5G Small Cells at Home

Last year, NGMN published a whitepaper on '5G Small Cells at Home'. The whitepaper is available here. The summary on the website states:

The first objective of this white paper is to explore the potential technologies that could help improve the performance of local connectivity at home.

In addition to this, the second objective is to look for solutions of radio resources management at home that would be controlled by the network. The current situation is that the local connectivity is selected by a connectivity manager embedded in the operating system of smartphones that may not have a complete view of what happens, for instance in terms of traffic on cellular networks.

The global objective for operators is then to keep home users connected wirelessly to their local – fixed access network based – connectivity (delivered e.g. by Wi-Fi, a “small cell at home”) with a “premium” quality of service instead of adding pressure on the Radio Access part of the mobile macro network. Challenges for mobile macro networks are for example a lack of (licensed) spectrum that can cover efficiently indoors from outdoor macro network (e.g. low bands spectrum), cost of the radio sites, incl. equipment.

The abstract from the whitepaper as follows:

It is observed that traffic offload - from cellular networks to indoor local Wi-Fi connectivity - takes place when users are at home, but tends to decrease, due to increasing cellular data volumes and due to sometimes better user experience (coverage, throughputs) offered by 4G compared to Wi-Fi 5 (mainly available today at home).

In order to reverse the current trend, this white paper proposes to consider 5G New Radio- Unlicensed (NR-U) technology (that will be part of the future 3GPP Release 16 – Dec. 2019) as a potential (additional) candidate for future small cells deployed at home.

It is expected that small cells at home using NR-U technology will provide – at least – radio performance as good as what Wi-Fi 6 could do, will enable the optimization of the management of radio resources as NR-U could be connected to operators’ core network. Furthermore, the deployment of small cells at home can ensure that the traffic generated at home will be transported via the fixed network, regardless if the Wi-Fi interface of the device is switched on or off.

It's available here.

Related Posts:

• The 3G4G Blog: 5G and Fixed-Mobile Convergence (FMC)
• The 3G4G Blog: Introduction to 5G ATSSS - Access Traffic Steering, Switching and Splitting
• The 3G4G Blog: Exploring Network Convergence of Mobile, Broadband and Wi-Fi
• Operator Watch Blog: BT's Converged Core to Launch in 2023
• 3G4G Small Cells Blog: Malaysia Looks at Small Cells for 5G
• 3G4G Small Cells Blog: 5G CrowdCell: World's First 5G OpenRAN Small Cell
• 3G4G Small Cells Blog: SK Telecom's In-building 5G NR Repeaters and 'Layer Splitter'

Hong Kong gets LAA via SmarTone Small Cells

According to Mobile World Live:

SmarTone, the smallest mobile operator in Hong Kong, said it installed small cells using licensed assisted access (LAA) technology in a number of congested areas in the territory and plans to extend the rollout to additional locations.

The operator, with a 17 per cent market share by subscribers, said its LTE network now makes use of both licensed and unlicensed spectrum as well as five-carrier aggregation to reach theoretical peak download speeds of 1Gb/s.

The LAA small cells were deployed in Central, Causeway Bay, Tsim Sha Tsui, Mong Kok and Shatin districts. By installing LAA small cells in strategic locations, the operator said its network can absorb traffic surges during festive and special events.

In June Hong Kong’s regulator allocated additional spectrum for the provision of public mobile services, a move it said would put the market at the forefront of adoption of advanced technologies including LAA. The Communications Authority officially allocated 580MHz of spectrum in the 5GHz band.

I have written about LAA on the 3G4G blog here. I have also expressed doubts here with increasing densification where Wi-Fi and Mobile signals will have to compete to deliver best end-user experience.

Disruptive Asia mentions that Ericsson is the vendor. Ericsson conducted trials with SmarTone last year, more details available on Ericsson's website here. As per Disruptive Asia:

The Ericsson LAA technology deployed by SmarTone combines licensed and unlicensed LTE carriers with 5CC carrier aggregation, 4×4 MIMO and 256 QAM to enable gigabit level speeds (at least theoretically – real-world speeds are likely to be around half of that, although that’s still way faster than current LTE speeds).

One catch with LAA is that it requires customers to use an LAA-compatible smartphone to take advantage of the faster throughput speeds – and there aren’t very many of those at the moment. According to the latest report from the GSA (July 2018), commercially available handsets supporting LAA include the Samsung Galaxy S8, Note 8 and S9, Sony’s Xperia XZ Premium and Xperia XZ1, HTC’s U11, LG’s V30 and V30+, and ZTE’s Nubia Z17.

One reason there aren’t many handsets is that the LAA ecosystem is still in its infancy, and few operators have commercially launched LAA – in fact, SmarTone is only the fifth cellco in the world to do so. Meanwhile, the GSA counts just 22 LAA trials and deployments in progress.

Test report on Licensed Assisted Access (LAA) using the unlicensed 5 GHz band by SmarTone Mobile Communications Limited is available on Hong Kong's Office of the Communications Authority website. See September 2018 report here and January 2018 report here.

HTCL (Hutchison Telephone Company Limited) also known as Three Hong Kong is also looking at LAA and is doing its own testing. Test report from The Communications Authority website is available here.

Related Posts:

• T-Mobile USA is deploying 25K small cells with LAA

T-Mobile USA is deploying 25K small cells with LAA

Source: PCmag

T-Mobile keeps talking up its small cells and 5G deployments. ICYMI, I recently wrote about the 5G rollout in 600MHz on 3G4G blog here. In a recent interview in Fierce Wireless, T-Mobile’s SVP of radio network engineering and development, Mark McDiarmid reminded everyone that the company plans to deploy up to 25,000 small cells this year, some just a few hundred yards away from one another.

This is all following on from the announcement last year that T-Mobile has contracted to deploy 28,000 small cells. Since then T-Mo has quietly changed its strategy from LTE-U to 3GPP standards based LAA. This was on back of a successful trial with Ericsson where they achieved speeds of 1.1 Gbps using 12-layer Licensed Assisted Access (LAA) technology – the first in the world to hit speeds beyond the 1 Gbps threshold on unlicensed spectrum.

We aren't announcing any other cities at this time. However, the small cells being deployed today are LAA ready while we upgrade existing small cells. These all use our existing bands.

— Neville (@NevilleRay) March 1, 2018

For the PCMag article, Milan Milanovic, Technical Evangelist for Ookla did some tests and the article had the following to say:

At a cell site at 45th St. and Third Avenue in Manhattan, T-Mobile is combining 20MHz of its Band 4 spectrum with 60MHz of LAA spectrum. Phones connect to the cell site and send data up using the 1700MHz/2100Mhz Band 4 spectrum, and then get downloaded data via a combination of Band 4 and LAA.

Those speeds are insane. In 13 tests, we got an average of 503Mbps down and 42.7Mbps up. Just to compare, in Ookla's Speedtest Intelligence database, the top 10 percent of T-Mobile download speeds in that ZIP code are only around 70Mbps down.

LAA-capable phones can get up to ten 100Mbps download streams on this cell site, with four on the licensed spectrum (4x4 MIMO) and two on each of three channels of LAA spectrum, Milanovic said.

Other users on this cell site will do well, but not as well as LAA users, Milanovic notes. The site is also equipped with T-Mobile's workhorse Band 2 and the low-frequency Band 12, which penetrates inside buildings.

LAA is only a solution for dense urban areas, though. This cell site has a coverage diameter of about four blocks (a bit over 1,000 feet), which is considered pretty good for LAA. That's a little better than what the coverage probably would be if the site was sending down 5GHz Wi-Fi, and it's a little better than New York's LinkNYC public Wi-Fi posts.

A nearby LinkNYC post doesn't appear to be interfering with the T-Mobile signal, Milanovic said. That's good news, because one of the concerns about LAA is whether or not it will coexist well with powerful public Wi-Fi.

You'll need the right phone to hit these speeds, and that's not an iPhone. Currently, LAA is supported by T-Mobile's Samsung Galaxy S8, Note 8, Galaxy S8 Active, Galaxy S9/S9+, LG V30, and the unlocked Huawei Mate 10 Pro £399.00 at Amazon. We'll make sure to test LAA when we go on the road with our Fastest Mobile Networks drive tests this spring.

Here is latest on the LAA speed front from Milan Milanović:

The Galaxy S9 puts you in a fast LAA lane even during the peak hours in the middle of Manhattan. @TMobile @SamsungMobile @QualcommTech pic.twitter.com/tWzUh4LoPT

— Milan Milanović (@milanmilanovic) July 17, 2018

Not everyone agrees that LAA has a long term potential or performs well where 5GHz Wi-Fi channels are very busy. Others (mainly vendors) disagree.

You may also enjoy reading Juny Song's article on LinkedIn!

Note: I should point out here that what T-Mobile refers to as Small cells are actually RRU's and not complete base stations. You may want to refer to my tutorial here to understand this better. The bottom picture on this post will help too.

Carrier Aggregation (CA) and Dual Carrier (DC) enhancements in Release-13

Recently I posted a summary whitepaper of 3GPP Release-13 by 5G Americas. This article from NTT Docomo technical journal complements that nicely and provides in depth analysis of selected features.

The article (embedded below) focuses on Carrier Aggregation (CA),Dual Carrier (DC) enhancements, LAA and LWA. In this post, I am going to restrict the discussion to CA and DC.

The following is from the magazine article:

Carrier Aggregation (CA):

Up to Release 12 CA, a maximum of 5 LTE carriers called “Component Carriers” (CCs) could be configured for a User Equipment (UE). This enables a maximum 100 MHz bandwidth for data communications, which achieves a theoretical peak data rates of approximately 4 Gbps, assuming eight Multiple Input Multiple Output (MIMO) layers and 256 Quadrature Amplitude Modulation (QAM) for downlink, and 1.5 Gbps assuming four MIMO layers and 64QAM for uplink.

In Release 13, the maximum number number of CCs that can be configured for a UE simultaneously was increased to 32 to archive higher data transmission rates with wider bandwidths. This enables a maximum 640-MHz bandwidth for data transmission, achieving peak data rates of approximately 25 Gbps for downlink with 8 MIMO layers and 256QAM, and 9.6 Gbps for uplink with 4 MIMO layers and 64QAM.
...
Release 13 introduced the new function to enable PUCCH configuration for a Secondary Cell (SCell) in addition to the PCell in uplink CA. When CA is performed with this function, CCs are grouped together either with the PCell or SCell with PUCCH (PUCCH-SCell). UE sends UCI for CCs within each group by using the PCell or PUCCHSCell. With this new function, uplink radio resource shortages can be resolved by offloading UCI from macro cell to the small cells while keeping the macro cell as the PCell.

Dual Carrier (DC):

Release 12 designed DC to achieve user throughput comparable with that of CA by aggregating multiple CCs across two eNBs. In release 13, DC was further enhanced with higher uplink throughput and more flexible deployment.

In DC, separate eNBs allocate uplink resources independently for a UE. Hence, Release 13 addresses how to allocate adequate uplink resources on multiple CCs for UE. Typically, eNB calculates the required uplink resources based on the uplink buffer amount reported from UE. In DC, since both eNBs calculate the amount of uplink resources based on the report and allocate them to the UE independently, excess uplink resource allocation over actual amount of remaining data will occur. In particular, with small data packets, if resources are allocated by both eNBs, the UE may send all data to only one of them, and send padding (meaningless bit strings) to the other eNB, which wastes radio resources.

To prevent the excess uplink resource allocation for the small data packets described above, new uplink transmission control methods were introduced. In Release 13 DC, UE buffer status reporting and uplink data transmission are controlled based on the amount of uplink data buffered in the UE.

If the amount of the buffered data is smaller than the threshold configured by the eNB, the UE performs buffer status reporting and uplink data transmission only to one of the eNBs, just like DC in Release 12. In contrast, if the amount of the buffered data is larger than the threshold, the UE transmits to both eNBs. This buffer size-based mechanism solves the uplink resource over-allocation problem since only one eNB is aware of the buffered data and allocates resources when the amount of the buffered data is small.


The paper is embedded as follows:

Related posts:

• Inside 3GPP Release-13 - Whitepaper by 5G Americas
• Dedicated Core Networks (DCN) for different traffic types
• New whitepaper on Narrowband Internet of Things
• LTE-Advanced Pro (a.k.a. 4.5G)

MulteFire: A double-edged sword

MulteFire has been a lot in news recently. ThinkSmallCell published a whitepaper and an interview with Stephan Litjens, Chairman of MulteFire Alliance, outlining its objectives and roadmap. Light Reading held a webinar, which is available here for anyone interested. The overview of the webinar says that the attendees will learn how MulteFire:

• Delivers LTE-like performance with WiFi-like deployment simplicity
• Compares to other LTE technologies operating in unlicensed spectrum
• Coexists harmoniously with other technologies in unlicensed spectrum, including Wi-Fi
• Broadens the LTE ecosystem to existing and new wireless providers
• Provides a neutral host to serve any user

I agree with LTE-LAA and MulteFire and they both have a potential to deliver amazing speeds and capacity for the operators and any service providers who would use it. While it is a great technology enhancement, MulteFire can potentially disrupt the industry as we know today. Let me explain.

Picture courtesy of Keith Parsons

The way every one is seeing MulteFire is that operators can use the freely (or nearly free) 5GHz spectrum that is available. While there are or will be some restrictions, it could be used with low power indoors. The WiFi service providers have been eyeing this spectrum from a log time and 802.11ac is one such standard that makes use of this spectrum.

The end user does not necessarily understand the technology very well. Even though Wi-Fi enhancements are quite good and complex, from an end users perspective, Wi-Fi is free and "why should I have to pay so much for Wi-Fi?" ThinkSmallCell wrote an article on this topic back in January here.

The same consumer will have no issues generally paying for a MulteFire kind of technology as the origin of that is from the cellular world. While I have seen articles suggesting that MulteFire is more efficient than Wi-Fi protocols, I think we can disregard the efficiency angle from this particular post.

My first point here is that end users may be more willing to pay for MulteFire than for Wi-Fi.

The second point is that there is nothing stopping these Wi-Fi service providers from using MulteFire. As that would be a standard out of the box technology, possibly available as small cells, they can use it in conjunction with their Wi-Fi hotspots to provide more 'premium' coverage. Of course they will have to use different parts of spectrum for both these technologies. So here is a possibility of Wi-Fi service providers providing limited mobile services.

Now there is nothing stopping a large Wi-Fi SP to become an MVNO and use 4G/5G for high mobility connections and Wi-Fi / MulteFire for low mobility connections.

This does not just stop here. Many big warehouses and industrial complexes use private LTE networks. In this case they lease the network from a company that may also have chunk of licensed spectrum they bought. In some cases some operators are also providing commercial networks with pico cells / small cells. With MulteFire being widely available, these businesses / warehouses can use out of box small cells with any available devices supporting the technology.

Here there will be disruption with the value of these private licensed spectrum falling to a very low value. These private LTE network providers will have to up their game and compete against new entrants. The focus would change from technology and hardware to services.

There is a possibility of similar kind of disruption happening in testing arena where the only reason some test & measurement companies charge so much is because of technology being niche. Mass availability of small cells in license exempt spectrum may change this equation.

While these are just my thoughts, I am hoping that you would provide your view in the comments so we can have a healthy discussion on this topic.

Wi-Fi: Future Roadmap and LTE

At the WBA Wi-Fi Global Congress, Intel provided a good summary of the way things are progressing in the WiFi world, including the standards updates that are going on. Luckily I found a video by the same author in from an IEEE conference which is also embedded below.

Wi-Fi is becoming important and a useful rule of thumb is that the spectrum in 5GHz is roughly around 10 times that of 2.4GHz and the spectrum is 60GHz is roughly around 10 times that of 5GHz. (not all spectrum is available everywhere so just use this as a rough guide).


As I mentioned in a presentation I gave this week, there are three different approaches being proposed at the radio level; LTE-U, LAA and LWA. I wrote a post on LWA not long back on the 3G4G blog here.



Dave Wright from Ruckus Wireless has kindly shared a recent presentation on different proposals for LTE operation in unlicensed spectrum. The timeline above shows how quickly things are moving. Here is a the presentation

It would be important from Wi-Fi vendors point of view that LTE-WiFI Link Aggregation is standardised as part of Release-13 as there would be an option which would be agreeable to everyone.

10 million small cells and growing?

There were some good news that was announced in MWC 2015. Here are some interesting points from Total Telecom:

• Operators around the globe have purchased more than 10 million small cells
• In excess of 75 operators worldwide are using small cells in their networks
• The majority of these to date have been deployed in residential scenarios, but we have also seen a significant step upward in the enterprise and urban sectors.
• 17,000 small cells have been deployed in rural or remote applications

While this all sounds good, Small Cells are facing many challenges. The biggest among them being WiFi. With the introduction of VoWiFi, many operators are starting to play a waiting game rather than deploy more small cells.

I blogged back in 2013 that AT&T planned to deploy 40,000 small cells by 2015 but it looks like they have now abandoned their goal. The reason being cited is that they acquired another small operator (Leap Wireless) which gave them additional macro sites, hence removing the need for small cells.

As per a report by the analyst firm ThinkSmallCell, TalkTalk, a UK based "thick" MVNO is trying to deploy an "Inside-out" Femtocell network. They have also been experimenting with 3MHz bandwidth in LTE and surprisingly, it works fine on most devices.


Another option could be to have LTE-LAA/LTE-U along with this and they could provide good speeds not only to the people indoor but also outdoor.

In any case, we will have to wait and see if operators continue rolling out small cells and if they do why, how, where and in which situations.

LTE-LAA updates - Jan 2015

There has been quite a few updates on LTE LAA in the past month. First, there is this good video from Ericsson explaining what it is:

The 3GPP chairman recently presented a status update about developments on unlicensed spectrum at an IEEE 802 meeting last month. His presentation is embedded below:

3GPP & unlicensed spectrum from Zahid Ghadialy

IEEE 802 group have their own presentation on the co-existence lessons learned. This is embedded below:

Ericsson has also got a recent presentation on this topic. As can be seen, they expect a solution to be available in 2016-17. Presentation embedded below (download link here)

Finally, if you watched the video by Ericsson, they mention that one of the key milestones of 5G is to be able to combine licensed and unlicensed technology. One of the technologies being proposed in 5G is called Multi-Stream Aggregation (MSA). MSA allows multiple access technologies over licensed and unlicensed bands effectively. The picture above shows how it would work in theory. It may be more difficult in practise though. 

Unlicensed LTE (LTE-U) for Small Cells

I first wrote about LTE-U (or U-LTE as referred by others) back in December last year pointing towards the Qualcomm presentation here. As things move fast in our industry, quite a few things have happened in the last 6 months. Huawei did a demo of U-LTE in Mobile World Congress this year and LTE-U has been a constant topic of discussion in various 3GPP meetings. A half-day workshop is due to take place in June to discuss this topic further. In the meantime I have summarised some of the discussions that took place (unofficially?) in Jan 2014 between the interested parties.

To be clear, the discussions for LTE-U are centred on the 5GHz unlicensed spectrum. As you can see from the picture above, there is a massive amount of spectrum that is available, either free to use (unlicensed) or in a lightly licensed way.

There are strict rules and regulations in place to make sure this license is not misused or monopolised. There will be a need for Dynamic Spectrum Access (DSA) techniques that I have discussed here. The current LTE standards do not have a DSA inbuilt and hence referred to as "Rude". The following is from a recent Light Reading article.

The technical concern with LTE-U, as Peters describes it, is that LTE is a "rude" technology. WiFi includes a "politeness protocol" that LTE lacks, meaning that WiFi will back off if it senses interference from other users. Eventually rude ol' LTE operating in WiFi's polite bands could take over the band.

The 3GPP called another unofficial meeting in January to discuss concerns around LTE-U, which also included the potential effect on the value of licensed spectrum, the need for international harmonization of the unlicensed bands used for LTE-U, and whether the technology would be for downlink only or uplink as well. The group met again in March, primarily to work out timing for the new technology's deployment.

Huawei presentation explains why unlicensed carrier offloading, see the embedded presentation for details.

NTT Docomo shows the various deployment scenarios and also lists the regulatory aspects, especially in Japan. See the complete presentation below:

Nokia has even gone ahead and done simulations for different scenarios. The scenario above shows LTE deployment in the same unlicensed band as WLAN as you can see, the results are similar to the interference in WLAN-WLAN case.

There is also a roadmap to how LTE-U standardisation will work in 3GPP, hopefully after the workshop in June, we will probably hear more.

As expected, some of the operators with heavy investments in WiFi (like AT&T) have some reservations on LTE-U. Some analysts on the other hand are sceptical on how much savings there would be, taking the interference into account. Note that spectrum is just one part of deployment costs, there are many other factors to consider. Personally, I don't have an issue whether this will work or not, it definitely would do but with all the advancements in LTE-Wi-Fi Interworking, I think we may be able to do a better job with just selective deployment of LTE-U and using technologies like MAPCON, IFOM, Hotspot 2.0, etc.

Added on 9th July 2014

3GPP held their workshop on unlicensed LTE on 13/06/2014. See the news on 3GPP website here. All documents are available here.

Dynamic Spectrum Access (DSA) techniques for Small Cells and Wi-Fi

Picture Source: Analysis Mason

There is a lot of spectrum which is used sparingly or is kept reserved for unlicensed or shared access. Any party that wishes and is allowed to use this spectrum has to co-ordinate with the license holders or others in similar situations. Hence we have different access mechanisms which are collectively called as Dynamic Spectrum Access (DSA) techniques.

An article by Analysis Mason on this topic suggests the following:

The term DSA has come to encompass a number of different approaches and techniques that aim to increase the utilisation of the radio frequency spectrum. At its most ambitious, it is hypothesised that cognitive and software-defined radios could intelligently choose when to transmit, so as to avoid other radio transmissions and also to avoid causing undue interference to fellow frequency users. Short-term propositions include near-real-time spectrum assignment in certain bands and greater use of long-term secondary spectrum leasing to authorised spectrum partners.

DSA is therefore all about making better use of radio spectrum through re-use of 'idle' bandwidth, being either frequencies that are not used in all locations, in which other systems could be deployed, or frequencies that are only used intermittently, and which could therefore be re-used outside these times. These 'gaps' in utilisation, which provide opportunities for DSA, arise for a number of reasons.

• Coverage: a licence holder might not be using its allotted licence in a specific region.
• Time: an area of spectrum might by less-frequently required at different times during a day (or on longer timescales).
• Lack of service users: there may be a limited number of subscribers taking advantage of a service.
• Licence technical parameters: the regulator may have mandated that a piece of spectrum can only be used for a specific purpose, while other technologies emerge during the life of a licence that can use the same spectrum.
• Pragmatic under-utilisation to prevent interference: empty guard bands are placed between spectrum bands to stop transmission leakage to prevent interference, which could be re-used by systems that have the appropriate characteristics to avoid interference.

One of the overarching drivers for DSA is to help overcome spectrum shortages – particularly noting that under-utilised bands may exist across a relatively wide range of the spectrum. Even in the economies where wireless communications have developed the most and usage restrictions have been removed, thus making spectrum use as flexible as possible, spectrum under-utilisation is still considered to be widespread.

The Cisco vision on the other hand seems far too optimistic and suggests the following:

TV White Spaces (TVWS) are spectrum allocated to TV broadcasts, but not being used in a given geographic location. TVWS radios allow for use of white space spectrum for unlicensed wireless access.

Authorized Shared Access (ASA) or Licensed Shared Access (LSA) allow a secondary licensee to use the “shared” spectrum when the primary licensee is not using it.

The United States Federal Communications Commission (FCC) has proposed a three-tier model for shared access in the 3.5-GHz band. Tier 1 would be for incumbent federal agencies, including military radar users. Tier 2 would be authorized prioritized access similar to ASA and LSA. Tier 3 would be generalized authorized access, which is similar to unlicensed access.

A number of DSA technologies already exist or are in exploration.

Geo-location, database-based spectrum sharing techniques have the most traction as a practical approach to spectrum sharing. Devices that want to use shared spectrum must geo-locate themselves and consult a database to determine what spectrum is available.

The geo-location database manages the spectrum resource allocation based on predefined policies and availability to ensure the primary licensee is not impacted. An enhanced version of the geo-location database system—called a Spectrum Access System (SAS)—is the basis for the FCC spectrum-sharing proposal in the 3.5-GHz band.

A second technology is cognitive radio, which senses and monitors the radio environment. This includes knowing the location and policies for self-regulation. Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) are cognitive radio techniques that allow co-existence with radar and satellite systems.

Another technology is Software-Defined Radio (SDR), which allows devices to adapt to local radio conditions and use the appropriate radio frequencies.

I came across this very interesting whitepaper by MIT that details all the DSA techniques and its progress. Paper embedded below:

New Models for Protected Shared Access - Toward More Efficient Spectrum Management from Zahid Ghadialy

We will discuss in the future post how the DSA techniques could be useful for using Small Cells in the unlicensed spectrum (a.k.a. LTE-U).

LTE-U: First step towards 'Operator-neutral' Small Cells

3GPP member companies have decided to take the Small Cells vs WiFi fight back into the Wi-Fi camp by unveiling the initiative to have LTE in the unlicensed band (officially known as LTE-U but another interesting term uLTEA has been proposed unofficially too). 

Mike Roberts wrote an interesting post on ITM Blog:

Qualcomm has launched a radical initiative to deploy LTE Advanced in the unlicensed 5GHz band, which has traditionally been the preserve of Wi-Fi devices. If the initiative gains support, it could be a hammer blow to carrier Wi-Fi, though Qualcomm says it is still a strong supporter of all types of Wi-Fi, given its Qualcomm Atheros division, which is a leading producer of Wi-Fi chipsets. 

Qualcomm CEO Paul Jacobs unveiled the company’s initiative for LTE Advanced in unlicensed spectrum at its financial-analyst day in New York on Nov. 20. It was interesting timing, considering that the main annual carrier Wi-Fi event, the Wireless Broadband Alliance’s Wi-Fi Global Congress, was taking place on the same day on the other side of the world, in Beijing. 

The chipset giant followed the announcement by its CEO with detailed presentations on the initiative at Informa’s LTE North America event in Dallas on Nov. 21-22. The essence of Qualcomm’s proposal is that it is complicated to integrate LTE and Wi-Fi to create carrier Wi-Fi, so a better option could be to use LTE Advanced to extend LTE into unlicensed spectrum, thus eliminating the need for Wi-Fi in that context....So how does Qualcomm plan to square this circle and offer reliable mobile services in unreliable unlicensed spectrum? By using LTE Advanced to create a hybrid system operating in both licensed and unlicensed spectrum at the same time. Specifically, Qualcomm is proposing a system that uses the carrier-aggregation (CA) feature of LTE Advanced to aggregate licensed LTE spectrum with unlicensed spectrum in the 5GHz band. The unlicensed spectrum, which would be aggregated with licensed spectrum on the downlink only, would only be used for data services. The licensed spectrum would be used for uplink and downlink and would support network control as well as voice and data services. Given the power limits placed on devices using the unlicensed 5GHz band, uLTEA would be used mainly in small cells, similar to Wi-Fi.

'All about 4G' did a good quick write-up on this topic from standards perspective, as follows:

Qualcomm has recently floated the idea of deploying LTE in unlicensed bands, particularly focusing on the 5GHz band, which is currently used mostly for WiFi. According to a document (RP-131635) submitted to the upcoming 3GPP plenary meeting, the proposal is to deploy LTE as Supplemental Downlink (SDL) in 5725-5850 MHz in USA, with the PCell (Primary Cell) always operating on a carrier in a licensed band. Verizon has also submitted a Work Item Proposal (RP-131680) to to introduce the new band for SDL usage. There’s also a Study Item proposal from Ericsson (RP-131788) is the rapporteur to study the modifications necessary to the LTE radio.

One of the big issue (though small cell vendors often play it down) that has been delaying the rollout of Small Cells has been interference management in co-channel deployment cases. The operators are worried about ad-hoc small cells creating interference with the properly planned and optimized Macro cells (though in practice its not as bad as they think it is). With LTE-U, this issue can be put to rest.

I can see LTE-U, if adopted, can also help create new business models around Small cells. Neutral Small cells, deployed in the hotspots like stadiums, shopping malls, etc. can serve users of all networks. The signalling can take care of each user connecting to its own network using backhaul.

Femto as a Service (FaaS) and Small Cells as a Service (SCaaS) would probably become a common approach as there would be no concerns about which spectrum is being used. 

There would be a small concern about interference between Wi-Fi and Small cells. Most of the existing Wi-Fi and other devices that use unlicensed spectrum use the 2.4GHz band with a few using 5GHz band now. If LTE-U uses the 'Listen Before Talk' approach, other technologies can be enhanced to probably do the same. Another thing worth remembering is that there is nearly 300MHz of spectrum in 5GHz band available universally. In certain countries the available spectrum can be as much as 500MHz. This should be enough for LTE-U as well as other technologies in the unlicensed spectrum.

The complete Qualcomm presentation is embedded below and is available to download from here: