Technical Options for improving in Building Coverage

A research study outlining options for improving mobile coverage in buildings. Published 09/01/2014

Existing indoor cellular coverage is increasingly important for both voice and high speed data services.

The study identifies a number of options including ongoing development and enhancements to existing wide area macro networks, such as MIMO antenna deployment and allocation of sub 1GHZ spectrum addressing the issue of deep indoor coverage. The recent 4G auction conducted by Ofcom extended the requirement for indoor coverage for one licence holder to 98%, in-building.

However in some circumstances, due to variations in construction materials and building geometries, there is no guarantee that the signal from outdoors will be able to penetrate inside all buildings. Even when this does not entirely exclude service, it can significantly degrade reliability for calls and reduces data speeds, placing a greater load on outdoor cells.

Ofcom commissioned the research in response to the increasing data demand consumption indoors & the ongoing developments in construction notably the increasing use of metal film on windows, reinforced concrete block building structures and external cladding which together act to attenuate mobile signal propagation. It is estimated that such techniques can contribute over 20dB of loss where older building types might normally be between 5 to 10dB.

The study highlights the potential benefits and challenges associated with deployment of dedicated indoor solutions including:

  • Self and carrier provided WiFi
  • Repeaters
  • Femtocells
  • Picocells
  • Distributed Antenna Systems
  • Distributed Basestations (CoMP, CPRI, X2)

Current Ofcom Activity

WiFi is increasingly been used for providing voice and high speed data services. Recognising this, Ofcom has consulted recently on extension of the existing 5GHz band for WiFi and this is an agenda item for discussion at WRC-15.

Repeaters have been deployed by operators in tunnels, on rail services and in building as part of a range of operator deployed solution addressing challenges of providing indoor coverage. Ofcom is working to identify the challenges in repeater deployment and will work with stakeholders to develop its policy on repeater use.

Femtocell deployment in the UK has increased by 50% this year to reach over 300K installed. The development of Multi Operator Femtocells is being tracked by Ofcom as this may increase their attractiveness for consumer and small business use.

Macro enhancements continue to deliver coverage improvements including techniques such as Carrier aggregation, Coordinated Multi Point, X2 Interface, CPRI & MIMO contributing to capacity increases on the macro network and Ofcom reviewing developments in fibre and other backhaul solutions.

robindhra.mangtani@ofcom.org.uk