Disaggregated Networking for 5G - What is Needed to Make it Work?

The Open Optical & Packet Transport (OOPT) group is a project group within Telecom Infra Project (TIP) that works on the definition of open technologies, architectures and interfaces in Optical and IP Networking. We looked at a detailed webinar from OOPT here.

The Disaggregated Cell Site Gateways (DCSG) within OOPT works on the definition of open and disaggregated whitebox cell site gateway devices that operators can deploy in their current 2G/3G/4G cell sites, as well as in the upcoming 5G deployments. The team produces technical specifications that define software, hardware and API requirements that represent the needs of mobile network operators and also works with industry partners to develop devices that meet the specifications.

At TIP Summit Latam in 2021, Ulrich Kohn, Director, Solutions Marketing, ADVA presented a talk on Disaggregated Networking for 5G where he looked at disaggregating high-end routers, DCSG, strategies of making white boxes timing aware and finally, disaggregated synchronization solutions.

His talk is embedded below.

You can check out ADVA's portfolio of TIP products here.

Related posts:

• Telecoms Infrastructure Blog: OpenSoftHaul - Disaggregated White Box Solution from TIP
• Telecoms Infrastructure Blog: TIP Webinar on Open Optical & Packet Transport (OOPT)
• Telecoms Infrastructure Blog: Ultimate Guide to the Telecom Infra Project (TIP)
• Connectivity Technology Blog: TIP has launched 'Non-Terrestrial Connectivity Solutions' Group
• Connectivity Technology Blog: Smart Cities Playbook from Telecom Infra Project (TIP) 

Synchronization for 5G - Requirements, Solutions & Architecture

Couple of months back, Oscilloquartz, an ADVA company, announced that BT is leveraging its high-capacity, future-proof Oscilloquartz synchronization technology to bring 4G coverage to previously underserved areas and begin the rollout of 5G services across the UK. Prior to this deployment, BT’s timing network was based purely on frequency synchronization. With the new solution, it can now distribute stable and accurate phase and time-of-day information, enabling BT to dramatically improve the use of its spectrum. The new synchronization network is built on the OSA 5430 and OSA 5440 and integrated with ADVA’s network management solution. The technology provides the sub-microsecond accuracy required for next-generation mobile applications together with hardware redundancy for unbeatable resilience.

At the Small Cell World Summit held earlier this month, Gil Biran's presentation outlined the key synchronization requirements and solutions for mobile networks in the era of 5G. Check out the slide deck embedded below to discover how longest holdover and highest precision can be achieved with the "industry's most comprehensive timing technology portfolio".

Synchronization for 5G: the requirements and the solutions from ADVA

This video of OSA 5430, the first high-capacity grandmaster clock available on the market to support PTP, NTP and SyncE over multiple 10Gbit/s Ethernet interfaces is also worth a watch. It's also the first device of its kind to provide redundancy and protection.

Sprint's Small Cells in the stadium

Sprint's CTO John Saw posted a few pics of small cells in the stadium. They also posted a few pics about outdoor small cells (see below).

Another tweet from John Saw was about SpeedTests within the stadium.

The question often asked is why are the upload speeds so poor. I answered this question when I talked about High Power UEs (HPUE) in an earlier post. As they use TDD Config 2, they are focusing on downloads rather than uploads. This may be a bit strange scenario for stadiums where people want to upload rather than download but because they want to use HPUE, they have to make sure that only a limited number of uplink slots (less than 50%) are used.

TDD also mandates very tight synchronization requirements thereby making most networks keep the same config throughout their network to avoid interference.

Its nevertheless interesting, would be good to see how the end users react to this approach.

Further reading:

• Sprint's Network Gears Up for the Big Game!
• High Power / Performance User Equipment (#HPUE)

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 Backhaul & Coordination

An interesting presentation from the Small Cells Backhaul Summit in June 2014. Time synchronization between Macro and Small cells are becoming very important for new features like eICIC, CoMP, etc. This presentation provides some insights into this.

MEF: LTE/LTE-A Small Cell Backhaul from Zahid Ghadialy