This is a small report I wrote on LTE and VoLTE. It's meant to be for anyone to read so the language doesn't get too technical.

LTE is a growing technology worldwide. There are now over 300 million 4G LTE subscribers in the world with the USA encroaching 150 million, Japan now has 50 million, China has over 40 million, South Korea is approaching 35 million and the UK has now reached over 10 million. Currently 584 operators are investing in LTE in 168 countries with plans to launch LTE, of that number a total of 330 operators have already launched LTE in 112 countries with that number looking to expand to 350 operators by the end of the year. There are currently over 1,050 LTE smartphones being sold and of that number only 146 LTE smartphones support VoLTE. So far there are only 11 operators that support VoLTE.

The first operators to launch VoLTE were SK Telecom and LG U+ in 2012, this VoLTE service was branded as HD voice to consumers to show the benefits of voice over LTE and differentiate itself from voice over 3G or 2G.

What is VoLTE?

VoLTE stands for voice over LTE and it’s more or less exactly what it says on the tin. It is voice calls over a 4G LTE network, rather than the 2G or 3G connections which are usually used. We tend to think of 4G as mostly being about downloading, streaming and web browsing, and indeed that’s primarily what it’s been used for so far, but it will also be used to support voice calls over IP.

At the moment calls can not be made over 4G, calls are still made over the 3G network via circuit switched fallback (CSFB). When a user makes a call the 4G network switches to 3G and then the call is placed. The main advantage of CS fallback is that it will enable network operators and device manufacturers to introduce LTE devices with a single cellular radio chip before VOLTE becomes available and networks are deployed widely enough to prevent having to hand over the call to UMTS or GSM too often.

The downside of the approach is the increased call setup time required due to the change of the access network and the potential location update procedure that may be required. For CSFB voice calls, the extra call establishment delay can be double the time it would take for a call to connect if you were already on 3G. In other words, the extra call establishment time is likely to be noticed by the customer who expects new technologies to work better than the previous ones and not worse. Another disadvantage can be the effect on battery life that CSFB can have and that voice calls over 2G and 3G will probably sound worse than voice calls over LTE.

Why is it called circuit switched fallback? It's because 3G technologies use a hybrid of circuit switching and packet switching. Circuit switching is a very old technology that has been used in telephone systems for a very long time. The downside to this technology is that it ties up the resource for as long as the connection is kept up. Packet switching is a technology that is very prevalent in computer networks but has since appeared in mobile phones as well. With packet switching, resources are only used when there is information to be sent across. The efficiency of packet switching allows the mobile phone company to squeeze more conversations into the same bandwidth. 4G utilises packet switching. It does not use circuit switching.

Why is VoLTE the next step for operators?

Voice is still a growing medium worldwide. Voice calls have grown by 10% in the last four years alone. By rolling out VoLTE, operators and consumers will benefit from the following

Better call quality:
-LTE Networks support QoS scheduling that ensures voice packets are being transmitted with a lower and tightly controlled latency and jitter.

Rapid call setup time:
-Calls can be setup in a fraction of the time using VoLTE which will ultimately improve the overall experience

Lower Power consumption:
-VoLTE enables the phone to dramatically reduce power consumption during inactive periods, as much as 40% lower consumption compared to 3G.

Better voice coverage:
-A number of networks use higher frequencies such as 2100Mhz or 1800Mhz on 3G. 4G is being used across a wide variety of bands with all networks using 800Mhz in the UK. The use of this lower band means that a 4G signal is more likely to reach indoors and provide better coverage than 3G can.

Interactive services
-Messaging, video and other interactive services can be used at the same time and during a call. Operators will be able to build these services on top of the same infrastructure.

No need for 2G/3G:
-Whilst this won't be apparent from day 1, Once 4G covers ~100% of the population 3G fallback won't be needed as everything can be done over 4G no matter where you are and what you need to do.

Better marketing:
-A number of networks worldwide have launched VoLTE as "HD Voice" or "Clear Voice" which has allowed them to show how VoLTE can benefit them.

For operators, the benefits can easily be seen. Better marketing as mentioned above is just one of many, circuit switched voice calls can be spectrally inefficient and having to manage multiple networks for voice and data can be a hassle. By allowing Voice, SMS, data and interactive services all on one network the operator can benefit hugely.

As I mentioned above though, not all the advantages will be seen straight away. Therefore there are short term and long term benefits but by starting the VoLTE roll out the benefits will gradually come through to consumers.

Short term benefits:
-Improved voice quality
-Shortened call setup time
-Better battery life
-Better coverage

Medium term benefits:
-Build new services on existing VoLTE architecture
-Video calling, advanced messaging, advanced voice services
-Reduce 3G/2G network dependancy and reduce number of CSFB calls.
-Introduce SRVCC to fall back to 3G mid call should the need arise.

Long term benefits:
-No need for 3G/2G CSFB anymore
-Re use old spectrum for 4G/5G data services.

For those wondering about medium term benefits, SRVCC stands for single radio voice call continuity. Some networks like Singtel already have this technology which allows voice calls over 4G to drop down to 3G mid call if you move out of a 4G area. If a 4G network has 100% coverage then SRVCC won't be needed but on a network like EE that has ~75% coverage then it will be very useful. Without SRVCC the call would drop when you move out of a 4G area. With SRVCC you can continue the call on the 3G network with no disruption. SRVCC can be evolved in the future to support the fallback of video calls and to improve call latency times when dropping down to 3G.

Eventually, all networks will look to go to LTE/IMS calling only which will eliminate fall back to 3G. This will probably go live when 2G and 3G networks are being phased out and when 4G has reached 100% coverage.

All you need to remember is that on 3G there are two separate voice and data to networks to manage that are circuit switched. On LTE there is only one network to manage and everything is packet switched including voice. In other words, Voice over LTE is just another term for delivering voice calls over the Internet. Calls will be routed in a similar way to VoIP calls through services like Skype. However, the main difference is that instead of delivering calls over the standard Internet protocol, VoLTE calls are delivered over a mobile 4G LTE broadband network.

When will this happen?

The average time to launch VoLTE is around 24 months from the start of the 4G roll out. In the UK we should see EE launch their VoLTE service first followed by Three and then Vodafone and O2. We should hear a lot more about VoLTE from all networks throughout 2015. VoLTE will bring a huge number of benefits to operators, manufacturers and the consumer. However consumers will probably notice the benefit the least apart from the improved call quality as most consumers generally don't care about the technological advancements as long as they can make a call, which they already can over 3G/2G.

So far EE have trialled the service as have Three and Vodafone.

Tom Bennett, EE’s director of network services and devices, said the launch date for VoLTE (early 2015) reflected the amount of testing necessary to get the service in the right shape for a commercial launch. “It’s the most complex thing I have ever worked on,” he said. However most 4G devices will not be able to access the service at launch, although some devices will be upgraded via a firmware update to use VoLTE.

Users care about voice, said EE – it is still the largest source of complaint from the customer base regarding the network, so the operator expends energy and money on improving coverage and quality of service despite its positioning as a 4G operator.

The UK’s largest operator – and 4G market leader – said it will invest £275 million in voice over 2G, 3G and 4G networks in 2014.

CASE STUDIES

Many of you will probably be saying why can't we use skype which is already a VOIP service and very similar to VoLTE. Good question. Operators have been competing with companies like Skype and Facebook Messenger fr a long time. These services are known as Over The Top (OTT) services. To tell the truth, when you look at it face on, there really isn't much difference between a skype call and a VoLTE call but when you look deeper you see the real differences. On Skype you're using your LTE or 3G connection through the internet, on VoLTE you're using the voice network that requires a quality of service component and uses the IMS core and new radio access network to ensure low latency and jitter as we talked about before.

An independent study ofAT&T in the USA found that compared to Skype, VoLTE used 10x less bandwidth, 4x fewer transmissions, 89% less signalling overhead and 2.3db less uplink power. The call quality was significantly higher than skype and 3G and the better like was between 60-90% longer than Skype. One interesting thing to mention is that when the network was loaded or concurrent data transactions were going on the phone, skype was unable to run the voice call smoothly but VoLTE had no impact. An example given was when Angry birds was being downloaded from google play, the VoLTE call continued as normal but the Skype call started to break up and eventually stopped and had to be reconnected.

AT&T said that call setup for VoLTE was just 2.9 seconds compared to over 5 seconds when using CSFB. VoLTE was 96% reliable in all test cases and would switch to 3G with ease thanks to sRVCC. The downsides that were noted was that LTE coverage was affecting how often a user was switching down to 3G mid call (quite a lot) and that 3G calls seemed more reliable for now. One un related issue seen was that phones that used CSFB and not VoLTE did not always return to LTE after the call. This has been seen in the UK as well.

It is clear that VoLTE works better than Skype and VoLTE is reliable and has all the advantages listed above in post 1. Thanks to eSRVCC calls are able to drop down to 3G when moving out of an LTE coverage area which can happen quite a lot when AT&T still has a number of areas with 3G coverage but no 4G.

Docomo in Japan launched VoLTE in June 2014 as Japan's first premium voice quality service. As of August 2014 there are 1 million VoLTE compatible devices in use on the network. Japan has 141 million mobile phone subscribers with 50 million of them now having a 4G phone and connection. Docomo holds 45% of the mobile market along with Softbank and Kiddi who hold the other 55%. So far Docomo has over 24 million 4G subscribers and has more than 98% 4G LTE coverage in Japan.

Docomo set up VoLTE to create a high quality voice network, a quck voice call set up time, a fast data network with voice and smooth video call streaming. Docomo are reported as saying that spectrum efficiency on LTE is three times better than 3G voice call services. Docomo set up their VoLTE network by focusing on user experience, they chose to implement SRVCC so that calls would drop down to 3G when they moved out of a 4G area. If they didn't implement this then calls over LTE would disconnect when out of an LTE area. Docomo also introduced High quality voice and video services over the LTE network. Docomo said that it took between 0.25-2.5 seconds to connect a call via VoLTE but over 7 seconds to connect a call via CSFB. Thus showing that call setup time had improved on VoLTE

Docomo says that their VoLTE network is now in place nationwide and the next step is for them to add VoLTE roaming for when other networks adopt VoLTE outside of Japan. Docomo have released a number of videos showing the following:

1. Voice quality on VoLTE vs 3G
2. Call setup time on VoLTE vs CSFB
3. Loading a map whilst on a call 3G Vs VoLTE
4. Transition from voice to video mid call

South Korea was the first country to launch VoLTE. South Korea has inter network VoLTE allowing users to make calls to people on other networks over VoLTE. There are currently 56 million mobile phone users in South Korea, 40 million of them own a smartphone and 34 million own a 4G smartphone and plan. The uptake of 4G in South Korea has been immense, 4G data use has exploded as well with 93% of all mobile data use now being through 4G and the remaining 7% being through 3G. Last month South Korea used over 110PB of data across 3G/4G which is more data than the entire UK used in the first 4 months of 2014. Bear in mind that the UK has more smartphone users. South Koreans are using 3.2GB 4G data per month with some users on unlimited data plans using as much as 16GB average per month.

LG U+ has 8 million 4G subscribers, Korea telecom has 10 million and SK telecom has 16 million. In this report we will be focussing on LG U+ as they are seen as leading the way despite being the smallest network with just a 20% share of the South Korean mobile market (2G/3G/4G). LG U+ launched 4G in July 2011 and currently have a 225Mbps LTE network with plans to expand to 300Mbps in 2015. As mentioned in medium term above, LG U+ have been launching a number of interactive services and this report will focus more on the services that VoLTE has helped to enable.

When launching VoLTE and other LTE services, U+ focused on a consumer centric model. They wanted to offer communication, web, media, life, payment, messaging and TV all over LTE. The key services they launched were Communication, Video and Personal. Lets look at these 3 areas in more detail.

Communication:
-Integrated address book which allows you to find your contacts, new friends, restaurants and more
-Multi tasking which allows you to take calls whilst using apps. e.g listen to music, make an appointment, share a sketch, send a location and more whilst in a call.
-Share with each other by watching videos and photos in real time whilst chatting on the phone. Think Samsung multi window here, you both have the same video playing on your device in real time whilst chatting.
-Spam filter registration which can be shared with other users in real time. This notifies the user if other users have reported the incoming call you're receiving as a spam number and gives a reason for it.

Video:
-Watch HD Quality video. Up to 90 live TV channels and 13,000 movies on demand.
-Can watch 2 or even 4 channels at the same time with no loss in quality.
-Video calls can be made whilst in a voice call.
-Rewind live TV and play in slow motion
-4D haptic feedback causes your phone to vibrate during an action scene.
-Videos can be shared whilst in a call.

Personal:
-Phone to phone or phone to IPTV broadcast
-Group navigation means you can share real time navigation maps with up to 5 people all driving.
-Incoming calls does not hide navigation screen whilst driving
-Send arrival time over LTE to other users.

South Korea has shown the world the benefits of broad LTE deployment, and increasing ARPU through delivery of VoLTE services. As evidenced above, Mobile operators that integrate an IMS core for VoLTE can also offer differentiated revenue-generating services, such as RCS, multimedia conferencing, Video RBT and multi-mode messaging to both SIP and WebRTC endpoints. In addition, by leveraging a common MRF to deploy these services, mobile operators can also achieve scale economies. And by adding end-to-end network visibility through service-aware policy control to improving quality of service, mobile network operators can further differentiate their integrated mobile communications offerings against OTT alternatives that don’t own the network, and consequently can’t control the end-to-end network experience.

Many use VOIP every day without realising it at work, as many office phone systems have been VOIP / SIP for years. the phones are plugged into the LAN though, wifi can be the issue, that's why VoLTE should improve things.

Three in Touch and Tugo etc are all just using secure SIP protocol, but the reason why the quality isn't great is the codec, the back end and the wifi networks they are used on. Once the networks update to the IMS core I assume VOIP will be just like it is on an office network, except with all the mobile VoLTE features you mentioned.

Interestingly Skype used to have main nodes that would channel calls and act at little hubs, but when Microsoft bought Skype, they just made all the special nodes their own, and put lots of servers around the world to carry out that function, rather than using user's machines to randomly assign that role.

One thing is, you mention using SatNav and having a call, well that works today on my 3G phone just fine, when I'm using the SatNav on my LG G3, if a call comes in it'll pop up over the top. In fact because I use bluetooth I have buttons on the steering wheel to answer and I never lose the SatNav screen or have to touch the phone. The other thing about sharing locations of other users doesn't need voice protocols on 4G either, it is all just software and would work on 3G or 4G today.

IP Multicast, which enables 'one to many' communication at the IP layer, rather than the session layer is already implemented on most mobile networks, allowing IPTV streams to be shared by many by just sending 'join' and 'leave' instructions to existing streams, meaning the host only needs to send 1 copy of the data and users opt in and out of the stream. That's how TV Catchup works, and why it requires your ISP to support multicast, which works well over 3G and 4G today without needing to do it over VOIP.

The LG U+ study was more about what they've done with both LTE and VoLTE. So the communication stuff is around VoLTE and the other stuff is more about LTE in general.

So you're right, VoLTE doesn't have much to do with some of the things listed there.

Thanks for a good read Jabbamk1. Lots of good clear info. Looking forward to Three rolling this out next year and the improvements we will see indoors with 800Mhz

Nicely written and VoLTE is clearly the future. I think though you are being a little harsh on CSFB as its performance is a key reason why we don't yet have VoLTE in the UK.

Lots of people (including DS posters) have been predicting the imminent arrival of VoLTE. Firstly in 2013, then by early 2014, then by the end of 2014 etc... This would have been possible from a technical and handset availability point of view but I've always tried to guide to expect a delay. The reason for this is when you spend a vast amount of money on a hugely complex system (which the networks have to do) it's not acceptable if the result is a worse overall experience. EE said that the metric to decide if they can go live with VoLTE is not that it be better that the current arrangement but that it be no worse! That's why we have to wait until 2015.

Now it's not that VoLTE isn't working as well as expected but rather CSFB has been much better than expected so the bar is higher. A few years ago there were CSFB horror stories regarding high failure rates and massive amounts of time being added to call setups. I think this is what you are referencing and why there was so much urgency over VoLTE a few years ago. However since then CSFB techniques improved massively and not only is reliability really good but the the extra setup time has been hugely reduced to little more than a second for most calls and there's room for that to come down further to even be below a native 3G call. Call setup times are not high on a list of things customers are dissatisfied with anyway.

The other benefits listed are real but it's arguable whether the industry can take advantage. They've already been there with video calls and failed. Similarly they don't have a great record with advanced message or data services and the OTT providers might have already eaten their lunch. SMS only worked because they thought it wouldn't! Sure, HD calls and better voice coverage can have some impact but they aren't benefits of VoLTE per se and may not apply in all markets.

So well done and I'm not deliberately trying to be negative. Ultimately we'll have VoLTE and we'll be glad when we do. It's just that it looks like I have a slightly different view on what we have now and perhaps less optimism in the ability of the industry to compete with OTT providers in non voice services. It still amazes me that the industry ended up like this over voice. Its greatest most advanced technology struggling with something that every earlier technology managed with ease.

I do agree with you, CSFB was seen as something that would be a hassle to implement and something that would cause more issues than ever. We did see some issues but nothing that had a super negative impact and in fact CSFB works quite nicely at the moment in the UK.

I mentioned in my post above that most consumers will be the last to notice the benefits of VoLTE because to them, a voice call is a voice call. Whether it's on 2G/3G or 4G it's all the same. And the only area the average consumer will really see the difference is with voice quality. Especially if they're jumping from 2G or a non HD Voice network to a 4G VoLTE network.

OTT services still rule when it comes to messaging but VoLTE should be able to claim back some of the voice call share due to the Quality and additional services and features that can be built on top.

And yeh, EE and Three were both planning to launch VoLTE in some form during Summer 2014 but looking back that probably would have been a mistake. Unlike other operators who have covered the nation (SK/JP/USA), the UK still has pretty poor 4G coverage outside of cities and towns and it wouldn't be worth investing in VoLTE.

2015 seems like a much better time to launch, and as you say it'll allow EE to launch it when it's better than the current arrangement. Then again I wouldn't mind waiting until all 18,000 sites had 1800Mhz broadcasting so we could get rid of 2G (or even 3G)

OK, a few points.

How will VoLTE HD voice be better than HD voice already implemented on Three?

What will people do with the couple of seconds saved on the set-up time?

Will there be any interoperability issues between networks like there are in the US?

HD Voice and VoLTE won't have a difference in quality per say. It's more how the voice call is made. On 3G you're still using the circuit switched network. On LTE you're using the packet switched network. What this means is that everything can be done on the LTE network and operators can choose to build additional services on top.

So it won't be better from a consumer point of view at first. Operators will benefit first.


Make a cup of tea...
Ok, while this sounds like a lame benefit it's still a benefit. Basically it saves battery life and takes a shorter time to connect the call. It's just better ok!


Probably. At first.

Hopefully we will get "HD voice" quality between networks using VoLTE - rather than the stupid situation where 3 of 4 networks now support HD Voice over 3G/UMTS and you only get the benefit if you call someone on the same network as yourself.

Here are some things that only take a second.

http://www.youtube.com/watch?v=BYyA4ekZvi8

Cross-Network support will likely not come at start but I know some networks have got Cross-Network VoLTE running now.

Hi

Quick question, when VoLTE is rolled out. Will it work on all handsets or only on newer handsets that have been released in the last year or so?

Thanks

Baz

I think it's easier to wait for a good 4G coverage than implement moving the call from 4G to 3G. Just dropping it when leaving the 4G area with low coverage isn't really acceptable I'd think.

Difficult question to answer, depends on the handset, and the chipset inside and the make. For example iPhone 5s won't and that is only just a year old, need a 6 or 6 Plus. On Android its even less clear as its not the version of Android but the modem firmware and the modem chip. It will be complex and nobody knows until a UK network launches.

It certainly won't work on all 4G handsets. Even some capable of supporting VoLTE won't work.

Expect any of the flagships that come out this upcoming year will work. Devices on Android that appear to work are the LG G3 and S5 they are working on both Verizon Wireless and T-Mobile US.

Only certain phones are the iPhone 6 and 6S though.

As of October there are around 150 VoLTE compatible handsets. And that's out of around 1,050 LTE compatible handsets.

So It'll only work on a small percentage of phones.

And even then you'll require a software update on those phones to use VoLTE.

So It'll be up to the network at first if you can activate VoLTE on your device or not.
Or you need a phone with firmware where VoLTE is active already.

In the future phones will "just work" on VoLTE.

Telefonica Germany has now deployed their VoLTE solution today. Commercial launch will be very soon.

Telefónica Germany, the largest mobile operator in terms of subscribers in Germany, selected Ericsson as main supplier to upgrade their network to support VoLTE. Telefónica is one of the first operators in Europe that has now completed the upgrade of their network to be ready for commercial VoLTE launch. VoLTE has been deployed in all areas where Telefónica has LTE coverage in Germany. The commercial launch will take place once Telefónica has secured the full VoLTE device eco-system for mass-market launch.

VoLTE will provide users with superior HD voice call quality, instant call-set-up, and allow simultaneous usage of superfast LTE data services during calls. Ericsson's SRVCC (Single Radio Voice Call Continuity) functionality enables seamless handover of ongoing voice calls from LTE to circuit-switched 3G and 2G networks.

EE have introduced a class of handsets they haven't sold before with 4G sims like this one. Maybe it's VoLTE ready? Good that you can get buy it with unlimited data too

http://shop.ee.co.uk/mobile-phones/p...#details-plans

Do you have a list?

Nope.

But the leading manufacturers in VoLTE compatible phones are Apple, Asus, Fujitsu, Huawei, LG, Pantech, Samsung, Sharp and Sony Mobile.

HTC am cry.

I thought HTC did make VoLTE devices I could of swore they were the ones who made a VoLTE for MetroPCS.

They're not one of the leading manufacturers.

In the USA no HTC phone has been enabled to work over VoLTE yet I believe.

Expect the upcoming M9 will have VoLTE now that 3 of the American networks have VoLTE up and working. Though in fairness AT&T only have a token VoLTE set up at moment. Both Verizon and T-Mobile have national support for it.

But that should be enough to give them good cause to support VoLTE on there upcoming 2015 Flagship.