Sunday, 26 July 2015

LTE vs TETRA for Critical Communications

Sometime back I was reading this interview between Martin Geddes and Peter Clemons on 'The Crisis in UK Critical Communications'. If you haven't read it, I urge you to read it here. One thing that stuck out was as follows:

LTE was not designed for critical communications.

Commercial mobile operators have moved from GSM to UMTS to WCDMA networks to reflect the strong growth in demand for mobile data services. Smartphones are now used for social media and streaming video. LTE technology fulfils a need to supply cheap mass market data communications.

So LTE is a data service at heart, and reflects the consumer and enterprise market shift from being predominantly voice-centric to data-centric. In this wireless data world you can still control quality to a degree. So with OFDM-A modulation we have reduced latency. We have improved how we allocate different resource blocks to different uses.

The marketing story is that we should be able to allocate dedicated resources to emergency services, so we can assure voice communications and group calling even when the network is stressed. Unfortunately, this is not the case. Even the 3GPP standards bodies and mobile operators have recognised that there are serious technology limitations.
This means they face a reputational risk in delivering a like-for-like mission-critical voice service.

Won’t this be fixed by updated standards?
The TETRA Critical Communications association (TCCA) began to engage with the 3GPP standards process in 2012. 3GPP then reached out to peers in the USA and elsewhere: the ESMCP project here in the UK, the US FirstNet programme, and the various European associations.

These lobbied 3GPP for capabilities specifically aimed at critical communications requirements. At the Edinburgh meeting in September 2014, 3GPP set up the SA6specification group, the first new group in a decade.

The hope is that by taking the critical communications requirement into a separate stream, it will no longer hold up the mass market release 12 LTE standard. Even with six meetings a year, this SA6 process will be a long one. By the end of the second meeting it had (as might be expected) only got as far as electing the chairman.

It will take time to scope out what can be achieved, and develop the critical communications functionality. For many players in the 3GPP process this is not a priority, since they are focusing solely on mass market commercial applications.

Similar point was made in another Critical communications blog here:

LTE has emerged as a long term possible replacement for TETRA in this age of mobile broadband and data. LTE offer unrivalled broadband capabilities for such applications as body warn video streaming, digital imaging, automatic vehicle location, computer-assisted dispatch, mobile and command centre apps, web access, enriched e-mail, mobile video surveillance apps such as facial recognition, enhanced Telemetry/remote diagnostics, GIS and many more. However, Phil Kidner, CEO of the TCCA pointed out recently that it will take many LTE releases to get us to the point where LTE can match TETRA on key features such as group working, pre-emptive services, network resilience, call set-up times and direct mode.
The result being, we are at a point where we have two technologies, one offering what end users want, and the other offering what end users need. This has altered the discussion, where now instead of looking at LTE as a replacement, we can look at LTE as a complimentary technology, used alongside TETRA to give end users the best of both worlds. Now the challenge appears to be how we can integrate TETRA and LTE to meet the needs and wants of our emergency services, and it seems that if we want to look for guidance and lessons on the possible harmony of TETRA and LTE we should look at the Middle East.
While I was researching, I came across this interesting presentation (embedded below) from the LTE World Summit 2015

The above is an interesting SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis for TETRA and LTE. While I can understand that LTE is yet unproven, I agree on the lack of spectrum and appropriate bands.

I have been told in the past that its not just the technology which is an issue, TETRA has many functionalities that would need to be duplicated in LTE.

As you can see from this timeline above, while Rel-13 and Rel-14 will have some of these features, there are still other features that need to be included. Without which, safety of the critical communication workers and public could be compromised.

The complete presentation as follows. Feel free to voice your opinions via comments.

Tuesday, 21 July 2015

TDD-FDD Joint Carrier Aggregation deployed

As per Analysis Mason, of the 413 commercial LTE networks that have been launched worldwide by the end of 2Q 2015, FD-LTE accounts for 348 (or 84%) of them, while TD-LTE accounts for only 55 (or 13%). Having said that, TD-LTE will be growing in market share, thanks to the unpaired spectrum that many operators secured during the auctions. This, combined with LTE-A Small Cells (as recently demoed by Nokia Networks) can help offload traffic from hotspots.

Light Reading had an interesting summary of TD-LTE rollouts and status that is further summarised below:
  • China Mobile has managed to sign up more than 200 million subscribers in just 19 months, making it the fastest-growing operator in the world today. It has now deployed 900,000 basestations in more than 300 cities. From next year, it is also planning to upgrade to TDD+ which combines carrier aggregation and MIMO to deliver download speeds of up to 5 Gbit/s and a fivefold improvement in spectrum efficiency. TDD+ will be commercially available next year and while it is not an industry standard executives say several elements have been accepted by 3GPP. 
  • SoftBank Japan has revealed plans to trial LTE-TDD Massive MIMO, a likely 5G technology as well as an important 4G enhancement, from the end of the year. Even though it was one of the world's first operators to go live with LTE-TDD, it has until now focused mainly on its LTE-FDD network. It has rolled out 70,000 FDD basestations, compared with 50,000 TDD units. But TDD is playing a sharply increasing role. The operator expects to add another 10,000 TDD basestations this year to deliver additional capacity to Japan's data-hungry consumers. By 2019 at least half of SoftBank's traffic to run over the TDD network.

According to the Analysis Mason article, Operators consider TD-LTE to be an attractive BWA (broadband wireless access) replacement for WiMAX because:

  • most WiMAX deployments use unpaired, TD spectrum in the 2.5GHz and3.5GHz bands, and these bands have since been designated by the 3GPP as being suitable for TD-LTE
  • TD-LTE is 'future-proof' – it has a reasonably long evolution roadmap and should remain a relevant and supported technology throughout the next decade
  • TD-LTE enables operators to reserve paired FD spectrum for mobile services, which mitigates against congestion in the spectrum from fixed–mobile substitution usage profiles.

For people who may be interested in looking further into migrating from WiMAX to TD-LTE, may want to read this case study here.

I have looked at the joint FDD-TDD CA earlier here. The following is from the 4G Americas whitepaper on Carrier Aggregation embedded here.

Previously, CA has been possible only between FDD and FDD spectrum or between TDD and TDD spectrum. 3GPP has finalized the work on TDD-FDD CA, which offers the possibility to aggregate FDD and TDD carriers jointly. The main target with introducing the support for TDD-FDD CA is to allow the network to boost the user throughput by aggregating both TDD and FDD toward the same UE. This will allow the network to boost the UE throughput independently from where the UE is in the cell (at least for DL CA).

TDD and FDD CA would also allow dividing the load more quickly between the TDD and FDD frequencies. In short, TDD-FDD CA extends CA to be applicable also in cases where an operator has spectrum allocation in both TDD and FDD bands. The typical benefits of CA – more flexible and efficient utilization of spectrum resources – are also made available for a combination of TDD and FDD spectrum resources. The Rel-12 TDD-FDD CA design supports either a TDD or FDD cell as the primary cell.

There are several different target scenarios in 3GPP for TDD-FDD CA, but there are two main scenarios that 3GPP aims to support. The first scenario assumes that the TDD-FDD CA is done from the same physical site that is typically a macro eNB. In the second scenario, the macro eNB provides either a TDD and FDD frequency, and the other frequency is provided from a Remote Radio Head (RRH) deployed at another physical location. The typical use case for the second scenario is that the macro eNB provides the FDD frequency and the TDD frequency from the RRH.

Nokia Networks were the first in the world with TDD-FDD CA demo, back in Feb 2014. In fact they also have a nice video here. Surprisingly there wasnt much news since then. Recently Ericsson announced the first commercial implementation of FDD/TDD carrier aggregation (CA) on Vodafone’s network in Portugal. Vodafone’s current trial in its Portuguese network uses 15 MHz of band 3 (FDD 1800) and 20 MHz of band 38 (TDD 2600). Qualcomm’s Snapdragon 810 SoC was used for measurement and testing.

3 Hong Kong is another operator that has revealed its plans to launch FDD-TDD LTE-Advanced in early 2016 after demonstrating the technology on its live network.

The operator used equipment supplied by Huawei to aggregate an FDD carrier in either of the 1800 MHz or 2.6 GHz bands with a TDD carrier in the 2.3 GHz band. 3 Hong Kong also used terminals equipped with Qualcomm's Snapdragon X12 LTE processor.

3 Hong Kong already offers FDD LTE-A using its 1800-MHz and 2.6-GHz spectrum, and is in the midst of deploying TD-LTE with a view to launching later this year.

The company said it expects devices that can support hybrid FDD-TDD LTE-A to be available early next year "and 3 Hong Kong is expected to launch the respective network around that time."

3 Hong Kong also revealed it plans to commercially launch tri-carrier LTE-A in the second half of 2016, and is working to aggregate no fewer than five carriers by refarming its 900-MHz and 2.1-GHz spectrum.

TDD-FDD CA is another tool in the network operators toolbox to help plan the network and make it better. Lets hope more operators take the opportunity to deploy one.

Sunday, 12 July 2015

S8HR: Standardization of New VoLTE Roaming Architecture

VoLTE is a very popular topic on this blog. A basic VoLTE document from Anritsu has over 40K views and my summary from last years LTE Voice summit has over 30K views. I assume this is not just due to the complexity of this feature.

When I attended the LTE Voice summit last year, of the many solutions being proposed for roaming, 'Roaming Architecture for Voice over LTE with Local Breakout (RAVEL)' was being touted as the preferred solution, even though many vendors had reservations.

Since then, GSMA has endorsed a new VoLTE roaming architecture, S8HR, as a candidate for VoLTE roaming. Unlike previous architectures, S8HR does not require the deployment of an IMS platform in VPLMN. This is advantageous because it shortens time-to-market and provides services universally without having to depend on the capability of VPLMN.

Telecom Italia has a nice quick summary, reproduced below:

S8HR simplicity, however, is not only its strength but also its weakness, as it is the source of some serious technical issues that will have to be solved. The analysis of these issues is on the Rel13 3GPP agenda for the next months, but may overflow to Rel14. Let’s see what these issues are, more in detail:

Regulatory requirements - S8HR roaming architecture needs to meet all the current regulatory requirements applicable to voice roaming, specifically:
  • Support of emergency calls - The issues in this context are several. For example, authenticated emergency calls rely on the existence if an IMS NNI between VPLMN and HPLMN (which S8HR does not provide); conversely, the unauthenticated emergency calls, although technically feasible in S8HR, are allowed only in some Countries subject to the local regulation of VPLMN. Also, for a non-UE-detectable IMS Emergency call, the P-CSCF in the HPLMN needs to be capable of deciding the subsequent action (e.g. translate the dialed number and progress the call or reject it with the indication to set up an emergency call instead), taking the VPLMN ID into account. A configuration of local emergency numbers per Mobile Country Code on P-CSCF may thus be needed.
  • ­Support of Lawful Interception (LI) & data retention for inbound roamers in VPLMN -  S8HR offers no solution to the case where interception is required in the VPLMN for inbound roamers. 3GPP is required to define a solution that fulfill such vital regulatory requirement, as done today in circuit switched networks. Of course VPLMN and HPLMN can agree in their bilateral roaming agreement to disable confidentiality protection to support inbound roamer LI but is this practice really viable from a regulatory point of view?
Voice call continuity – The issue is that when the inbound roamers lose the LTE coverage to enter into  a 2G/3G CS area, the Single Radio Voice Call Continuity (SRVCC) should be performed involving the HPLMN in a totally different way than current specification (i.e. without any IMS NNI being deployed).
Coexistence of LBO and S8HR roaming architectures will have to be studied since an operator may need to support both LBO and S8HR VoLTE roaming architecture options for roaming with different operators, on the basis of bilateral agreement and depending on the capability.
Other issues relate to the capability of the home based S-CSCF and TAS (Telephony Application Server) to be made aware about the VPLMN identity for charging purposes and to enable the TAS to subsequently perform communication barring supplementary services. Also, where the roaming user calls a geo-local number (e.g. short code, or premium numbers), the IMS entities in HPLMN must do number resolution to correctly route the call.
From preliminary discussions held at Working Group level in SA2 (architecture) and SA3 (security) in April, it was felt useful to create a new 3GPP Technical Report to perform comprehensive technical analysis on the subject. Thus it is expected that the discussions will continue in the next months until the end of 2015 and will overheat Release 13 agenda due to their commercial and “political” nature. Stay tuned to monitor the progress of the subject or contact the authors for further information!
NTT Docomo also did some trials back in February and got some brilliant results:

In the trials, DOCOMO and KT achieved the world's first high-definition voice and video call with full end-to-end quality of service. Also, DOCOMO and Verizon achieved the world's first transoceanic high-definition VoLTE roaming calls. DOCOMO has existing commercial 3G and 4G roaming relations with Verizon Wireless and KT.
The calls were made on an IP eXchange (IPX) and network equipment to replicate commercial networks. With only two months of preparation, which also proved the technology's feasibility of speedy commercialization, the quality of VoLTE roaming calls using S8HR architecture over both short and long distances was proven to be better than that of existing 3G voice roaming services.

In fact, NTT Docomo has already said based on the survery from GSMA's Network 2020 programme that 80% of the network operators want this to be supported by the standards and 46% of the operators already have a plan to support this.

The architecture has the following technical characteristics:
(1) Bearers for IMS services are established on the S8 reference point, just as LTE data roaming.
(2) All IMS nodes are located at Home Public Land Mobile Network (HPLMN), and all signaling and media traffic for the VoLTE roaming service go through HPLMN.
(3) IMS transactions are performed directly between the terminal and P-CSCF at HPLMN. Accordingly, Visited Public Land Mobile Network (VPLMN) and interconnect networks (IPX/GRX) are not service-aware at the IMS level. The services can only be differentiated by APN or QoS levels.

These three technical features make it possible to provide all IMS services by HPLMN only and to minimize functional addition to VPLMN. As a result, S8HR shortens the time-to-market for VoLTE roaming services.

Figure 2 shows the attach procedure for S8HR VoLTE roaming. From Steps 1 to 3, there is no significant difference from the LTE data roaming attach procedure. In Step 4, HSS sends an update location answer message to MME. In order for the MME to select the PGW in HPLMN (Step 5), the MME must set the information element VPLMN Dynamic Address “Allowed,” which is included in the subscribed data, to “Not Allowed.” In Step 6, the bearer for SIP signaling is created between SGW and PGW with QCI=5. MME sends an attach accept message to the terminal with an IMS Voice over PS Session Support Indication information element, which indicates that VoLTE is supported. The information element is set on the basis of the MME’s internal configuration specifying whether there is a VoLTE roaming agreement to use S8HR. If no agreement exists between two PLMNs, the information element will not be set.

The complete article from the NTT Docomo technical journal is embedded

Sunday, 5 July 2015

A tale of two Smart Cities

Over the last few months I heard quite a few talks about Smart Cities. Here are two that I thought its worth posting and a very good TEDx talk at the bottom

I think we all agree that more and more people will move from rural to urban areas and the cities will not only grow in population but also in size. The infrastructure will have to grow to be able to cope with the influx of people and increased demand on services.

I guess in most developed nations we have the 1.0 Era Digital City which is long way away from the 3.0 Era Smart City.

To be a full fledged 3.0 Smart City, every aspect of our life may need to evolve into "Smart". Anyway, here is the complete presentation:

While IoT would be important, access, big data, applications, etc. all will have a role to play.

If you want to find out more about the Milton Keynes smart city, also see this video on Youtube. There are driverless pods and other autonomous cars which may be considered as initial step towards smart cities, see this interesting video here.

Finally here is the TEDx talk about designing these smart cities for future: