How Multiband-Cells are used for MORAN RAN Sharing

In the previous blog post I have explained the concept of multi-band cells in LTE networks and promised to explain a bit deeper how such cells can be used in Multi-Operator RAN (MORAN) scenarios. 

MORAN is characterized by the fact that all network resources except the radio carriers and the Home Subscriber Server (HSS) are shared between two or more operators. 

What this means in detail can be see in Step 1 of the figure below. 

The yellow Band #1 spectrum of the multi-band cell is owned by Network Operator 1 while the blue spectrum of Band #2 and Band #3 belongs to Network Operator 2.

Band #1 is the default band. This means if a UE enters the cell is always has to establish the initial RRC signaling connection on Band #1 as shown in step 1.

The spectrum owned by Network Operator 2 comes into the game as soon as a dedicated radio bearer (DRB), in the core network known as E-RAB, is established in this RRC connection. 

Then we see intra-frequency (intra-cell) handover to Band #2 where the RRC signaling connection is continued. Band #3 is added for user plane transport as a secondary "cell" (the term refers to the 3GPP 36.331 RRC specification). 

The reason for this behavior can be explained when looking a frequency bandwidths. 

The default Band #1 is a low frequency band with a quite small bandwidth, e.g. 5 MHz. as it is typically used for providing good coverage in rural areas. Band #2 is also a lower frequency band, but Band #3 is a high frequency band with maximum bandwidth of 20 MHz. So Band #3 brings the highest capacity for user plane transport and that is the reason for the handover to the spectrum owned by Network Operator 2 and the carrier aggregation used on these frequency bands. 

However, due to the higher frequency the footprint of Band #3 is lower compared to the other two frequency bands. 

For UEs at the cell edge (or located in buildings while being served from the outdoor cell) this leads quite often to situations where the radio coverage of Band #3 becomes insufficient. In such cases the UE typically sends a RRC measurement event A2 (means: "The RSRP of the cell is below a certain threshold."). 

If such A2 event is received by the eNB it stops the carrier aggregation transport and releases the Band #3 resources so that all user plane transport continues to run on the limited Band #2 resources as shown in step 3.

And now in the particular eNB I observed a nice algorithm starts that could be seen as a kind of zero-touch network operation although it does not need big data nor artificial intelligence. 

10 seconds after the secondary frequency resources of Band #3 have been deleted they are added again to the connection, but if the UE is still at the same location the next A2 will be reported soon and carrier aggregation will be stopped again for 10 seconds and then the next cycle starts.

This automation loop is carried out endlessly until the UE changes its location or the RRC connection is terminated. 

Related Posts:

• The 3G4G Blog: What is a Multi-Band Cell? 

DCCA Features and Enhancements in 5G New Radio

In another new whitepaper on 5G-Advanced, Nokia has detailed DCCA (DC + CA) features and enhancements from Rel-15 until Rel-18. The following is an extract from the paper:

Mobility is one of the essential components of 5G-Advanced. 3GPP has already defined a set of functionalities and features that will be a part of the 5G-Advanced Release 18 package. These functionalities can be grouped into four areas: providing new levels of experience, network extension into new areas, mobile network expansion beyond connectivity, and providing operational support excellence. Mobility enhancements in Release 18 will be an important part of the ‘Experience enhancements” block of features, with the goal of reducing interruption time and improving mobility robustness.

Fig. 2 shows a high-level schematic of mobility and dual connectivity (DC)/Carrier Aggregation (CA) related mechanisms that are introduced in the different 5G legacy releases towards 5G-Advanced in Release 18. Innovations such as Conditional Handover (CHO) and dual active protocol stack (DAPS) are introduced in Release 16. More efficient operation of carrier aggregation (CA), dual connectivity (DC), and the combination of those denoted as DCCA, as well as Multi-Radio Access Technology DC (MR-DC) are introduced through Releases 16 and 17.

For harvesting the full benefits of CA/DC techniques, it is important to have an agile framework where secondary cell(s) are timely identified and configured to the UE when needed. This is of importance for non-standalone (NSA) deployments where a carrier on NR should be quickly configured and activated to take advantage of 5G. Similarly, it is of importance for standalone (SA) cases where e.g. a UE with its Primary Cell (PCell) on NR Frequency Range 1 (FR1) wants to take additional carriers, either on FR1 and/or FR2 bands, into use. Thus, there is a need to support cases where the aggregated carriers are either from the same or difference sites. The management of such additional carriers for a UE shall be highly agile in line with the user traffic and QoS demands; quickly enabling usage of additional carriers when needed and again quickly released when no longer demanded to avoid unnecessary processing at the UE and to reduce its energy consumption. This is of particular importance for users with time-varying traffic demands (aka burst traffic conditions).

In the following, we describe how such carrier management is gradually improved by introducing enhancements for cell identification, RRM measurements and reduced reporting delays from UEs. As well as innovations related to Conditional PSCell Addition and Change (CPAC) and deactivation of secondary cell groups are outlined.

The paper goes on to discuss the following scenarios in detail for DCCA enhancements:

• Early measurement reporting
• Secondary cell (SCell) activation time improvements
• Direct SCell activation
• Temporary RS (TRS)-based SCell Activation
• Conditional Secondary Node (SN) addition and change for fast access
• Activation of secondary cell group

The table below summarizes the DCCA features in 5G NR

Related Posts: 

• The 3G4G Blog: ATIS Webinar on '5G Standards Development Update in 3GPP Release 17 and 18'
• The 3G4G Blog: 3GPP's 5G-Advanced Workshop Summary
• The 3G4G Blog: What Is the Role of AI and ML in the Open RAN and 5G Future?
• The 3G4G Blog: Conditional Handover (Rel. 16) Explained
• The 3G4G Blog: Understanding the Dual Active Protocol Stack (DAPS) Handover in 5G
• Free 6G Training: Deep Learning in the 6G Air Interface
• Free 6G Training: Kyocera Develops Transmissive Metasurface Technology for B5G and 6G
• Free 6G Training: 6G and B5G Prospects for Vertical Industry
• Free 6G Training: The Potential of Full Duplex in Beyond 5G and 6G
• Free 6G Training: Using a Dielectric Waveguide as a Pinching Antenna for B5G and 6G 

5G Reality Check - Data Rates

One of the common questions that we encounter is why are 5G speeds so low as we were promised 5G downlink speeds of 20 Gbps. Most people do not understand how the 5G speeds are calculated and what do they depend on. In many cases, the network won’t be capable of delivering higher speeds due to some or the other limitation. 

In a new presentation, I try to explain the theoretical speeds and compare them with real world 5G data rates and even try to map it to why these speeds are what they are. Hopefully people won't mind me adding some humour as I go along.

Video and Slides embedded below

Opinion – 5G Reality Check: Speeds from 3G4G

Embedded below is the Twitter thread on Speedtests 😂

Speed Tests are 5G killer app 😉, @HarriHolma provides details in replies: Elisa 100 MHz 5G (8T8R radio) on 3.5 GHz with LTE dual connectivity (EN-DC). LTE phone gives 200-250 Mbps in the same spot. The configuration uses L800+L1800+L2100 #5GKillerApp https://t.co/5ZnS2UeFkL

— 3G4G (@3g4gUK) November 18, 2019

Related Posts: 

• The 3G4G Blog: IMT-2020 (5G) Requirements
• The 3G4G Blog: Would 5G NSA undergo Sunset? When?
• The 3G4G Blog: The Politics of Standalone vs Non-Standalone 5G & 4G Speeds
• The 3G4G Blog: 5G SpeedTests and Theoretical Max Speeds Calculations
• The 3G4G Blog: Theoretical Throughput Calculation of FDD 5G New Radio (NR)
• The 3G4G Blog: The path from 4.5G to 5G
• The 3G4G Blog: Throughput Comparison for different wireless technologies
• Operator Watch Blog: EE Combines More 4G and 5G Spectrum for Even Higher Data Rates
• Operator Watch Blog: USA has an interesting mix of different types of 5G
• Operator Watch Blog: Is Saudi Arabia Winning the 5G Race?
• Operator Watch Blog: LG Uplus Tests 5G in 28GHz band using 800MHz Bandwidth. Sees AR as 5G Killer App 

Carrier Aggregation (CA) and Dual Connectivity (DC)

This topic keeps coming up every few months with either someone asking me for clarifications or someone asking us to make a video. While I don't think I will mange to get round to making a video sometime soon, there are some excellent resources available that should help a new starter. Here they are in an order I think works best



The first resource that I think also works best is this webinar / training from Award Solutions. It covers this topic well and the image at the top of the post is a god summary for someone who already understands the technology.

It may also help to understand that in the 5G NSA can have 4G carrier aggregation as well as 5G carrier aggregation in addition to dual connectivity.

If you saw the video earlier, you noticed that DC actually came as part of LTE in Release-12. We covered it in our Telecom Infrastructure blog here. NTT Docomo Technical journal had a detailed article on 'Carrier Aggregation Enhancement and Dual Connectivity Promising Higher Throughput and Capacity' that covered DC in a lot more technical detail, albeit from LTE point of view only. The article is available here. A WWRF whitepaper from the same era can also provide more details on LTE Small Cell Enhancement by Dual Connectivity. An archived copy of the paper is available here.

Another fantastic resource is this presentation by Rapeepat Ratasuk and Amitava Ghosh from Mobile Radio Research Lab, Nokia Bell Labs. The presentation is available here and details the MCG (Master Cell Group) Split Bearer and SCG (Secondary Cell Group) Split Bearer, etc. This article from Ericsson also provides more detail on this topic while ShareTechNote takes it one level even deeper with technical details and signalling here and here.

So hopefully this is a good detailed starting point on this topic, until we manage to make a simple video someday.

How the A6 Measurement Event triggers Secondary Cell Change in LTE Carrier Aggregation Calls

Last week I read in Martin Sauter's blog about the LTE RRC A6 measurement event.

Although I am quite interested in RRC measurements I have never seen the A6 event in action. Rather the eNB vendors have implemented carrier aggregation in a way that the UE provides its capabilities and according to the this the maximum possible numbers of component carriers is added to the connection. There is no RRC measurement report before adding secondary LTE cells to the connection. So what is the A6 event good for and is it used at all?

Surprisingly I needed only 2 attempts to find an example of using the A6 event in a live network configuration. It is used when more component carriers are available than the UE can simultaneously handle. E.g. if there are 4 or more cells with different carrier frequencies available in the same antenna sector the A6 event ensures after the initial CA configuration that the cells with the best radio conditions are selected as secondary cells.

Let's have a look at this scenario in detail. Figure 1 shows the report configuration for the A6 event. Keep the reportConfigId = 3 in mind.

Figure 1: Report Configuration for Event A6

The next step is the configuration of the Measurement ID as shown in figure 2. Here the reportConfigId is combined with a measObjectId that represents the carrier frequency of the potential SCell.

Figure 2: Measurement ID for Event A6

Now, if the event A6 is triggered in the UE a RRC Measurement Report with this measId = 3 is sent to the eNB as shown in Figure 3.

Figure 3: RRC Measurement Report for Event A6

There we see the RSRP and RSRQ of the primary cell (PCell) and of the currently serving secondary cells (SCells). By the way the servFreqId stands for the sCellIndex value that was linked to the physical cell ID (PCI) when this SCell was added in a previous RRC Connection Reconfiguration procedure. 

And as one can see the neighbor cell with PCI = 470 has significantly better RSRP and RSRQ to offer than both currently used SCell. 

Consequently the eNB decides to replace the SCell with sCellIndex value 1 with the better cell (PCI 470). This is again done with a RRC Connection Reconfiguration procedure as shown in figure 4. And this is the way how the A6 event is used.

Figure 4: Change of SCell

  

R&S Webinar on LTE-A Pro and evolution to 5G

Rohde & Schwarz recently uploaded a webinar video on their YouTube channel. I found it really useful. It's embedded below.

Topics covered:

• LTE-M / NB-IoT
• feMTC
• UE Category M2
• OTDOA based positioning
• UE Categories
• Unlicensed Spectrum Overview
• LTE in Unlicensed Spectrum
• LWA, LWIP
• LAA, eLAA
• Wi-Fi
• LBT
• LWA mobility
• Carrier Aggregation Enhancements
• Multi-user superposition transmission (MUST)
• Single cell - point to multipoint transmission (SC-PTM)
• SC-PTM Channel Structure
• SC-PTM Channel Flow
• Massive MIMO
• V2X Overview
• eNB scheduling - transmission mode 3
• Distributed scheduling - transmission mode 4
• Direct communication
• LTE Advanced Pro (Release 15)
• Further NB-IoT Enhancements
• Even further enhanced MTC - eMTC4 (Rel-15)

Related Posts:

• LTE-Advanced Pro (a.k.a. 4.5G)
• New LTE UE Categories (Downlink & Uplink) in Release-13
• Mission Critical Services update from 3GPP - June 2017

5G SpeedTests and Theoretical Max Speeds Calculations

Right now, Speed Tests are being described as 5G killer apps.

SpeedTests are the 5G killer app right now 😂. Thread 👇 https://t.co/jjyk0PheT6

— 3G4G (@3g4gUK) July 2, 2019

A good point by Benedict Evans

What was the killer app for 3G? The internet. What’s the killer app for 5G? More internet, mostly.

— Benedict Evans (@benedictevans) January 18, 2019

Everyone is excited and want to see how fast 5G networks can go. If you use Twitter, you will notice loads and loads of speed tests being done on 5G. An example can be seen above.

I recently heard Phil Sheppard, Director of Strategy & Architecture, '3 UK' speak about their 5G launch that is coming up soon. Phil clearly mentioned that because they have a lot more spectrum (see Operator Watch blog post here and here) in Capacity Layer, their 5G network would be faster than the other UK operators. He also provided rough real world Peak Speeds for Three and other operators as can be seen above. Of course the real world speeds greatly depend on what else is going on in the network and in the cell so this is just a guideline rather than actual advertised speeds.

I have explained multiple times that all 5G networks being rolled out today are Non-Stand Alone (NSA) 5G networks. If you don't know what SA and NSA 5G networks are, check this out. As you can see, the 5G NSA networks are actually 4G Carrier Aggregated Networks + 5G Carrier Aggregated Networks. Not all 4G spectrum will be usable in 5G networks but let's assume it is.

To calculate the theoretical maximum speed of 5G NSA networks, we can calculate the theoretical maximum 4G Network speeds + theoretical maximum 5G Network speeds.

I have looked at theoretical calculation of max LTE Carrier Aggregated Speeds here. Won't do calculation here but assuming 3CA for any network is quite possible.

I also looked at theoretical calculation of 5G FDD New Radio here but then found a website that helps with 5G NR calculation here.

If we calculate just the 5G part, looking at the picture from Three, we can see that they list BT/EE & O2 speeds as 0.61 Gbps or 610 Mbps, just for the 5G part.

Looking at the calculation, if we Input Theoretical max values in this equation:

Calculating just for DL

J - number of aggregated component carriers,
maximum number (3GPP 38.802): 16
input value: 1

v(j)Layers - maximum number of MIMO layers ,
3GPP 38.802: maximum 8 in DL, maximum 4 in UL
input value: 8

Q(j)m modulation order (3GPP 38.804)
For UL and DL Q(j)m is same (QPSK-2, 16QAM-4, 64QAM-6, 256QAM-8)
input value: 8 (256QAM)

f(j) Scaling factor (3GPP 38.306)
input value: 1

FR(j) Frequency Range 3GPP 38.104:
FR1 (450 MHz – 6000 MHz) и FR2 (24250 MHz – 52600 MHz)
input value: FR1

µ(j) -value of carrier configuration (3GPP 38.211)
For DL and UL µ(j) is same (µ(0)=15kHz, µ(1)=30kHz, µ(2)=60kHz, µ(3)=120kHz)
input value: 0 (15kHz)

BW(j)- band Bandwidth, MHz (3GPP 38.104),
should be selected with Frequency Range and µ(i) configuration:
input value: BW:40MHz FR1 µ:15kHz:

Enter a PRB value (if other)
default: 0

Rmax (if you don't know what is it, don't change)
Value depends on the type of coding from 3GPP 38.212
(For LDPC code maximum number is 948/1024 = 0.92578125)
default: 0.92578125

*** Only for TDD ***
Part of the Slots allocated for DL in TDD mode,
where 1 = 100% of Slots (3GPP 38.213, taking into account Flexible slots).
Calculated as: the number of time Slots for DL divided by 14
default value: 0.857142

Part of the Slots allocated for UL in TDD mode,
where 1 = 100% of Slots (3GPP 38.213, taking into account Flexible slots).
Calculated as: 1 minus number of Slots for DL
default value: 0.14285800000000004

Calculated 5G NR Throughput, Mbps: 1584


As you may have noticed, BTE/EE has 40 MHz spectrum while Vodafone in UK have 50 MHz of spectrum.

Changing
BW(j)- band Bandwidth, MHz (3GPP 38.104),
should be selected with Frequency Range and µ(i) configuration:
input value: BW:50MHz FR1 µ:15kHz:

Calculated 5G NR Throughput, Mbps: 1982

Now Three UK has 100 MHz, immediately available for use. So changing

µ(j) -value of carrier configuration (3GPP 38.211)
For DL and UL µ(j) is same (µ(0)=15kHz, µ(1)=30kHz, µ(2)=60kHz, µ(3)=120kHz)
input value: 1 (30kHz)

BW(j)- band Bandwidth, MHz (3GPP 38.104),
should be selected with Frequency Range and µ(i) configuration:
BW:100MHz FR1 µ:30kHz:


Calculated 5G NR Throughput, Mbps: 4006

In theory, a lot of speed is possible with the 100 MHz bandwidth that Three will be able to use. We will have to wait and see who can do a theoretical max SpeedTest. In the meantime remember that a 1Gbps speed test will use over 1 GB of data.



Related Posts:

• Tutorial on 5G Spectrum
• Theoretical Throughput Calculation of FDD 5G New Radio (NR)
• Theoretical calculation of EE's announcement for 429Mbps throughput

5G Forecasts and 5G Deployed Claim

Source: GSA

5G forecasts have been arriving steadily with many different figures. Here are some numbers:

Date	Predicted by	Number of Connections	Year	Any other comments
23-Aug-16	Strategy Analytics	690 million	2025	"690M Connections and 300M Handset Shipments"
15-Nov-16	Ericsson	500 million	2022	"North America will lead the way in uptake of 5G subscriptions, where a quarter of all mobile subscriptions are forecast to be for 5G in 2022."
30-Nov-16	ABI Research	500 million	2026	"500 Million 5G cmWave and mmWave Subscribers Will Bring $200 Billion in Service Revenue through 2026" - what about non mmWave/cmWave 5G subs?
12-Apr-17	CCS Insight	100 million	2021	"Smartphones sales will rise to 1.90 billion in 2021, when smartphones will account for 92 percent of the total mobile phone market."
26-Apr-17	GSMA	1.1 billion	2025	"5G connections are set to reach 1.1 billion by 2025, accounting for approximately one in eight mobile connections worldwide by this time."
16-May-17	Ovum	389 million	2022	"Ovum now forecasts that there will be 111 million 5G mobile broadband subscriptions at end-2021, up more than fourfold from Ovum’s previous forecast of 25 million 5G subscriptions at end-2021"
14-Aug-17	Juniper Research	1.4 billion	2025	"an increase from just 1 million in 2019, the anticipated first year of commercial launch. This will represent an average annual growth of 232%."
17-Oct-17	GSMA	214 million in Europe	2025	"30 per cent of Europe’s mobile connections will be running on 5G networks by 2025"
23-Oct-17	CCS Insight	2.6 billion	2025	"1 Billion Users of 5G by 2023, with More Than Half in China", "broadly similar path to 4G LTE technology...more than one in every five mobile connections."

If we just look at 2025/2026, the estimates vary from 500 million to 2.6 billion. I guess we will have to wait and see which of these figures comes true.

I wrote a post earlier titled '4G / LTE by stealth'. Here I talked about the operators who still had 3G networks while most people had 4G phones. The day the operator switched on the 4G network, suddenly all these users were considered to be on 4G, even if they didn't have 4G coverage just yet.

I have a few questions about what 5G features are necessary for the initial rollout and when can an operator claim they have 5G? In fact I asked this question on twitter and I got some interesting answers.

Question: How many 5G sites does an operator have to deploy so that they can say they have 5G?

— Zahid Ghadialy (@zahidtg) October 18, 2017

Just having a few 5G NR (new radio) sites enough for an operator to claim that they have deployed 5G? Would all the handsets with 5G compatibility then be considered to be on 5G? What features would be required in the initial rollouts? In case of LTE, operators initially only had Carrier Aggregation deployed, which was enough to claim they supported LTE-A. Would 100MHz bandwidth support be enough as initial 5G feature?

Please let me know what you think.

5G Dual Connectivity, Webinar and Architecture Overview

One of the things that will come as a result of NSA (Non-StandAlone) architecture will be the option for Dual Connectivity (DC). In fact, DC was first introduced in LTE as part of 3GPP Release 12 (see 3G4G Small Cells blog entry here). WWRF (Wireless World Research Forum) has a good whitepaper on this topic here and NTT Docomo also has an excellent article on this here.

A simple way to understand the difference between Carrier Aggregation (CA) and Dual Connectivity (DC) is that in CA different carriers are served by the same backhaul (same eNB), while in DC they are served by different backhauls (different eNB or eNB & gNB).


We have produced a short video showing different 5G architectures, looking mainly at StandAlone (SA) and Non-StandAlone (NSA) architectures, both LTE-Assisted and NR-Assisted. The video is embedded below:

Finally, 3GPP has done a short webinar with the 3GPP RAN Chairman Balazs Bertenyi explaining the outcomes from RAN#77. Its available on BrightTalk here. If you are interested in the slides, they are available here.

Related posts:

• 5G Core Network, System Architecture & Registration Procedure
• 5G: Architecture, QoS, gNB, Specifications - April 2017 Update
• 5G Security Updates - July 2017
• Enhanced 5G Security via IMSI Encryption
• 5G – Beyond the Hype
• Network Sharing is becoming more relevant with 5G

Inside 3GPP Release-13 - Whitepaper by 5G Americas

The following is from the 5G Americas press release:

The summary offers insight to the future of wireless broadband and how new requirements and technological goals will be achieved. The report updates Release 13 (Rel-13) features that are now completed at 3GPP and were not available at the time of the publication of a detailed 5G Americas report, Mobile Broadband Evolution Towards 5G: 3GPP Release 12 & Release 13 and Beyond in June 2015.

The 3GPP standards have many innovations remaining for LTE to create a foundation for 5G.  Rel-12, which was finalized in December 2014, contains a vast array of features for both LTE and HSPA+ that bring greater efficiency for networks and devices, as well as enable new applications and services. Many of the Rel-12 features were extended into Rel-13.  Rel-13, functionally frozen in December 2015 and completed in March 2016, continues to build on these technical capabilities while adding many robust new features.

Jim Seymour, Principal Engineer, Mobility CTO Group, Cisco and co-leader of the 5G Americas report explained, “3GPP Release 13 is just a peek behind the curtain for the unveiling of future innovations for LTE that will parallel the technical work at 3GPP on 5G. Both LTE and 5G will work together to form our connected future.”

The numerous features in the Rel-13 standards include the following for LTE-Advanced:

• Active Antenna Systems (AAS), including beamforming, Multi-Input Multi-Output (MIMO) and Self-Organizing Network (SON) aspects
• Enhanced signaling to support inter-site Coordinated Multi-Point Transmission and Reception (CoMP)
• Carrier Aggregation (CA) enhancements to support up to 32 component carriers
• Dual Connectivity (DC) enhancements to better support multi-vendor deployments with improved traffic steering
• Improvements in Radio Access Network (RAN) sharing
• Enhancements to Machine Type Communication (MTC)
• Enhanced Proximity Services (ProSe)

Some of the standards work in Rel-13 related to spectrum efficiency include:                                                                                                                       

• Licensed Assisted Access for LTE (LAA) in which LTE can be deployed in unlicensed spectrum
• LTE Wireless Local Area Network (WLAN) Aggregation (LWA) where Wi-Fi can now be supported by a radio bearer and aggregated with an LTE radio bearer
• Narrowband IoT (NB-IoT) where lower power wider coverage LTE carriers have been designed to support IoT applications
• Downlink (DL) Multi-User Superposition Transmission (MUST) which is a new concept for transmitting more than one data layer to multiple users without time, frequency or spatial separation

“The vision for 5G is being clarified in each step of the 3GPP standards. To understand those steps, 5G Americas provides reports on the developments in this succinct, understandable format,” said Vicki Livingston, Head of Communications for the association.

The whitepaper as follows:

Related posts:

• Tweets from NGMN Industry Conference & Exhibition 2016
• 3GPP Release-13 whitepapers and presentations
• LTE-Advanced Pro (a.k.a. 4.5G)
• New whitepaper on Narrowband Internet of Things

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. 
• It should be mentioned that the target is to reach 300 million subscribers by end of 2015.
• 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.

3GPP Release-13 work started in earnest

The 3GPP news from some months back listed the main RAN features that have been approved for Release-13 and the work has already started on them. The following are the main features (links contain .zip files):

• LTE in unlicensed spectrum (aka Licensed-Assisted Access) - RP-150055
• Carrier Aggregation enhancements - RP-142286
• LTE enhancements for Machine-Type Communications (MTC) - RP-141865
• Enhancements for D2D - RP-142311
• Study Item Elevation Beamforming / Full-Dimension MIMO - RP-141831
• Study Item Enhanced multi-user transmission techniques - RP-142315
• Study Item Indoor positioning - RP-141102
• Study Item Single-cell Point-to-Multipoint (SC-PTM) - RP-142205

Another 3GPP presentation from late last year showed the system features that were being planned for Rel-13 as shown above.

I have also posted a few items earlier relating to Release13, as follows:

• LTE Category-0 low power M2M devices
• Update on Public Safety and Mission Critical communications
• 3GPP Rel-12 and Future Security Work
• Elevation Beamforming / Full-Dimension MIMO
• LA-LTE and LAA
• LTE-Hetnet (LTE-H) a.k.a. LTE Wi-Fi Link Aggregation (LWA)

Ericsson has this week published a whitepaper on release 13, with a vision for 'Networked Society':

The vision of the Networked Society, where everything that benefits from being connected will be connected, places new requirements on connectivity. LTE is a key component in meeting these demands, and LTE release 13 is the next step in the LTE evolution.

Their whitepaper embedded below:

It should be pointed out that 5G work does not start until Release-15 as can be seen from my tweet

Nice picture of "5G Radio Interface development timeline" by @alainmouradUK pic.twitter.com/ANFfujJGS5
— Zahid Ghadialy (@zahidtg) April 4, 2015

xoxoxo Added Later (26/04/2015) xoxoxo
I came across this presentation from Keysight (Agilent) where Moray Rumney has provided information in much more detail.

LTE-Hetnet (LTE-H) a.k.a. LTE Wi-Fi Link Aggregation (LWA)

We have talked about the unlicensed LTE (LTE-U), re-branded as LTE-LAA many times on this blog and the 3G4G Small Cells blog. In fact some analysts have decided to call the current Rel-12 non-standardised Rel-12 version as LTE-U and the standardised version that would be available as part of Release-13 as LTE-LAA.

There is a lot of unease in the WiFi camp because LTE-LAA may hog the 5GHz spectrum that is available as license-exempt for use of Wi-Fi and other similar (future) technologies. Even though LAA may be more efficient as claimed by some vendors, it would reduce the usage for WiFi users in that particular spectrum.

As a result, some vendors have recently proposed LTE/WiFi Link Aggregation as a new feature in Release-13. Alcatel-Lucent, Ruckus Wireless and Qualcomm have all been promoting this. In fact Qualcomm has a pre-MWC teaser video on Youtube. The demo video is embedded as follows:



The Korean operator KT was also involved in demoing this in MWC along with Samsung and Qualcomm. They have termed this feature as LTE-Hetnet or LTE-H.

The Korean analyst firm Netmanias have more detailed technical info on this topic.

Link aggregation by LTE-H demonstrated at MWC 2015 (Source: Netmanias)

As can be seen the data is split/combined in PDCP layer. While this example above shows the practical implementation using C-RAN with Remote Radio Head (RRH) and BaseBand Unit (BBU) being used, the picture at the top shows LTE Anchor in eNodeB. There would be a need for an ideal backhaul to keep latency in the eNodeB to minimum when combining cellular and WiFi data.

Comparison of link level Carrier Aggregation technologies (Source: Netmanias)

The above table shows comparison between the 3 main techniques for increasing data rates through aggregation; CA, LTE-U/LAA and LTE-H/LWA. While CA has been part of 3GPP Release-10 and is available in more of less all new LTE devices, LTE-U and LTE-H is new and would need modifications in the network as well as in the devices. LTE-H would in the end provide similar benefits to LTE-U but is a safer option from devices and spectrum point of view and would be a more agreeable solution by everyone, including the WiFi community.

A final word; last year we wrote a whitepaper laying out our vision of what 4.5G is. I think we put it simply that in 4.5G, you can use WiFi and LTE at the same time. I think LTE-H fulfills that vision much better than other proposals.

Detailed whitepaper on Carrier Aggregation by 4G Americas

4G Americas has published a detailed whitepaper on Carrier Aggregation (CA). Its a very good detailed document for anyone wishing to study CA.

Two very important features that have come as part of CA enhancements were the multiple timing advance values that came as a part of Release-11 and TDD-FDD joint operation that came part of Release-12

While its good to see that up to 3 carriers CA is now possible as part of Rel-12 and as I mentioned in my last post, we need this to achieve the 'Real' 4G. We have to also remember at the same time that these CA makes the chipsets very complex and may affect the sensitivity of the RF receivers.

Anyway, here is the 4G Americas whitepaper.

LTE Carrier Aggregation Technology Development and Deployment Worldwide from Zahid Ghadialy

You can read more about the 4G Americas whitepaper in their press release 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.

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