If there is one subject that has rocketed up the agenda over the last two years it has been the various proposals for deploying LTE in Wi-Fi bands. As Qualcomm’s VP, Business Development, Neville Meijers pointed out at SCWS 2016 (9-12 May) the variants now include: LTE-U/LAA, LWA, MulteFire and Wi-Fi - 802.11ax.
LTE-U and LAA are the options most likely to appeal to operators as they involve aggregating licensed spectrum with Wi-Fi spectrum. Meijers said: ‘We are ensuring that if you deploy LTE-U you can upgrade it to LAA.
‘The two variants are perhaps the fruit of particular regulatory environments (LTE-U does not deploy ‘listen before talk’, which is mandatory in many regions) and we think if operators are looking to aggregate licensed and unlicensed spectrum they will probably use LAA.’
That seemed to chime with the view of Benoit Graves at Orange in a later panel session on LTE and Wi-Fi co-existence when he said: ‘All options will be on the table in a couple of years’ time, but the most straightforward to us is LAA. It is an advanced version of 4G and we don’t have to change anything in terms of billing and the way we address the technology, unlike LWA.’
LWA is more challenging for operators as they have to integrate Wi-Fi into their back-end systems, although if the operator has already deployed it own Wi-Fi they will have already addressed that issue.
But it is MulteFire that is the option that seems to be catching everyone’s attention. The big difference is that although it uses LTE technology, there is no need for an LTE anchor channel.
Specifications for MulteFire are being worked on by the MulteFire Alliance, as 3GPP has not included it in its current LTE Release programme. The Alliance was founded late last year by Qualcomm and Nokia, quickly followed by Ericsson and others. It now has 20 members and multiple working groups
MulteFire Alliance founded late last year by Qualcomm and Nokia, who were quickly followed by Ericsson and it now boasts some 20 members with multiple working groups.
Uplink and downlink in unlicensed spectrum
Speaking to Wireless, Stephane Daeuble, Head of Small Cells and HetMet Product Marketing at Nokia, explained the origin of MulteFire. ‘When 3GPP started looking how MNOs could leverage unlicensed spectrum three or four years ago, it went down the LTE-U and LAA route, as having an LTE licensed anchor channel provides some degree of reliability.
‘But at Nokia we thought; why don’t we go a step forward and look at ways to use both the uplink and downlink in unlicensed. 3GPP’s work gave us the foundation for MulteFire as we could leverage a lot of what it had done especially with LAA. We are basing the MulteFire standard on LAA Release 13, which focuses on the downlink only.
‘But it brings in the element of co-existence. To deploy listen before talk (LBT) you need to change the LTE frame level (1ms or 1mm usually), but you need to make that longer to allow LBT.
MulteFire uses the same concept. LTE Release 14 will do the same thing coming on the uplink – control channel and supplemental downlink, explained Daeuble.
‘At MWC 2016, we showed LAA and MulteFire as very good neighbours with Wi-Fi in a densely packed cell. It could handle the interference and it provided a good experience even at the edge of the cell,’ said Daeuble.
New business models
One benefit that comes with unlicensed spectrum is that it opens up hundreds of different business models. The lack of multi-operator small cell solutions has hindered their deployment in businesses and hotels. They would like a neutral host but it is hard to deploy and limited in terms of scale??
‘Small cells are coming,’ said Daeuble, ‘but for an enterprise user getting a neutral host solution is difficult. Mobile operator core network (MOCN) can be done, but not all MNOs can do it because of the regulatory environment they operate in.
‘But if you remove the barrier of licensed spectrum and having to work with MNOs, an enterprise can build its own network. In the mining industry or oil and gas, MulteFire can complement Wi-Fi networks by carrying the more voice critical traffic or connectivity for self-driving trucks on MulteFire.
‘However, we shouldn’t forget that even the MNOs can expand using MulteFire (Softback has joined the Alliance) as they can lead the small cell deployment in a hotel and sell the solution on to other MNOs. So, they can expand into places where they do not have spectrum today,’ said Daeuble.
Other areas include the Internet of Things, which could be deployed as another layer on top of Wi-Fi to form an additional network with increased coverage and reliability, but less cells and you will need increased capacity. It is a complementary type of solution where IoT can use NB-IoT (the forthcoming Narrowband IoT standard in LTE) with no problems.
CCTV is another very attractive propostion for MNOs and with MulteFire they can deploy unlicensed LTE solutions very quickly to meet increased demand. MulteFire is also looking at LANs where it could be an ideal solution – 5GHz is so vast – lots of capacity there – better exploit spectrum for multi-user in lTE –
Daeuble cited Nokia’s recent Nokia Flexi Cell small cell deployment for the Chinese F1 Grand Prix where it 840 active users, but he says with MulteFire it could bring in many more users. With the F1 event we also deployed a MEC system that can apply to MulteFire as well for unicast video to 200,000 spectators etc (or whatever the figure was) – It can enable lots of things to work together.
Release 1 of the MulteFire standard is due out in early Q4 2016, after which the Alliance will then work on a certification interoperability programme. Daeuble said that we will not have to wait too long for chipsets.
Qualcomm has everything integrated in system on a chip, so they just need to create the link. The baseline for LAA is already being worked on. LTE-U will be ready quite soon and LAA next year, but they won’t freeze the chipset until the standard is complete, so it is not a big stretch to get to MulteFire and for Nokia the hardware is not a big stretch for us. We can go to trial very rapidly using our Flexi Zone technology.
In terms of which of the unlicensed options is best used for what, Daeuble said LAA seems to the best option for outdoors because of its range, while LWA and LWIP is more useful indoors where there are existing Wi-Fi APs.
We may have MulteFire and a Wi-Fi module in the same box, which can serve multiple operators. You split the technology according to what you want to do with it. The interest we are seeing is very high from operators and from likes of cities for smart cities applications using MulteFire for IoT.
But for the MNOs, MulteFire solves a big issue for them. They may invest indoors in big, important subscriber buildings and provide femtocells for residential use at the other end, but it is all that mass in the middle that is the problem. The MNOs don’t want to invest in indoor coverage for those customers and so they then change operator. But MulteFire provides a solution for both parties.