Trouble maker: LTE at 800MHz needs Wi-Fi says Kineto


In lieu of VoLTE, mobile providers need to help consumers out with Wi-Fi for voice calls or risk irritating new 4G users, claims Kineto

By Keith Mumford, vice president of technology, Kineto

Travel on a London Underground train this summer, or read a Sunday newspaper in the UK, and you may well spot an advertisement warning of the potential for interference between new 4G mobile networks and broadcast TV signals.

The advert directs the reader to the at800 website, which is funded by UK mobile operators who will be launching new 4G mobile services at 800MHz. It provides advice and solutions for any TV interference problems that may occur for consumers.

Problems for mobile usersHowever, while interference between 4G and TV signals is predicted to impact a comparatively small number of UK households, the introduction of 4G at 800MHz may, ironically, prove rather more problematic to mobile phone users themselves than to the average TV viewer.

The reason that 800MHz is such a sought after frequency for the LTE (4G) network is that the laws of physics result in lower frequency signals being more able to penetrate building walls with much greater efficiency than higher frequency signals. Therefore a mobile operator with LTE at 800MHz will likely enable better indoor service coverage than another operator with LTE at 1800MHz or 2100MHz. 

This all sounds like great news; however, as 4G (LTE) networks are rolled out, early LTE phones will be enabled for 4G data services only. So an early user benefit of 800MHz LTE is to support improved coverage for data services indoors, exactly where most smartphone users may already experience a good data service from their fixed broadband provider. To support voice calling, these devices 'fall back' to the older 2G and 3G mobile networks to either make or receive a phone call, and this is where the user experience may degrade.

Shattered 4G illusionsImagine you are a user in an area where the 2G/3G indoor coverage from your mobile operator is poor and you are often unable to make or receive a call. You hear about the new 4G network and upgrade your phone to enable you to experience it. Operating at 800MHz, you now receive a great LTE signal in your house or workplace with five bars of coverage in all locations. Now you wish to make a voice call. As soon as you hit 'send' the phone will drop the LTE connection and search for a 2G or 3G signal to use for the voice call.

Incoming calls fair no better. When a call is received by the network it alerts the phone, which then drops its LTE connection and again attempts to find a 2G or 3G signal on which the user may then receive the call. If there is no good 2G/3G coverage at the current location, or if the phone cannot lock on to the 2G/3G signal in good time, then the user will not receive the call even with five bars of LTE service showing just before the call was received.

In practice, there is potential for the voice calling experience on a 4G LTE data-only phone to be worse than that of the existing 2G/3G network for those mobile operators that do not also have 2G/3G service in the lower frequency bands!

The longer term solution to this problem is a technology called Voice over LTE (VoLTE) that will enable voice services as well as data services to use the LTE 4G signal, but there will be a gap for some period of time before all LTE phones and networks become VoLTE enabled.

What is to be done?Many indoor locations (residential, workplace, transportation and retail) are Wi-Fi enabled, with residential and workplace locations accounting for typically greater than 95% of all Wi-Fi traffic from smartphones.  Perhaps if Wi-Fi can be simply re-used to support the mobile operator's voice service, then this would provide an excellent interim solution for their customers caught in the LTE technology gap.

Happily, such Wi-Fi calling solutions do exist and are completely compatible with the same infrastructure that must be deployed in support of longer term plans for VoLTE.

Mobile providers that choose such a solution can make available downloadable apps for Android and iOS that enable full support for both incoming and outgoing voice calls over any Wi-Fi access network (even those abroad if required). For the mobile operator and smartphone user alike, using Wi-Fi to support critical voice services at locations reachable with 800MHz LTE signals but not by higher frequency 2G/3G signals may prove to be a smart choice.

Kineto is a key innovator and leading supplier of telco-OTT solutions to the mobile industry.


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