Shared spectrum, in the form of use of 150 MHz of spectrum supplied by the Citizens Broadband Radio Service (CBRS), is thought to be a major new means of improving indoor coverage, in addition to outdoor uses in more-traditional “mobile access” applications.
In part, that is because of the structuring of licenses, which allow a single entity to control indoor use on a secondary basis, on the model of Wi-Fi, where a venue owner creates the network. Outdoor access will operate more like the mobile licensing model, where multiple providers can use different blocks of spectrum in the same area.
In-building coverage has been a customer irritation almost since the beginning of mobility service, it might be argued, as terrain, building construction materials and other obstructions as well as cell network design, device capabilities and application type (voice or data) can limit mobile signal strength inside buildings.
That problem has gotten worse over time, in one sense, as use of higher-frequency signals means less robust indoor signal strength.
Highlighting the importance of that issue is the observation that 80 percent (or more) of mobile phone use happens in an indoor setting. On the other hand, the indoor signal strength issue is vexing as solving the last Nth part of any problem always is quite expensive.
Vodafone has noted that, despite having coverage to 99.7 percent of population, 19 percent of U.K. users regularly encounter coverage problems inside their homes.
A survey by the Small Cell Forum showed 21 percent of consumers in the United Kingdom experienced dropped calls at least monthly when making calls at home .
Some 22 percent experienced poor voice quality at least one to three times a month. An Ofcom survey suggests 76 percent of U.K. consumers are satisfied with their ability to make and receive calls at home, but only 66 percent say they are satisfied with workplace coverage.
The source of poor indoor service can be due to the user being a long distance from the closest cell site (low signal strength); being inside a building which has particularly challenging construction materials or geometry; or being on a high rise building suffering from interference from multiple serving cells.
One analysis by Real Wireless for Ofcom, the U.K. communications regulator, shows that although voice coverage is about 98 percent for the 50 percent of most densely populated areas of the United Kingdom.
The caveat is that this coverage represents the coverage of the best operator in each area. Considering every supplier, in every area, coverage can drop to between 90 percent and 96 percent, Real Wireless says.
In the case of data services, while the existing coverage level is lower than voice but overall still quite high, it is anticipated that indoor coverage from “outside-in” solutions will improve greatly in coming years in particular as lower frequencies become more widely deployed for 3G and LTE services.
As a rule, distributed antenna systems make sense for large enterprise locations, while Wi-Fi makes most economic sense for consumer locations. Repeaters and femtocells (fed by a fixed network connection) make sense for consumer locations. Small cells will make more sense for larger business locations and venues.
It might remain the case that the simple consumer “fix” for data access inside buildings typically is Wi-Fi, using their own internet connection at home or a hotspot outside the home.
Solutions for voice have been more challenging, in part for financial reasons, but voice over Wi-Fi is one possible solution for that problem, and relies on existing Wi-Fi coverage.
Wi-Fi customer premises equipment is paid for by the customer, not the service provider in a direct sense. For larger enterprise locations, distributed antenna systems (and other methods) are used to boost indoor coverage.
Approaches to improving in-building service levels fall largely into two categories: Outside-in solutions where the user receives a mobile signal from a network outside of the building i.e. from the existing outdoor cellular network or some enhancement to this approach.
Dedicated in-building solutions (“inside-in”) where the user receives a mobile signal from some form of access point within the building which is dedicated to serving just that building.
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