Vendors and operators are aligned in agreeing that defining 5G requirements is about defining the overall user experience – bringing the whole network to bear on reducing latencies and increasing capacities – rather than “merely” a definition of a new air interface.
Operator group NGMN, which held a press conference at Mobile World Congress to announce that it will be producing a white paper defining requirements for 5G later this year, lined up several operator CTOs to agree the party line.
Yet that’s not to say there won’t be new air interface and radio technologies being deployed within 5G systems.
Tod Sizer, VP Wireless Research, Bell Labs (Alcatel-Lucent) said the company had been working for five years on a new air interface called UFMC, which stands for Universal Filtered Multi-Carrier.
UFMC is a new, non-orthogonal, waveform designed to provide a much more efficient way of enabling networks to serve both broadband users and very narrowband “short data” devices such as any embedded sensor or M2M module. Simply put, the non-orthogonal waveforms allow transmission of small data packets in a number of adjacent subcarriers.
There are other waveforms under consideration for certain applications within 5G research programmes such as METIS, these include Generalized Frequency Division Multiplexing, Filter Bank Multicarrier (FBMC) and Bi-orthogonal Frequency Division Multiplexing.
These waveforms are identified as suiting particular traffic types. Researchers at 5GNOW(5th Generation Non-Orthogonal Waveforms for Asynchronous Signalling), for example, have identified four basic traffic types, which you can think of as having different throughput, signalling and latency requirements. The four types are Sensor Type Communcations (Type Four), Machine Type Communications (MTC) (Type 3), High Volume Data transmissions in heterogenous and cell edge areas (Type 2), and the classical “bit pipe” traffic type (Type 1).
I’d love to have a system that can put a million radiation and chemical sensors on every intersection in New York City
If you take the MTC type – machines – Sizer outlined some of the issues. When there are 100,000 devices per cell, the signalling payload in the network needs to be drastically reduced. That should also help with battery life.
Sizer said, “I live in NY, I lived through 9/11, I’d love to have a system that can put a million radiation and chemical sensors on every intersection in New York City. We all know it’s a target why can’t we put a radiation or chemical sensor on every intersection. Well the reason is you had a million sensors with a one year battery you’d be changing batteries all year long.
“In order to enable that million sensors, or parking monitors, or myriad of applications, none of them can happen unless you have a very long battery life. So how as a network can we allow a little user device to be asleep 99.999 per cent of the time, then wake up without any coordination, talk, and go back to sleep. That’s a network problem, it has nothing to do with the terminal or device.
“Similarly we have apps email which are very bad for having enormous amounts of little information – Got any email? No. Got an email? No – enormous amounts of little packets of information that right now we have to get up a full 20MHz band in order to make happen.
“Can you handle those short message packets in a better way? There need to be new signalling protocols, and that’s why we’re developing a new air interface.”
Sizer said UFMC would enable small data rate users to operate at much lower power levels, or at the same power levels be reach much deeper in basements and in buildings.
“Primarily it’s to provide flexibility, so the way you talk to machines on the radio link can be flexible, from a broadband user to a very narrowband user.”
Sizer said that any such new radio technology would work within a system approach that used software defined network elements that may locate content or services that are latency-sensitive very close to users.
“We are really maniacally looking at how to make customers happy – so the Air Interface is connected to backhaul, to metro, to content networks. So we need solutions that can manage high responsiveness – that’s not latency, it’s responsivity [sic].”
There are other radio technologies beginning to raise their profile Kumu Networks, said it has developed full duplex radio – essentially the ability to send and receive radio signals in the same channel. You can see a video presentation on the full duplex technology here.
There has also been talk of adapting already-defined technologies such as mmWave to the access environment. This means taking a technology that works well in a line of site, fixed-link deployment and making it work for users and devices that are moving around and being obscured. Additionally, there is work on combining different chunks of spectrum, perhaps in unlicensed bands but also by “sharing” spectrum that largely goes unused, such as white space or some military or radar bands.
In general to date, though, the major vendors have been reluctant to talk about new air interfaces. Partly because they genuinely don’t want to be seen as fuelling hype, but more so because they are still in a research phase and don’t want to go public too early.
Also, Sizer may have been on to something when he said, with humour, “We haven’t talked about it. You don’t talk about 5G when you’re trying to get customers to buy 4G, because then they don’t buy your 4G, they wait for your 5G. And that’s not a good thing.”