A 5G indoor story needs real-time access to the interference drivers of 5G small cells to make it fly

A 5G indoor story needs real-time access to the interference drivers of 5G small cells to make it fly

“Lightly licenced” or “over-licensed” 5G spectrum carries risks of harmful interference to the MNO’s granted preferential spectrum licenses. There have been several approaches to controlling the risk of harmful interference beyond mandating the use of very low radiated powers:

  • A centralised approach using data bases that contain all the locations to be protected and their characteristics to avoid situations where harmful interference may arise
  • A de-centralised approach using cognitive radio and sensing technologies with algorithms to avoid harmful interference

The decentralised approach is potentially more efficient but demands a high degree of confidence it will be reliable enough and particularly when regulators are dealing with millions of potential interferers in the hands of consumers. The high cost of getting it wrong makes regulators very risk averse.

The IET Communications Policy Panel have been working on a new approach that is optimal mix of decentralised and centralised technology and has somebody who is ultimately accountable.  It revolves around the creation of a new entity to be accountable:

Triangle of Trust

This new entity is termed the “Trusted Interference Manager” or TIM, trusted by consumers to access their home hubs for the purpose of interference management, trusted by the primary spectrum license holders that they will not be getting harmful interference and trusted by the regulator that it is worth taking larger risks with lightly licensed spectrum. To help everyone visualise who TIM’s might be, let’s assume the task is taken on by Mobile Network Operators. It could also be third parties but MNO’s have an added incentive as it is their primary spectrum at risk from interference and the consumers involved are also likely to be their customers.

Why it is worth positioning the MNO’s to take on the role of Trusted Interference Agents as it then become a natural progression to build on this relationship with consumers to secure agreement to every home hub becoming a mini-Open Host. In fact, right up front it should be a type approval condition that private access to valuable public 5G spectrum is paid for, not in cash, but a willingness to allow a small percentage of the capacity of the private cell to be pooled for the common good – securely controlled access by visitors and passers-by.

This create a very innovative model that create enormous potential consumer value:

  1. The consumers get access to valuable 3.5 GHz spectrum that provides an optimal mix of high capacity (1-3 Gb/s) and reasonable indoor coverage (better than 5 GHz).
  2. When fibre eventually reaches every home it ensures the wireless routers in place will not be a bottleneck.
  3. The Trusted Interference Manager can also deal with interference between private 5G cells. At the same time interference between WiFi units can be far better managed with a bit of central direction.
  4. When the circumstances allow eg remoter properties and commercial premises, the power levels can be increased and bandwidths widened above their lower default values to deliver considerably better performance.
  5. Visitors to homes and places of work with the new 5G/WiFi kit can get secure access to the Internet without the hassle of asking for passwords or compromising the high security of home and office wireless hubs.
  6. Ensuring high security of both private and mini-Open Host use
  7. Energy saving can be an added value function for TIM’s
  8. And the biggest prize of all in the longer term…the aggregation of inside-out coverage of 10-12 million private 5G wireless hubs to provide a very substantial boost to 5G suburban coverage for the benefit of entire communities

The consumer proposition is simple:

Consumer TIM proposition

The function of the Trusted Interference Manager can be clearly defined:


And the system is easy to implement and enforce through type-approval:

TIM type approval mark

Whilst the approach has been focussed on the deployment of 5G dense small cell networks, the same principle could be applied to:

  • new multi-occupancy buildings and new commercial building that could be “pre-wired” for 5G indoor coverage and contribute to the 5G coverage story
  • 700 MHz spectrum in rural areas unserved by public cellular networks eg a farm provides its own 700 MHz cell to modernise its processes but provides public coverage to those working or visiting the farm, using public footpaths across the farm, emergency services etc

The Trusted Interference Manager create a triangle of trust upon which spectrum re-use can be stepped up by orders of magnitude and deliver the sort of transformational impact many are suggesting 5G is capable of…but 5G can only transform what it covers…and aggregating small cell coverage into something big is a long term game best achieved by governments, regulators, mobile network operators and vendors working collaboratively towards the common end goal of pervasive 5G coverage to support a Gb/s society.

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