Good indoor coverage – only for the largest customers?

By: Geir Ove Jenssen, CTO, Cloudberry Mobile

”Mobile coverage is the problem, not capacity”, Caroline Gabriel at :Rethink Wireless writes on the 3rd of February this year. I could not agree more!

With green buildings, enterprises are realising that indoor coverage has become a problem. New office buildings with insulated walls and windows with multiple metal coatings comply with new environmental standards. However, they do not only hinder heat loss, mobile signals are also stopped. With a mobilized work force, enterprises are in for a problem. Property owners and tenants alike are realizing that putting thousands of employees in highrise buildings is a dangerous cocktail.

Some customers get help. The largest enterprises get distributed antenna systems (DAS) retrofitted. This is the socalled “passive” part of the solution. The base station, or “active” part of the solution, is often set up in a data room in the premises. A fiber connection is used as backhaul to the mobile operator core network. The DAS solution is radio planned to fit into the overall mobile network.

DAS systems are costly, and is only cost efficient for the largest enterprises. Mobile operators are willing to take the cost to keep the customer for a set number of years. DAS gives good coverage and sufficient capacity in many large buildings. 10.000 square meters has been mentioned as a lower limit in size where DAS is cost efficient. This size is corresponding to a 4-storey building with length/width 50 meters. Retrofitting a DAS solution in an existing building is more costly, because you need to open the suspended ceiling and install dedicated coaxial cabling on the floors, while the building is in use.

For the large enterprise segment, there has lately been competition to DAS. These solutions often depend on a local controller or server and dedicated data cables going to distributed radio nodes across the building. The cost for these solutions is probably lower than DAS, but it is assumed that these solutions are cost-efficient for the largest buildings.

What solutions are there for the smaller enterprises?

Most enterprise users are employed at small and medium enterprises (SME). Probably more than 80% of users are employed in enterprises smaller than 200-300 employees and with buildings less than 10.000 square meters.

Ofcom, the UK telecom regulator – in August 2014 published a survey stating that 30% of consumers have no or little mobile signal. The problem is probably as big or bigger for enterprises, as these have higher requirements for indoor coverage than consumers. This means that very many enteprises have a big problem with their everyday mobile service.

Our impression is that these users are willing do pay for indoor coverage, but that there are only a few alternatives in the market. Repeater solutions fit SME with premises up to 500 square meters. A repeater repeats the signal from the outdoor mobile network, but requires a good signal in order to work. A repeater does not build new capacity, but extends the existing.

Small cells (femtocells)

Femto-based small cells (hereafter called small cells) are based on a technology that is cost efficient for buildings smaller than 10.000 square meters. Small cells are mini base stations that provide their own coverage and capacity. The physical size is like a wireless router. The coverage radius is 10 to 50 meters, depending of the size of the small cell and the local infrastructure. The fewer walls that stop the signal, the better the coverage will be. Small cells are scalable and provides cost efficient indoor coverage apartments/homes, SOHO, SME and upwards. Small cells can be combined in groups (socalled “grid”) for covering larger premises.

Small cells reuse the customer´s own broadband connection (fiber, xDSL, cabel broadband) by setting up a secure connection to a centrally located small cells gateway, which is again connected to the mobile operator´s core network. New and expensive backhaul/fiber is not needed. Small cells rely on the existing data network in the building, so dedicated cabling is not needed. Another positive property about small cells is that it – like DAS – reuses the mobile operator´s radio frequency spectrum. Small cells require no outdoor coverage in order to provide indoor coverage.

Small cells self configure in order to support handover of calls from the small cells to the outdoor mobile network. A disadvantage with small cells is that there is limited room in the neighbour lists in the macro network (outdoor mobile network), in order to support handover of calls the other way – from the mobile network to the small cells. However, experience shows that customers accept this limitation.

Internationally the largest mobile operators has used small cells for several years – AT&T in the USA, Vodafone in UK and other markets, 3 in UK, SFR in France, Softbank in Japan, and others. 8,5 million small cells have been deployed worldwide. Appearantly, for customers and mobile operators, the advantages of small cells outweigh the disadvantages.

The quality of broadband connections in Europe is good. European enterprises are increasingly going 100% mobile, so small cells solutions should be good solution for customers that suffer from bad indoor coverage, also for the smaller enterprises. Can the mobile industry afford to ignore the smallest enterprises?