5G Spans Last Mile to Handset

　　5G cellular will start with fixed-wireless services,lead to big changes in smartphones and ultimately rack up some staggering numbers,according to a keynote from a senior Ericsson engineer.

　　Verizon and AT&T have already announced plans to use 5G at 28 and 39 GHz as a last-mile access technology starting late next year.“It will be easier to plop a pole in a neighborhood than connect homes via fiber,”said Dave Allen,a distinguished engineer at Ericsson speaking at Hot Interconnects last week.

　　Thanks in part to such services,Ericsson expects by 2027 more traffic will run over wireless than wired nets.The initial 5G fixed-wireless services will act as neighborhood extensions of carriers’core LTE networks.

　　The collaborative 4G/5G roll out is different from the past,in part because pure 5G requires a fair amount of heavy lifting.

　　For example,millimeter wave transmitters and receivers will need to use massive MIMO antennas with beam forming on both sides.The techniques compensate for about 40 dB signal loss leaping from traditional 3 to 5G 39 GHz radios.

　　At those frequencies,interference can come from“radio passing through my body,flocks of birds and trucks driving by…there’s 10 million times higher loss than on wired nets,”Allen said.

　　5G services aim to cover the waterfront.Click to enlarge(Image:Ericsson)

　　He described massive MIMO as“a form of spatial multiplexing…assigning multiple low speed signals to different antennas in an array,[with bandwidth]limited by the smallest number of antennas on either end.”

　　Beam forming was first described in 1905.It uses constructive interference techniques that don’t work that well in lower frequencies.

　　MIMO and beam forming together help maximize spectrum reuse.“When you have a scarce resource,you can afford to throw a truckload of math at it,”he quipped.

　　Packing MIMO and beamforming into handsets will be one of the toughest challenges of 5G,Allen said.“Handsets will calculate math transforms to stay focused on a tower using no moving parts,just by changing the phase and manipulating signals to reposition themselves instantly,”he said.

　　Similarly,5G base stations will use so-called coordinated multipoint techniques to relay beam-forming jobs among towers.Despite the difficulty of the electronics,buying spectrum and rights to towers makes up more than half the costs of radio access.

　　“Modern church steeples are designed specifically to be antenna hotels—a well situated church can earn$30,000 a year,”for providing carrier access,he said.

　　But the big numbers are on the carrier’s side.Ericsson estimates by the time 5G is launched in 2020 there will be 9.5 billion cellular subscribers,6 billion using smartphones.By that time,the average user will consume 22 Gbytes of mobile data a month,up from 3.8 GB in 2015.

　　“These numbers are staggering…and they require architecture and technology responses to support that growth,”Allen said.That’s why so much of today’s tech industry is focused on“making things scale out,we have become scale junkies—Moore’s law was just a gateway drug,”he said.

　　For example,the round-trip time for a packet to move between the 5G new radio(NR)and the radio access network and back is three milliseconds,down from 20 for LTE.NR will support frequencies from 600 MHz to 100 GHz,channels from 20 to more 100 MHz,and it can dynamically change the ratio of upstream to downstream traffic it supports.

　　Overall,5G is“trying to expand radio to new verticals and adjacent markets”from massive IoT deployments on farms to latency-sensitive robots on the factory floor.Meanwhile engineers aim to push the cost of the radio down to$1 for some IoT uses.

　　“That is really compelling,and the amount of information we collect will be massive,”he said.In summary,“no one thing defines 5G—we are trying to put all the technologies on the table,”he added.