Sunday, 11 May 2014

Spectrum Allocation Plans for WiFi in the UK (2014)

Plans for new spectrum allocation for WiFi networks in North America are regular fodder for many blog and news articles that I  see scrolling past in the many RSS feeds that I monitor for WiFi related news.

However, information about plans for additional spectrum allocation within the UK isn't quite so widely covered (in fact, I'd go so far as to say that it is largely ignored). But, here in the UK we still face the same issues as many other areas of the world: an explosion in mobile devices, massive deployment of WiFi networks in homes and businesses, and an ongoing increase in bandwidth demands.

WiFi in the UK operates on both the 2.4GHz and 5GHz bands. We have 13 channels allocated for WiFi on 2.4GHz, but for practical purposes, only 3 may be used across a wireless LAN. On the 5GHz band, we have 19 channels allocated to WiFi, but are generally limited to using only 16 of those channels due to restrictions in supporting 3 channels that may interfere with weather radar systems.

The latest and greatest WiFi standard, 802.11ac, will (theoretically) provide Gigabit WiFi speeds which will hopefully keep up with the growing demand for bandwidth via WiFi neworks. 

However, 802.11ac only operates on the 5GHz band. This is in recognition of the fact that the 5GHz band has much greater capacity than the 2.4GHz band (16 channels vs 3 channels) and so will be able to support the greater bandwidth required for the higher data rates that 802.11ac brings. Additionally, the 5GHz band generally has much lower noise and interference (compared to the 2.4GHz band) from other co-existing devices and services, making it more suitable for high speed services.

In April 2014, OFCOM (the UK communications regulator) published a report that outlines the current considerations around the use of RF spectrum by WiFi networks in the UK. It also discusses considerations for M2M (Machine to Machine) communications and the IoT (Internet of Things), but my interest was limited to the WiFi aspects of the report. It provides some interesting insight in to the services currently using the 5GHz band and considerations for making more spectrum available within the band.

If you'd like to take a look at the report, you can get hold of it here: "The future role of spectrum sharing for mobile and wireless data services  - Licensed sharing, Wi-Fi, and dynamic spectrum access" (section 3 is the main area of interest from a WiFi perspective)

Here are the highlights of the report around current and future WiFi spectrum usage here in the UK:
  • WiFi usage is growing rapidly and there is a need to keep pace with the increasing speeds of broadband connectivity in to homes and businesses.
  • The requirement for increased speed will have to leverage the new 802.11ac standard (for example being able to leverage the 80MHz and 160Mhz channel widths that 802.11ac provides)
  • WiFi networks using more spectrum in close proximity to other homes and  businesses will require more available channels to be able to use the required access speeds
  • Other alternatives (below) are available within homes and businesses, but WiFi is the only viable option for wireless devices
    • limited to a single room: WiGig (802.11ad) and Li-Fi
    • Around home/business: Powerline adapters (depends of quality of wiring), Ethernet cabling (expensive/disruptive) - both still require wireless access points to connect wireless devices
  • There is insufficient bandwidth in 2.4GHz band for higher speed WiFi standards
  • Proposals to extend the allocation for WiFi within the  5GHz band are being considered in preparation for the World Radiocommunication Conference in 2015. The extensions under consideration is shown in the figure below:

  • From studies carried out, it is expected that the current spectrum allocation in 2.4GHz and 5GHz is likely to be under pressure (from a capacity perspective) by 2020.
  • The report also highlights concerns from a number of other interested parties who already have services existing in the areas of proposed spectrum expansion and may be impacted by WiFi co-existing in their area of spectrum. It provides the following illustration of existing services in the 5GHz band that may be affected by any spectrum allocation expansion:

  • Due to the requirement for co-existence with these existing services, work is being undertaken to consider technical solutions for sharing the spectrum. These include dynamic frequency selection (DFS), transmit power control (TPC), restriction to indoor-use only and geolocation databases
  • Some concerns have been raised by existing users of the areas of spectrum that are proposed for sharing (e.g. ESSS - earth exploration satellite services), as they rely on equipment which detects low level signals which has incurred significant investment and cannot be modified once deployed.
  • Ofcom is carrying out a number of technical studies in preparation for the World Radiocommunication Conference in 2015 to understand the viability of spectrum sharing. However, at this time, there has been no definitive opinion formed by Ofcom around whether or not they should support the proposed extensions.
In summary, it is interesting to see that Ofcom are actively considering expanding the provision of spectrum on 5GHz for WiFi services within the UK. However, it is unclear at this point if more spectrum will be made available, or how much additional spectrum will be allocated. It looks as though we will be waiting until the World Radiocommunication Conference in 2015 before any decisions will be made.


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