2010 Archive of 4G Phones and Mobiles
About
4G Phones and Wireless Communications
Fourth-generation
(4G) cellular services, intended to provide mobile data at rates of
100Mbits/sec or more, were originally scheduled for 2010. Some cell
phone companies have moved the target up to 2006, while rival wireless
systems could bring similar bandwidth to a few fortunate networkers
a lot sooner.
Alas, the enthusiasm for 4G isn't due to accelerated progress; it's
because third-generation (3G) services have proven so disappointing.
Instead of one standard worldwide, there are three incompatible
systems in the United States alone. Voice is carried over the circuit-switched
infrastructure inherited from second-generation (2G), not the promised
IP. The touted streaming video is just a low-resolution slideshow.
Most importantly, the data rates are closer to dial up than DSL.
This is partially due to the technology's immaturity: 3G systems
rolled out so far could be considered beta versions, with the real
thing still in the future. But 3G will never live up to its creators'
promises. Despite early excitement about data, the main economic
incentive for 3G is increased capacity for narrowband voice. Though
data rates will increase, there isn't enough bandwidth to transfer
large e-mail attachments quickly, let alone stream audio or video
at broadcast quality as the cell phone vendors first claimed.
If you believe the industry, 4G will enable all this and more: Many
companies talk of holophones, remote-controlled cars, and mobile
virtual reality. Given their past record of hype, there are good
reasons not to believe the more outlandish predictions, but there
are also reasons to think that some aspects of 4G could be real.
According to the Fourth-Generation Mobile Forum (www.4gmobile.com),
companies will have invested more than $30 billion in 4G by the
end of 2002. And unlike previous generations, 4G won't be a product
of the cellular industry alone. While the most advanced plans have
come from Japanese and European mobile operators, fixed wireless
carriers in the United States are beating a separate path to mobility.
Most exciting, new types of wireless LAN technology already offer
speeds approaching those of 4G.
2020 VISION
Despite its apparent novelty, 4G has been in gestation for more
than a decade. The first research took place in Europe during the
early 1990s, and was intended to investigate very high data rate
technologies that could serve the needs of mobile communications
until 2020.
The most advanced project was the Mobile Broadband System (MBS),
a collaboration between several companies and universities overseen
by the European Commission. MBS' inventors intended to create a
cellular system with low latency, guaranteed QoS, and a data rate
of OC-3 (155Mbits/sec)-thousands of times faster than anything available
today, let alone ten years ago. Incredibly, they succeeded.
Built in 1995, the MBS prototype had a data rate of "only"
E3 (34Mbits/sec), though higher rates could be achieved by using
several links in parallel. It was tested in several indoor and outdoor
environments, including driving around a city block at around 30
miles per hour. MBS' physical layer was based on a variant of Time
Division Multiple Access (TDMA), used by most 2G phones, and its
higher layers were based on ATM-at that time, still considered the
networking protocol of the future.
MBS' inventors recognized that a prototype isn't the same as a functional
network, estimating that the system would take 15 years to commercialize:
The first deployments would be in 2010, with widespread services
by 2020. Halfway through that time, the specification has changed.
The physical layer will be based on Orthogonal Frequency Division
Multiplexing (OFDM), a technology designed to resist interference
caused by a radio signal's multiple paths. And ATM has been abandoned
in favor of IPv6.
There are also ongoing discussions over what radio spectrum the
system can use. The prototype used the 60GHz band, where there's
a large amount of unused bandwidth, but range is limited to about
100 meters (m). Therefore, a nationwide network would require millions
of base stations, each one at the center of tiny "picocells."
Europe's Wireless Strategic Initiative (www.ist-wsi.org) is also
considering spectrum at 40GHz, which would allow larger cells and
reduce the cost of constructing networks.
While other wireless generations have focused on voice, perhaps
combined with other types of traffic such as short messages (see
table), MBS is intended to be service-independent: It's a big pipe
for data, which devices can use for any applications. Japan is so
far the only country where mobile data has proven popular and profitable,
so it's no surprise that Japanese operators are leading the race
to 4G.
The popularity of the i-mode service, which provides limited Web
access through cell phones, surprised everyone-even its creators.
"We were skeptical," says Nobuharo Ono, president and
CEO of NTT DoCoMo U.S.A (www.nttdocomo.com). "The display wasn't
very big, the data rate was only 9.6Kbits/sec. We thought, maybe
it's not attractive to customers."
Instead, i-mode made DoCoMo the world's largest ISP. The company
hopes that true mobile broadband will enable it to replace fixed
access entirely, and it plans to have a 4G system operational by
2006. Ono also predicts that the future of mobile data is more than
Web surfing and access to corporate servers. DoCoMo thinks there's
a big market for "machine-to-machine" communication: vehicles
that take directions from a central traffic computer, or domestic
appliances that automatically reorder supplies.
DoCoMo also hopes to improve 3G systems so they reach the hyped
data rates. Vendors once claimed that 3G would enable full duplex
access at 2Mbits/sec, but every real system built so far has an
absolute maximum speed of 384Kbits/sec downstream, 64Kbits/sec upstream.
"In the near future 2004, we will have 2Mbit/sec access,"
says Ono.
Just as current upgrades that add packet switching to digital cellular
systems are known as "2.5G," improved versions of 3G are
often called "3.5G." The upgrade closest to reality, set
to be standardized in 2002, is called High Speed Downlink Packet
Access (HSDPA). This uses better modulation techniques to reach
up to 10Mbits/sec. All users in a cell share the capacity, but in
a very efficient way called "extreme unfairness," which
gives more bandwidth to people in interference-free areas instead
of trying to portion it out equally.
HSDPA only works with Wideband Code Division Multiple Access (W-CDMA),
the worldwide 3G standard developed in Europe. Many American operators
are instead using narrower-band CDMA systems, which are theoretically
more spectrally efficient. (See "Waiting for Wireless in the
United States," December 2001, page 54.) They achieve this
efficiency by using the same modulation techniques as HSDPA, leaving
no room for expansion.
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