Most 5G events are full of starry-eyed projections about how the network will transform every part of our daily lives from working to surgery to watching a movie. Not so at Light Reading's recent "Building America's 5G Ecosystem" event in NYC.

That's not to say our diverse and incredibly knowledgeable speakers lacked that twinkle, but there was a much more practical approach being taken to what 5G would look like, when it would get here and most importantly, how. As such, there was also much discussion about the role 4G networks would play -- and the conclusion was, it's a big role well into a 5G future. (See Why 5G Matters – Now! and 5G: What Is It & Why Does It Matter?)

This is important for both operators and vendors that have invested a lot in 4G and have a hard time grappling with the notion of dumping it for 5G. As Heavy Reading Gabriel Brown put it, "It's no secret that the emergence of 5G is just a little bit annoying for all these companies that are embedded in and have committed immense resources into 4G development." (See Heavy Reading Q&A: Getting to the Heart of 5G .)

There is time and energy spent on LTE-M, LTE-Broadcast, LTE-Unlicensed, SDN and NFV -- all technologies designed for a 4G world. And, as Dan Warren, the GSM Association (GSMA) 's outgoing senior director of technology, pointed out, a lot of what is being touted for 5G, such as 90% power consumption reduction or 15-plus years of battery life, isn't actually unique to 5G. It's something the industry should be striving for anyway. (See LTE Reaches Half a Billion Users Worldwide.)

"When you take all the stuff we're already doing, it just leaves you with ultra-low latency and bandwidth as the new things we need to deliver," Warren said of 5G.

He echoed statements made by Phillip Deibert, general manager of the Next Generation Mobile Networks (NGMN) Ltd. , that 5G is primarily being driven by a desire to work with new industry verticals like healthcare, the automotive industry and the Internet of Things. Deibert said smartphones will continue to drive mobile growth well into the future, but that the key for operators deploying 5G will be partnerships on the application side and supporting those partners for authentication and operation on the network. (See NGMN Chairman Outlines His 5G Vision and 5G Use Cases, Pre-Standards Groups Proliferate .)

That -- the fact that 5G is being built for new use cases, rather than the other way around -- is what's most unique about it and why it's important to have well-performing 4G and 5G networks.

Operators will not one day flip on 5G networks. They will involve the gradual introduction of new features, much like operators have done with LTE and LTE-Advanced updates. Brown said that even the progressive brand-name operators are thinking they can't get it fully off the ground until the 2022 to 2025 time frame. Only initial drops of the standard will start in 2018 to 2020 as the Korean operators have promised.

In the meantime, "LTE-Advanced will continue in parallel and provide enhancements in a similar direction to 5G," Rasmus Hellberg, senior director of technical marketing for Qualcomm Inc. (Nasdaq: QCOM), added at the show.

For more on 5G, visit the dedicated 5G section here on Light Reading.

Making the networks complementary hinges on a new air interface, as Hellberg and other speakers stressed throughout the day. Both Håkan Andersson, head of 5G product strategy of the Radio Business Unit at Ericsson AB (Nasdaq: ERIC), and Michael Peeters, CTO of wireless for Alcatel-Lucent (NYSE: ALU), also made the case for a new, unified 5G interface that takes into account all networks. (See What's in the Air for 5G? and 5G: Just an Expensive New Interface?)

"At Ericsson, we're trying to decouple 4G from just being LTE," Andersson said. "We want LTE to become part of 5G. The technology components we associate with 5G can be added to LTE, bringing LTE up to 5G."

Wanting to eke the most life out of 4G means that most operators will likely use the sub-6Ghz bands in part or whole. Even Satoshi Nagata, a manager at NTT DoCoMo Inc. (NYSE: DCM), which is bullish on the above-6Ghz bands, said that the carrier would start with sub-6Ghz first and then move to millimeter wave second. (See 5G: Generation Gap and Anite Puts Forth 5G Radio Channel Models .)

Qualcomm's Hellberg noted that the lower bands would provide a base-layer for mobile and mission critical services, while the higher bands will be important for broadband enhancement. And, he said, carrier aggregation will be "a core part of being able to leverage 4G investments when 5G is being deployed."

Alcatel-Lucent's Peeters agreed that 5G will be made up of two components -- ultra-broadband for mobility and ultra-narrowband to support the IoT. LTE, evolving to LTE-Advanced, will continue to serve the broadband use case, he said.

"We will drive 4G as far as possible, but at the same time, we have to define early on what are the new and enhanced use cases to do better in 5G," Hellberg added. "It's a two car track, [and we'll] drive both as far as possible."

— Sarah Thomas, , Editorial Operations Director, Light Reading