Release 14 – the start of 5G standardization
Release 14 will mark the start of 5G work in 3GPP. In addition to the continued LTE evolution, a new radio access technology will be standardized, and these two technologies together will form 5G radio access. In this blog post, I will shed some light on a number of the key areas – low latency communication, spectrum flexibility, machine type communication, multi-antenna and multi-site transmission techniques, and ultra-lean design – and how they can be part of the upcoming 5G work in 3GPP.
3GPP, the standardization organization behind LTE, is currently working on LTE release 13, which I have described in an earlier blog post as well as in a Tech Talk video. Work on release 14, with strong emphasis on 5G, is scheduled to start early 2016 and discussions about its content are starting now.
5G will consist of LTE evolution together with a new radio-access technology, which we call “NX” in the following. LTE evolution will focus on backwards-compatible enhancements in existing spectrum up to ~6 GHz, while NX will focus on new spectrum, i.e. spectrum where LTE is not deployed. Although large amounts of contiguous spectrum are less cumbersome to find at higher frequencies, lower frequencies are important for wide-area coverage and the first NX deployments may very well target moderately high frequencies. NX will therefore be able to operate from below 1 GHz up to close to 100 GHz.
Let’s start by taking a closer look at the LTE evolution in release 14. The evolution should have high ambition levels, striving to meet the 5G requirements. Some of the main technology areas we see for the LTE evolution include:
- Latency reduction. Not only is reduced latency important for an improved end-user experience and to fully exploit the high data rates provided by LTE, it can also provide better support for new use cases, for example critical machine-type communication. As a follow-up to the ongoing release 13 study, instant uplink access - where uplink transmissions can take place without a prior request-grant phase - and a shorter transmission-time interval, 0.5 ms or less, are likely to be part of release 14 work.
- Unlicensed spectrum has received a lot of attention in release 13 and will continue to be in focus also in the coming releases. Currently, the carrier-aggregation framework is used to aggregate licensed and unlicensed spectrum and forms the basis for downlink-focused license-assisted access in release 13. In practice, carrier aggregation implies that the same node is handling licensed as well as unlicensed spectrum. A natural enhancement is to extend license-assisted access to build upon the dual-connectivity framework. This will provide additional deployment flexibility as physically separate nodes can handle the two spectrum types. Full support for uplink transmissions in unlicensed spectrum is also a natural part of release 14.
- New use cases will be addressed by LTE, for example in the area of Intelligent Transportation Systems (ITS), including vehicular-to-vehicular and vehicular-to-infrastructure communication. Traffic safety and transportation efficiency can be greatly improved by enabling information exchange between vehicles as well as between vehicles and the infrastructure. Compared to alternative solutions, the existing widespread deployment of LTE is a great advantage. The usage of mainstream LTE technology also makes it possible to include a wide range of road users, e.g. pedestrians and bicyclist, in an overall traffic safety work. The existing device-to-device framework can serve as a basis for the work on vehicular-to-vehicular communication.
- Massive machine-type communication (MTC) is a vital part of the overall vision of a networked society. LTE has already been enhanced in previous releases and is well positioned to combine low device cost with long battery lifetime - two of the main requirements for massive machine-type communication. Release 14 will further improve the MTC capacity as well as look into new features for MTC devices such as MBMS support for delivering software upgrades and device-to-device relaying for coverage extension.
- Massive MIMO, or full-dimension MIMO as it is called in 3GPP, is about using a large number of antenna elements, e.g. for two-dimensional beamforming and/or multi-user MIMO. The focus of release 14 will be to extend the current massive MIMO framework to an even larger number of antennas (more than 16) and to secure the development of requirements and test methodologies to facilitate real-life deployment of these technologies.
NX - new radio access technology
Although the LTE evolution will be capable of addressing many of the 5G requirements, there is a need for an additional radio-access technology. NX will go beyond the LTE evolution and not take backwards compatibility into account. Some of the driving forces behind NX are even higher performance, extreme use case requirements, and the need to exploit spectrum not addressed by LTE evolution.
A selection of NX technology components are illustrated below.
The possibility to address higher frequency bands is one characteristic of NX. Due to the properties at high frequencies, coverage is more ’local’. high frequency bands are therefore primarily used to boost capacity and data rates in specific areas, while wide-area coverage is provided by lower, current frequency bands. This calls for a tight interworking between high and low frequencies. Hence, with LTE already being deployed in lower frequency bands, tight interworking between LTE and NX will play an important role. Such interworking is much tighter than ‘traditional’ handover and may build on frameworks similar to carrier aggregation or dual connectivity in LTE. The benefits of tight interworking can be seen already at moderately high frequencies, around 4 GHz and higher, so it is not a feature for the very high frequencies only.
Another key aspect of NX is the ultra-lean design. In short, ‘always on’ signals should be kept to an absolute minimum. This reduces energy consumption and unnecessary interference, and provides a good foundation for forward compatibility when NX is further evolved in the future. One example is cell-specific reference signals, which in LTE are constantly broadcasted in a cell and this is something that should be avoided in the NX design. ‘System control plane’ is a novel framework where only the minimum amount of system information necessary to access the network is broadcasted, possible only by some of the network nodes, and the rest of the information is provided ‘on demand’. This is a good step towards the goal of an ultra-lean design.
Multi-antenna techniques such as beamforming and massive MIMO, and multi-site connectivity will play important roles in NX. At higher frequencies, beamforming is a necessity to handle the challenging link budget. The ongoing trend of integrating RF components closer to the antenna elements contributes to make advanced multi-antenna techniques a reality. Multi-site connectivity, where the terminal is simultaneously connected to multiple sites, is very useful to ‘guarantee’ delivery of data packets within a tight latency budget. This is important in some critical machine-type communication applications, for example remote control of machinery. It can also be used for distributed MIMO to provide higher data rates.
Since 5G to a large extent is about addressing a wide range of use cases beyond mobile broadband, NX will of course also include components addressing for example massive and critical machine-type communication.
Some of these technology components have already been demonstrated in our 5G testbed, shown to a larger audience at Mobile World Congress this year. The testbed has been used to demonstrate multi-Gbps data rates with beamforming and OFDM modulation at 15 GHz carrier frequency. We also use the testbed to try different advanced antenna setups and to evaluate coverage indoors as well as outdoors.
Designing a new radio-access technology such as NX is a major task. The work on NX will therefore span multiple releases in 3GPP. Channel modelling work is expected to start already towards the end of this year, followed by a study phase in release 14. Actual specification work is expected in release 15, resulting in a first version of NX specifications in the latter half of 2018 to facilitate initial commercial deployment in 2020. This set of specifications will fulfill a subset of the 5G requirements. Complete fulfillment of all 5G requirements is targeted in release 16 by the end of 2019. This is also the release that will be provided to ITU.
I hope I have given some insight into the upcoming work on 5G, including LTE evolution and NX. LTE evolution and NX are both very important tools for realizing the continued development of the networked society. We certainly have some very interesting years ahead of us!
Principal Researcher, Ericsson Research
These previously published items provide additional reading about some of the above topics:
Licensed Assisted Access: Operation Principles
Licensed Assisted Access: Practical Coexistence Solutions
Tech Talk video: On the road to smarter and safer transport systems
Device to Device communication
Massive beamforming in 5G radio access
High network energy performance with 5G
Ericsson White Paper: 5G radio access – technology and capabilities
Ericsson news center: Ericsson first with key 5G advances