5G Technology Requirements

What is 5G ? As a result of this blending of requirements, many of the industry initiatives that have progressed with work on 5G (see Appendix A) identify a set of eight requirements: 
  • 1-10Gbps connections to end points in the field (i.e. not theoretical maximum) 
  • 1 millisecond end-to-end round trip delay (latency) 
  • 1000x bandwidth per unit area 
  • 10-100x number of connected devices 
  • (Perception of) 99.999% availability 
  • (Perception of) 100% coverage 
  • 90% reduction in network energy usage 
  • Up to ten year battery life for low power, machine-type devices 
Because these requirements are specified from different perspectives, they do not make an entirely coherent list – it is difficult to conceive of a new technology that could meet all of these conditions simultaneously. 

Equally, whilst these eight requirements are often presented as a single list, no use case, service or application has been identifed that requires all eight performance attributes across an entire network simultaneously. Indeed some of the requirements are not linked to use cases or services, but are instead aspirational statements of how networks should be built, independent of service or technology – no use case needs a network to be significantly cheaper, but every operator would like to pay less to build and run their network. It is more likely that various combinations of a subset of the overall list of requirements will be supported ‘when and where it matters’. 

Finally, while important in their own right, six of these requirements are not generation-defining attributes. These are considered below: 

Perceived 99.999% availability and 100% geographical coverage: 

These are not use case drivers, nor technical issues, but economic and business case decisions. 99.999% availability and 100% coverage are achievable using any existing technology, and could be achieved by any network operator. Operators decide where to place cells based on the cost to prepare the site to establish a cell to cover a specific area balanced against the benefit of the cell providing coverage for a specific geographic area. This in turn makes certain cell sites and coverage areas - such as rural areas and indoor coverage - the subject of difficult business decisions. 

Whilst a new generation of mobile network technology may shift the values that go in to the business model that determines cell viability, achieving 100% coverage and 99.999% availability will remain a business decision rather than a technical objective. Conversely, if 100% coverage and 99.999% availability were to be a 5G ‘qualifying criteria’, no network would achieve 5G status until such time as 100% coverage and 99.999% availability were achieved. 

Connection density (1000x bandwidth per unit area, 10-100x number of connections): 

These essentially amount to ‘cumulative’ requirements i.e. requirements to be met by networks that include 5G as an incremental technology, but also require continued support of pre-existing generations of network technology. The support of 10-100 times the number of connections is dependent upon a range of technologies working together, including 2G, 3G, 4G, Wi-fi, Bluetooth and other complementary technologies. The addition of 5G on top of this ecosystem should not be seen as an end solution, but just one additional piece of a wider evolution to enable connectivity of machines. The Internet of Things (IoT) has already begun to gain significant momentum, independent of the arrival of 5G. 

Similarly, the requirement for 1,000 times bandwidth per unit area is not dependent upon 5G, but is the cumulative effect of more devices connecting with higher bandwidths for longer durations. Whilst a 5G network may well add a new impetus to progression in this area, the rollout of LTE is already having a transformational effect on the amount of bandwidth being consumed within any specific area, and this will increase over the period until the advent of 5G. The expansion of Wi-fi and integration of Wi-fi networks with cellular will also be key in supporting greater data density rates. 

Meeting both of these requirements will have significant implications for OPEX on backhaul and power, since each cell or hotspot must be powered and all of the additional traffic being generated must be backhauled. 

Reduction in network energy usage and improving battery life:

The reduction of power consumption by networks and devices is fundamentally important to the economic and ecological sustainability of the industry. A general industry principle for minimising power usage in network and terminal equipment should pervade all generations of technology, and is recognised as an ecological goal as well as having a significant positive impact on the OPEX associated with running a network. At present it is not clear how a new generation of technology with higher bandwidths being deployed as an overlay (rather than a replacement) on top of all pre-existing network equipment could result in a net reduction in power consumption. 

Some use cases for M2M require the connected device in the field to lie dormant for extended periods of time. It is important that innovation in how these devices are powered and the leanness of the signaling they use when becoming active and connected is pursued. However, this requirement is juxtaposed with 5G headline requirements on data rate – what is required for mass sensor networks is very occasional connectivity with minimal throughput and signaling load. Work to develop such technology predates the current 5G requirements and is already being pursued in Standards bodies. 

5G
These six requirements should be and are being pursued by the industry today using a range of techniques (some of which are covered later in the paper) but these amount to evolutions of existing network technology and topology or opportunities enabled by changing hardware characteristics and capabilities. These will in turn open business opportunities for operators and third parties. However, none of these business opportunities exist today – they are constrained by limitations greatly governed by economics, and much of these six requirements are motivated by improving the economic viability of those opportunities, rather than filling technological gaps that explicitly prohibit these opportunities, regardless of the amount they might cost to enable. 

Thus in the strictest terms of measurable network deliverables which could enable revolutionary new use case scenarios, the potential attributes that would be unique to 5G are limited to sub-1ms latency and >1 Gbps downlink speed.