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.

Saturday, 5 December 2015

Small Cells in the Lamp posts

This lamp post does look a bit weird and ugly but it could be the future. 'SmartPoles', developed by Philips in conjunction with Ericsson delivers LED lights and LTE powered mobile broadband. According to the official press release:

With cellular data traffic expected to grow 9 times by 2020, according to the Ericsson Mobility Report, and current telecoms infrastructure struggling to respond to this demand, Philips SmartPoles are enabling seamless mobile wireless 4G/LTE connectivity, with the small cell technology from Ericsson housed in the poles to enable increased data capacity in the telecoms network.  Philips SmartPoles were specifically designed and tested to accept FCC licensed wireless mobile network operator equipment. This enables an alternative deployment methodology for 4G LTE broadband services which will connect each pole through a fiber link to its core network.

Back in February TTP in partnership with IP.Access, Quortus and Freescale demoed another concept of small cell on the lamp post. The case study on Freescale's website says:

TTP’s new eNodeB based on the QorIQ Qonverge® BSC9131 addresses these challenges. It fits into a photocell socket of a standard lamp post, providing the quickest possible installation without any modification to the lighting column or its power supply. The solution incorporates LTE Access Point software from ip.access and has been demonstrated with the Quortus ECX Core evolved packet core. It is targeted at 50 metre cells, supporting up to 32 active users at downlink rates of up to 100 Mbps.

TTP have also made an interesting video on this:

This conceptual lamppost above was conceived as a part of Oakland Innovation Project in 2013. While its good, its not ambitious enough as it talks about just WiFi for connectivity.

On the other hand, V-Pole (Vancouver Pole) concept by Canadian writer and artist Douglas Coupland shows what may be possible in the distant future. It is a wireless data, electrical vehicle charging, neighbourhood bulletin board post that is also an LED lamp post that could eliminate some of that clutter. I think it will still take quite a few years before technology can make this possible. Press release from 2012 available here.

I look forward to the day when street lights and lamp posts can do more than simply provide lighting and be a hub for providing connectivity and much more.

Related posts:

Saturday, 7 November 2015

Saturday, 17 October 2015

Interference cancellation in high density small cells deployment

I looked at some 3GPP Release-12 small cells enhancements in an earlier blog post here. David Chambers, ThinkSmallCell has also published a post on 3GPP small cells enhancements in Release-12 and Release-13 which is available here.

In a recent NTT Docomo technical journal, there is an article that focuses on Interference suppression and cancellation techniques that have been introduced as part of 3GPP Release-12. These techniques can be used in conjunction with high density small cells Hetnet deployment. The article is embedded below.