With the hype around the upcoming 5G cellular technology growing every day, Nokia says it's often forgotten that optical transport networks able to deliver sufficient bandwidth, flexibly and with minimal latency will be essential to 5G’s success.
Australia’s mobile carriers have already been staging tests of 5G technology.
Ray Owen, Nokia’s head of Oceania, told Computerworld: “In our view 5G has already started, and it starts with things like optical transport networks to enable the 5G network edge to be able to offer the capacity needed.”
He added: “We keep talking about standards in 5G, but we believe that a revolution needs to happen behind the scenes in the transport networks to support those kinds of capacities and we have customers that are investing significantly right now on upgrading optical transport networks.”
Nokia’s head of optical networks, Sam Bucci, said 5G would drive capacity demands well beyond their current levels.
“One of the studies we have done shows that, for a typical 5G implementation in a metro area, you are looking at 100G of capacity to serve an area of one square kilometre,” Bucci said.
Owen and Bucci were speaking on the sidelines of Nokia’s annual event for its Asia Pacific optic networks customers, held this year in Sydney.
Bucci said programmability would also be essential for optical networks backhauling 5G networks. “The optical network must be much more flexible, not just a big pipe, so capacity can be called up when needed. It must be able to react to what is happening in the 5G world,” the Nokia executive said.
“Also latency will be an important element. Dialling up that latency according to the application will be important, so the optical network must be much more flexible.
“Although latency is determined by the velocity of light, if you pick the wrong path you will likely end up with too much latency, so the application must be able to find the right path through the network and that is where some of the innovations we are bringing to the table are centred.”
Bucci said standards were being developed to enable 5G networks to communicate the latency needs of an application to the fibre network and for the fibre network to be able to respond appropriately.
Heading for 65 terabits per fibre with PCS
Nokia is also working to increase the carrying capacity of optic fibre, particularly on long-haul submarine networks where there are few fibre pairs and where the cost of adding capacity with more fibre is massive.
Bucci said that, in a recent trial with Facebook, Nokia had been able to double the capacity of a transatlantic fibre: “Facebook needed very large scale capacity around the world and they looked to us to see what capacity they could get on subsea fibre. Using a commercially available product we were able to achieve 200g per wavelength and a total capacity of 17.2 [terabits per second] between Long Island and Shannon in Ireland, some 5500 kilometres.”
He said the company was close to commercialising technology that would increase capacity even further. “We have an innovation we have been working on called probabilistic constellation shaping [PCS] that has come out of Bell Labs. We hope to bring it to market in a little while and that allowed us to get close to 32Tbps down one fibre optic link.”
He said that with PCS instead of the same modulation being applied to every bit of data to encode it onto the optical signal the modulation is changed to maximise capacity. “PCS essentially looks at all the bits coming in and uses our proprietary technology to shape them in a way that maximises performance.
“It’s a pretty cool piece of technology. We are going to be first to market with this, and it is our own intellectual property.”
With the modulation schemes widely used in optical and cellular networks, some signal patterns require lower energy and resist noise better than others. PCS is able to increase capacity by transmitting these better performing signal patterns more frequently than the others.
Bucci said the 32Tbps had been achieved over an operating network. Nokia is reported to have achieved a throughput of 65Tbps over 6600kms of fibre using PCS in a laboratory trial.