Sunday 27 November 2016

Antennas for Small Cells and C-RAN

While a special antenna is not required for Small Cell deployment in general, they do require the right kind of antennas to make sure the original purpose of deployment is achieved.

Specifications for base-station antennas for use with small cells developed by NTT DOCOMO are shown in the picture above. The following is from the NTT Docomo Technical Journal:

These antennas feature dual polarization and can be shared among the 1.5 GHz and 1.7 GHz frequency bands. A separately developed compact duplexer is installed between the SRE and antenna to separate and combine signals of these frequency bands. The compact configuration of these antennas simplifies their installation.

When planning a service area by placing small cells next to each other, deterioration in signal quality due to interference between small cells is an issue of concern. To resolve this issue, downward tilting in the vertical plane is effective to reduce the interference caused by that antenna’s signals on adjacent cells while also to raise the receive level within the antenna’s own cell. The end result is improved throughput. The following summarizes the features of three types of antennas developed by NTT DOCOMO taking interference reduction and diverse installation environments into account.

1) Rod Antenna (Two Types): Having an omnidirectional radiation pattern in the horizontal plane, this type of antenna is installed on the wall or ceiling of a building to form a service area in its periphery. Two types of rod antennas have been developed: one with tilting for an interference-reduction effect and the other with no tilting for a compact configuration. The rod antenna with tilting consists of multiple vertically aligned antenna elements, the amplitude and phase of each of which is adjusted to produce an electrical tilt. The tilt angle, however, is predetermined.

2) Plane Antenna: This type of antenna has high gain while having a unidirectional radiation pattern making it applicable to installation on high places like building roofs to form a service area in a spot-like manner. A plane antenna can be given a mechanical tilt with a metal fixture to reduce interference.

Interested readers can download the article from here.

I also posted an article on the 3G4G blog titled 'Antenna evolution: From 4G to 5G'. The presentation by Kathrein provides more details on Small Cells and mmWave antennas. Why mmWave? Because most of the industry thinks that mmWave 5G will be small cells.

The relevant part is embedded below

As always, comments, insights and suggestions welcome.

Monday 21 November 2016

Wednesday 16 November 2016

Small Cells for Public Safety Communications

One of the many use cases for Small cells is for public safety communications. In case of emergency situations (earthquake, floods, terrorism, etc.) when the macro network is damaged or as it generally happens, the power supply is disrupted, small cells can quickly come in action and provide a coverage solution. This was discussed in an earlier post here.

Another scenario is when dedicated public safety coverage needs to be provided for hard to reach places or in a stadium kind if scenario, small cells be fill the void.

While in USA there is a dedicated band (Band 14 – 700MHz) available for use with public safety communications, most other countries do not rely on dedicated spectrum. In case there is no dedicated spectrum, there are still many different approaches to make sure that the personnel from emergency services can continue communication (as long as there is coverage available).

Parallel Wireless*, a Small Cells solution provider based in Nashua, NH, USA specializes in public safety and rural coverage solutions using small cells. The following slide pack contains some of their stories of deployments, demos and trials:

Further Reading:

*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.

Thursday 10 November 2016

Multi-vendor LTE Small Cells SON

Before we proceed further, in case the reader is not aware of Self-Organizing Networks (SON), please refer to my old tutorial here.

BT has recently published a white paper on multi-vendor LTE SON based on tests using LTE small cells provided by Node-H and Qucell. From the news posted on Node-H website:

The white paper focuses on the important issue of interference management between small cells. The paper is the result of a joint effort by British Telecom's Research and Innovation group and the technical teams of Qucell and Node-H. It addresses some of the major challenges of LTE HetNets and expands on the work of the 2016 ETSI Plugfest, which was run under the auspices of the Small Cell Forum. The authors’ conclusion is that interoperability between different vendors' SON implementations is achievable and so operators can look forward to robust, seamless and tailored solutions from multiple vendors.
The white paper shows that it is possible to operate mobile networks in which the individual LTE cells execute different ICIC algorithms. These findings challenge preconceptions about SON that are common in the mobile industry and make the case towards larger multi-vendor deployments of LTE small cells and call for bolder efforts in multi-vendor SON testing.
The ICIC algorithms used during these tests have been developed independently and without exchange of technical details between two separate HeNB vendors. Despite this, it has been shown that both algorithms can gracefully co-exist in the same LTE network. ICIC standardization efforts within 3GPP, along with the Small Cell Forum's Plugfest activities, have been key to this success.

The whitepaper embedded as follows and is available to download from here:

Related posts:

Saturday 5 November 2016

Small Cell Installation Challenges

Today I decided to focus on an area which I don't normally look at much detail. While going out and about in the field, I can always notice the different types of deployments. Some are nice and clean while others are really messy like the ones in picture above.

While all of the situations cant be fixed easily, some of them require clever connectors that can simplify the connections. This presentation from Huber+Suhner embedded below provides some good solutions and examples.

Thursday 20 October 2016

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:

Saturday 8 October 2016

Thursday 22 September 2016

Small Cell Forum workshop on 5G

I was having a twitter discussion earlier today as to whether 2G/3G should be switched off to make room for the more efficient 4G/4G+. While I agree with regards to the efficiency of 4G/4G+, there is still plenty of room for existing technologies, including 2G for a long time. 

While 5G is great and as can be seen in the picture above, a very optimistic picture has been painted with regards to LTE/5G.

Small cell forum recently held a workshop on 5G in Rome. Though it doesn't say explicitly, I am assuming the focus was Small Cells and 5G. It wouldn't be surprising as most of mmWave deployments would be comparatively small as compared to macrocells today.

I like this picture below as it shows that there are practical problems to solve today then worry about the 5G deployments of 2020. Having said that, the mobile community has to start preparing for it now to be ready by early 2020's  

Huawei had another interesting concept of how 5G HetNets will look

Nokia suggested that the lessons learned from Small Cells will help vendors with 5G deployments.

You can see all the presentations available here.

If you found something very interesting, please share in comments.

Monday 5 September 2016

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:

Thursday 25 August 2016

Small Cells vs Macro Cells Densification

Here is a presentation by KPN from Small Cells World Summit 2016 explaining how densification using small cells makes more sense than using macro cells. They have presented case study of Rembrandtplein to explain this. Feel free to add your views as comments.

Related posts:

Wednesday 17 August 2016

Drone cells are becoming a reality

Back in early 2015, the then EE CEO Olaf Swantee said, "We will begin exploring 'Air Masts', essentially aerial small cells positioned in the sky above a hard-to-reach area, using either tethered balloons or unmanned craft, bridging the UK's transmission gap."

The vision has not changed a lot. I recently blogged about 'EE's vision of Ultra-Reliable Emergency Network'. If you look at the slide above you will notice temporary solutions include Air masts, UAV's and Network in a box (NIB).

Nokia recently did a trial with EE where they used a drone to carry a tiny base station to remote areas around Inverness. Weighing in at only 2 kg, the Nokia Flexi Zone Pico cell has all the punch of LTE in a very compact package, allowing 4G services to be provided wherever a drone can reach. High quality LTE voice calls between responders, video streaming and up to 150 Mbps data throughput were all achieved, with no need for a connection to an external core network.

While it doesn't exactly say the area that was covered, I would expect it to be able to do at least 1 km diameter to be effective in an emergency scenario.

According to a recent International Business Times article, US operator AT&T is trying something similar to deal with the struggle to provide enough wireless data are large venue events to please customers. The mobile operator says that drones known as "Flying Cell on Wings (COWs)" could make all the difference. The idea would be that the drone would be tethered to the ground so they would hover in one place, sort of like a portable hovering small cell. 

Finally, Ericsson and China Mobile conduct world’s first 5G drone prototype field trial. In their recent press release it says:

In the trial, held in Wuxi in China’s Jiangsu province, a drone was flown using operator’s cellular network with 5G-enabled technologies and with handovers across multiple sites. In order to demonstrate the concept’s validity in a real-world setting, the handovers were performed between sites that were simultaneously in use by commercial mobile phone users.

The potential use cases for this technology include mission-critical applications such as support for emergency services. However, end-to-end low latency needs to be guaranteed by the operator’s network to ensure the safety and reliability of such services.

I am sure we will be hearing more on this topic soon.

Tuesday 2 August 2016

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.

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.

Sunday 24 July 2016

LIGHT-Net: China Unicom's mobile service booster

Another presentation from the Small Cells Word Summit 2016. China Unicom refers to LIGHT-Net. The definition of LIGHT-Net can be seen above but based on the translation of the press release here, LIGHT-Net stands for LTE Technology Innovation and Network Evolution Solutions. Continuing from the press release:

Experts said, LIGHT-Net will have five characteristics: First, the asset-light (the Low-cost) , the software-defined (SDN) to achieve a flexible network, reducing CAPEX and OPEX ; followed by intelligence (the Intelligent) , will enable the network automatic planning, optimization and automatic interference avoidance; third is green (green) , to achieve low power consumption, low radiation, low noise; fourth is efficient (High-efficiency) , improve resource scheduling capabilities and spectrum utilization efficiency; the fifth is close (Tight) , to achieve macro-micro coordination and heterogeneous integration.
Overall, LIGHT-Net research program can be divided into three steps. The first stage, based on the interference coordination LIGHT-Net microsite deployment: the introduction of micro-station deployment, absorbing macro hotspot network data traffic; the introduction of interference coordination technology to solve interference problems caused by increased cell. The second phase, enhanced collaboration processing, macro and micro interoperability: Promoting co-processing technology macro and micro cells, pico cells between the cell edge coverage to enhance performance and user access experience. The third stage, an access integration, multi-stream merge: the ideal backhaul carrier aggregation, non-ideal backhaul dual link technology between macro and micro HSAP / LTE -system multi-stream merger.

I think the small cells maybe Huawei's lampsite as I had mentioned earlier.

Anyway, the presentation is embedded below. As usual, if you have more details, please add as comments below.

Saturday 9 July 2016

MEC, Small Cells & IoT

Here is a presentation from Vodafone on how Mobile Edge Computing and Small Cells can play a big role in Internet of Things.

Vint Cerf, who is universally recognised as one of the founding fathers of Internet recently said that there will be 1 Trillion devices on the net by 2036, many of them being IoT devices.

This presentation also lays out use cases for IoT. As always, I am interested in hearing your thoughts.

Sunday 26 June 2016

Underground Small Cells

Following on from my earlier post on 'Small Cells & Wi-Fi in the pavements & roads', here are some more details about these underground small cells, see video below.

From Ericsson's press release:

Swisscom and Ericsson have deployed the world’s first vault site for LTE and small cells in Switzerland. Some 250 further rollouts are due in the country’s cities during 2016.

Swisscom and Ericsson have proved that city manholes can be used worldwide to improve capacity with small cells – even below street level – using the Ericsson Vault Remote Radio Unit and Kathrein’s Street Connect, an in-ground microcell antenna system. The use of existing street manholes where fiber and power already exists lowers total cost of ownership by 50 percent.

This, the world’s first vault site for LTE and small cells has been approved by the Swiss authorities, and 250 new rollouts are due during 2016 in the country’s cities. The solution effectively addresses cities’ needs by enabling the reuse of existing assets and underground space.

This site solution offers the best network capabilities in Switzerland by supporting the upcoming rollout of 5G.

Here is the video:

Related Posts:

Monday 6 June 2016

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.

Friday 13 May 2016

Small Cells Deployment Stories

I recently got an opportunity to hear about the small cell deployment studies, organised as SCWS pre-conference workshop. The combined slides from the presentation are embedded below and available to download from Small Cell Forum page here.

Friday 6 May 2016

HetNets On The Bus

Earlier in March, I helped organise 'The Gigabit Train' seminar'. The intention was to look at the connectivity options inside the trains and its monetisation. While connectivity in the trains is challenging, thinking back about it, due to a predictable route it can be sometimes easy to deploy. It could be more of a challenge for cars and buses that go through unpredictable routes and conditions.

I also discussed the "Vehicular CrowdCell" or "Vehicular Small Cell" concept here to look at some advantages of such a solution option.

Some of you may be aware that I recently joined Parallel Wireless. We were selected by M1 Limited, Singapore’s most vibrant and dynamic communications company, to support its WiFi-On-The-Go service as a part of the HetNet trial.

This is the architecture of the On-Bus Hetnet. Some of you would find it self-explanatory.

The mobile operators in Singapore are looking for innovative technologies to address spectrum scarcity as subscriber demand is growing rapidly with smartphone penetration reaching 130 devices per 100 people. Maximizing utilization of the spectrum and easing network congestion in areas with heavy human traffic is necessary to meet Infocomm Development Authority of Singapore (iDA) vision of connecting the whole nation as a part of world’s-first Smart Nation initiative.

Real-time HetNet orchestration and traffic prioritization is made possible by HetNet Gateway (HNG). All bus riders receive seamless, high throughput connectivity from an on-bus multi-mode LTE/Wi-Fi Converged Wireless System (CWS) small cell with integrated backhaul including licensed assisted backhaul.  By enabling carrier aggregation for backhaul, the end user throughput can be increased 10 times (up to 300 Mbps) allowing transit passengers to enjoy multimedia content without buffering.

Here is a presentation that gives the complete story:

Some questions on this demo from Linkedin:

Q: Does seamless handover are available with no drop in data throughput through out the travel route of Bus? 
A: Yes, handover is seamless, no dropped data or voice calls. This was one of the iDA trial requirements. We can do seamless VoLTE to VoWiFi handover and back.

Q: What is the maximum data rates does the system accommodate for all seamless data transfers? Does the system support motion video play from N/W. If so of what bandwidth and data rates? 4. How many users does the system support and what data rates?
A: It will depend on the backhaul. We can increase backhaul capacity with CA on 4G + to 300 Mbps shared bandwidth.

Q: This seems to be a relay device ( a femto or pico grade small cell with UE backhaul). an their innovative hetnet gateway for traffic engineering ( LBS support ). 
A: Our in-vehicle unit is a Small cell (LTE/Wi-Fi for access) with any backhaul incl UE backhaul. The HetNet Gateway, in addition to performing 3G, 4G, WI-Fi gateway functionality and real-time SON with ICIC, will also do the traffic engineering.

And demo from inside the bus:

Further reading:

Sunday 10 April 2016

LTE-A, Hetnets and Phase Timing

I was going through my old presentations looking at frequency and phase requirements for LTE-A and HetNets. The slide above is some years old but it does summarise the requirements well. There is also an interview by Martin Kingston & Andy Sutton of EE on this topic which is available here. I would think that with 5G latencies often quoted as less than 1ms (but in practice it may be up to 10ms) would have very critical frequency and phase timing requirements.

ThinkSmallCell recently held a webinar on this topic. The write-up is available here and slides/video is embedded below. Here is something I found interesting:

In the past, a central Grand Master supplied a common signal that was hardwired throughout the network. Today, we now see distributed master clocks appearing almost everywhere. Typical requirements are for 50ppb frequency and 1.5us phase timing over the air, driven from 16ppb and 1.1us into the base station.
Frequency sync requires a Primary Reference Clock (PRC), whereas Timing sync requires a Primary Reference Time Clock (PRTC). The latter must come from a satellite GNSS source, such as GPS, and be traceable to Universal Co-ordinated Time (UTC).
The end-to-end Inter-Cell time error budget of 1.5us (1500nanoseconds) is split into three parts:
  • A time source, with an error of up to 100n
  • The transmission network, with up to 1000ns
  • The small cell (eNodeB), with up to 400ns
The transmission network may have up to 10 boundary clocks with a combined total of 500ns error. The remaining allowance is split equally between dynamic time errors and network asymmetry. It is especially important that packets travelling in each direction (uplink/downlink) incur similar amounts of delay variation – if the time taken to send and receive packets varies differently, then phase timing errors would mount up rapidly.
It is this asymmetry of packet delay variation which is the biggest problem with engineering phase timing throughout a large network.
The ITU has defined two different time profile standards related to transmitting the phase sync signal.
G.8275.1, which relies on full on-path support. Each node in the backhaul transmission network must be fully aware of the phase timing component and actively support its transmission. Each router or node would have its own boundary clock that synchronises and re-generates the timebase locally. This may be feasible for new product but would otherwise require replacement or upgrade for existing routers and backhaul transmission equipment.
G.8275.2 was recently consented and only requires partial on-path support. One or more boundary clocks are installed at the most effective points in the backhaul path, with many legacy routers/nodes being unaware of the special importance of the PTP packets.
It is crucial to take into account the existing technical infrastructure and also cost for deployment. As part of this effort, it is critical to engineer the network so that asymmetry correction can be considered.
In cases where full on path support is deployed, the mitigation of uplink versus downlink asymmetries are extremely important and usually requires a manual calibration of each link which is extremely costly.
Here are the slides with Video in the end. Video can also be directly viewed on Youtube here.

*** Edited 11/04/16 - 10.30 ***

RTT has just published an article on related topic titled 'A second look at time', available here.

Sunday 6 March 2016

Current-State and Future of In-Building Tech

From a talk presented by John K. Bramfeld (@johnbramfeld) in Wireless Training Seminar & Networking Event - DASpedia West. The talk was 60 minutes but there are just 26 slides; most of the info was in the commentary. Anyway, it is an interesting presentation.

Friday 26 February 2016

"Vehicular CrowdCell" or "Vehicular Small Cell" and the 5G plan

In the recent Mobile World Congress, Vodafone and BMW introduced the Vehicular CrowdCell concept, a small cell providing coverage in the car when people are in it and outside when the car is parked. The presentation is embedded later on in the post.

The following is from the BMW press release:

...the BMW Group is unveiling the research project “Vehicular CrowdCell”. This project extends the concept of the “Vehicular Small Cell” presented last year in Barcelona. While the “Vehicular Small Cell” is a mobile femtocell that optimises the mobile radio reception inside vehicles, it is now also capable to enhance the capacity and coverage of mobile radio networks. The BMW Group is teaming up with peiker and Nash Technologies to present a prototype of the “Vehicular CrowdCell” integrated into a BMW research vehicle.

The rapid growth of mobile data traffic, e.g. due to the increasing use of multi-media services such as music or video streaming with mobile devices, requires even more powerful mobile radio networks in the future. One strategy to increase the capacity and coverage of future networks is the integration of a large number of small cells and relays in addition to the existing base stations.

In 2015 the BMW Group, together with its partners peiker and Nash Technologies, presented the world’s first mobile femtocell in a vehicle. The “Vehicular Small Cell” optimises the reception available to mobile devices inside vehicles via the vehicle’s aerial. Now the concept has been extended to create the “Vehicular CrowdCell”. Based on data traffic and coverage demands, the mobile femtocells are dynamically activated to locally enhance mobile radio networks.

The benefits of Vehicular CrowdCells in practice.
One possible application of “Vehicular CrowdCells” are car-sharing fleets – in particular with electric vehicles. Here, a large number of vehicles spread over cities and regions could serve as local radio relays when parked. If one or more users are located close to a mobile femtocell, it is activated on demand in order to increase the bandwidth or provide additional network coverage. In such a way, the performance of the existing network can be dynamically optimized. Benefits for mobile phone users in hotspots include a higher data rate and the absence of reception white spots – especially in areas where the signal coverage is low.

“The “Vehicular Small Cell” will optimise in-vehicle connectivity of mobile devices for our customers,” explains Dr. Peter Fertl, project manager at the BMW Group. “At the same time, the integration into a network of “Vehicular CrowdCells” will enable the ubiquitous and seamless availability of high-quality mobile radio connections outside the vehicle as well.”

Nash innovations have more details about the earlier version of this, The "Vehicular Small Cell" here and here.

Before we go any further, check out the Vodafone presentation embedded below:

I wrote a blog on this topic back in May 2014 here. In that article I mentioned that for a small cell in the car, the biggest challenge is backhaul. One approach is to use one particular frequency for backhauling to the small cell and then the small cells output another frequency. This approach was mentioned in another blog post here. In this approach, TD-LTE was used for backhaul and it created an FDD LTE small cell inside the train.

Why do I think this kind of approach work with 5G. In my other post about 5G spectrum, I mentioned that 5G will need multiple frequencies. Low frequencies for coverage, high frequencies for capacity and very high frequencies for very high speed throughput's. Because the very high frequencies, do not travel very far as compared to the low frequencies (with the same power), beamforming would be used. These very high frequency beams can be directed towards the Vehicular small cells, which in turn would create a much larger cell at a lower frequency.

This approach would typically only be used in urban environments as in rural areas there is plenty of unused spectrum (until more uses are found - quite possible with the IoT device explosion). The small cells would also need advanced sensing and SON capability to work in harmony with the macro network.

If you have an opinion, feel free to add it in the comments section.

Saturday 6 February 2016

Small Cells Forecasts...

Small Cell Forum published a report last year titled 'Crossing the Chasm: Small Cells Industry 2015' in which draws on the findings of three very different pieces of research to show that, in 2015, for the first time outside the residential segment, small cells moved from trials and smaller deployments, to large-scale roll-outs, and this process of densification will accelerate from 2016 through to the end of the decade. The three studies each targeted a different base of respondents and so the plans and opinions of three key stakeholder groups – mobile operators, the component ecosystem, and enterprises – are all brought together to create a uniquely multidimensional view of the state of the market today. The report is available here to download.

ThinkSmallCell held their annual analyst forecast with Caroline Gabriel of Rethink Technology Research and Joe Madden of Mobile Experts. Their slide deck (with Video at the end) is embedded below. The webinar could also be viewed directly on Youtube here.

Feel free to add your opinion in the comments section on if you agree or disagree with these forecasts and statistics.

Sunday 24 January 2016

Wireless densification via HetNet orchestration

According to a whitepaper that was published late last year by ThinkSmallCell:

There are commonly thought to be three ways to densify wireless traffic capacity:
1. More spectrum (expensive, limited)
2. More spectrally efficiency (e.g. LTE rather than 2G)
3. More spatial reuse (i.e. small cells)
But there is also a fourth aspect which can deliver significant additional benefit
4. Orchestration and tighter control. (e.g. SON (Self Organising Networks), traffic steering/shaping across and between all available wireless resources)

This has been a key factor driving replacement of outdated macrocells with “Single RAN” basestation equipment that supports all generations of radio interface. These specifically address (1) and (2) above. What’s needed next is investment in tools and equipment that provides similar flexibility for (3) and (4), scaling to cope with an influx of small cells and introducing real-time management and co-ordination across all available wireless technologies, both cellular and Wi-Fi.

While we dont generally hear a lot about SON nowadays, I know most of the vendors have implemented some or the other aspects of SON in their equipment. Orchestration can definitely have a much bigger impact than SON by itself on the densification.

In 5G, we talk about 'edgeless cells', 'no-edge networks', etc. Orchestration of the network will have a big part to play in this too.

Anyway, here is the whitepaper embedded below and available to download from Slideshare

Sunday 17 January 2016

Small Cells & Wi-Fi in the pavements & roads

Back in October last year, Thinksmallcell reported that Vigin Media in UK is deploying WiFi in pavements.

ISPreview reports that:

Ordinarily most operators prefer to install WiFi access points above ground, not least because it helps the 2.4GHz signal to propagate, but telecoms infrastructure owners like Virgin Media have a lot of manholes around the place that can also be used (makes it easier to tap directly into their core capacity links) and apparently this approach can still cover an area of up to 80 metres.

The use of a submerged rainproof access point, which sits beneath a specially developed resin cover, is certainly a different twist on the usual deployments. Never the less Virgin Media are also using plenty of traditional access points too, which have been discreetly installed on local street furniture.

Wireless antenna maker Kathrein has teamed with Ericsson and Swiss operator Swisscom to develop an in-ground antenna system that will help provide additional wireless coverage in densely populated areas. The technology, called the Kathrein Street Connect, was developed to help operators deploy additional cell sites in places where site acquisition is difficult due to zoning issues.

Kathrein designed the antenna while Ericsson provided the radio. The rugged solution was designed to withstand deploying in streets with heavy vehicle traffic. Currently there are 17 sites piloting the technology in Switzerland with plans for commercial deployment in 2016, said Jim DeKoekkoek, product line manager for antennas and filters at Kathrein, in an interview with FierceInstaller.

Kathrein also has a video on Youtube explaining this:

Its interesting to see that pavements and roads may become the new battleground for providing connectivity through Wi-Fi and Small Cells.

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