With 3GPP recently completing the first 5G NR standard — a huge milestone achieved by the entire mobile industry — we are now on track to see the first 5G NR commercial deployments in the first half of 2019. As we all know, the lifeblood for wireless communication is spectrum and as we enter the 5G era, spectrum availability is as important as ever. The good news is that 5G has been designed to support a wide range of spectrum bands, from sub-1 GHz all the way up to mmWave bands. Licensed spectrum is, and will continue to be, the foundation for ubiquitous wireless connectivity and the industry’s top priority, to deliver the multi-gigabit, ultra-reliable, and ultra-low latency connectivity. But to make the best use of all potential spectrum, 5G NR is also being designed to operate in shared/unlicensed spectrum, through the use of a flexible 5G NR framework.
The work to introduce shared/unlicensed spectrum in 5G NR has already been kicked off with a new 3GPP study item and we expect the work in 3GPP to start next month. To jumpstart this effort, we hosted an industry wide workshop Oct 3-4, 2017 in San Diego. The focus of this workshop was to share ideas on 5G NR spectrum sharing (NR-SS). The workshop was a great success and we discussed new concepts covering a wide range of topics, including deployment models, spectrum/regulatory, radio access design, support of standalone mode, and network architectures. It was exciting to see such broad participation from the more than 50 delegates representing 20+ companies — including vendors, mobile operators, and cable operators — from around the world.
For the first phase of the NR-SS effort, we expect the focus to be on extending the spectrum sharing technologies that we pioneered in LTE to 5G NR, such as:
- Licensed Assisted Access (LAA), which enables the carrier aggregation of licensed and unlicensed spectrum to offer Gigabit LTE services by more operators globally.
- MulteFire, which enables LTE to operate as a standalone, only using unlicensed spectrum, to enable new types of deployments such as neutral host and private LTE networks.
- Citizens Broadband Radio Service (CBRS), which opened the 3.5 GHz spectrum band in the U.S. for LTE operation by enabling new wireless entrants to use the spectrum without disrupting the incumbents.
In other words, the first thing that needs to be done is to create an NR-based LAA and an NR-based 5G MulteFire. I think of this as the ‘evolutionary’ path because it uses existing techniques that we pioneered in LTE to use shared/unlicensed spectrum for cellular. But we can do even better for 5G NR. We also see an opportunity to introduce a ‘revolutionary’ path with more significant gains by exploring new spectrum sharing paradigms.
So, what are some new sharing paradigms that we should explore? One big opportunity is to develop tighter coordination among users of unlicensed/shared bands by using time synchronization among the nodes sharing the spectrum. Already today, the CBRS Alliance is introducing time slot synchronization to reduce interference between deployments. In 5G NR we can combine time synchronization with new sharing concepts. Here are some examples:
- Support of guaranteed resources that provide each operator with Quality of Service from a guaranteed bandwidth, like you would get from licensed spectrum, while still enjoying the benefit of spectrum sharing.
- Support of a flexible sharing framework to cope with more complicated spectrum situations such as incumbents, sharing rules and deployment models, including ‘vertical sharing’ between operators at the different priority levels.
- Support of advanced techniques such as spatial division multiplexing (SDM) and coordinated multipoint transmission (CoMP) to increase spectrum efficiencies and to get a more consistent user experience, especially at higher traffic load and at cell edges.
By exploring this ‘revolutionary’ path, we have the opportunity to change the way we think about shared and unlicensed spectrum and provide significant gains, both in terms of spectrum efficiencies that translate to higher data speeds for the users and enabling new capabilities such as guaranteed bandwidth. In the end, it can provide more operators, both existing and new-entrants, with more ability to offer fiber-like 5G experiences.