5G CrowdCell: World's First 5G OpenRAN Small Cell

I explained about Open RAN in a tutorial here. In the recent TIP Summit, there was a lot of discussion of Open RAN. In their presentation, Miguel Marin, Technology Director, AMAP, Vodafone talked about world's first 5G OpenRAN small cell. Known as the crowdcell, it can be seen in the picture below.

I wrote about Crowdcell earlier here. While it was more in an initial stage then, it is already working and under trials in Turkey. The video below shows a demo of crowdcell from TIP Summit 2019



You can learn more about CrowdCell on TIP website here.

This video from Lime Microsystems from last TIP Summit explains the CrowdCell concept.

TIP Summit 2018 from Lime Microsystems on Vimeo.

It should be borne in mind that the TIP website says that CrowdCell is intended for extending indoor coverage. Sprint's / Airspan's MagicBox is solving exactly the same issue. You can read more about that here. The only real difference here is that CrowdCell is based on OpenRAN architecture and principles.

Parallel Wireless has a similar solution for outdoors. You can read more about that here and here.

Related Posts and Articles:

• A quick tutorial on Open RAN, vRAN & White Box RAN
• TIP Summit 2019 Opens the Floodgates for Democratised Telco Infrastructure
• CrowdCell heads for TIP
• Ultimate Guide to the Telecom Infra Project (TIP)
• Small Cells at Mobile World Congress 2017 (#MWC17)
• "Vehicular CrowdCell" or "Vehicular Small Cell" and the 5G plan

Autonomous Relaying Drones

Came across this post from Prof. David Gesbert about the project ERC PERFUME are involved in. The post says:

Autonomous Flying Cellular Relay Robots

The team of ERC Advanced PERFUME project (www.ercperfume.org) at EURECOM under Prof. David Gesbert recently pioneered autonomous flying base station relays. The aerial robots  use machine learning to self-optimize their position based on suitable radio measurements and provide end-to-end enhanced connectivity to mobile users carrying off-the-shelf commercial terminals.  The communication layer builds on the OpenAirInterface developped at EURECOM's Communications Systems Department.

A first video was just unveiled here:


I have written about drones multiple times in the past (see here, here & here for example). Last week I looked at the relays (or Relay Nodes, RNs) as defined by 3GPP. We could safely assume that this autonomous relaying drone is Layer 3 Type 1a/1b RN.

I have heard multiple operators talking about this kind of approach where a person or group of people can get preferential services via drones in festivals and events. Of course it would make sense that these people are on some VIP package or emergency services workers.

Its an interesting concept but there will be many open questions. It would have to be tried for a long time to identify and iron out all the issues.

Do you agree / disagree?

Relays (RN) and Donor eNode Bs (DeNB)

Relays a.k.a. Relay Node (RN) in standards has been a part of the standards for a while but I don't hear about them often. The only time recently when I heard about them were with Airspan's MagicBox small cells deployed in Sprint (see news here). In fact the article speculates:

LTE UE Relay was specified within 3GPP’s Release 10. There are different types of Relay and it would seem Sprint’s will be Type 2, which sees the Relay Node (or MagicBox) retransmit on the same code as provided by its macro “donor” cell.

While I don't have any further details about it, I am not too sure about it. Type 2 relays are complex and require change in the existing eNodeB's. I should clarify here that we are talking about Layer 3 relays in this post. An earlier presentation from Airspan mentioned that they use Type 1a/1b relay architecture. See here.

The presentation below has some nice simple explanation of the Relay nodes and its workings

In case of Type 2 relays, there is a much more architecture change involved. This architecture change requires modification of the existing eNB to Donor eNB (DeNB).

Going back to 3GPP TS 36.300: E-UTRA and E-UTRAN Overall description; Stage 2 document:

The DeNB hosts the following functions in addition to the eNB functions:
- S1/X2 proxy functionality for supporting RNs;
- S11 termination and S-GW/P-GW functionality for supporting RNs.

Further on, in section 4.7

E-UTRAN supports relaying by having a Relay Node (RN) wirelessly connect to an eNB serving the RN, called Donor eNB (DeNB), via a modified version of the E-UTRA radio interface, the modified version being called the Un interface.

The RN supports the eNB functionality meaning it terminates the radio protocols of the E-UTRA radio interface, and the S1 and X2 interfaces. From a specification point of view, functionality defined for eNBs, e.g. RNL and TNL, also applies to RNs unless explicitly specified. RNs do not support NNSF.

In addition to the eNB functionality, the RN also supports a subset of the UE functionality, e.g. physical layer, layer-2, RRC, and NAS functionality, in order to wirelessly connect to the DeNB.

The RN terminates the S1, X2 and Un interfaces. The DeNB provides S1 and X2 proxy functionality between the RN and other network nodes (other eNBs, MMEs and S GWs). The S1 and X2 proxy functionality includes passing UE-dedicated S1 and X2 signalling messages as well as GTP data packets between the S1 and X2 interfaces associated with the RN and the S1 and X2 interfaces associated with other network nodes. Due to the proxy functionality, the DeNB appears as an MME (for S1-MME), an eNB (for X2) and an S-GW (for S1-U) to the RN. 

In phase II of RN operation, the DeNB also embeds and provides the S-GW/P-GW-like functions needed for the RN operation. This includes creating a session for the RN and managing EPS bearers for the RN, as well as terminating the S11 interface towards the MME serving the RN.

The RN and DeNB also perform mapping of signalling and data packets onto EPS bearers that are setup for the RN. The mapping is based on existing QoS mechanisms defined for the UE and the P-GW.

In phase II of RN operation, the P-GW functions in the DeNB allocate an IP address for the RN for the O&M which may be different than the S1 IP address of the DeNB.

Based on the complexity and additional changes required for Type 2 relays, I am not surprised that they are not very popular. If you think otherwise, do let me know.

Thanks to Dr. Kit Kilgour for providing insights into this topic.

Sprint's Magic Box

Is Sprint doing Small Cells? That's a question probably asked too many times. Back in January, their COO Günther Ottendorfer said the company’s small cell partners conducted a range of trials last year in order to determine fast and efficient methods to deploy small cells, a situation he said led to some misunderstandings in the market. However, he said those trials are largely behind the carrier and that he expects the carrier’s small cell efforts to expand this year.

“There was a learning process in 2016. We did a lot of trials in the beginning. We had some trials that led to misunderstandings, when you have a lot of boxes there because you were trialing different things, different—for example—transmission methods,” said Ottendorfer, Sprint’s chief operating officer for Technology, in a recent interview with FierceWireless. “But now we have streamlined the concepts and so I’m very confident that with streamlined and very elegant small cell solutions we will have a good rollout this year.”

They again mentioned about their small cells commitment at MWC. Finally this week, they announced the Magic Box.

Sprint has billed it as "World’s First All-Wireless Small Cell". This is a point where I would disagree with them, mainly for two reasons.The first being that for an all-wireless claim, they have to get wireless power to the small cell and secondly, this has already been done for a while. I have explained about In-band backhaul here and have provided examples of how Parallel Wireless has been using this for a while.

The Magic Box is made by Airspan and is 4G/LTE only in band 41 (2500 MHz TD-LTE). One of these units provide an average coverage of 30,000 square feet indoors and can benefit adjacent Sprint customers inside the building. The signal can also extend coverage 100 meters outside a building, benefiting customers in nearby buildings and improving street–level network performance. It does not use the closed subscriber group (CSG) feature hence anyone can camp on it and use it.

Source: FierceWireless

Sprint has a large amount of 2.5GHz spectrum available, as a result they are able to use dedicated spectrum for the Magic Box. This ensures that interference is kept to minimum. They also announced the availability of HPUE that will allow this band reach to improve. See my blog post here for details.

“It’s a far cry from just a repeater,” he said, explaining that it improves the efficiency of the network as long as it has a good connection to the macro cell. It will work with any Sprint phones using 2.5 GHz. The backhaul channel uses 2.5 GHz or 1.9 GHz, but ideally it would use 2.5 GHz because that offers a lot more capacity.

The Magic Box includes self-organizing network (SON) capabilities and operates on its own channel in Sprint’s spectrum, allowing it to decrease the noise level and increase the capacity of the overall system, which is the big difference from repeaters, explained Sprint Technology COO Guenther Ottendorfer.

Some of the details I couldn't find but hopefully some of the readers would know and can answer are:

• Whats the power output of these small cells?
• I am assuming they will support VoLTE calling for voice - even though generally that feature is transparent to small cells?
• Does the small cell radiate a single 20MHz channel?
• Does the backhaul do carrier aggregation?

Further Reading:

• Sprint Fiscal 4Q16 Results - some good insights on small cells
• CTO Blog: The World's First All-Wireless Small Cell - Sprint Magic Box
• Sprint Announces World’s First All-Wireless Small Cell – The Sprint Magic Box
• Can Sprint’s New “Magic Box” Live Up to Its Name? - Wireless Week
• Sprint introduces Magic Box, and it’s not a simple repeater - Fierce Wireless
• Sprint's new MagicBox is an LTE-A UE Relay node, made by manufacturer Airspan.

Backhauling problems driving up deployment costs?

Going through iDate Digiworld Yearbook 2016, I came across this section on small cells. What caught my attention was the last sentence stating that in Europe, small cells deployments are "being hampered by installation and backhauling problems which are driving up deployment costs".

While this is generally true, there are ways around it when it comes to coverage rather than capacity. When small cells are being used for capacity, there needs to be a high throughput backhaul. Where capacity is the main reason, its generally time and cost which is of essence.

I have talked about how in-band backhaul (IBBH) could be used in case of providing rural coverage and emergency / temporary communications.

I get asked about IBBH many a times. A simple way to explain would be to use the diagram above. If the operator has enough spectrum, the macro layer (frequency f1) can provide backhaul to a small cell that transmits on another frequency (f2). This way there is no interference between macro cells and small cells. In case of in-band backhaul, the small cell would be transmitting at the same frequency (f1). Here, managing interference between macro cell and small cells is the biggest challenge.

Even though I have shown mesh links in the pictures above, its not a must. It just provides flexibility of expanding the coverage further in case the macro connectivity cannot reach other sites.

IBBH is not just a cheap option for backhauling, it also allows very quick deployments. I have seen sites go up within a few hours based on this option. While not perfect, it is a good compromise for extending the coverage.


Related posts and links:

• Small Cells: Best solution for rural coverage?
• Telecoms Infrastructure Blog: Flying Small Cells are here...
• Discrete levels of inband and out of band small cell backhaul - ThinkSmallCell

LTE Relay as a disruptive backhaul technology for Small Cells?

Came across this interesting presentation from Airspan which their CTO Paul Senior delivered at Small Cells World Summit in May. Here they are suggesting that relays could be used used on the cell edge to backhaul small cells and hence improve throughput for a UE that is camped on small cell. Probably much easier to understand from the picture below.

This approach is similar to in-band backhaul that is used by other vendors. I gave an example of in-band backhaul from Parallel Wireless in my Rural coverage post here. The advantage of relays & in-band backhaul is that the small cells could be deployed easily and also moved/relocated later on as there is no limitation due to backhaul provision.

In an article from last year on ThinkSmallCell, Paul said:

The 3GPP standard includes a feature to support remote relays at the cell edge, which only needs power to rebroadcast the signal into poor coverage areas. However, this requires a separate protocol stack in the macrocell – something which not all vendors have implemented.

Instead, we've built a simple relay using a directional antenna to the macro which operates at a different frequency band, say 2.6GHz TD-LTE, and rebroadcasts at 1800MHz FDD-LTE. The antenna form factor and design enables much better utilisation of the link that when serving smartphones directly, using 64QAM rather than QPSK to achieve much higher throughput within the same spectrum and macrocell resources. The short range radio link to the end users also provides the potential for higher speeds and better service quality. It's a quick and effective solution for enterprise buildings at the edge of coverage.

The potential capacity of an LTE Relay isn't insignificant. If we used LTE with 256QAM, 8x8 MIMO we could see a consistent throughputs of 450Mbps.

I could also see this being useful in transport applications, such as for Connected Cars. We'll be releasing products later this year for vehicle based solutions at various frequency bands.

They did demo some of the products in SCWS2016, which can be seen in another ThinkSmallCell report here.

The Airspan presentation is as follows:

Related posts:

• Radio relay technologies in LTE-Advanced
• Mobile Relay Nodes (MRN) in Rel-12
• Small Cells for the 'Connected Car'
• Airspan squeeze high system performance from urban small cells - ThinkSmallCell

Small Cells: Best solution for rural coverage?

I drive around the UK a great deal. While I rely mostly on my phone to call and message/text, I also use it to check tweets, Facebook, emails and most important of all as a Satnav (I'm a big fan of Waze). I often end up in scenarios where I have no coverage so a wrong turn results in my Satnav route failure. This can mean I have to drive around for miles before I can get back on route.

In most countries (including UK) when an operator mentions its coverage, its means population based coverage. The problem is that one may have reasonable coverage in a big town/cities but not on small roads and villages but the operator would have still met their coverage obligation. However this will be changing, at least in UK, with the announcement by EE that they will do a 95% geographic coverage. Kudos to them!

Picture Source: Point-Topic

This map I came across recently shows the rural challenges in Europe for providing connectivity. Whilst not that detailed, I can definitely say from a UK point of view, there are many places outside big towns and cities that have coverage gaps.

Picture Source: GSMA: Digital inclusion in Latin America and the Caribbean - Feb 2016

Picture Source: GSMA: Consumer barriers to mobile internet adoption in Africa - July 2016

As can be seen above, a similar problem is present in Africa and Carribean and Latin America (CALA). In these regions, in addition to the coverage gap, affordability and lack of relevant content are also major issues.

To put it simply in most countries, there is that last 10% of the population for whom coverage is not deemed feasible for the operator.  The problem is that the investment would generally outweigh the revenues. The installation (site, backhaul, etc.) and the maintenance cost would almost always outweigh the profits.

This is one of the challenges that Parallel Wireless* is trying to solve.

What if you can make the deployment very simple and reduce the installation cost and have minimal maintenance cost?

The operator would be far more willing to give it a try. There was an announcement between Parallel Wireless and Telefonica I+D for exactly this reason recently. The small communities wherein these small cells are deployed also have a vital role to play. Not only could they help by making sites available, they can have directly report any issues that would arise. An example of this can be seen in the picture above, demonstrating a small cell deployment in a community center.

An important thing to bear in mind is the support for different types of backhaul for small cells. While cellular/LTE backhaul can allow quick deployment, additional type of backhaul can become available much quicker than anticipated. The small cell deployment should be flexible enough to be able to handle this new change.

A real life example of the above statement can be seen in the picture from a recent site survey.

Finally, I would like to embed this video that explains the Parallel Wireless Rural Solution very well.


Please feel free to add your suggestions in the comments below.

*Full Disclosure: I work for Parallel Wireless as a Solutions Architect. This blog is maintained in my personal capacity and expresses my own views, not the views of my employer or anyone else. Anyone who knows me well would know this.

Small Cells for the 'Connected Car'

Couple of weeks back I was in an event where Connected cars were a big focus. A few discussions centred around Small Cells in the cars. It may be a bit of a challenge but it should still be possible to have Small cells in the cars. The biggest challenge would be the backhaul. You cant have the standard backhaul for cars, especially as its moving, generally at high speeds. 

Some tricky solutions where one of the frequencies is used for backhauling small cells while small cells would provide coverage to the passengers of the car may be doable but it may not be worth the effort. 

Generally, the focus right now is to have something like a MiFi device in the car. The device can receive the mobile network signals and create a Wi-Fi hotspot.

Another solution being discussed was the use of Mobile Relay Node (MRN). As far as I understand, MRN has been pushed out of Release-12. Another issue is that the practical gain may not be as good as expected. Most of all, small cells or relay would only be useful if all the passengers in the vehicle reply on the same mobile network operator. As far as I have seen, this is generally not the case.

In light of this, it would make sense to continue on the current solution of having Wi-Fi hotspots in the cars backhauled to the mobile network.

Your thoughts please.