FORGET the concept of the phone. And while you’re at it, forget about phone
numbers, too. Both will vanish when the third-generation mobile phone networks
arrive in the next year or two. Your mundane mono-tasking mobile will be
replaced by do-everything devices more like the communicators of Star
Trek.
The big idea behind 3G is to give you “the same services on mobiles as you
get on desktop computers today”, says Håkan Eriksson, head of research at
Swedish cellphone maker Ericsson. On your mobile you’ll be able to watch colour
video, download CD-quality music from your collection at home, buy a plane
ticket, send e-mail, browse the Web, use positioning services—and make
old-fashioned phone calls, too.
To make all that happen 3G networks will need to run a lot faster than
today’s inefficient GSM digital cellphone system. GSM sets up a dedicated
channel for every call—wasting a lot of valuable transmission capacity.
And sending or receiving data on this single channel can be painfully slow, as
any WAP user knows.
Advertisement
Pass the parcel
The 3G networks will be much more flexible. They will send signals from many
mobiles over a single channel, moving voice, text, video and audio using a
technique called packet switching—the same way data is sent around the
Internet. Packet switching slices up information into packets of data that are
sent as separate chunks to their destination. Every packet is treated like a
parcel going through the postal system: it is routed through the network
according to the address written on its front. Because of this, says Eriksson,
we will have Internet-style addresses instead of phone numbers. Your phone will
be like an e-mail box or a website, with its own unique address.
Doing things this way means that when a 3G mobile is switched on, it will be
like an “always-on” Internet connection—permanently ready to use. This
will revolutionise the way we pay for the service. “Charging will not be per
minute, it will be per byte or per data packet. If you don’t send anything, you
don’t pay anything,” says Jan Uddenfeldt, chief technology officer at Ericsson.
Again, it’s like the postal service, Eriksson adds. “You don’t pay to have a
mailbox on your front door—you only pay when you send a letter.”
Japan has already had a taste of always-on technology with its hugely
successful—but very slow—i-mode system.
Right now, GSM is being upgraded to a system called the General Packet Radio
Service. GPRS gangs together GSM channels to move data packets fast. “GPRS
mobiles can handle up to 100 kilobits per second,” says Uddenfeldt. “In fact it
may be limited to 56 kilobits per second, like standard PC modems. But that’s
still four or five times faster than a WAP user gets today—and it’s coming
out this year.” GPRS speeds will be limited by the need to keep down the
radiation dose to the head and to stop overheating
(91av, 7 October, p 21).
An enhanced version of GPRS, called EDGE, due out in two years
time, will push speeds up to 380 kilobits per second.
But GPRS and EDGE will be left standing by 3G devices. Each will have access
to a 5-megahertz channel, against GSM’s puny 25 kilohertz. “3G will ultimately
provide users up to 2 megabits per second,” claims Uddenfeldt. “Even in the
early days it will provide up to 384 kilobits. So the changes are going to be
پ.”
Several engineering challenges need to be overcome before 3G becomes a
reality. One of the biggest is maintaining an always-on Internet connection
while you are on the move, and keeping it live as you move from one base station
cell to another. This switch-over, called the “hand-off”, is far from perfect on
today’s networks.
The GSM network measures the strength of a phone’s signal received at every
nearby base station, and locks on to the strongest. But as anyone who’s used a
mobile in a car or train knows all too well, calls have a habit of dropping out
in mid-sentence when the link is lost.
To minimise the chance of this happening to always-on links, 3G networks will
adopt standards such as the Universal Mobile Telecommunications System. This
uses a trick called soft hand-off. “If a 3G mobile detects two good base
stations, it sets up connections to both of them at once,” says Uddenfeldt. This
makes it much less likely you will lose the call, and means signal quality
should improve as well, because the network can always listen to the best
available station.
The 3G development teams are also collaborating to re-engineer the data
packets the networks will carry. One problem is the Internet packet
header—the “envelope” on which are written the source and destination
addresses. On the Net, more than half of every packet is devoted to this kind of
information. “That’s a tremendous waste of network resources,” says Eriksson. It
effectively halves the network’s capacity. Today, it takes 40 bytes of header to
carry 33 bytes of data. In 3G networks, compression will bring this down to just
3 bytes of header.
It won’t just be the network that will benefit from new ideas. The 3G mobiles
themselves will be packed with ultrafast signal processors to handle the
expected new applications, like streaming video. Says Uddenfeldt: “It will be
great for watching news flashes or soccer highlights, and a lot of kids would
love to be able to store all their music somewhere and stream it online.” At the
promised 2 megabits a second, it should also be possible to stream video from a
3G camcorder back to your video recorder at home, perhaps making tiny tapeless
camcorders a reality. Ericsson is even thinking ahead to when it will enhance 3G
to 8 megabits a second, anticipating the arrival of 4G.
“People are going to stop carrying around things like laptops,” Uddenfeldt
predicts. “More and more devices are going to fit in your pocket. People will
discover that their mobile can handle video, work like a Palm Pilot and be a
phone. It’s much more powerful than what they have at home.”
And what will we call these new non-phones? “We’re calling them
communicators,” says Uddenfeldt. James T. Kirk would have been proud. Next stop,
presumably, the tricorder.
