LTE Device-to-device (D2D) Use Cases

Device-to-device is a popular topic. I wrote a post, back in March on LTE-Radar (another name) which has already had 10K+ views. Another post in Jan, last year has had over 13K views. In the LTE World Summit, Thomas Henze from Deutsche Telekom AG presented some use cases of 'proximity services via LTE device broadcast'

While there are some interesting use cases in his presentation (embedded below), I am not sure that they will necessarily achieve success overnight. While it would be great to have a standardised solution for applications that rely on proximity services, the apps have already come up with their own solutions in the meantime.



The dating app Tinder, for example, finds a date near where you are. It relies on GPS and I agree that some people would say that GPS consumes more power but its already available today.



Another example is "Nearby Friends" from Facebook that allows to find your friends if they are nearby, perfect for a day when you have nothing better to do.

With an App, I can be sure that my location is being shared only for one App. With a standardised solution, all my Apps have info about location that I may not necessarily want. There are pros and cons, not sure which will win here.

Anyway, the complete presentation is embedded below:

Enabling proximity services via LTE device broadcast from Zahid Ghadialy

For anyone interested in going a bit more in detail about D2D, please check this excellent article by Dr. Alastair Bryon, titled "Opportunities and threats from LTE Device-to-Device (D2D) communication"

Do let me know what you think about the use cases.

Wireless Charging: A must-have technology with maturing standards

Wireless charging has been in news recently with the discovery that Apple has found a brilliant way to wireless charge iPhones, iPads and iWatches. While we continue to wait for the details of that one, I thought its worth providing a bit of round up from the LTE World Summit not so long back. A summary of market by IHS is embedded as follows:

Qi (pronounced Chee), probably the most well known standard, not just because its already available in devices like Google Nexus 5 phone and Nexus 7 tablet  but also because its 1.2 standard allows devices to be charged from some distance away. They had an excellent presentation outlining their progress and technology as follows:

Finally, any discussion on Wireless Charging wont be complete without the mention of other big player, Alliance For Wireless Power (A4WP). The above shows a comparison between different standards and the presentation from A4WP is as follows:

Finally, if you haven't seen our concept of futuristic 'Smart Batteries' (crossed 10K+ views) then check it out here.

New LTE-A UE Category 9 and 10 in Rel-11

Its been a while since we saw any new UE categories coming but then I noticed some new categories came earlier this year for Release-11. The latest 3TPP TS 36.306 have these new Category 9 and Category 10 as follows.

For those who are aware of the categories of the UE's being used in practice may be aware that the most common ones have been 'Category 3' with 100Mbps max in DL and 50Mbps max in UL. The new 'Cat. 4' devices are becoming more common as more manufacturers start bringing these devices to the market. They support 150Mbps max in DL and 50Mbps max in UL. Neither of them supports Carrier Aggregation.

Having said that, a lot of Cat. 4 devices that we may use in testing actually supports carrier aggregation. The next most popular devices soon to be hitting the market is Cat. 6 UE's with 300Mbps max in DL and 50Mbps max in UL. Category 6 UE's support 2 x 20MHz CA in downlink hence you can say that they can combine 2 x Cat. 4 UE's in DL but they do not support CA in uplink hence the UL part remains the same as Cat. 4 device.

Cat. 9 and 10 are interesting case as Car. 8 was already defined earlier to meet IMT-A requirement as shown below.

To meet IMT-A requirements of peak data rates of 1Gbps in UL and DL, LTE-A had to define category 8 with 5 band CA and 8x8 MIMO to be able to provide 3Gbps max in DL and 1.5Gbps max in UL. No one sees this device becoming a reality in the short term.

The new categories will have to be defined from Cat. 9 onwards.

Cat. 9 allows 3 x Cat. 4 device CA in the downlink to have the maximum possible downlink data rates of 450Mbps but there is no CA in the uplink. As a result, the UL is still 50Mbps max. Cat. 10 allows carrier aggregation in the uplink for upto 2 bands which would result in 100Mbps max in UL.

The LG space website gives a better representation of the same information above which is shown below:

A UE category 9 transmits Rel 11 category 9 + Rel 10 category 6 + Rel 8 category 4

With Release-12 due to be finalised later in the year, we may see new UE categories being defined further.

Multi-Frequency Band Indicator (MFBI)

I am sure we all know that LTE bands have been growing, every few months. All the 32 bands for FDD have now been defined. The 33rd band is where TDD bands start. What if we now want to have more FDD bands? Well, we will have to wait to fix that problem.

Picture Source: LG Space

Anyway, as can be seen in the above picture, some of the frequency bands overlap with each other. Now you may have a UE thats camped onto one frequency that is overlapping in different bands. Wouldn't it be useful to let the UE know that you are camped in more than one band and you can change it to another frequency which may be a different band but you were already on it in the first place (it may sound confusing).

Here is a much simpler table from the specs that show that when a UE is camped on band 5, it may also be camped on bands 18, 19 and 26. Remember the complete bands may not be overlapping but may only be partially overlapping.

An example could be Sprint that used Band 38 TDD (BW 50MHz) for its legacy devices but is now able to use Band 41 (BW 194MHz) as well. The legacy devices may not work on Band 41 but the new devices can use much wider band 41. So the transmission would still say Band 38 but the new devices can be informed of Band 41 using the System Information Block Type 1. AT&T has a similar problem with Band 12 and 17.

Even though this was implemented in Release-8, it came as a part of Late Non-critical extensions. Its a release independent feature but not all UE's and Network have implemented it. The UE indicates the support for MFBI using the FGI (Feature Group Indicator) bits. 

Observed Time Difference Of Arrival (OTDOA) Positioning in LTE

Its been a while I wrote anything on Positioning. The network architecture for the positioning entities can be seen from my old blog post here. 

Qualcomm has recently released a whitepaper on the OTDOA (Observed Time Difference Of Arrival) positioning. Its quite a detailed paper with lots of technical insights.

There is also signalling and example of how reference signals are used for OTDOA calculation. Have a look at the whitepaper for detail, embedded below.

Observed Time Difference Of Arrival (OTDOA) Positioning in 3GPP LTE from Zahid Ghadialy

LA-LTE and LAA

Recently came across a presentation by Ericsson where they used the term LA-LTE. I asked a few colleagues if they knew or could guess what it means and they all drew blank. I have been blogging about Unlicensed LTE (a.k.a. LTE-U) on the Small Cells blog here. This is a re-branding of LTE-U

LA-LTE stands for 'Licensed Access' LTE. In fact the term that has now been adopted in a recent 3GPP workshop (details below) is Licensed Assisted Access (LAA).

Couple of months back I blogged in detail about LTE-U here. Since then, 3GPP held a workshop where some of the things I mentioned got officially discussed. In case you want to know more, details here. I have to mention that the operator community is quite split on whether this is a better approach or aggregating Wi-Fi with cellular a better approach.

The Wi-Fi community on the other hand is unhappy with this approach. If cellular operators start using their spectrum than it means less spectrum for them to use. I wrote a post on the usage of Dynamic Spectrum Access (DSA) Techniques that would be used in such cases to make sure that Wi-Fi and cellular usage does not happen at the same time, leading to interference.

Here is a presentation from the LTE-U workshop on Use cases and scenarios, not very detailed though.

Finally, the summary presentation of the workshop. As it says on the final slide "The current SI proposal focuses on carrier aggregation operations and uses the acronym LAA (Licensed Assisted Access)", you would be seeing more of LAA.

3GPP workshop on LTE in unlicensed spectrum, June 13, 2014: Chairman Summary from Zahid Ghadialy

Case Study: LTE for real time news gathering by Sky News

Back in May, I had the pleasure of listening to a talk by Richard Pattison from Sky News where he talked about how they have managed to start replacing their Satellite trucks (which are extremely expensive to own and run) with the new solutions using LTE.

One of the advantage of LTE over 3G/HSPA+ is that the uplink is as good as the downlink which wasn't really the case in earlier generations. What this means is that you can use your phone to do a live video call and use that for broadcasting of real time information. The Sky News Tech team has some interesting tweets on this.

We're broadcasting live from a Bradford City supporters bus on the M1 using a smartphone. Here's my view. pic.twitter.com/i2MXtXNht8
— Nick Martin (@NickMartinSKY) February 24, 2013

An example of the video quality could be seen from this clip here:

The Dejero App is an interesting one that can allow bonding of Cellular + WiFi and provide a combined data rate.

I was having a discussion yesterday on Twitter because we term this bonded cellular and WiFi as 4.5G. There are many proprietary solutions available for using them together but the standardised one is coming in standards soon.

Sky news have managed to set up new standards by having 12 feeds simultaneously broadcasting  (all based on Iphones and Ipads) during the European elections.



All this has been possible due to an amazing 4G network by EE and being able to negotiate a 500GB (0.5TB) data package.

In case you've ever wondered, this is what 500GB of mobile data looks like... #EE #4GEE pic.twitter.com/7v27RncK
— Sky News Tech Team (@skynewstech) February 19, 2013

Anyway, you can read the complete paper below:

Taking 5G from vision to reality

This presentation by Moray Rumney of Agilent (Keysight) in Cambridge Wireless, Future of Wireless International conference takes a different angle at what the targets for different technologies have been and based on that what should be the targets for 5G. In fact he has an opinion on M2M and Public safety as well and tries to combine it with 5G. Unfortunately I wasnt at this presentation but from having heard Moray speak in past, I am sure it was a thought provoking presentation.

Taking 5G from vision to reality from Zahid Ghadialy

All presentations from the Future of Wireless International Conference (FWIC) are available here.

Cell capacity and Opportunistic Use of Unlicensed and Shared Spectrum

One very interesting presentation from the LTE World Summit was about Improving the cell capacity by using unlicensed and shared spectrum opportunistically. Kamran Etemad is a senior advisor to FCC & UCMP and even though he was presenting this in his personal capacity, it reflected some interesting views that are quite prevalent in the USA.

If you don't know about Dynamic Spectrum Access Schemes, I wrote a post on the Small Cells blog here. The slide above is quite interesting as it shows the possibility of a 'Generalized' Carrier Aggregation in 3GPP Release-13. Personally, we believe that LTE + WiFi working together will be far more successful than LTE + LTE-U (unlicensed). As the blog readers would be aware, we have been pushing our vision of LTE + Wi-Fi working together; which we are calling as 4.5G. In case if you have not seen, our whitepaper is here.

The presentation is embedded below for reference:

Improving Cell Capacity of 5G Systems Through Opportunistic Use of Unlicensed and Shared Spectrum from Zahid Ghadialy

Case Study: Migrating from WiMAX to TD-LTE

I was glad to hear this case study by Mike Stacey where they have a WiMAX network already deployed and are in process of moving to TD-LTE. Along with the technical issues there are also business and customer issues that need to be taken into account while doing this technology swap. Surprisingly 3.5GHz is also not a very popular band because there are very few deployments in this spectrum. On the other hand, most of the companies worldwide that have been able to get their hands on this spectrum, generally got a big chunk (60-100MHz) so they would be able to do CA easily (bar the technical issues of Intra-band interference).

Anyway, the presentation is embedded below. Hope you find it useful. If you know of similar experiences, please feel free to add them in the comments.

Overcoming Interference Challenges when migrating from WiMAX to LTE from Zahid Ghadialy