Tuesday, 18 September 2018

5G NR: NOKIA looking ahead to 5G

Three key development areas in 5G

The continuing growth in demand from subscribers for better mobile broadband experiences is encouraging the industry to look ahead at how networks can be readied to meet future extreme capacity and performance demands. Nokia, along with other industry partners, believes that communications beyond 2020 will involve a combination of existing and evolving systems, like LTE-Advanced and Wi-Fi, coupled with new, revolutionary technologies designed to meet new requirements, such as virtually zero latency to support tactile Internet, machine control or augmented reality. 5G will be the set of technical components and systems needed to handle these requirements and overcome the limits of current systems


Unlike 2G, 3G and 4G, it is unlikely that 5G will be a single new Radio Access Technology (RAT) nor will it replace macro cells. It will be a combination of existing RATs in both licensed and unlicensed bands, plus one or more novel RATs optimized for specific deployments, scenarios and use cases. In particular, Nokia has identified the need for a new RAT for ultra-dense deployments, with the aim of providing a virtual zero latency gigabit experience.
Nokia is already undertaking extensive research to map out the scope of 5G and has a clear vision of the three key pillars that will make this future network a reality

1. More spectrum must be pressed into service

More radio spectrum for mobile networks is vital to meet the increased capacity and coverage demand. New spectrum will need to be allocated and put into use quickly. Without sufficient spectrum, communities beyond the reach of wired broadband will miss out on the benefits of future services and entire countries could lose ground. The amount of spectrum available needs to be expanded by adopting new frequency bands and by using available spectrum more efficiently, both in terms of frequency and with regard to when and where it is employed. 

2. Networks will become much denser with many more cells

The second pillar of 5G will be to use many more base stations, deployed in a heterogeneous network (HetNet), combining macro sites with smaller base stations and using a range of radio technologies. These will include LTE-A, Wi-Fi and any future 5G technologies, integrated flexibly in any combination.

3. Raising the overall performance of networks 

The third major goal will be to get the best possible network performance by evolving existing radio access technologies and building new 5G wireless access technologies. For example, it is generally accepted that latency must decrease in line with rising data rates. Sustained research and development in these three areas will be necessary to create a 5G environment that can meet market demands such as 10,000 times more traffic, virtually zero latency and a much more diverse range of applications. What’s more, all this must be achieved at an affordable cost to enable operators to maintain and improve their profitability. The Nokia vision is that: “5G will enable a scalable service experience anytime and everywhere and where people and machines obtain virtual zero latency and gigabit experience where it matters”. Let’s now look at each of the three development areas in more detail.


Bridging the spectrum gap with 5G



Networks to become denser with small cells

Network densification is needed to meet the throughput and latency demands likely to arise in 2020 and beyond. By 2020, small cells are expected to carry a majority of traffic with overall data volume expected to grow up to 1,000 times (compared to 2010). Nokia’s analysis shows that sufficient network capacity at a minimum downlink user data rate of 10 Mbit/s can be achieved using a LTE heterogeneous network configuration (LTE, small cells and well integrated Wi-Fi), which is how networks are expected to evolve until 2020.


Beyond this date, a new approach will be needed to achieve ultra-dense small cell deployments and this is where we expect to see innovative 5G components emerging. Whether deployed in ‘traditional’ frequencies (<6 GHz) or in new centimeter and millimeter wave bands, these new technology blocks will need to enable ultra-low latency, higher data rates (peak rates exceeding 10 Gbps, with user data rates greater than 100 Mbps even under high load conditions or at the cell edge) and more flexibility, for example in backhaul or duplexing schemes.


The key to meeting these requirements is to bring the access point closer to the user, with smaller cells making more radio resources available to active users. This will also substantially reduce the radio round trip time for lower latency and increase overall network efficiency by creating sub-networks to handle a proportion of the traffic locally.


The increase in achievable data rates for 5G (10,000 times more traffic) cannot be achieved without reducing the cell size and increasing the frequency re-use rate. This is already happening today, especially for indoor traffic that is inefficient to handle with outdoor macro cells. Over the next few years this trend will accelerate as the use of data-hungry applications rises. Ultimately, the need for small-cell-optimized RAT will be one of the triggers for 5G. 

New applications will require ultra-low latency to support online gaming, augmented reality and to control uses such as tactile Internet and remote surgery. It is clear that the need for low latency will become much more important in the future and will need to be addressed. New, small-cell-optimized RAT for 5G can deliver latency as low as 1ms.

The mass roll out of IPv6 and the emerging ‘Internet of things’ will lead to more connected devices and also new use cases for small cell deployments. 5G will use some IP mechanisms (e.g. IPv6 Neighbor Discovery Protocol) to simplify the creation of sub-networks that will handle some traffic locally, while autonomous deployment mechanisms, such as mobility and traffic steering, will make roll out more efficient.

With such an increase in access point density there will be ongoing development of interference coordination schemes for data offload from bigger to smaller node types and resource usage coordination between nodes. With many different equipment types and devices, HetNets will have a wide range of performance demands, making self-aware networks essential.


Network performance

With 5G, a range of performance measures will become more important – a multitude of applications and different use cases need to be addressed, with novel technologies for each specific case to ensure the limitations of mobile communications systems don’t limit the overall development of the technology. 

In particular, it is not economically feasible to build ultra-dense networks everywhere and it must be accepted that a virtual zero latency gigabit connectivity will only become available “where it matters”. Therefore, while ‘traditional’ performance indicators, such as peak data rates, will improve, the key to 5G will be flexibility and support for new use cases. 

More important than just peak data rate or spectral efficiency will be enabling the same 5G system (integrated from different radio access technologies including new ones) to support requirements such as: 
• Few devices demanding huge downloads 
• Ultra-high numbers of sensors sending just small data packages 
• Remotely-controlled robot applications (low latency needed for control) 
sending back UHD video (high upload capability required). 

The scalable service experience in 5G will be all about tailoring the system to extremely diverse use cases in order to meet specific performance requirements. A uniform service experience can still be achieved in most use cases by tighter coupling between RAN and transferred content, for example, making APIs between the application and network layer to adjust application demands or by caching data locally. Furthermore, local sub-networks can be set up, where several devices create a high performing direct connectivity within a local area.

The key performance measures that will need to be met include: 


Round Trip Time (RTT) 
Ultra-low latency will be a key aspect of 5G communications systems because we are moving towards the era of the tactile Internet where wireless communications will be increasingly used for distributed control rather than merely content distribution. Also it is predicted that the maximum data rates per device will increase substantially faster than Moore’s law, meaning that if the cost of, for example, HARQ buffers at the device side is to be kept constant, any increase in air interface bandwidth must be complemented by a decrease in air interface latency. 

The target RTT for 5G is likely to be lower than 1 ms to provide a virtual zero delay experience and to facilitate a new palette of time critical Machine Type Communications (MTC). 

Spectral efficiency 
We will still see improvements and demanding requirements for spectral efficiency in terms of average bit/s/Hz/cell for ultra-dense deployments. However, this will probably not be as important as in the past for the design and optimization of 3G and 4G radio access technologies, which were mainly optimized for wide area deployments. Using higher frequency bands, large transmission bandwidth combined with low transmit power automatically limits the coverage. What matters more for the new radio access design is the total deployment cost in terms of cost/area considering a certain traffic density and a typical experienced user data rate. 

Low power consumption 
Nokia believes that power consumption for mobile networks must be kept to a minimum. Low power consumption is also essential for battery operated terminals to prolong time between battery charges. Many new potential MTC use cases are more limited by a power hungry radio access than the offered data rate or latency.

Ultra-low cost per access node 
As networks become denser, it is of utmost importance that the cost per access node is reduced substantially, with an OPEX virtually close to zero. This means that 5G will have to be fully “plug and play”. Therefore, the radio access technology needs to be fully autoconfigured and auto-optimized, and any hierarchy or relation between network entities, for example, to centralize or distribute radio resource management, has to be fully self-establishing. 

Higher layer protocols and architecture 
The Internet of things will greatly multiply the number of connected devices and this connectivity will be heterogeneous. The adoption of IPv6 is accelerating and the protocol will probably have become mainstream by 2020 after which 5G will be launched. Ethernet is another technology becoming more widespread. “Ethernet over Radio” could become a simple and cost-effective solution to encompass 5G HetNets.




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