Urban Small Cells

During the recently concluded Mobile World Congress (MWC), Small Cell Forum launched their 'Release 3' on Urban Small Cells. The following is an extract from their press release:

Release Three: Urban Foundations has been developed to help operators with the rollout of small cells in the important public access arena. It builds on two earlier releases that focused on the established market for residential small cells (Release One) and the growing market for enterprise small cells (Release Two).

Release Three addresses a step change in market evolution: the commercial deployment of small cells in the urban environment. It establishes the business case and market drivers for urban small cells. It also identifies and starts to address many of the technical, economic and operational challenges to successful deployment and the opportunities this market could offer.

As part of its Release Three output, the Forum commissioned an independent operator survey from consulting firm Maravedis-Rethink. The survey found that capacity, value-added services and the opportunity to integrate Wi-Fi were among the most commonly cited market drivers for urban small cells. Backhaul, optimal site acquisition, monetization and network management were identified as the primary concerns. 

Release Three addresses these varied issues realistically and coherently. Alongside the authoritative body of Small Cell Forum work it can already draw on, this Release includes 18 new and updated documents aimed at identifying demand and supporting operators in the deployment of urban small cells. These range from economic and commercial issues such as market drivers, business case and service opportunities to technical areas such as self-organizing networks, backhaul, Wi-Fi integration and network architecture as well as regulatory challenges and deployment processes.

To a lot of extent, this blog has focussed on Urban small cells mainly. Often, the Urban Small Cells are referred to as Metrocells. The term Meadowcells is now being used to differentiate the rural small cells. Urban Small cells come with their own set of problems, hence the release includes quite a few documents to help the operators look into their deployment. A list of documents from the Scf.Io is as follows:

SCF103	Urban Small Cells: Release overview
SCF096	Deployment issues for urban small cells
SCF095	Backhaul for urban small cells: a topic brief
SCF091	Small cell application programmers’ guide
SCF090	Small cell services in the urban environment
SCF089	Next generation hotspot-based integrated small cell Wi-Fi
SCF088	Urban small cell network architectures
SCF087	Business case for urban small cells
SCF086	Market drivers for urban small cells
SCF082	LTE eNB L1 API definition
SCF077	Urban SON use cases
SCF076	Regulatory aspects of small cells
SCF075	Synchronisation for LTE small cells
SCF050	Market status statistics Q1 2014 - Mobile Experts

A presentation made by the Small Cell Forum chairman, Gordon Mansfield is embedded below:

ThinkSmallCell has written an excellent report on MWC that is available here. A quick extract from that summary on the Urban Small cells as follows:

Tuesday saw the Small Cell Forum issue Release 3: Urban Foundation which contained a surprising number of documents (19). Gordon Mansfield, Chairman of SCF, told me it exceeded his expectations, especially since it followed so closely after December's Enterprise release. The same release co-ordination team have presided over another mammoth edition. The complete Urban document set will be published in June, now renumbered Release 4, and the roadmap for updates and further releases will be finalised in April. The Forum also has a new CEO, Sue Monihan, who brings expertise from running the GSMA North America organisation and I'm sure will continue to expand the remit, membership and influence of the organisation. She will continue to work part time for both organisations concurrently.

Many (but not all) organisations now seem to be focussing on LTE+Wi-Fi rather than 3G/LTE/W-Fi multi-mode for urban capacity solutions - something that Vodafone specifically stated during the conference.

Mike Schabel, VP Small Cells at Alcatel-Lucent, pointed out the radical shift from voice to data is still fairly recent and has had huge impact for operators. Their commercial activity in Small Cell trials and business opportunities has never been busier. Speaking at the conference, he said "I can't keep up" with the number of RFPs today. They are working with 65 operators around the world (without double counting). This is happening in all regions - it's all over the world. While the technologies are the same across the small cell sector, what varies are the different business drivers found across their different customers.

Randy Cox, Head of Small Cells at NSN, showed me their latest LTE+Wi-Fi Urban Small Cell. This is quite a compact unit (about the size of a large dinner plate), capable of up to 400 concurrent sessions/calls. It's very much a downsized macrocell, reusing the same TI silicon chipset and optionally connected through a Flexi-Zone controller. They aren't planning a 3G/LTE multi-mode product at the moment, believing that LTE is the future. "We are in this for the long term" he told me. They continue to support their existing femtocell customers (using NSN's femtocell gateway and Cisco/Ubiquisys small cells), but it seemed to me that their Small Cell focus had shifted firmly to LTE.

NEC bring their own LTE expertise from Japan, with a range of in-house products complemented by partner solutions, both for Small Cells and wireless backhaul. They'veselected Radisys as their LTE Small Cell software supplier for their next in-house products. They position themselves as a one-stop shop for the new last mile, offering to handle everything from the initial planning through operational management of a portfolio of equipment. They told me that where macrocell deployments might have had four or five standard templates or scenarios, they've seen more like 400 to 500 different use cases. I do hope that's an exaggeration!

I saw several supporting technologies to de-risk HetNet deployments, ranging from smarter RF planning tools with more Small Cell features, SON vendors making further inroads, test validation and performance loading. There is a wider ecosystem here, finding newer and smarter ways to plan, manage and validate the network which wouldn't be cost effective at scale using traditional methods. Highlights included ERCOM's integration with Infovista/Mentum, allowing emulation of huge numbers of users in real-world scenarios, characterising the behaviour of small and macrocells that can be fed back into the planning tool. IXIA also have a comprehensive test and validation suite, de-risking the rollout of new features or vendor equipment by pushing the envelope and exploring the limits - not just conformance testing against standards. Sources of usage data now include directly from the handset, not just the network. OpenSignal published their "Global State of LTE Report" with actual performance results from 6 million users worldwide. Apparently Sweden has the fastest LTE in the world. The average speed worldwide is now just over 10Mbps. This whole area of back office planning and network management is evolving rapidly with many new technologies, tools and approaches coming on stream. Don't be distracted by the concepts of SDN and NFV - there are many more relevant and beneficial changes to how networks are managed coming along.

Meadowcells (a.k.a. Rural Small Cells)

Picture Source: Wilson Street

I last remember mentioning a Meadowcell in September when we had our Cambridge Wireless event.

We have the term #MeadowCell being thrown about today at #CWSmallCell - thanks to @simon_saunders :-)
— Zahid Ghadialy (@zahidtg) September 19, 2013

and then I forgot all about it till I saw this:

What the hell is a meadowcell? We're talking about it here: http://t.co/evsEwxgz8c via @Light_Reading
— Dan Jones (@Dan_LRMobile) February 12, 2014

So, based on the discussion on Light Reading, Simon Saunders says the following:

However I've found one additional category helpful: "Meadowcell" to contrast rural public access small cells against their "metrocell" urban counterparts. And we've found certain regulators to be enthusiastic about the opportunities they bring. The electronics for 'meadowcells'  may not be so very different from their metro counterparts though issues like backhaul may be. Its a trickier more diverse market, but given government incentives I think there is scope for the market to be comparable in size to the metro market - vendors should leap on it!

In another discussion in Forum Oxford last year, Simon stated the following:

The terms aren’t interchangeable, but likewise they don’t have hard boundaries. Femtocells = typically home and small office/SoHo. Picocells = Enterprise, retal etc (mainly indoors), Metrocells = busy cities, outdoors, “Meadowcells” = rural outdoor application of metrocells.

From what we see above, the big challenge with Meadowcell is probably the backhaul. See my earlier post on Satellite backhaul for Rural Small Cells here.

IP.Access: From Startup to Volumes

We heard from Nick Johnson last month in our Cambridge Wireless event, talking about Enterprise Small cells. He gave us some very good real life deployment examples of Small cells in public and enterprise scenarios. One such slide is shown above and others can be seen from his presentation below.

IP.Access also did a webinar with ThinkSmallCell recently in which they expanded on their offering, approach and solutions. Considering that they are one of the leaders and pioneers in the Small cells arena, it may be worthwhile hearing the webinar. The video of the webinar is embedded below and the slides are available from Slideshare here.

LTE C-RAN / Fronthaul Architectures

Its been a while since I talked about C-RAN on this blog. Meanwhile on the 3G4G blog, a presentation by Orange labs have proved to be very popular. Netmanias have posted couple of slideshares on the C-RAN architecture. They are as follows:

The first one is NTT Docomo's advanced C-RAN architecture. I have posted a presentation on Slideshare as well on this topic. It can be viewed here for more details.

The next one is the Fronthaul and Backhaul architecture by SK Telecom. I have a slideshare on a similar topic by SK Telecom here. In fact a post on 3G4G blog from the iGR whitepaper here is an interesting read on this topic as well.

Small Cells and WiFi Forecast 2012 - 2018

I have been following and having some interesting discussions on a Linkedin group where the main argument is that Small Cells may never really take off as its not a good solution and doesn't make a good business case. I think that kind of discussion is best left to do on Linkedin.

ThinkSmallCell held a webinar recently inviting couple of leading experts to discuss their forecasts for Small cells. The webinar slides and videos are embedded below. Here is a quick comparison of what these independent leading experts had to show:

The main point to note above is that we will hopefully hit 1 million public access small cells probably around/after 2015. My view on why operators have been slow in deploying small cells have been mainly to do with interference management. As we know, Small cells are deployed for Coverage and Capacity and is mainly deployed in Co-channel (same carrier as Macro). If there is no or little coverage, Small cells deployment is not an issue. With higher frequencies, the reception in the houses goes down so deploying Femtocells make sense. With public access small cells, interference (especially on 3G) has to be managed. Surprisingly the practical results for co-channel public access outdoor small cells deployed for capacity purpose is not too bad but there is a no coverage area created as a result of interference at the edge of the small cell. This can cause handover issues.

In LTE-A, Interference techniques like (f)eICIC will help handle these situations so I wont be surprised if there are lots of deployments next year with this interference management capability.

The main thing to note is that WiFi will play a huge part for the connected devices of the future. Most of the small cells deployed with also have a WiFi capability so operators can use that to offload traffic from the cellular on Wi-Fi.

My understanding is that in future we will see Macro cells mainly serve high-mobility connections (including connected cars) and Small cells and WiFi will be used for low mobility and fixed access. I guess the real advantage of cellular over Wi-Fi in this low mobility scenario is that since Wi-Fi is unlicensed, there could be interference from many unpredictable sources. Licensed cellular bands dont generally have this issue.

Anyway, the presentation and video from webinar is embedded below:

Business case for Enterprise Small Cells

In our recent Cambridge Wireless SIG event where we discussed about Enterprise small cells, Simon Saunders from Real Wireless presented a business case on Enterprise small cells. David Chambers from ThinkSmallCell has also written an excellent summary that is available here.

The presentation from Real wireless is embedded below. A more detailed study from Small cell forum is available on Scf.Io here.

Enterprise Small Cells: The Business Case from Zahid Ghadialy

Quortus: Evolving architectures for Small Cells in the Enterprise

Continuing on our theme of Enterprise Small cells, here is slightly old presentation by Quortus from the Small Cell World Summit 2013

An Introduction to 'Enterprise Small Cells'

A nice presentation by David Chambers from ThinkSmallCell summarising Enterprise Small Cells from our recent Cambridge Wireless event 'Small Cells and the Enterprise'

Enterprise Small Cells from Zahid Ghadialy

Dual-connectivity, Bearer split and other Release-12 small cell enhancements

3GPP TR 36.842 has some interesting details on the small cells enhancements for Release-12. There is too much details for me to go through at the moment but there is some discussions. One of them is on the Dual connectivity and another is Bearer split. The concept of Master eNB (MeNB) and Secondary eNB (SeNB) seems to have been introduced. Here are some interesting definitions:

Bearer Split: in dual connectivity, refers to the ability to split a bearer over multiple eNBs.

Dual Connectivity: Operation where a given UE consumes radio resources provided by at least two different network points (Master and Secondary eNBs) connected with non-ideal backhaul while in RRC_CONNECTED.

Master Cell Group: the group of the serving cells associated with the MeNB.

Master eNB: in dual connectivity, the eNB which terminates at least S1-MME and therefore act as mobility anchor towards the CN.

Secondary Cell Group: the group of the serving cells associated with the SeNB.

Secondary eNB: in dual connectivity, an eNB providing additional radio resources for the UE, which is not the Master eNB.

Xn: interface between MeNB and SeNB. Since the current E-UTRAN architecture was selected as baseline in this study, Xn in this TR means X2.

There is also the concept of RRC diversity which can help mobility. as per 36.842

RRC diversity is a potential solution for improving mobility robustness. With RRC diversity, the handover related RRC signalling could additionally be transmitted from or to a potential target cell as illustrated in Figure 7.1.3-1.  RLF could in this case be prevented as long as the UE is able to maintain a connection to at least one of the cells.  This will eventually lead to a more successful handover performance (i.e. avoiding UE RRC re-establishment procedure). The RRC diversity scheme could also be applied for handovers from the macro to pico cells, between macro or between pico cells.

Finally, the security aspects for this Bearer split and dual connectivity is also being discussed. See the latest Rel-12 security update here.

Carrier Wi-Fi: Automatic handovers in the next generation Wi-Fi

Ericsson published a paper in their journal last month about how the next generation of Wi-Fi and its integration in the 3GPP core would help moving between Wi-Fi networks and the Cellular network seamlessly.

People who read the 3G4G blog regularly would know that this is done using the Access Network Discovery and Selection Function (ANDSF). For details see here.

Another post from the 3G4G blog explains the key challenges in moving between the Cellular and Wi-Fi technology. If not done properly, the QoE can be really off putting for the end user.

The Ericsson paper highlights the following as the top-three priorities for the next generation carrier Wi-Fi:

• Traffic steering 3GPP/Wi-Fi – to maintain optimal selection of an access network so quality of experience can be ensured and data throughput maintained;
• Authentication – to provide radio-access network security for both SIM- and non-SIM-based devices; and
• DPI, support for unified billing and support for seamless handover – achieved by integrating with the core infrastructure already deployed for 3GPP access.

3GPP has been working extensively in the new releases to come up with new features that would solve some of the issues and limitations that is affecting widespread deployment of carrier Wi-Fi and seamless roaming between the different technologies. Sometime back I provided the list of the features that are being released as part of different 3GPP releases, available here.

The Ericsson paper is available on Slideshare, embedded below: