TRANSMISSION speeds from new GPRS cellphones, due to be launched in Britain
this year, will be held down to keep them within radiation absorption guidelines
and to stop them overheating, 91av has discovered. Cellphone
companies seem not to have learned from their massive over-hyping of WAP
services, and risk crippling the fledgling market for GPRS by making hollow
promises about speed.
“We have known for ages about these limitations,” says Rainer Lischetzki of
phone maker Motorola. “We regret the sales talk and data rate exaggeration.”
With today’s WAP phones you get a cut-down form of Web access. But users have
been turned off by slow download speeds, and some phones’ small screens. Surfing
is expensive because networks charge by the minute for slowly downloaded
pages.
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The new GPRS (General Packet Radio Service) services are meant to provide a
higher speed. They will also charge per bit of data instead of per minute, so
you will only pay for what you download. Even better, GPRS is an “always on”
service, so you will see e-mails instantly.
In two years’ time, third-generation cellphone systems will offer ultra-fast
access. But cellphone companies want people to upgrade to the intermediate GPRS
system in the meantime.
The GSM system now widespread in Europe uses channels sliced into eight
slots. Each slot is allotted to a different phone and carries data at 9.6
kilobits per second—one-sixth the speed of a PC modem. People are charged
for the time they use the slot.
GPRS lets users harness more than one available slot. But while you could
theoretically bunch together four or five slots for GPRS reception, handsets may
overheat if they transmit on more than one slot, causing circuits to burn out.
Above two slots, the phone’s microwave radiation could exceed European
guidelines on the energy that can be absorbed by the brain, says Lischetzki.
Early GPRS phones will only use one transmission slot, with two slots for
receiving. Later models will move to four reception slots, boosting download
speeds, but they will stick with one transmission slot to stay within emission
guidelines. Single slot transmission will avoid excessive heating and battery
drain, but will limit the speed of, for example, video phone output.
Yet Motorola’s website and briefing documents promise speeds up to 171.2
kilobits per second with “streaming and live video content”. A press statement
from the network operator BT Cellnet promises GPRS can “send and receive data up
to five times faster than is currently possible (and) up to ten times faster in
the coming months”.
But according to Lischetzki, “The realistic maximum rates we can get from
GPRS are 64 kbps into the handset and 30 kbps out.” Privately, a BT Cellnet
engineer was even more conservative, promising a best case scenario of 10 kbps
transmission and 40 kbps reception.
People who think GPRS will give desktop multimedia will be sorely
disappointed. Streaming even low-quality MP3 hogs two whole slots. And with that
download capacity, videophones will manage about two frames per second.