Critical infrastructure requires precise timing to operate. This reliance makes the infrastructure vulnerable to disruptions in timing that can be either intentional or unintentional. Intentional disruptions can be caused by GNSS jamming or spoofing or network attacks.. Unintentional disruptions are usually caused by equipment failures or acts of nature.
Back in April 2022, Alliance for Telecommunications Industry Solutions (ATIS) hosted a webinar on this topic, a precursor to the Annual Workshop on Synchronization and Timing Systems (WSTS). The webinar featured top industry experts delivering insight into the latest techniques for adding resilience and robustness to timing infrastructure. It covered the most critical topics in timing resilience, including:
Redundancy
Holdover
Management
Monitoring
Alternative reference time sources
Examples address networks used for critical industry applications such as:
Power grids
Telecommunications
Finance systems
Broadcast/media
The video of the webinar as follows:
Experts participating in the webinar and their presentations are as follows:
A new 3GPP Technical report, TR 38.858 (draft not available yet) will look at Study on evolution of NR duplex operation (FS_NR_duplex_evo) in Rel-18. RP-213591 provides a justification on why this new duplex evolution needs to be studied:
TDD is widely used in commercial NR deployments. In TDD, the time domain resource is split between downlink and uplink. Allocation of a limited time duration for the uplink in TDD would result in reduced coverage, increased latency and reduced capacity. As a possible enhancement on this limitation of the conventional TDD operation, it would be worth studying the feasibility of allowing the simultaneous existence of downlink and uplink, a.k.a. full duplex, or more specifically, subband non-overlapping full duplex at the gNB side within a conventional TDD band.
The NR TDD specifications allow the dynamic/flexible allocation of downlink and uplink in time and CLI handling and RIM for NR were introduced in Rel-16. Nevertheless, further study may be required for CLI handling between the gNBs of the same or different operators to enable the dynamic/flexible TDD in commercial networks. The inter-gNB CLI may be due to either adjacent-channel CLI or co-channel-CLI, or both, depending on the deployment scenario. One of the problems not addressed in the previous releases is gNB-to-gNB CLI.
This study aims to identify the feasibility and solutions of duplex evolution in the areas outlined above to provide enhanced UL coverage, reduced latency, improved system capacity, and improved configuration flexibility for NR TDD operations in unpaired spectrum. In addition, the regulatory aspects need to be examined for deploying identified duplex enhancements in TDD unpaired spectrum considering potential constraints.
Samsung has a technical white paper on this topic which they refer to as XDD (Cross Division Duplex), available here. The abstract says:
XDD (Cross Division Duplex) is one of the key technologies that Samsung is proposing as part of Rel-18 NR (5G-Advanced) to address the coverage issue observed during the initial phase of 5G deployment. XDD provides improved coverage, capacity, and latency compared to conventional TDD. Instead of relying solely on orthogonal time resources for DL-UL separation as in TDD, XDD allows simultaneous DL-UL operation by using non-overlapping frequency resources within a carrier bandwidth.
This white paper provides a high level description of XDD concept, benefits, and implementation challenges. First, an overview of XDD including a comparison with conventional TDD and FDD is provided. Next, the implementation challenges of XDD especially at the base station to handle self-interference mitigation is provided. Furthermore, several features that we consider critical in realizing XDD in actual deployment scenarios are provided along with some performance results. Finally, Samsung’s view on XDD for the next phase of 5G (5G-Advanced) is provided.
An open access IEEE Access paper, 'Extending 5G TDD Coverage With XDD', written by Samsung researchers provides a much more detailed insight into this topic. The abstract says:
In this paper, an advanced duplex scheme called cross-division duplex (XDD) is proposed to enhance uplink (UL) coverage in time division duplex (TDD) carriers by utilizing self-interference cancellation (SIC) capability at a base station. With XDD, it is possible to combine TDD’s ability to efficiently handle asymmetric UL and downlink (DL) traffic with frequency division duplex’s coverage advantage. To do so, XDD simultaneously operates UL and DL on the same TDD carrier but on different frequency resources. Such operation leads to severe interference on the received UL signal at the base station which requires two levels of SIC implementation; antenna and digital SIC. More than 50 dB of interference is removed through the antenna SIC using electromagnetic barriers between the transmitting and receiving antennas. The remaining interference is removed by the digital SIC based on estimating the non-linear channel of the circuit at the receiver baseband. It is verified by simulation and analysis that with the proposed XDD, the UL coverage can be improved by up to 2.37 times that of TDD. To check the feasibility of XDD, a Proof-of-Concept was developed where it was observed that the benefits of XDD can indeed be realized using the proposed SIC techniques
In the segment of the video embedded below, Dr. Hyoung Ju Ji, Principal Engineer, Samsung Electronics, Korea explains how XDD is a Realistic Option for Full Duplex Realization.
Qualcomm has been busy promoting its advanced 5G solutions these last few months in the run up to Mobile World Congress (MWC). You can find a detailed write-up on their website here as well as a feature which they did with RCR wireless here.
One of the innovations that caught my attention was Sub-band Half-Duplex (SBHD). In the first glance it looks like the Enhanced Interference Mitigation & Traffic Adaptation (eIMTA) solution we discussed long back here.
Their article talks about how their 5G multi-cell over-the-air (OTA) test network can now support subband half-duplex, allowing for more flexible service multiplexing as well as improved latency and coverage.
While you can get an idea of what SBHD is from the diagram above, here is a video explaining it further.
Let us know what do you think about how important will this feature be in future 5G networks.
In frequencies below 6GHz (referred to as frequency range 1 or FR1 in standards), there is a probability to use both FDD and TDD bands, especially in case of re-farming of existing bands. In frequencies above 6GHz (referred to as frequency range 2 or FR2 in standards, even though FR2 starts from 24.25 GHz), it is expected that all bands would be TDD.
Interesting to see that the cell phase synchronization accuracy measured at BS antenna connectors is specified to be better than 3 μs in 3GPP TS 38 133. This translates into a network-wide requirements of +/-1.5 microseconds and is applicable to both FR1 and FR2, regardless of the cell size.
Frequency Error for NR specified in 3GPP TS 38.104 states that the base station (BS) shall be accurate to within the following accuracy range observed over 1 ms:
Wide Area BS → ±0.05 ppm
Medium Range BS → ±0.1 ppm
Local Area BS → ±0.1 ppm
The presentation specifies that based on request by some operators, studies in ITU-T on the feasibility of solutions targeting end-to-end time synchronization requirements on the order of +/-100 ns to +/-300 ns
There is also a challenge of how the sync information is transported within the network. The conclusion is that while the current LTE sync requirements would work in the short term, new solutions would be required in the longer term.
If this is an area of interest, you will also enjoy watching CW Heritage SIG talk by Prof. Andy Sutton, "The history of synchronisation in digital cellular networks". Its available here.
3GPP refers to HPUE as High Power UE while the US operator Sprint prefers to use the term High Performance UE.
HPUE was initially defined for US Public Safety Band 14 (700MHz). The intention was that this high power UEs can increase the coverage range from 4km to 8km. This would mean larger coverage areas and less number of cells.
While the commercial UE's (class 3) transmit at +23dBm (max 200mW), the Public Safety people intend to use class 1 UE transmitting +31 dBm (max 1.25W). It was felt that this feature could be beneficial for some TDD bands that do not have to worry about backward compatibility. One such band, pushed by Sprint was TDD Band 41 (2500MHz). As this band is for the commercial UE's, instead of class 1, class 2 power at +26dBm (max 400mW) was proposed.
3GPP TS 36.886 provides the following justification:
Currently, 3GPP has defined only Power Class UE 3 as the type of UE supported for TDD LTE band 41 operations. This definition was based on aligning TDD LTE Band 41 UE power classes with prior work in 3GPP related to other bands. However, it should be mentioned that 3GPP UE Power Class 3 definition (i.e. 23dBm) was mainly driven to ensure backward compatibility with prior technologies (i.e. GSM/UMTS) [2] so that network deployment topologies remain similar. Furthermore, maintaining the same power class UE definition (i.e. Class 3) as previous technologies would maintaining compliance with various national regulatory rulings, particularly in terms of SAR, for FDD LTE duplexing mode. However, TDD LTE band 41 does not have any 3GPP legacy technologies associated with it, hence the backward compatibility consideration is not applicable in its case. Also, since band 41 is defined as a TDD LTE band, it is less susceptible to SAR levels that FDD LTE bands due to SAR definition. Therefore, defining a new UE power class with higher than 23dBm Tx power for TDD LTE Band 41 operations would not compromise any of 3GPP foundational work, while improving UE and network performance. It should also be mentioned that 3GPP has done similar work on other bands (i.e. band 14) when defining a higher power class UE, hence the concept presented in this document is a continuation of that process. The present document carries out a feasibility analysis for defining a UE Power class 2 (i.e. 26dBm) for operation on TDD LTE band 41. The document analyses current and future technological advancements in the area of UE RF front-end components and architectures that enable such definition while maintaining 3GPP specification and other regulatory bodies' requirements. It should be emphasized that this proposal only relates to single carrier UL operations on TDD band 41 (i.e. TM-1/2 modes) without affecting current 3GPP definition for UL carrier aggregation on band 41.
Iain Gillott, iGR points out that HPUE applies to Sprint’s 2.5 GHz TDD network and associated spectrum, and the company claims up to 30 percent increase in cell cover from the new technology. It should be noted that HPUE is a 3GPP standard that applies to the 2.5 GHz TDD band (Band 41) and is also to be used by China Mobile and Softbank. HPUE was developed as part of the Global TDD LTE Initiative (GTI) which includes Qualcomm Technologies, Samsung, ZTE, Broadcom, MediaTek, Skyworks Solutions, Alcatel, Motorola, LG and Qorvo... The cool part: the improvement in coverage comes from simply improving the device uplink power. So Sprint, China Mobile and Softbank will not have to visit their cell sites to make changes; they just need 2.5 GHz TDD devices with HPUE to get the benefit.
Milan Milanović recently wrote about Sprint’s Gigabit Class LTE network goes live in New Orleans. One of the questions I had was why is the uplink so rubbish as compared to downlink. He kindly pointed out to me that this is TDD config 2
Sprint expects HPUE to appear in postpaid devices starting in 2017, including new devices from Samsung, LG, HTC, and Moto. It’s expected that all of Sprint’s new devices will have HPUE support within the next two years.
I think it would be interesting to see how this impacts when there are a lot more users and devices. I am quite sure there will be more requests for HPUE in further TDD bands.
Continuing with the updates from 5G RAN workshop, part 1 and part 2 here.
Dish network wants to have a satellite based 5G network. A recent article from Light Reading shows the following:
Dish states that there are misconceptions about what satellite technology can deliver for 5G networks. Essentially Dish says that satellites will be capable of delivering two-way communications to support 5G. A hybrid ground and space 5G network would use small satellites that each use a "spot beam" to provide a dedicated area of two-way coverage on the ground. This is different than the old model of using one satellite with a single beam to provide a one-way service like a TV broadcast over a landmass. Dish argues that newer, smaller satellites, equipped with the latest multi-antenna arrays (MIMO) would allow for "ubiquitous connectivity through hybrid satellite and terrestrial networks," the operator writes. In this model, satellites could connect areas that it would be hard to network otherwise like mountains and lakes.
The presentation from Dish is as follows:
Alcatel-Lucent provided a whitepaper along with the presentation. The paper provides an interesting view of 5G from their point of view. Its embedded below:
The presentation from Kyocera focused on TD-LTE which I think will play a prominent role in 5G. In case of wide channels, TD-LTE can help predict the channel accurately, which is a drawback for FDD at high frequencies. Their presentation is available here.
The presentation from NEC focussed on different technologies that will play a role in 5G. Their presentation is available here.
The final presentation we will look at this time is by the South Korean operator, KT. What is interesting to see is that in the part 1 we saw in the chairman's summary that 5G will come in two phases; Rel-15 will be phase 1 and Rel-16 will be phase 2. In the summary slide in KT's presentation, it looks like they are going to consider Rel-14 as 5G. Its not at all surprising considering that Verizon has said that they want to commercialise 5G by 2017, even though 5G will not be fully specified according to 3GPP by then. Anyway, here is the presentation by KT.
3GPP held a 5G Workshop in Phoenix last week. 550 delegates and over 70 presentations contributed to the discussion, which covered the full range of requirements that will feed TSG RAN work items for the next five years. I will eventually look at all the presentations and highlight the ones that I find interesting as a part of this blog. Due to the vast number of presentations, I will split them into a few blog posts.
Lets start with the chairman summary. The chair highlighted three high level use cases that 5G needs to address (This has been highlighted in many presentations, see here for example):
Enhanced Mobile Broadbandare
Massive Machine Type Communications
Ultra-reliable and Low Latency Communications
As can be seen in the picture above, 3GPP is planning to split the 5G work into two phases. Phase 1 (Rel-15) will look at a subset of requirements that are important for the commercial needs of the day. Phase 2 (Rel-16) will look at more features, use cases, detailed requirements, etc.
Here is the chair summary of the workshop:
The presentation (RWS-150002) from Motorola/Lenovo highlighted the need to handle different spectrum. For sub-6GHz, the existing air interface could work with slight modifications. For spectrum between 6GHz and 30GHz, again a similar air interface like 4G may be good enough but for above 30GHz, there is a need for new one die to phase noise.
The presentation by CATT or China Academy of Telecommunication Technology (RWS-150003) is quite interesting and is embedded below. They also propose Pattern Division Multiple Access (PDMA).
Orange (RWS-150004) has definitely put a thought into what good 5G would be. Their presentation is embedded below too:
The presentation from Huawei (RWS-150006) introduced the concept of Unified Air Interface, UAI.
They presentation also explains the concept of Adaptive Frame structures and RAN slicing very well. For those who may be wondering, uMTC stands for ultra-reliable MTC and mMTC stands for massive MTC. RAN slicing enables the RAN to be partitioned such that a certain amount of carriers are always dedicated to a certain services independently of other services. This ensures that the service in the slice is always served reliably.
The final presentation is the vision and priorities by 5GPPP as follows:
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.
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.
People often ask at various conferences if TD-LTE is a fad or is it something that will continue to exist along with the FDD networks. TDD networks were a bit tricky to implement in the past due to the necessity for the whole network to be time synchronised to make sure there is no interference. Also, if there was another TDD network in an adjacent band, it would have to be time synchronised with the first network too. In the areas bordering another country where they might have had their own TDD network in this band, it would have to be time synchronised too. This complexity meant that most networks were happy to live with FDD networks.
In 5G networks, at higher frequencies it would also make much more sense to use TDD to estimate the channel accurately. This is because the same channel would be used in downlink and uplink so the downlink channel can be estimated accurately based on the uplink channel condition. Due to small transmit time intervals (TTI's), these channel condition estimation would be quite good. Another advantage of this is that the beam could be formed and directed exactly at the user and it would appear as a null to other users.
This is where 8T8R or 8 Transmit and 8 Receive antennas in the base station can help. The more the antennas, the better and narrower the beam they can create. This can help send more energy to users at the cell edge and hence provide better and more reliable coverage there.
How do these antennas look like? 8T8R needs 8x Antennas at the Base Station Cell, and this is typically delivered using four X-Polar columns about half wavelength apart. I found the above picture on antenna specialist Quintel's page here, where the four column example is shown right. At spectrum bands such as 2.3GHz, 2.6GHz and 3.5GHz where TD-LTE networks are currently deployed, the antenna width is still practical. Quintel’s webpage also indicates how their technology allows 8T8R to be effectively emulated using only two X-Polar columns thus promising Slimline antenna solutions at lower frequency bands. China Mobile and Huawei have claimed to be the first ones to deploy these four X-Pol column 8T8R antennas. Sprint, USA is another network that has been actively deploying these 8T8R antennas.
There are couple of interesting tweets that show their kit below:
Sprint's John Saw showing of TD-LTE 8T8R and Network Vision. Room for expansion. pic.twitter.com/Mydzasg3F6
Sprint's deployment of 8T8R (eight-branch transmit and eight-branch receive) radios in its 2.5 GHz TDD LTE spectrum is resulting in increased data throughput as well as coverage according to a new report from Signals Research. "Thanks to TM8 [transmission mode 8] and 8T8R, we observed meaningful increases in coverage and spectral efficiency, not to mention overall device throughput," Signals said in its executive summary of the report. The firm said it extensively tested Sprint's network in the Chicago market using Band 41 (2.5 GHz) and Band 25 (1.9 GHz) in April using Accuver's drive test tools and two Galaxy Note Edge smartphones. Signals tested TM8 vs. non-TM8 performance, Band 41 and Band 25 coverage and performance as well as 8T8R receive vs. 2T2R coverage/performance and stand-alone carrier aggregation. Sprint has been deploying 8T8R radios in its 2.5 GHz footprint, which the company has said will allow its cell sites to send multiple data streams, achieve better signal strength and increase data throughput and coverage without requiring more bandwidth. The company also has said it will use carrier aggregation technology to combine TD-LTE and FDD-LTE transmission across all of its spectrum bands. In its fourth quarter 2014 earnings call with investors in February, Sprint CEO Marcelo Claure said implementing carrier aggregation across all Sprint spectrum bands means Sprint eventually will be able to deploy 1900 MHz FDD-LTE for uplink and 2.5 GHz TD-LTE for downlink, and ultimately improve the coverage of 2.5 GHz LTE to levels that its 1900 MHz spectrum currently achieves. Carrier aggregation, which is the most well-known and widely used technique of the LTE Advanced standard, bonds together disparate bands of spectrum to create wider channels and produce more capacity and faster speeds.
Alcatel-Lucent has a good article in their TECHzine, an extract from that below:
Field tests on base stations equipped with beamforming and 8T8R technologies confirm the sustainability of the solution. Operators can make the most of transmission (Tx) and receiving (Rx) diversity by adding in Tx and Rx paths at the eNodeB level, and beamforming delivers a direct impact on uplink and downlink performance at the cell edge. By using 8 receiver paths instead of 2, cell range is increased by a factor of 1.5 – and this difference is emphasized by the fact that the number of sites needed is reduced by nearly 50 per cent. Furthermore, using the beamforming approach in transmission mode generates a specific beam per user which improves the quality of the signal received by the end-user’s device, or user equipment (UE). In fact, steering the radiated energy in a specific direction can reduce interference and improves the radio link, helping enable a better throughput. The orientation of the beam is decided by shifting the phases of the Tx paths based on signal feedback from the UE. This approach can deliver double the cell edge downlink throughput and can increase global average throughput by 65 per cent. These types of deployments are made possible by using innovative radio heads and antenna solutions. In traditional deployments, it would require the installation of multiple remote radio heads (RRH) and multiple antennas at the site to reach the same level of performance. The use of an 8T8R RRH and a smart antenna array, comprising 4 cross-polar antennas in a radome, means an 8T8R sector deployment can be done within the same footprint as traditional systems.
Anyone interested in seeing pictures of different 8T8R antennas like the one above, see here. While this page shows Samsung's antennas, you can navigate to equipment from other vendors.
Finally, if you can provide any additional info or feel there is something incorrect, please feel free to let me know via comments below.
We all know about the two type of transmission schemes which are FDD and TDD. Normally, this FDD and TDD schemes are known as full duplex schemes. Some people will argue that TDD is actually half-duplex but what TDD does is that it emulates a full duplex communication over a half duplex communication link. There is also a half-duplex FDD, which is a very interesting technology and defined for LTE, but not used. See here for details.
One of the technologies being proposed for 5G is referred to as Full Duplex. Here, the transmitter and the receiver both transmit and receive at the same frequency. Due to some very clever signal processing, the interference can be cancelled out. An interesting presentation from Kumu networks is embedded below:
The biggest challenge is self-interference cancellation because the transmitter and receiver are using the same spectrum and will cause interference to each other. There have been major advances in the self-interference cancellation techniques which could be seen in the Interdigital presentation embedded below:
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.
From a recent NTT Docomo presentation (embedded below). Whereas right now 3GPP has only been working on FDD or TDD scenarios, this proposal is a combination of FDD as P-Cell and TDD as S-Cell. Inter-Technology carrier aggregation is another possible option. Anyway, the complete presentation is below.
TDD deployments are gathering pace. An earlier GSA report I posted here, highlighted the many devices that are TD-LTE ready.
The main thing that is being emphasised is that from the standards point of view, not much additional efforts are required for a TDD device as compared to an FDD device. Of course in practice the physical layer would be different and that could be a challenge in itself.
Qualcomm published a presentation on this topic that is embedded below. Available to download from here.
eIMTA is one of the features being discussed in 3GPP Rel-12. The pictures above and below provide the details.
As can be seen, at the moment all the eNodeB's associated with a network has to transmit the same UL/DL pattern throughout out the system. With eIMTA, each eNodeB can decide the UL/DL pattern itself depending on the load.
The main challenge would be interference management while using this scheme.
See also, this slideshare presentation for details:
Some of the interesting findings from the conference include:
TD-LTE is gaining momentum, and its beyond WiMAX operators and China mobile, many APAC operators are considering it for unpaired spectrum and to efficiently meet the asymmetric capacity requirements of mobile broadband which is mainly download
Software defined radio and self-organizing networks are proving critical to manage operational costs
Single RAN is proving the best way to manage network performance
Signaling is in a mess - what is the good of standards when it creates such a mess?
IMS gaps continue - what is the good of standards when it doesn't meet basic migration needs?
The SS7 guys have reinvented themselves as the Diameter guys
Business model innovation - LTE is not just for mobile devices, LTE is for quad play and an interesting array of business applications
The 3G network of many operators is congested - forcing the move to LTE
CSFB (Circuit Switched Fall Back) works
VoLTE testing / roaming / network issues remain - given voice remains by revenue the core service, our industry should be ashamed we're having so many problems with VoLTE
A belief on OTT partnering, but not quantification on the OTT's willingness to pay for QoS (Quality of Service)
Many operators have a question mark on the use of WiFi off-load - its not a technology issue rather one of economics and customer experience, LTE-A and small cells in hotspots appears to be the focus.
Briefly reviewing the slides shown below:
LTE Data Points
96 Commercial LTE deployments mainly in the 1.8 and 2.8GHz bands
APAC has 40% of LTE subscribers, likely to be the high growth region
Drivers for LTE: Throughput, efficiency and low latency
TD-LTE: 12 commercial deployments, 24 contracts and 53 Trials
Streaming video dominates traffic on handheld devices, with YouTube being the top traffic generator at 27% of peak traffic
South Korea Data Explosion
South Korea has seen OTT explode, Kakao Talk 51 mins of usage per day
20 times smartphone growth in 2 years (28M in June 2012, 53% penetration)
60 times mobile data growth to 37TB per month in 2 years, 32% is from LTE devices
LTE subs use 2.9GB per month compared to 3G sub on average use 1.2GB
LTE subs reached 10M, 141% monthly growth
Customer drive for LTE is speed (37%) and latest device (31%)
Challenge Jan 2010 and Jan 2012 ARPU fallen from $48-$35 while data use risen from 180MB to 992MB
Focus beyond voice, messaging and data into VAS: virtual goods (Korean thing), ICT (Information and Communication Technology) and cloud services / solutions (focus on enterprise)
HK CSL Migration to LTE
3G is congested, LTE is not
Key is LTE devices available, unlike the early 3G days
Migrating customers away from unlimited plans to family and shared plans that deliver value
LTE sub uses 2-5 times the data of 3G subs
CSFB works
Average speed seen is 20 Mbps
Using Software Defined Radio, Single vendor RAN, Self-Organizing Networks
Migration to LTE-A, small cells and WiFi where appropriate
Starhub's migration to LTE (they launched LTE at the event)
50% of voice traffic is still on 2G
Using AMR to re-farm 2G spectrum to LTE
Site access is critical - drive to software defined radio to avoid site visits
NTT DoCoMo's VoLTE Evolution
70% devices in portfolio are now LTE
All smartphones support CSFB
Drive to VoLTE is simply to switch off 3G voice (2G already off)
BUT IMS has missing functionality / standards - migration from 3G to VoLTE is not easy - example of failing in standards on basic issues
Yes: Example of innovative converged 4G operator in an developing market that uses web principles for service delivery
Role of Mobile Identity in BYOD (Bring Your Own Device)
BYOD is as significant a trend if APAC as any other market
Provides a nice review of the approaches in managing BYOD
LTE Quad-Play in Emerging Markets: TD-LTE case study
Smartphone growth implications: Review of the signaling problem and mitigation strategies across 3G and LTE. Highlights challenge current standards process
In Japan, they love to re-brand the standard technologies into something more interesting to attract people's attention. In a way they are right as they want to offer a service rather than a technology. Couple of years back NTT Docomo launched its Crossy service, that was offering LTE with upto 75Mbps dl speeds. Yesterday, I read about Softbank launching their 4G service that is based on AXGP format.
I did blog about XGP many years back but AGXP, which stands for Advanced XGP may not be very well related to XGP. According to ZTE Technologies magazine:
In November 2011, Japan’s third largest mobile operator, Softbank, made AXGP commercially available. AXGP is similar to TD-LTE, and has been deployed in Japan in conjunction with ZTE and Huawei. Two thousand base stations were built in the fi rst phase, and there will be up to 10,000 base stations built in the second phase. Ninety-nine percent of the Japanese population will be covered by 2012. So far, the Softbank network is the largest commercial TD-LTE network in the world. Wang Jianzhou, chairman of China Mobile, said, “If in the past the TD-LTE network was just a stratagem on paper, now it has turned into a reality.”
The following are some more details edited from a Japanese website (translation via Chrome):
High-speed data communication service Wireless City Planning of the SOFTBANK Group (Wireless City Planning, WCP) will be scheduled after February 2012, adopted a new communication method AXGP is, in excess of up to 100Mbps downlink high-speed communication is a feature . It was an opportunity to use the test machine prior to the start of service for general users, to report a sense of its use.
"AXGP" was developed inherit the "PHS" next generation of Willcom
"AXGP" high-speed data transmission technology WCP employs a technology that was originally planned to use the 2.5GHz band has been assigned from the Ministry of Internal Affairs and Communications Willcom to deploy as "PHS" next generation. Had to expand the limited service area and some intended for users under the name of "WILLCOM CORE XGP" PHS is then the next generation, business is XGP is "Wireless City Planning" of Softbank subsidiary company under the reorganization proceedings of Willcom inheritance. Provide the service as "AXGP" form of communication is an evolved version of XGP in WCP.
AXGP, in addition to the XGP also hand while inheriting the "micro cell" was characteristic of PHS, PHS has been developed as the next generation, that have become compatible with the method of TD-LTE. Including China and India, that are compatible with the TD-LTE system is expected to expand in many parts of the world, the benefits can be expected that international expansion is expected.
Service is initially started up to 76Mbps. The first bullet is the mobile router products
AXGP is at present, but services have been provided for users in a small part had been using the service test XGP Willcom old, since the February 2012 service "SoftBank 4G for general users as MVNO Softbank Mobile plans to start ". The communication speed up to 110Mbps downstream and 15Mbps and maximum upstream and downstream speeds in excess of 100Mbps for speed has become a feature.
At the start of service, the mobile router will "101SI" made of (SII) will be released at the same time Seiko Instruments. However, 101SI has become a maximum 76Mbps to 110Mbps falling down is the theoretical value of the service, at the start of the service is not provided in the full spec. Terminal is planned to also provide support AXGP Then, in the year 2012 is also powered smartphone will be compatible with AXGP. In addition, "101SI" to support (42Mbps maximum downlink, 5.7Mbps uplink maximum) "ULTRASPEED" Softbank mobile.
Ultra-high speed in the area. Hope to plan area at the time of service and rates
Although a measurement with the outdoor area was limited, with respect to communication speed was very good results with the results fit. Most favorable conditions and even the user does not exist before the start of the service say that already provide services as high-speed data communication, "Xi" of NTT DoCoMo, Inc., or UQ Communications 37.5Mbps, which is the maximum theoretical value of outdoor (Kurosshi~i) It was also a number greater than the maximum 40Mbps "UQ WiMAX" of is very encouraging.
However, the decisive factor in mobile data communications is not only communication speed, three elements of the communication charge is important and easy-to-use, deployment area, including "ease of connection." In the area at the moment of some are very fast and are limited in the Yamanote Line, but is a matter of course in order before the service, ease of connection of the fact there are many parts of the still unknown. Also, I'd be anxious and services are provided in the fee structure what.
SoftBank is to introduce a flat-rate voice among their users ahead of any other mobile phone operators so far, campaigns expand the iPhone however any inexpensive flat-rate packet. Further has a track record of just made me started to increase subscribers by the "straight-line with anyone" WILLCOM has also continued to decline in subscribers. Softbank Mobile also be deployed as a MVNO, at the time of release of the service that you want to use the AXGP expect a bold expansion of unique services and Softbank WCP, which is the same group Softbank.
In countries where FDD and TDD are both in use, it would be interesting to see Dual-mode LTE terminals that would support both TDD and FDD and it should be possible to do a reselection as well has handovers from one mode to another.
It should be noted that the Structure of TDD and FDD frames are different as shown above.
If you are wondering why we need both FDD and TDD modes in the same geographical location, its because of Spectrum being available as well as with TDD allows possibility of different UL/DL data rates which generally means more efficient use of spectrum.
