5G cellular standards continue to take shape.
The Third Generation Partnership Project (3GPP) Radio Access Network (RAN) plenary met in early March to flesh out the work item that will serve as the foundation of the 5G Phase 1 standard, to be included in 3GPP Release 15. Although many have been talking about 5G for what seems like a very long time, it's still in a nascent stage and will likely evolve over time. Here are some key takeaways from Dubrovnik, including what's proposed for the first work item.
In defining a new network from the ground up, two distinct and different architectures, separated by time, have emerged. In the short term, the 3GPP must define elemental components to be used with the existing Evolved Packet Core (EPC) infrastructure — i.e., 4G — to expedite the adoption of the new technologies. This hybrid system is referred to as Non-Stand Alone (NSA). Using the existing infrastructure will deliver new features and benefits of 5G while expediting the commercialization and deployment.
The second architecture, referred to as Stand Alone, or SA, proposes a bit longer timeframe to define the new 5G Core Network (5GCN) by reusing the components proposed in the hybrid system. Both approaches must start at the bottom and work upward, and the 3GPP has made much progress defining the lower layers of the protocol — particularly Layer 1 and Layer 2 — which will be the fundamental building blocks of 5G New Radio, or 5G NR.
Also of note, the 5G NR RAN1 working group delivered an early framework for a flexible numerology physical layer (Layer 1) based on OFDM with up to eight component carriers (Figure 1). The physical layer is targeted to operate in frequency bands below 6 GHz and between 24 and 40 GHz. There have a been a myriad of spectrum proposals and RAN4 must vet the proposed frequency combinations to ensure satisfactory performance levels to meet the objectives. At first glance, Enhanced Mobile Broad Band (EMBB) appears to be a prioritized use case. End-to-end low latency cannot be achieved solely based on the physical layer as other elements of the system must be better defined and evaluated. The proposed framework provides an opportunity to address faster data and faster response simultaneously.
Figure 1. The 5G physical layer 1 consists of eight component carriers.
From the singular 5G work item, other technologies and use cases may be added in the future and these topics included as study items. The 3GPP will investigate the study items with the possibility of kicking off a formal work item for inclusion in the standard. One, some, or all may evolve to work items in future meetings. After successful completion of the work item phase, the 3GPP may add technologies/use cases to 3GPP Release 15 or possibly a later release. Study items related to non-orthogonal waveforms (NOMA), non-terrestrial networks, Vehicle-to-Vehicle (V2V) and Vehicle-to-Everything (V2X), and Integrated Backhaul Access (IAB) are just some of the items that will be further studied.
Surprisingly, LTE is not yet finished. In Dubrovnik, new work items to further evolve the LTE standard were introduced, and inevitably, LTE will continue to live on and evolve. In addition to work on NarrowBand IoT (NB-IoT) and LTE for Machine-Type Communications (LTE-MTC) for M2M communications and IoT being introduced, an expanded scope of V2V and V2X, fixed wireless access encompassing 1024 QAM modulation, and enhanced reliability were just some of the topics also submitted for inclusion in Release 15. This means that 5G NR may not be expected to fully address all objectives and goals, but instead will use a combination of LTE with 5G NR to satisfy the demands of the market.
Finally, the 3GPP agreed to accelerate the 5G deliverables by up to six months. A complete Non-Stand Alone (NSA) architecture is expected to be finalized by March of 2018 with the SA version using a 5G core network coming six months later. Working backward, Layer 1 and Layer 2 for 5G NR must be largely finalized by December 2017. This is all very ambitious, and the 3GPP is making excellent progress buoyed by the hard work, commitment, and investments of the 3GPP membership. While there is a lot of work left to be done, Dubrovnik was a clear and important milestone on the road to a 5G future.