Phantom Cell Concept — In the current deployments, there are a number of capacity solutions for indoor environments such as WiFi, femtocells, and in-building cells using distributed antenna systems (DAS). However, there is a lack of capacity solutions for high-traffic outdoor environments that can also support good mobility and connectivity. Thus, we propose the concept of macro-assisted small cells, called the Phantom Cell, as a capacity solution that offers good mobility support while capitalizing on the existing LTE network. In the Phantom Cell concept, the C-plane/U-plane are split as shown in Fig. The C-plane of UE in small cells is provided by a macrocell in a lower frequency band, while for UE in macrocells both the C-plane and U-plane are provided by the serving macrocell in the same way as in the conventional system. On the other hand, the Uplane of UE in small cells is provided by a small cell using a higher frequency band. Hence, these macro-assisted small cells are called Phantom Cells as they are intended to transmit UE-specific signals only, and the radio resource control (RRC) connection procedures between the UE and the Phantom Cell, such as channel establishment and release, are managed by the macrocell. The Phantom Cells are not conventional cells in the sense that they are not configured with cell specific signals and channels such as cell-ID-specific synchronization signals, cell-specific reference signals (CRS), and broadcast system information. Their visibility to the UE relies on macrocell signaling. The Phantom Cell concept comes with a range of benefits. One important benefit of macro assistance of small cells is that control signaling due to frequent handover between small cells and macrocells and among small cells can be significantly reduced, and connectivity can be maintained even when using small cells and higher frequency bands. In addition, by applying the new carrier type (NCT) that contains no or reduced legacy cell-specific signals, the Phantom Cell is able to provide further benefits such as efficient energy savings, lower interference and hence higher spectral efficiency, and reduction in cellplanning effort for dense small cell deployments. To establish a network architecture that supports the C/U-plane split, and interworking between the macrocell and Phantom Cell is required. A straightforward solution to achieve this is to support Phantom Cells by using remote radio heads (RRHs) belonging to a single macro eNB. This approach can be referred to as intra-eNB carrier aggregation (CA) using RRHs. However, such a tight CA-based architecture has some drawbacks as it requires single-node operation with low-latency connections (e.g., optical fibers) between the macro and Phantom Cells. Therefore, more flexible network architectures should be investigated to allow for relaxed backhaul requirements between macro and Phantom Cells and to support a distributed node deployment with separated network nodes for each (i.e., inter-eNB CA).
Femtocells were introduced many years back as a residential, closed group, small base station. The intention was to provide coverage at home for high speed data (primary) and voice (secondary). It was more for coverage than capacity. In these good old days smart phones were far and few and feature phones were many. WiFi on the phone made it expensive and power hungry so cellular was the way to go.
There were many opportunities for Femtocells to take the centre stage as the concept is technologically sound but the operators have been not very willing to deploy it soon enough. Some operators were more willing to give it a try to fix their own issues, for example Softbank which gave free femtocells, in open access mode, to improve its coverage issues. Femtozone services that promised value addition provided with the Femtocells, never took off. Other promises of exclusive broadcast content using Femtocells for example never materialised due to lack of availability of the handsets and content.
Lot has changed since then. The smartphones and tablets have taken over the market, all of them have inbuilt WiFi that is generally more efficient than the cellular radio, coverage issues have become secondary and capacity issues are a bigger concern. Femtocell players have realised that except for the publicity, there isn't much to gain from the Femtocells. As a result Femtocells were replaced by the term Small cells that represents much more than the old Femtocells. The residential Femtocells have been reduced to being just voice boosters.
The different types of Small cells can be seen in the picture above. Except for the residential, the other types of small cells operate in either the open mode or the hybrid mode. Personally, I differentiate closed Femtocells from the other Small Cells. Metrocell is the upcoming type of Small cell that I believe everyone is focussing on. They operate always in the open mode and have been chosen as the promised one to solve the two major problems of capacity and coverage.
According to the Small Cell Forum introductory whitepaper, Metrocells would see an increased growth in the next few years when the operators start deploying more of them and less of the Macrocells.
So for those of you who don't know, and would like to learn more, an introductory presentation on Metrocells is available here.
If this is an area of interest and you are interested in having and in-depth understanding then we invite you to attend our Metrocells Masterclass which is a one day workshop explaining ins and outs of Metrocell.
If you are a big organisation and would like us to provide you with a private workshop, please feel free to contact us for details.
We have also started the Metrocells Blog that I will use to post information related to Small Cells and Metrocells in future. Please feel free to take a look at: http://metrocells.blogspot.com/
Here is AT&T's attempt in comparing the small cells. The above comparison is probably based on the assumption that LTE Small cells are not yet widely available. Once they are, then LTE can be put in for most columns in the Technology part.
Hotspot 2.0 is about certifying the hotspot itself, providing authentication using SIMs or certificates and the 802.11i standard, and using the recent 802.11u standard to provide performance and other information about the hotspots visible to a device. This will allow you to roam onto a hotspot with good connectivity that you have the right account to use, doing away with the need to select the network or enter your details into a web page, as you do today. The Wi-Fi Alliance deals with the Wi-Fi hardware and the authentication specification under the name Passpoint, but this certification doesn't cover everything. The Wireless Broadband Alliance is a group of mobile and Wi-Fi operators that takes the Passpoint certification and ensures interoperability with other parts of the network — including authenticating to carriers' remote access RADIUS (Remote Authentication Dial-In User Service) servers, as well as roaming and billing. "Next Generation Hotspot is the implementation of Hotspot 2.0 into a real, live network", explains Nigel Bird, the NGH Standardisation Manager at Orange Group.
A new program called Next Generation Hotspot (NGH) - using the latest HotSpot 2.0 specification1 - allows a mobile subscriber to connect automatically and securely to Hotspots using his service provider credentials while maintaining roaming visibility for the operator. NGH enables operators to continuously monitor and manage “cellular-like” service over Wi-Fi domestically and internationally so as to enhance performance and meet the demand for mobile data services over heterogeneous RANs - cellular and Wi-Fi. This enables mobile operators to simultaneously optimize backhaul throughput, offload specific traffic rapidly (e.g. video) and achieve better economics than traditional, cellular-only solutions.
The Wireless Broadband Appliance (WBA) and Small Cells Forum recently announced collaboration on this topic, see here.
More details are available in this presentation embedded below:
Some 4 years back, I posted my first presentation here, titled "LTE Femtocells: Stepping stone for 'killer apps' presentation". I had couple of apps in mind that I thought could benefit from both LTE and Small Cells (or Femtocells to be specific).
The first was your phone acting as a Wireless Hard Disk Drive (HDD) that can be used to store things remotely in a server somewhere. This is similar to what is known as the Cloud nowadays.
The other day when I read why LTE is suitable for cloud connectivity, I could see that my old idea could start to become a reality. The article is here. Selective abstract as follows:
The LTE network lends itself well to cloud connectivity because it:
provides high-bandwidth connections
is IP- and Ethernet-oriented, the technologies used to connect to the cloud and within data centers
offers tools that operators didn't have in 2G and 3G (such as more granular ability to manage traffic flows and a better, DPI-based view of traffic running on the network)
features low latency, which is vital to the small flows and sessions that characterize M2M communications.
The rise of both cloud services and LTE creates a virtuous cycle. Cloud services continue to grow, which helps operators sustain their LTE business model. That growth enables them to accelerate LTE investments. Then operators can support new types of enterprise services, including cloud-based applications.
To take full advantage of this opportunity, operators have to deploy the right backhaul infrastructure. In addition to IP awareness and content awareness, the right backhaul network can leverage the technical advantages that LTE presents:
flattened architecture that helps distribute compute and storage resources
seamless migration from 2G and 3G for various physical mediums and networking protocols
an increase in capacity that starts to put mobile connectivity on par with fixed broadband access.
My reasoning for Small Cell here is, in most cases when you are doing operations that require large amounts of data to be transferred, you will be indoors, either at home or in office or in a low mobility scenario. The requirement for high security and at the same time high speed data transfer that should not be affected by other users in the cell (capacity issues) can be easily solved by using a Small cell (Femtocell for indoors, Metrocell for outdoors).
The other application I had in mind was the Home Security System. I read the following on TotalTele the other day:
3UK's wholesale division on Friday detailed plans to capture high-margin machine-to-machine traffic by partnering with service providers that are likely to have higher-than-average bandwidth requirements.
As a 3G-only operator, the company cannot go after high volume, low margin M2M traffic because it typically only requires a 2G connection. However, there are opportunities to use its 3G network to address more data-hungry verticals that will generate higher traffic volumes.
"The margin on one CCTV M2M connection is more than 50 times bigger than the margin on a smart meter connection," claimed Tom Gardner, lead wholesale manager at 3UK, during Breakfast with Total Telecom in London.
"There is one CCTV camera for every 14 people in the U.K.," he said. "If I can put a SIM in every one of them I'll be a very happy man."
3UK, which on Thursday launched its Ericsson-based wholesale M2M platform, sees a big opportunity in CCTV, particularly for mobile and temporary installations at festivals, for instance. Other potentially lucrative sectors it has identified include digital signage, back-up for fixed Internet connections, and backhauling WiFi traffic from public transport.
I am sure some of you may be thinking that '3' UK uses HSPA network, not LTE, which is true. The point here is that it could be done better using LTE and Small Cells.
The reason for using LTE would be to provide higher data rates, meaning that information can be sent faster, with higher resolution and more regularly. This will help identify the problems earlier. If the CCTV is used indoors or in high usage areas, it would make sense that it connects via Small Cell to avoid creating capacity issues in the Macro network.
Here is the embed again, of my old presentation just in case if it interests you:
I have blogged about FaaS in the past that is now undergoing trials. I also blogged about SCaaS from our last Cambridge Wireless event that shows the seperation between the operator and the services provided by Small Cell service provider. In the recent Small Cells Global congress, Kevin Baughan from Virgin Media gave an interesting talk on their recent trials. This is the architecture they are proposing.
They would do site acquisition and maintenance, provide the backhaul and power, any mobile network operator (MNO) can come and put their small cell on the furniture to provide the coverage. I am not sure if multiple operators would pitch for the same sites but I wouldnt think of this as a problem as I am sure there would be multiple sites available in the same location.
A real killer from Virgin media could have been that it does something similar to Free, the French mobile operator that has apparently got Femtocells inbuilt in the set top boxes.
We will have to wait and see how many operators are willing to have third party host their small cells and how many.
We had quite a few interesting discussions in the Small Cells Global Congress, Operator Mindshare session. Here are some of the things that were discussed:
Licensed v/s Unlicensed deployments:
Many operators are now deploying WiFi in the unlicensed spectrum. This can help in the short term to alleviate the capacity problems but as more and more of this unlicensed spectrum nodes get deployed, they create interference between each other and make them unusable for anyone. An example was provided about Tokyo where in some areas, too many free WiFi hotspots means its unusable for anyone. One solution is to have one operator do all the logistics for the deployment and other operators can pay to use the service. Who (operator) would be the first one to go through the process of deploying everything first? Everyone would prefer wait and watch approach.
Providing free WiFi:
The consensus was that the free WiFi provided by operators don't give any additional benefit to them and there isn't much of a business case.
Consumer awareness for residential Femtocells:
Globally, not much effort is being done by the operator to make the end users aware of residential Femtocells and this is hampering the take-up A point was made about when Vodafone launched their product, Vodafone Access Gateway (VAG), it was perceived as negative thing because the ads show that if the coverage was poor you can install this to improve coverage. From a users perspective, it showed that the network had poor coverage. Still consumer awareness is important, how to do it?
Placement of Small Cells:
Where should the public small cells (metrocells) be placed. The Biggest challenges are:
* Site Acquisition is the biggest problem. - This is a bigger problem if lap posts are sought to deploy on public locations
* Power - Lamp posts are centrally switched off, so small cells on laamp posts may need alternative sources
* Power meter if used in a shared location
* Bullet proof (especially in the US)
* Backhaul - especially is non line of sight case.
* Health concerns (if visible)
* Visual appearance
Operators should be clearer in what they want. Right now the vendors are pushing the solutions that operators not necessarily need and not giving what the operators want. The Backhaul should be more flexible and future proof. It should be able to cater for upcoming technologies like Carrier Aggregation, CoMP, etc.
Shared v/s Dedicated carrier for 3G Small Cells:
Dedicated carrier is ideal but is not easily possible for most operators. When shared carrier is used it causes interference and handovers are not easy.
Interoperability in the new hardware equipment for support of small cells:
Certain vendors are still not creating the the networks that can interwork with other vendors equipment. As we are moving towards LTE, this seems to be a much bigger problem. Sprint for example has 3 completely different networks in the US with no interoperability between them. Standards are not helping either as they do not dictate implementation.
Some Interesting discussions on Case studies, Business Cases, etc.
* Deployed residential Femtocells
* Deployed for coverage purpose
* Dont have handover capability yet
* Want to be able to deploy Microcells/Small Cells on Highways, around 1-2Km radius
* Their typical Microcells use 40W output power
* The cost of deployment if Macro using cabinet, antenna, etc is roughly 100K per site.
Telefonica, O2 trials in UK
* To get access to council lamp posts, it was required that the bidder offer free WiFi
* O2 set a high bar by paying lot of money to the councils in London, but this is not a sustainable model
A Business case for carrier neutral WiFi on light pole in Lima, Peru
* Each light pole can have 3 different locations
* The retail business case is to get the user to usse the offering and maybe offer the operator services, tempting to move to this operator from current one
* There can be a wholesale case of selling the WiFi capacity in bulk to companies, organisations
Some interesting statistics thrown up:
* WiFi cell radius is 30m in South America
* 83% of people in US think that operators should provide free WiFi because of lousy coverage of the mobile network.
* The first 4000 customers of a WiMax operator were using an average of 750 MB per day, 22.5GB per month.
* Some fixed Internet operators are now thinking of putting a cap on unlimited offering at 350GB per month.
There were no consensus and conclusions for many items so feel free to write your opinion in the comments.