Cellular Network Generations
A "Wireless Solutions Fast Start" Article
We read in the press that cell phone carriers
are offering 2.5 services, and even 3G services. This article (longer than most
but easy) will explain the various generations of cellular networks.
This is not just a history lesson. An enterprise may have customers or
employees distributed over a wide geography, and that servicing them will
require providing services on a variety of technologies that are completely
incompatible or have vastly different performance characteristics.
First generation services were analogue
services for cell phones. These
were (and are) for voice only; the technology didn't provide for SMS or other
1G is circuit switched.
This means that when you place a call, a connection is established for
you, and is maintained until you hang up. You are billed for the duration of the
call, regardless of how much talking occurred. This is appropriate for voice communication where one person
or the other is talking at any point in time.
Moving from 1G to 2G saw the transition from
analogue to digital. As in other
areas, the impact of going digital was revolutionary.
The transition provided the ability to store, copy, encrypt and compress
data, and allowed data transmission without loss and with error-correction.
It provided wireless cellular data services
such as internet access, with speeds of 14.4.kbps (theoretical), 9.6 kbps - 19.2
kbps (real). In addition, voice
quality improved. 2G was also
circuit-switched; you still paid for total connection time.
This is less appropriate for data than voice, as data is often "bursty",
with periods of transmission activity and then periods of silence.
This is not a good deal for the consumer or the carrier. The consumer has
to pay for dead time, and the carrier has to reserve a slice of spectrum which
could be sold to someone else.
Competing 2G Technologies
The generic term for 2G services is PCS
(Personal Communications services). There
are two 2G technologies in Canada, GSM and CDMA, that are incompatible with each
other in every respect. This
incompatibility explains some things about the evolution of the market and
- GSM stands for Global System for Mobility. It
is based on a time-sharing process in which a slice of spectrum is shared
between multiple users, by dividing creating small time-slices and allocating a
slice to each user in turn. One of
the big benefits of GSM is its coverage. It is the standard 2G technology in
Europe, with the potential for roaming 90+ countries with same phone. Globally,
70% of the world's digital subscribers are on GSM.
Both Rogers Wireless and Microcell use GSM.
- CDMA stands for Code Division Multiple Access.
It is an elegant technology, but also a complicated one that cannot be described
in a few words. Both Bell Mobility
and Telus Mobility use CDMA.
Moving from 2G to 2.5G / 3G introduced another
revolutionary change, the introduction of packet switching for data rather than
circuit switching. Packet switching
is an unlikely seeming technology that breaks a message into pieces and sends
each piece individually across the network, together with control information on
whether it is the first, second, etc packet in the set. The packets travel through the network to their destination,
possibly taking different paths depending on network conditions, where they are
reassembled in the correct order.
For the consumer, packet switching provides two
benefits. First, the
commodity being sold is packets, not network time connected, so the pricing
model becomes more data oriented. The
consumer does not have to pay for dead time.
Carriers provide a large variety of data oriented plans, just as they do
with basic cell phone plans. For
example, 1MB of data sent might cost up to $6 -7.
Each packet requires a significant amount of control information to route
and sequence the packet, so your actual data may be less than 1MB.
The second benefit to the consumer is that the
internet is "always-connected" or "always-on".
There is no need to make a connection or hang up; users experience
constant connection to the internet, just like home subscribers of ADSL or cable
There is another benefit to consumers of 2.5 /
3G services, and that is speed. They have a theoretical maximum speed of 115
kbps, with real speeds around 56 kbps (a common speed for dial-up connections to
The two 2G technologies in Canada extend to two
2.5G technologies, GSM/GPRS and 1XRTT, likewise incompatible in every respect.
- GPRS stands for General Packet Radio Service,
and is a data-oriented technology extending the GSM voice services. Rogers and
Microcell use GSM/GPRS. Microcell
was the first player out of the gate in June 2001, but is now wondering if it
can stay in business. Rogers
AT&T Wireless provides GPRS coverage to more than 93% of the Canadian
population. This does not mean
coverage of 93% of the Canadian geography, due to the concentrations of
population, and there are many places where coverage would be desirable but is
unavailable, such as in the oil patch and rural areas.
- 1XRTT is an abbreviation for CDMA2000 1XRTT and
is usually abbreviated further to 1X. It
is the current generation system used by Bell and Telus. Bell launched their
service early in 2002 in the greater Toronto Area early 2002. Bell claimed cruising speeds of 86 kbps, compared to 56 kbps
for dialup modems.
specifications call for even higher speeds 144 kbps in vehicles, 384 Kbps for
pedestrians outdoors, and 2.48 Mbps in indoor offices.
Some carriers are calling their current deployments 3G.
This is contested by others as being the lowest rung of the 3G
specification, and hence prefer to use the term 2.5G.
As expected, each of the 2.5G technologies has a forward path to the 3rd
- EDGE (Enhanced Data Rates for Global [or GSM]
Evolution) is the true 3G offering along the GSM path.
It provides data rates three times greater than GSM/GPRS, with speeds in
the range 100 - 130 kbps (up to 200 kbps in bursts). EDGE was rolled out across Canada in 2004.
Being an extension of GSM/GPRS, EDGE will be widely available
internationally, and supported by network operators in many countries, and over
60 network operators in over 40 countries have committed to EDGE for their next
- There are a couple of forward paths from
CDMA2000 offering substantially higher data rates. Neither of the CDMA based
carriers (Telus Mobility, Bell Mobility) had announced offerings or pilots at
the time or writing.
There are specifications for higher speed
services. We will update you when
these become closer to reality in Canada.
|Martin Stares is a respected speaker, author and coach in the field of wireless solutions and strategy for business, helping companies find innovative wireless solutions for their organizations. For more information and resources, visit Greyfriars Consulting Group at www.greyfriars.net.
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