5G Standards Frontline Report – High Speeds and High Capacity or Ultra High Confidence and Low Latency, Which Should Come First: Two Sides of a Debate at the 3GPP

Takahiro Nakamura
5GMF Strategy and Planning Committee Deputy Chairman,
NTT DOCOMO 5G Laboratory Office Project Leader

Satoshi Nagata
3GPP TSG-RAN WG1 Chairman,
NTT DOCOMO 5G Laboratory Office member

Debates about 5G are now in full swing at the 3GPP. The first release related to 5G was discussed at the September meetings there. The discussions revolved around the scope of 5G, focusing on what kinds of requirements were needed for 5G, to standardize 5G as soon as possible.

There have been 3 major requirement proposals listed:

– eMBB (enhanced Mobile Broadband), capacity enhancement
– URLLC (Ultra-Reliable and Low Latency Communications), ultra-high reliability and low latency
– mMTC (massive Machine Type Communications), massive connectivity

5G is expected to be ready to be put on the market by 2020. Without these requirements being decided first, however, it is difficult to work on research and development or hold verification trials. In order to achieve the targets for 5G, discussions on 5G requirements need to proceed in an orderly fashion.

As of September, opinions had broken into two camps. The first is that eMBB needs to be specified first while the other says that URLLC does.

Promoting eMBB specifications are Japanese companies, with DOCOMO leading the way, along with Korean companies as well as vendors like Ericsson, Nokia, and Qualcomm. This group argues that if the specifications for high speed and high capacity for 5G are decided first, these key qualities of 5G will be in place by the time 5G is ready for the market in 2020. 5G will be given a boost with the establishment of hotspots, which will increase traffic and offer a stable data transmission environment to users.

Those promoting URLLC are centered around telecommunications firms in China as well as some in Europe. URLLC is not only concerned with latency, but also has the goal of raising confidence in wireless communications. This is due to the expected use cases for 5G, which differ from needing only high speeds and high capacity, such as self-driving automobiles, remote medical care, tactile communication, agricultural sensors and other IoT applications. The group promoting URLLC hopes to increase the value of these services that differ from the traditional mobile telecommunication services that have relied solely on high speeds and high capacity.

It is generally agreed that mMTC does not need to be specified first, since it can be securely buit on using the standards and requirements of LTE technologies. Therefore, these current debates begun with Release 15 should not pose a problem to mMTC requirements as we move ahead to Release 16.

Since the debate on whether eMBB or URLLC should be specified first has only just begun, the path which 5G development will take will ultimately be decided at a later date.

One technical issue related to eMBB technology, which is also related to URLLC, is that low latency may be an outcome of the attempts to achieve high speeds and high capacities in the higher frequency bands that 5G will utilize. Current LTE subcarrier space at 15kHz has a resource block structure that is divided into one millisecond segments. In order to interact at higher frequency bands, for example a subcarrier space at 60kHz, the resource block structure will need to be reduced one-fourth to .25 seconds. This means there is the possibility that it will naturally guarantee a lower latency than LTE currently provides.

While the discussions on whether eMBB or URLLC are specified first are ongoing, we want to also look at which way the technology may progress based on which specifications are decided.