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12:02 14 June 2017
As well as the prospect of being considerably faster than existing technologies, 5G holds the promise of applications with high social and economic value, leading to a ‘hyper-connected society’ in which mobile will play an ever more important role in people’s lives.
There are currently two definitions of 5G
Discussion around 5G falls broadly into two schools of thought: a service-led view which sees 5G as a consolidation of 2G, 3G, 4G, Wi-Fi and other innovations providing far greater coverage and always-on reliability; and a second view driven by a step change in data speed and order of magnitude reduction in end-to-end latency. However, these definitions are often discussed together, resulting in sometimes contradictory requirements.
Sub-1ms latency and >1Gbps bandwidth require a true generational shift
Some of the requirements identified for 5G can be enabled by 4G or other networks. The technical requirements that necessitate a true generational shift are sub-1ms latency and >1Gbps downlink speed, and only services that demand at least one of these would be considered 5G use cases under both definitions.
Achieving sub-1ms latency is a hugely exciting challenge that will define 5G
Delivering 1ms latency over a large scale network will be challenging, and we may see this condition relaxed. If this were to happen, some of the potential 5G services identified may no longer be possible and the second view of 5G would become less clear. This paper looks at some of the challenges that must be overcome to deliver 1ms latency.
At the same time 4G will continue to grow and evolve.
Technologies such as NFV/SDN and HetNets are already being deployed by operators and will continue to enable the move towards the hyper-connected society alongside developments in 5G. Considerable potential also remains for increasing 4G adoption in many countries, and we expect 4G network infrastructure to account for much of the $1.7 trillion the world’s mobile operators will invest between now and 2020. Operators will continue to focus on generating a return on investment from their 4G (and 3G) networks by developing new services and tariffing models that make most efficient use of them.
Clarifying 5G Technology
In summary, there are three key questions to ask:
1.What is 5G?
2.Potential 5G use cases?
3.Implications of 5G for mobile operators?
What is 5G?
Evolution beyond mobile internet
From analogue through to LTE, each generation of mobile technology has been motivated by the need to meet a requirement identified between that technology and its predecessor (see Table 1). For example, the transition from 2G to 3G was expected to enable mobile internet on consumer devices, but whilst it did add data connectivity, it was not until 3.5G that a giant leap in terms of consumer experience occurred, as the combination of mobile broadband networks and smartphones brought about a significantly enhanced mobile internet experience which has eventually led to the app-centric interface we see today. From email and social media through music and video streaming to controlling your home appliances from anywhere in the world, mobile broadband has brought enormous benefits and has fundamentally changed the lives of many people through services provided both by operators and third party players.
More recently, the transition from 3.5G to 4G services has offered users access to considerably faster data speeds and lower latency rates, and therefore the way that people access and use the internet on mobile devices continues to change dramatically. Across the world operators are typically reporting that 4G customers consume around double the monthly amount of data of non-4G users, and in some cases three times as much. An increased level of video streaming by customers on 4G networks is often cited by operators as a major contributing factor to this.
The Internet of Things (IoT) has also been discussed as a key differentiator for 4G, but in reality the challenge of providing low power, low frequency networks to meet the demand for widespread M2M deploymentis not specific to 4G or indeed 5G.
Two views of 5G exist today:
View 1 – The hyper-connected vision: In this view of 5G, mobile operators would create a blend of pre-existing technologies covering 2G, 3G, 4G, Wi-fi and others to allow higher coverage and availability, and higher network density in terms of cells and devices, with the key differentiator being greater connectivity as an enabler for Machine-to-Machine (M2M) services and the Internet of Things (IoT). This vision may include a new radio technology to enable low power, low throughput field devices with long duty cycles of ten years or more.
View 2 – Next-generation radio access technology: This is more of the traditional ‘generation-defining’ view, with specific targets for data rates and latency being identified, such that new radio interfaces can be assessed against such criteria. This in turn makes for a clear demarcation between a technology that meets the criteria for 5G, and another which does not.
Both of these approaches are important for the progression of the industry, but they are distinct sets of requirements associated with specific new services. However, the two views described are regularly taken as a single set and hence requirements from both the hyper-connected view and the next-generation radio access technology view are grouped together. This problem is compounded when additional requirements are also included that are broader and independent of technology generation.
Potential 5G use cases
Imagining the mobile services of the next decade
As with each preceding generation, the rate of adoption of 5G and the ability of operators to monetise it will be a direct function of the new and unique use cases it unlocks. Thus the key questions around 5G for operators are essentially:
a.What could users do on a network which meets the 5G requirements listed above that is not currently possible on an already existing network?
b.How could these potential services be profitable?
Virtual Reality/Augmented Reality/Immersive or Tactile Internet
These technologies have a number of potential use cases in both entertainment (e.g. gaming) and also more practical scenarios such as manufacturing or medicine, and could extend to many wearable technologies. For example, an operation could be performed by a robot that is remotely controlled by a surgeon on the other side of the world. This type of application would require both high bandwidth and low latency beyond the capabilities of LTE, and therefore has the potential to be a key business model for 5G networks.
However, it should be pointed out that VR/AR systems are very much in their infancy and their development will be largely dependent on advances in a host of other technologies such as motion sensors and heads up display (HUD). It remains to be seen whether these applications could become profitable businesses for operators in the future.
Autonomous driving/Connected cars
Enabling vehicles to communicate with the outside world could result in considerably more efficient and safer use of existing road infrastructure. If all of the vehicles on a road were connected to a network incorporating a traffic management system, they could potentially travel at much higher speeds and within greater proximity of each other without risk of accident - with fully-autonomous cars further reducing the potential for human error.
While such systems would not require high bandwidth, providing data with a command-response time close to zero would be crucial for their safe operation, and thus such applications clearly require the 1 millisecond delay time provided in the 5G specification. In addition a fully ‘driverless’ car would need to be driverless in all geographies, and hence would require full road network coverage with 100% reliability to be a viable proposition.
Wireless cloud-based office/Multi-person videoconferencing
High bandwidth data networks have the potential to make the concept of a wireless cloud office a reality, with vast amounts of data storage capacity sufficient to make such systems ubiquitous. However, these applications are already in existence and their requirements are being met by existing 4G networks. While demand for cloud services will only increase, as now they will not require particularly low latencies and therefore can continue to be provided by current technologies or those already in development. While multi-person video calling - another potential business application - has a requirement for lower latency, this can likely be met by existing 4G technology.
Machine-to-machine connectivity (M2M)
M2M is already used in a vast range of applications but the possibilities for its usage are almost endless, and our forecasts predict that the number of cellular M2M connections worldwide will grow from 250 million this year to between 1 billion and 2 billion by 2020, dependent on the extent to which the industry and its regulators are able to establish the necessary frameworks to fully take advantage of the cellular M2M opportunity.
Typical M2M applications can be found in ‘connected home’ systems (e.g. smart meters, smart thermostats, smoke detectors), vehicle telemetric systems (a field which overlaps with Connected cars above), consumer electronics and healthcare monitoring. Yet the vast majority of M2M systems transmit very low levels of data and the data transmitted is seldom time-critical. Many currently operate on 2G networks or can be integrated with the IP Multimedia Subsystem (IMS) – so at present the business case for M2M that can be attached to 5G is not immediately obvious.
Implications of 5G for mobile operators
The progress from initial 3G networks to mobile broadband technology has transformed industry and society by enabling an unprecedented level of innovation. If 5G becomes a true generational shift in network technology, we can expect an even greater level of transformation. There are varying implications of providing an increased level of connectivity or developing a new radio access network (RAN) to deliver a step change in per connection performance, or a combination of the two. This means that the final design of a 5G network could be any one of a range of options with differing radio interfaces, network topologies and business capabilities.
While a shift to 5G would be hugely impactful, the industry will need to overcome a series of challenges if these benefits are to be realised, particularly in terms of spectrum and network topology.
5G spectrum and coverage implications
While there are a number of spectrum bands which could potentially be used in meeting some of the 5G requirements identified to date, there is currently a substantial focus on higher frequency radio spectrum. As discussed in Appendix A, operators, vendors and academia are combining efforts to explore technical solutions for 5G that could use frequencies above 6GHz and reportedly as high as 300 GHz. However, higher frequency bands offer smaller cell radiuses and so achieving widespread coverage using a traditional network topology model would be challenging.
It is widely accepted that ‘beam-forming’ - the focussing of the radio interface into a beam which will be usable over greater distances – is an important part of any radio interface definition that would use 6GHz or higher spectrum bands. This however means that the beam must be directed at the end user device that is being connected. Since the service being offered is still differentiated from fixed line connections on the basis of ‘mobility’, the beam itself will have to track the device. This is innovation that could make 5G an expensive technology to deploy on large scale, since each cell may have to support several hundred individual beams at any one time and track the end users that are connected via these beams in three dimensional space.
High-order MIMO (Multi-Input, Multi-Output) is another method for increasing bandwidth that is often discussed. This is where an array of antennae is installed in a device and multiple radio connections are established between a device and a cell. However, high-order MIMO can have issues with radio interference, so technology is required to help mitigate this problem. This tends to focus on a need for the radio network to adjust its beam to take into account the specific orientation of the antenna at any given time.
All of this is incremental research and development over and above that currently being conducted for 4G. The use of bands higher than 6GHz will likely require operators to invest in an entirely new RAN since it will have fundamentally different masthead requirements. Given the level of infrastructure required to achieve the desired network topology, operators may be forced to rethink their existing business models. New technology is rarely a cheap option, and the nature of the new technology that is required in the radio network makes it very power-intensive, hence counter to the stated requirement for significant reduction in overall network power consumption.
That said, vendors are researching ways to include beam forming and MIMO technology in mobile devices. As a result, the process of identifying and aligning internationally around common bands for 5G will have a clear dependency on the technology that can be identified to overcome band usage in high frequencies for wide area coverage.
Can 1 millisecond latency be achieved?
Achieving the sub-1ms latency rate identified as a technical requirement for 5G necessitates a new way of thinking about how networks are structured, and will likely prove to be a significant undertaking in terms of technological development and investment in infrastructure.
Despite the inevitable advances in processor speeds and network latency between now and 2020, the speeds at which signals can travel through the air and light can travel along a fibre are governed by fundamental laws of physics. Subsequently services requiring a delay time of less than 1 millisecond must have all of their content served from a physical position very close to the user’s device. Industry estimates suggest that this distance may be less than 1 kilometre, which means that any service requiring such a low latency will have to be served using content located very close to the customer, possibly at the base of every cell, including the many small cells that are predicted to be fundamental to meeting densification requirements. This will likely require a substantial uplift in CAPEX spent on infrastructure for content distribution and servers.
If any service requiring 1 millisecond delay also has a need for interconnection between one operator and another, this interconnectivity must also occur within 1 kilometre of the customers. This could well be the case in a service such as social networking content pushed into augmented reality. Today, inter-operator interconnect points are relatively sparse, but to support a 5G service with 1 millisecond delay, there would likely need to be Interconnection at every base station, thus impacting the topological structure of the core network. Roaming customers would need to have visited network contextual roaming capabilities, and have content relevant to their applications available directly from the visited network, posing challenges for the existing roaming model.
In the most extreme case, it would make sense for a single network infrastructure to be implemented, which would be utilised by all operators. This would mean all customers could be served by a single content source, with all interaction and interconnect with localised context also being served from that point at the base station. This would also imply that only one radio network would be built, and then shared by all operators.
Such a model would considerably reduce CAPEX in the network build (since rather than say four operators building four parallel networks, only a single network would be built) but would require unprecedented levels of co-operation between operators. It would also impact the nature of inter-operator competition, shifting focus to services rather than data rate and coverage differentiation. It would also make spectrum auctions somewhat irrelevant, since only one radio network being built would mean there would only be one bidder and one license per market.
Once this is all realised, it is likely that requirements for sub-1ms delay will be relaxed or possibly removed entirely from 5G, rather than industry committing to the massive upheaval and resource acquisition that would be implied. If this were to happen, it may draw into question the viability of coupling services such as augmented and virtual reality, immersive internet and autonomous driving with mobility. However, if those services were removed from the expected service set, the justification for the technological view of 5G would also become questionable.
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