Driven by the enormous increase in mobile data traffic and flourishing user demands, we need to look beyond 4G. The mobile communications community has already conducted significant research into systems for the next decade and 5G is the acronym for next generation mobile communication systems. It is generally anticipated that 5G will be commercially available around 2020 at the earliest. Questions arise about what 5G will look like, what it will comprise and what will be the underlying technology?
The Nokia Siemens Networks 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”.
We see Heterogeneous Networks (HetNets) as a key enabler for this vision. 5G is unlikely to be a single new Radio Access Technology (RAT) nor will it replace macro cells – most likely it will be a combination of existing RATS in both licensed and unlicensed bands, plus one or more new RATS optimized for dedicated deployments, scenarios and use cases. In particular, we have identified the need for a new RAT for ultra-dense deployments, with the aim of providing a virtual zero latency gigabit experience.
Scalable services and applications
Let’s face it – it is not economically feasible to build ultra-dense networks everywhere and we have to accept that a virtual zero latency gigabit connectivity will only become available “where it matters”. Upcoming services have to be scalable according to the performance of the HetNet connectivity. 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 scalable service experience in 5G will be all about tailoring the system to extremely diverse use cases in order to meet specific performance requirements.
Which are the relevant KPIs and functional requirements for 5G?
Nokia Siemens Networks is researching technology building blocks to achieve 10 Gbps peak data rates and to accommodate greater than 100 Mbps as typical user data rates, even in high load conditions or at the cell edge. The ultra dense deployments with many complex use cases and scenarios set many other targets and functional requirements for a new system, which are illustrated and briefly explained below.
The Round Trip Time (RTT) target of the new RAT is set to be lower than 1 ms to provide a virtual zero delay experience and to facilitate a new palette of time critical machine type communication. Latency will be a key aspect of 5G communications systems, as:
- we will see more applications that require ultra-low end-to-end latency, such as real-time video processing in the infrastructure to aid augmented reality
- 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, and finally
- 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.
Spectrum availability is a key issue in reaching these targets. So far, spectrum for mobile communication has only focused on frequency ranges below 6 GHz and we will soon need to also look for spectrum above 10 GHz and potentially up to 100 GHz to meet requirements in 2020-2030. Depending on the carrier frequency, we expect that beyond 2020, spectrum needs will include: large chunks of spectrum in high(er) bands, TDD mode in unpaired bands and flexible use of spectrum by means of secondary or shared usage in more heavily used bands.
Spectral efficiency. We will still see improvements and demanding requirements for spectral efficiency in terms of average bit/s/Hz/cells 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.
Inbuilt support of self-backhauling and direct device-to-device. In terms of connectivity, a new RAT must obviously support radio access between a terminal and an access point connected to the Internet cloud by wire or wirelessly. For ultra-dense deployment, self-backhauling and direct connectivity is becoming important to balance cost and performance of connectivity.
Low power consumption is a key design element. First, Nokia Siemens Networks wants to keep power consumption for mobile networks at a minimum. Secondly, low power consumption is essential for battery operated terminals to prolong time between battery changes. Many new potential Machine Type Communication (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. Clearly, as we go to more and more dense deployments, 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”. This means the radio access technology needs to be fully auto-configured 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.
Lastly, higher layer protocols and architecture are important ingredients of our 5G vision – the Internet of things will greatly multiply the number of connected devices and the connectivity will be heterogeneous. The trend we see is that IPv6 is accelerating and will likely have become mainstream in 2020 when 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.
It is clear that with 5G, performance measures other than just spectral efficiency will become more important – a multitude of applications and different use cases needs to be addressed, with novel technologies designed to fit each specific case, ensuring the limitations of mobile communications system don’t limit the overall development of the technology.
Thanks to Nokia Networks Blog!