ZTE kickstarts NSA 5G NR tests: What is it and why should we care?

-August 02, 2017

5G New Radio (5G-NR) was a hot topic for discussion at Mobile World Congress in February; it got formal recognition as RP-170741 by the 3GPP at its meeting in Dubrovnik in March; and on July 10, it got real, with ZTE and China Unicom collaborating on tests in the 3.5-GHz band.

To understand what this means, let’s unpack all that, starting with a quick description of 5G NR and an introduction to NSA 5G NR, the version that got approved at Dubrovnik.

5G NR derived from work led by Qualcomm to develop a unified air interface and network to address the need for enhanced mobile broadband with gigabit-per-second speeds; mission-critical automotive, medical and industrial services; and the “massive” Internet of things (IoT) now unfolding (Figure 1).

Figure 1 The end game is a fully unified connectivity platform, but between now and then, the 5G NR effort needs to split into SA and NSA and run in parallel, before converging again in 2018. (Source: Qualcomm)

The new radio interface was designed to address these applications, while also incorporating a flexible approach to spectrum usage and overall lower latency and cost per bit.

Building upon LTE, the interface and modulation scheme of choice for 5G NR is an optimized version of multiple-access OFDM with dynamic, low-latency TDD and FDD, making it both backward compatible with current infrastructure, and forward compatible with where LTE is headed. It also emphasizes the use of massive MIMO, operation both below and above 6 GHz, beamforming, and low-density parity check (LDPC).

The choice of multiple-access OFDM was relatively easy. OFDM is already widely used and understood, from Wi-Fi’s early days with the formation of 802.11g, to mobile’s LTE and LTE Advanced Pro.

That was the end of the easy part. The hard part was getting agreement on a 5G NR standard in a timely fashion to meet rapidly increasing demand for high-speed data.

Wisdom of Solomon splits 5G NR at Dubrovnik

That effort started by establishing there was enough interest to justify yet another parallel track in the overall 5G standards process. That was demonstrated at MWC in Barcelona when a number of companies joined with Qualcomm to promote the 5G NR approach. They included NTT DoCoMo, SK Telecom, Vodaphone, and Ericsson.

But they still had a dilemma. The 5G NR proposal would change everything from the edge interface to the core network, and yet following that path would take too much time; data requirements were (are) already increasing too rapidly at the edge.

At the subsequent 3GPP Radio Access Network (RAN) Plenary meeting in Dubrovnik, a group of 5G NR backers, including AT&T, British Telecom, Alcatel-Lucent, Broadcom, Deutsche Telecom, Ericsson, Huawei, Nokia, and Qualcomm, proposed a way out of the dilemma. They offered a proposal (RP-170741) to split 5G into non-standalone (NSA) and standalone (SA) 5G NR. The bifurcated approach would keep the momentum going on the 5G NR front end, while giving the core network proposals time to take shape.

NSA will use the current LTE radio and core infrastructure as an “anchor” for mobility management and coverage, while adding a new 5G carrier. The proponents of RP-170741 will focus on developing an enhanced mobile broadband (eMBB) 5G NR in 2019. This is a year sooner than the 2020 timeframe initially planned for 5G NR as part of 3GPP Release 15. In 3GPP parlance, the fast-tracked radio is referred to as “NSA 5G NR deployment scenario Option 3.”

Note, however, that the proposers of RP-170741 are not off the hook with regard to 5G NR and SA (Figure 2). They must still ensure commonality and compatibility between the NSA and SA variants. SA 5G NR will include full user and control-plane capability for 5G NR, using the 5G core network architecture being done in 3GPP.

Figure 2 As part of RP-170741, the backers must complete Stage 3 for NSA 5G NR by December, with an implementable version due in March 2018 (ASN.1). (Source: 3GPP)

According to RP-170741, the Stage 3 for NSA 5G NR is due by December this year (2017), and an implementable version is due by March of 2018. The proposal also states that complete Stage 3 for L1 and L2 user plane for both SA and NSA are also due by December 2017. In addition, the current schedule for SA 5G-NR in Rel-15 must be maintained (Stage 3 completion due June 2018, with ASN.1 freeze in September 2018).

ZTE and China Unicom test sub-6-GHz NSA 5G NR network

It’s worth noting at this point that the 3GPP proposal provides only a six-month head start for NSA 5G NR, versus waiting for a full implementation. However, these are the timelines under which the industry is now operating, and it provides some perspective for the recent announcement of 5G NR network tests by ZTE and China Unicom in Guangdong, southern China.

On July 10th, the duo announced that they had achieved data rates of 2 Gbits/s in the 3.5-GHz band using massive MIMO techniques. ZTE is a backer of the NSA/SA split proposal, so its trials will feed into the NSA proposal’s development. However, other trials are underway with collaborators that include Qualcomm, Ericsson, and ZTE, who have announced trials with AT&T, China Mobile, NTT DoCoMo, SK Telecom, Telstra, and Vodaphone. Bands of interest include 3.3 to 5 GHz, as well as 28 GHz and 39 GHz.

Stay tuned for the next installment of Standards Watch, where we will update you on how the standards work is doing, as well as the status of cellular-V2X.

Patrick Mannion has a long association with EDN, EE Times, and other publications, and currently leads an independent content engineering firm specializing in technology analysis, editorial, and media services.

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