ETRI working on Small Cell Base Station in a Backpack and 5G Indoor Femtocells

Came across this slightly old news in March issue of ETRI Webzine:

Following the development of the LTE small-cell base station SW in 2016, ETRI announced on February 7 that it successfully developed a SW supporting LTE-TDD dual connectivity.

These technologies are evaluated as core technologies for future 5G communication through upgrading of conventional SW technologies, since they may be applied to buildings, stadiums, and homes.

The technologies are suitable for the locations where the traffic is rapidly increased, such as stadiums, department stores, disaster-stricken areas, and military camps. The small cells may be attached, like a wireless LAN AP, to walls inside and outside buildings, utility poles, and communication antennas, or may be carried in the form of a backpack. The research team explained that the size of the small-cell was minimized as the size of a wireless LAN AP for indoor purposes and as the size of a shoe box for outdoor purposes. The small-cell backpack weighs about 10 kg.

These accomplishments will remove the communication shadows and blind spots between cells, and will help to develop independent technologies by replacing the conventional products from other countries.

In a more recent news on this topic (September 2018):

Following the successful localization of software for LTE Small Cell, which is used in the same manner as wireless access points operating within tens of meters to 1 km, while serving as a small base station, ETRI researchers began research to localize small cell equipment essential to establishing 5G infrastructure going forward. The focus of the research is on the development of technology capable of increasing the maximum transmission speed (eMBB), which is one of the most critical criteria for 5G technology, and especially the perceived transmission speed on the user side.

According to Yonhap News (translated by Google translate):

SK Telecom will be participating in 'Intelligent 5G Small Cell Technology Development Task' together with Korea Electronics and Telecommunications Research Institute (ETRI), domestic wireless communication equipment company Teltel and U Cast. The project is sponsored by the Ministry of Science, Technology and Information and is organized by ETRI.

In this project, SK Telecom sets up requirements for small cell system development. In addition, ETRI and equipment companies provide a test environment for small cell equipment verification. ETRI develops software, and Contela and Yu Cast develop hardware.

SK Telecom and other collaborative research groups plan to open API (application programming interface) to small cell. This reduces the burden of SMEs and start-ups to develop their own interfaces.

SK Telecom and ETRI are planning to develop international standard technology and secure original patents in the small cell field based on research results.

SK Telecom announced on February 23 that it will participate in 'Intelligent 5G Small Cell Technology Development Task' together with Korea Electronics and Telecommunications Research Institute (ETRI), Kontela and U Cast of domestic wireless communication equipment. A joint research team is taking a commemorative photo in front of the first workshop at Daejeon ETRI fusion technology research and production center. 2018.8.23

SK Telecom Park Jong-kwan, director of Network Technology, said, "In the 5G era, 80% of total traffic will occur indoors." "We will take the lead in 5G technology development so that customers can fully enjoy virtual reality and hologram services."

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.

Small Cells on the Train - A 2 hop solution

An Ericsson blog post some time back talked about the 2 hop solution for trains. Thinking about it, I quite like the idea. The post talks about 3 main challenges on high speed trains:

There are mainly three reasons communication services on high-speed trains is challenging:

First, large penetration loss via the shield of the train. This penetration loss is expected to be 20 to 30 dB.

Second, large numbers of handovers in very short time. This is due to hundreds or thousands of users needing handover from one site to another concurrently/sequentially. This phenomenon affects system stability and eats up capacity.

Third, high power consumption of user equipment (UE). This is because UE-s on the train need higher power to overcome the large penetration loss in uplink as well.

A common currently adopted solution for high speed trains is to densify the network along the railway to combat the large penetration loss. However, this will make the second issue more severe, as handover frequency is increased due to smaller site- to-site distance. Another way is to increase the transmission power of the base stations, which helps to solve the large penetration loss as well. However this cannot solve the third issue. And neither of these solutions are cost-effective.

Another solution I have discussed before is the Mobile Relay Node which was designed with avoiding multiple handovers when the vehicle moves between different macro cells. Not sure about its status in the standardisation process right now.

Anyway, coming back to the Ericsson post on Small cells on the train, while the Macro cells provide the TD-LTE backhaul outside, Radio Over Fiber (ROF) is used inside the tunnels to provide the same coverage.

Within the train Small cells (I guess multiple small cells will be needed in practical deployments, one for each carriage) can provide good coverage to the users and avoid the need for handovers.

Embedded is the video from Ericsson Taiwan that provides more details about this trial

Is 2013 the year of Metrocells?

A recent market market report by Informa for the Small Cell Forum has highlighted the following:

• December last year marked the first launch of a dual mode 3G/LTE femtocell by NTT DoCoMo which allows CS fallback and will be used to promote the migration from 3G to LTE. Orange France has also launched consumer femtocells, diversifying its small cell offerings.
• The small-cell market is growing at a rapid pace: The largest deployments have already reached 1 million active cells. Initial metrocell deployments are taking place while all the operators in several markets now offer femtocells.
• Both SKT and KT have launched LTE small cells for public access in South Korea.
• According to Informa Telecoms & Media’s estimates, the small cell market will generate US$22 billion during 2016, 73% of which will be driven by public area small cells.
• The number of small cells deployed overtook the total number of macrocells between October and November 2012 and consumer femtocells overtook macrocells during February 2013.
• The femtocell market now includes several deployments that reach well into hundreds of thousand units, including Vodafone, Softbank and SFR. Sprint’s deployment reached 1 million units as of October 2012 and analysts estimate that AT&T’s deployment has reached similar numbers.
• As of February 2013, there are 46 commercial services and a total of 60 deployment commitments.

According to this report: The Small Cell Forum released these numbers here at the Mobile World Congress. Gordon Mansfield, chairman of the Small Cell Forum, said 2013 is the "year of public access" small cells, noting that by 2016 public access small cells will drive $16.2 billion in revenue despite the fact that they only make up 4 percent of small cells today.  Mansfield also said 98 percent of mobile operators believe small cells are essential; however, of the 46 operators that have deployed small cells, the majority are larger operators.

The Informa report does provide a definition of the type of Small Cells but clearly mentions that these are for guidance only. I have posted my views earlier about what Metrocells are here and here. I much prefer to use the term 'Indoor Metrocells' rather than Picocells as Picocells are associated with legacy networks without an intelligence (SON, etc.) of its own. The same is true in outdoor case as I prefer 'Outdoor Metrocells' rather than Microcells. Having said that Microcells are still available from vendors and are comparatively more expensive but provide capability to cover larger areas and more simultaneous number of users.

The Small Cell Forum has also embarked on a Release plan to help speed up operator deployments. 'Release One' was released in the Mobile World Congress 2013 with focus on Home, the future releases with focus on Enterprise and Metrocells. An Infographic on releases is available here.

Below are some of the announcements regarding Metrocells from the last couple of weeks:

• Russia Is Bringing High-Speed Fiber to All Its Towns and will also provide cellular coverage in those towns using Metrocells. See here and here.
• ALU and China Mobile unveil TD-LTE lightRadio. The TDD lightRadio Metro Radio houses two of ALU's now-famous 'cubes' (highly compact radios which can be installed on lamp posts) integrated with a directional antenna. This enables a level of coverage which would normally require a far larger remote radio unit linked to an external antenna via cable. Details here.
• Node-H supports Broadcom’s Dual-Mode Small Cell SoC Family. Details here.
• Giza Systems and Bluwan Partner to Accelerate Middle East Heterogeneous Network Rollouts. Details here.
• CEVA and Mindspeed Extend Relationship to Address LTE-Advanced Small Cells. Details here.
• Aricent and Mindspeed Raise the Bar — Announce Launch of a High-Performing 20MHz Small Cell Reference Solution. Details here.
• Jin-Magic and Ubiquisys Join Forces to Improve Small Cell Performance. Details here.

David Chambers from ThinkSmallCell has written an excellent report rounding up Small Cells from the MWC which is available here.

Finally, there is one last chance to come to out Metrocell Masterclass in Cambridge on the 21st of March. Details here.