With 5G still five or more years away from commercial deployments, there may be more questions than there are answers right now, but there's still a lot to be said about the emerging network standard.

To shed some light on both the answers and the right questions to ask, Light Reading caught up with Heavy Reading Senior Analyst Gabriel Brown, fresh from attending the Next Generation Mobile Networks (NGMN) Ltd. 's 5G industry event in Frankfurt, Germany. We grilled him on everything from the definition of 5G to its use cases to its challenges and real potential. Read on to find out what he had to say. (See 5G: What Is It & Why Does It Matter?)

Figure 1: Experts Wanted Everyone was a 5G expert -- or naysayer or hype man -- at Mobile World Congress 2015, but only Ericsson had official jackets made.

For more on 5G, visit the dedicated 5G section here on Light Reading, and register to attend the upcoming "Building America's 5G Ecosystem" event in NYC.

On defining 5G: At this stage, there is not a definition of 5G, so we don't know what it is exactly. There is no threshold that you have to pass or not to be so-called 5G defined yet. What's happening at the moment is the industry is gathering and generating performance requirements. Ultimately, 5G will probably be defined through the International Telecommunication Union (ITU) process called IMT-2020 and Beyond. They are looking to have specifications in place in and around 2020. What the industry needs to do is backfill that and actually develop the technology and standards to be ready for 2020. The ITU itself is developing requirements this year and next. So although ITU is in principle the final arbiter, that's not all that useful today because the industry needs to work on this beforehand.

On 5G's use cases: The Next Generation Mobile Networks (NGMN) Ltd. is developing use cases and user experience requirements ahead of standardization, which is a little different from the traditional process. They are talking about things like 300 Mbit/s downlink in the wide area, indoor ultra-high speed access at 1-gigabit per second or performance of 50 Mbit/s everywhere. And there are things like 1-millisecond latency, ultra-reliable communications and IoT at massive scale. I think there will be overlap between 4G-Advanced and 5G -- overlap particularly in use cases and some overlap in the technology.

On the spectrum for 5G: Spectrum is a big deal, of course. It falls into two parts -- sub-6Ghz low bands and above 6Ghz, known as high bands. The higher bands will use centimeter and millimeter wave technologies, and there is a lot more spectrum available. You'll get much higher data rates, but the propagation is poorer. 5G should, in theory, scale across high and low bands. The problem is you need to optimize technologies differently according to the band. Things like massive MIMO works better in high-band TDD systems than low-band FDD.

At the moment it is not clear. If you go to high band, you have all this spectrum and can leverage massive MIMO for high data rates, but others say that isn't as useful in practice. You want to look at low bands to support mobility and things like that. My feeling is there is a lot of hype around the high bands, but the focus, and I'm not by any means certain about this, will end up going on the lower-bands initially… It depends on a lot of factors. It's hard to call. It might be both simultaneously. For the low band 5G needs to be substantially better than 4G-Advanced for operators to adopt it.

Next page: Standardization, challenges, business models & more

On 5G standardization: The aim is to have this standardization in time for IMT-2020. The 3rd Generation Partnership Project (3GPP) has just this month approved the work plan. Standardization will kick off in earnest in the September meeting this year and ultimately it is likely that the ITU will accept the 3GPP standards as IMT-2020. The first release of standards will come in 2020, driven by the fact that Japan wants to launch something for the summer Olympics in 2020. That is the plan, to have a viable system ready for that, so that will be the start of 5G. At that point it's not expected that all the capabilities will be available. It'll literally just be the start, just like with 3G and 4G.

On Korea's prototype 5G: Before that, at the Korean Winter Olympics in 2018, their government wants something to put a sticker on and call it prototype 5G. So there is a push from the Koreans to have an early drop of the standards, something they can call prototype 5G. It's extremely ambitious and will probably be a prototype, but it's good to have a challenging target. There might be an early drop of the standards to enable the Koreans to meet that deadline in some form. One idea is have only the user plane standardized or frozen at that point. The control plane might have to wait until 2020.

On the 5G rollout: It will be introduced like 4G was to 3G in islands and bits of pieces. The network itself will need to provide interworking between the access technologies. In terms of geographies, it's fairly clear it will be Korean and Japan operators leading the way.

On 5G's challenges: The challenges are elementary. One good way of thinking about it is the performance targets are extremely challenging and they are also quite diverse. On the one hand you want ultra-broadband or you want massive scale for IoT. On the other you want ultra-reliability for public safety or self-driving cars. And, you want all of this across a really wide spectrum range of many different bands. And you want it to be one global standard. The challenge is bringing very diverse use cases and requirements under a common technology. I think there is always a saying in this process -- what the expectations are now are probably not what we are going to have in 2020. One millisecond latency is extremely demanding, and it may not be economically viable.

On 5G's business model: The business model is always a challenge. The intent of the mobile/wireless and telecom sector is to enroll other vertical sectors in the standardization and development process much earlier in the cycle. Go to energy, or healthcare, or IoT, or car companies and find out what types of requirements they need for the apps and use cases they could envision and build that in during the development phase rather than spend five years doing it and realize you haven't taken into account something critical for, say, the healthcare industry. There's a big push to reach out to other vertical sectors. That is something the telecom industry is doing very well, but they need to do more of it.

Next page: Network slicing, IoT & the tactile Internet

On the opportunity to network slice: One thing that looks interesting, and is a paradigm shift from the business model perspective, is network slicing, a term that comes from the SDN world. You have the segmentation of different traffic types of applications and users in the cloud, in your virtual network. You can apply that to telecom networking not just in the cloud or data center, but right into the radio network. The idea is you can create a network slice, or service slice, which is specific to a particular user group, or customer type, or application. That network slice would have particular QoS requirements and other performance attributes that went right through the network. They would have it all the way through the network end-to-end. The idea of 5G network slicing will be a really big deal. It's about tailoring the network configuration to the requirements of that slice.

On the biggest vertical opportunities: It's pretty early days -- everyone is talking about the car industry. There could be other things. It's all a bit speculative, like connected cities or smart cities. You wouldn't say that is substantially more than a good idea at the moment. The challenge is who in these verticals is capable of engaging in this discussion and who wants to commit resources to implementing it. Say you're a car company, even a global one, do you have the expertise and interest to make a meaningful contribution? It's similar with healthcare. The main thing is to support many use cases.

On IoT on 5G: IoT is somewhat challenging in LTE for various reasons. A lot of industries want to design more efficient systems so connected devices can last five to eight to ten years. The way LTE is currently built, there is overhead and inefficiency for low-powered, low data rates, sensor-type devices, so 5G is supposed to address supporting massive numbers of devices at scale, but also have them work in an unconnected state. Devices don’t have to be registered on the network. They only create a connection when they need one. Some of this is addressed in a new standard called LTE-M as well, causing some confusion. That’s an example of the overlap I talked about.

On the coming tactile Internet: The other thing -- perhaps the most exciting thing -- is the tactile Internet. There are some really good examples there, of doing remote control for surgery or controlling a digger, or robot. This is where the latency that is almost imperceptible to the human eye is important. And that’s where the one millisecond comes in. The potential here is incredible, and these are types of things you couldn't do with 4G.

— Sarah Thomas, , Editorial Operations Director, Light Reading