available in North America and 450 MHz is available in Europe. With 450 MHz available spectrum, the sustained throughput would be capped at around 400 Mbps at the most, under the idealized ‘802.11ax generation technology only’ assumptions in the dense deployment scenarios underlying the study. In the North American case, the cap would be around 500 Mbps. In real life, with multiple generations of technology in networks and less ideal reuse planning, this overlapping network interference driven cap will likely be much lower.

The dramatic impact of deployment density

One of the key insights from the study is the dramatic impact that the density of Wi-Fi networks packed together has on achieving performance targets. For example, to achieve 1 Gbps coverage in a single dwelling with a similar layout as the apartment in the dense residential scenario (above) and no overlapping networks (a 10m x 10m, four-room bungalow on the prairie) requires 160 MHz of spectrum with a single AP per dwelling. This is assuming four antenna clients. In the dense residential case, this required 1280 MHz of spectrum (an eight-fold increase). The same eight-fold increase in spectrum required between no overlapping networks compared to many overlapping networks applies to the enterprise scenario.

What’s next

What becomes clear from this analysis it that to enable future Wi-Fi applications such as AR/VR and envisioned usage scenarios, regulators should plan for around 1280 MHz of unlicensed spectrum centered around the 5 GHz band.
Another set of implications dealing with product configuration, deployment topologies, and feature support are more relevant for product vendors, service providers, consumers, enterprise network managers, and building construction companies and are the topic of another Beacon blog coming soon.

*Scenarios and assumptions
The analysis models downlink performance, assuming full buffer traffic throughout the network coverage area. One could look at this as modeling the results of a downlink ‘speed test’ application, while calculating the overall amount of spectrum needed to achieve 1 Gbps throughput in 99% of the coverage area.

The dense residential scenario assumes a three-story apartment building with 30 apartments overall. Each apartment is dimensioned 10m x 10m, with four rooms per apartment. The enterprise scenario assumes one floor in an office building consisting of eight rooms, with 4 access points (APs) per room (in total 32 APs).

This forward looking analysis assumes that the best available, 802.11ax generation Wi-Fi technology is deployed in the 5 GHz frequency band. Further details on deployment scenarios and modeling assumptions are included in the Qualcomm Technologies whitepaper.