I have a friend who lives in a village in a rural area of the UK. Wireline broadband service is fairly poor, with very low data rates via DSL. Despite UK wired broadband rollout being ahead of plan, those in outlying rural areas can be limited to data rates of 100Kbps or less which isn't compatible with many of today's image intensive websites. Being limited to one voice call per line means sharing it between business and domestic use which can be awkward.

Wireless service is variable – voice coverage is usually available even indoors but data sessions can be intermittent. Data service can be disrupted at busier times of day without warning.

My friend has configured and connected an all-IP SIP based telephone exchange (PBX) for private and business use, and tried to route all voice calls using 3G wireless data from a nearby macrocell.

Voice is treated differently to Data

What's quickly become apparent is how differently the data sessions are dealt with compared to voice calls. As the nearby macrocell fills to capacity, it appears to prioritise the voice calls and drops data sessions at the edge of the cell. This doesn't appear to be just "cell breathing", where the coverage radius of the macrocell is reduced during peak traffic periods but active termination of sessions.

Direct discussions with 2nd line support at the mobile operator involved confirms this action, although I couldn't say what the specific planned behaviour and configuration options are.

This effectively rules out using an all-IP "over the top" approach for voice and data that simply uses a data bearer on the 3G network. Since the data sessions are being dropped, I wouldn't expect other OTT (Over the Top) services such as Skype or Viber to be any more effective.

With relatively low prices for bundled voice minutes, I encouraged my friend simply to use standard 3G voice for his business calls. The price of international and some premium rate calls can be a major deterrent to that approach. Just last week, I was being asked to join a conference call that would have cost $30 from my cellphone. Pricing vary widely in other countries where it may not be such a significant issue.

What this means for OTT voice

This behaviour just highlights that treating voice as data and using OTT services isn't quite as straightforward as it might appear. The quality, priority and continuity of the underlying data bearer has to be at least as good as the 3G voice service before customers will trust it with their regular voice service. This scenario isn't limited to rural areas and can also be found in-building and other more difficult to reach locations.

As LTE continues to be rolled out, especially in areas where it can benefit from using additional spectrum at lower frequencies, the coverage from macrocells continues to improve. But in order to use OTT voice as the primary voice option, the data bearer has to be reliable and consistent enough to deliver good service.

Perhaps one of the reasons we haven't seen VoLTE (Voice over LTE) deployed more widely is that the underlying LTE service hasn't yet reached this level of maturity to match that of 3G voice, although I'd expect that to be the case in several countries in the near future.

So what can my friend do?

In the short term, a satellite broadband service would give access to faster broadband Internet. This could be used for voice but may suffer from some latency issues unless optimised. My friend could also make direct use of the 3G voice service, perhaps installing a repeater to improve indoor coverage since the DSL broadband isn't sufficient for a normal residential femtocell. Products such as Cel-Fi are approved and permitted by mobile operators for such use cases.

And what are the implications for mobile network deployment?

Full coverage of rural population for either wired or wireless broadband service isn't nearly as commercially attractive to service providers as urban or suburban areas. The relatively low utilisation of expensive cell tower equipment in some rural areas discourages further investment.

My view would be that building on the wireline broadband rollout, deploying Small Cells directly in residential, business and public areas (e.g. village squares) would be the most effective long term strategy. This will offload traffic for stationary users from the expensive macrocell towers, releasing capacity and resource for them to focus on the faster moving/wide area coverage.

It is this mix of Macrocell and Small Cells working efficiently and effectively together to address different types of traffic mix that should deliver the best solution overall.

In the short term and for areas which wireline service will never reach, satellite broadband may be a cost effective option.