THE EVOLUTION OF THE G

1. 1
UNIVERSITY OF HORMUUD
Date: 15-Sep-2015
Course Name: Wireless communication
Lecturer: Eng-Burhan Omar
Topic: History of Cellular phone
Student name: Ali-Yare Mohamed Warsame ID: 069

2. 2
1G
Our journey begins in the early 1980s with the introduction of several groundbreaking network
technologies: AMPS in the US and a combination of TACS and NMT in Europe. The meanings
of those acronyms are unimportant -- there won't be a quiz later. All you really need to know is
that unlike earlier systems, these new standards were given enough spectrum for reasonably
heavy use by subscribers, were fully automated on the carrier's end without requiring any human
operator intervention, and used electronics that could be miniaturized enough to fit into smallish
packages (think Motorola DynaTAC -- early prototype pictured right). Though there were
several generations of mobile telephone services before these that date all the way back to the
1950s, the trifecta of AMPS, TACS, and NMT is commonly considered to be the first generation
-- "1G," if you will -- because they made cellphones practical to the masses for the very first
time. They were robust, reliable, and would eventually come to blanket the entirety of many
industrialized nations around the world.
Thing is, no one was thinking about data services in the 1G days; these were purely analog
systems that were conceived and designed for voice calls and very little else. Modems existed
that could communicate over these networks -- some handsets even had them built-in -- but
because analog cellular connections were susceptible to far more noise than conventional
landlines, transfer speeds were ridiculously slow. And even if they'd been fast, it wouldn't have
really mattered; per-minute rates on AMPS networks in the 80s made cellphones luxuries and
Wall Street powerbroker business necessities, not must-haves for the everyman. Besides, the
technology didn't exist for an awesome smartphone that could consume that much data anyhow.
Oh, and YouTube had yet to be invented. The stars simply hadn't yet aligned.
2G
The early nineties saw the rise of the first digital cellular networks, which had a number of
obvious benefits over the analog networks they were supplanting: improved sound quality, better
security, and higher total capacity, just to name a few biggies. GSM got off to an early start in
Europe, while D-AMPS and an early version of Qualcomm's CDMA known as IS-95 took hold
in the US. (You might remember D-AMPS better as "TDMA," though that's technically not
descriptive enough -- GSM also employs the TDMA multiplexing scheme, even though the two
standards are incompatible.) No one disputes that these systems collectively represented the
second generation of wireless networks -- they were authentically different and revolutionary.
Furthermore, a solid decade had gone by at that point since the first 1G networks had gone live.
This stuff was definitely borne of a new generation.

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Still, these nascent 2G standards didn't have intrinsic, tightly-coupled support for data services
woven into them. Many such networks supported text messaging, though, so that was a start --
and they also supported something called CSD, circuit-switched data. CSD allowed you to place
a dial-up data call digitally, so that the network's switching station was receiving actual ones and
zeroes from you rather than the screech of an analog modem. Put simply, it meant that you could
transfer data faster -- up to 14.4kbps, in fact, which made it about as fast as an early- to mid-
nineties landline modem.
At the end of the day, though, CSD was a hack -- a way to repurpose these voice-centric
networks for data. You still had to place a "call" to connect, so the service wasn't always
available. The experience was very similar to using a dial-up modem at home: either you were
online, or you weren't. Services like push email and instant messaging to your phone were
basically science fiction. Furthermore, because a CSD connection was a call, you were burning
minutes to get connected -- and these technologies were in play at a time when monthly minute
buckets on cellular plans were measured in the dozens, not the hundreds or thousands. Unless
you had a company writing a check for your wireless bill every month, using CSD for anything
more than an occasional novelty wasn't practical.
2.5G
In the past, many telecommunication service providers moved to 2.5G networks before entering
into 3G networks. It is already understood that 2.5G technology was much more advanced and
faster than 1G and 2G and at the same time, it was much cheaper to upgrade to 3G from 2.5G.
The 2.5 generation of mobile phones offered extended features and additional capacity that was
more than 2G networks. These new features were High Speed Circuit Switched or HSCSD,
General Packet Radio System or GPRS, EDGE or Enhanced Data Rates for Global Evolution,
IS- and IS-136B 95Bm. The European and U.S network carriers moved to 2.5G in 2001 while
Japan got straight from 2G to 3G in 2001. Every transformation from 1G to 2G, 2G to 2.5G, and
2.5G to 3G networks helped in communicating better and better.
3G, 3.5G, and 3.75G
In addition to the aforementioned speed requirements, the ITU's official 3G specification also
called out that compatible technologies should offer smooth migration paths from 2G networks.

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To that end, a standard called UMTS rose to the top as the 3G choice for GSM operators, and
CDMA2000 came about as the backward-compatible successor to IS-95.
Following the precedent set by GPRS, CDMA2000 offered CDMA networks an "always-on"
data connection in the form of a technology called 1xRTT. Here's where it gets a little confusing:
even though CDMA2000 on the whole is officially a 3G standard, 1xRTT is only slightly faster
than GPRS in real-world use -- 100kbps or so -- and therefore is usually lumped in with GPRS as
a 2.5G standard. Fortunately, CDMA2000 also defined the more advanced 1xEV-DO protocol,
and that's where the real 3G money was at, topping out at around 2.5Mbps.
The first CDMA2000 and UMTS networks launched between 2001
and 2003, but that wasn't to say that manufacturers and standards
organizations were standing still with the 2G technology path,
either. EDGE -- Enhanced Data-rates for GSM Evolution -- was
conceived as an easy way for operators of GSM networks to
squeeze some extra juice out of their 2.5G rigs without investing
serious money on UMTS hardware upgrades and spectrum. With an
EDGE-compatible phone, you could get speeds over double what
you got on GPRS; not bad at the time. Many European operators
didn't bother with EDGE, having already committed to going big
with UMTS, but Cingular -- likely looking to buy itself time --
jumped at the opportunity and became the first network to roll it out
in 2003.
So where would EDGE fit, then? Depends who you ask. It's not as
fast as UMTS or EV-DO, so you might say it's not 3G. But it's clearly faster than GPRS, which
means it should be better than 2.5G, right? Indeed, many folks would call EDGE a 2.75G
technology, eliciting sighs from fraction-haters everywhere. The ITU doesn't help matters,
officially referring to EDGE as an ITU-2000 Narrowband technology -- basically, a 2G standard
capable of eking 3G-esque speeds.
As the decade rolled on, CDMA2000 networks would get a nifty software upgrade to EV-DO
Revision A, offering slightly faster downlink speeds and significantly faster uplink speeds -- the
original specification (called EV-DO Revision 0) only allowed for uploads of about 150kbps,
impractical for the rampant picture and video sharing we're all doing with our phones and laptops
these days. Revision A can do about ten times that. Can't very well lump an upgrade that big in
with 3G, can you? 3.5G it is, then! Ditto for UMTS: HSDPA would add significantly faster
downlink speeds, and HSUPA would do the same for the uplink.

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4G
History
The first generation of mobile communications started with the Advanced Mobile Phone
Systems (AMPS), which was an analogue system. AMPS can be thought of as 1G. From there,
we progressed to GSM and CDMA-one (pretty much regarded as 2G) and then to UMTS and
EV-DO, which are 3G technologies. The latest technologies that are regarded as candidates for
4G are LTE (from the 3GPP group) and 802.16m (from the IEEE). In the case of 802.16m, the
candidate for 4G is also known as WirelessMAN Advanced, or WiMAX2. LTE progresses
through versions known as releases. The latest release that qualifies as being 4G is release 10,
often called LTE-Advanced.
The ITU specification
The group that designates technologies as 4G is the International Telecommunications Union
(ITU). The ITU issued a press release on October 21, 2010, that qualified LTE-Advanced and
WiMAX2 as meeting the requirements for 4G. The report produced by the ITU is "Report ITU-R
M.2134." It's a fairly short report, but I'll pick out the main points, as these give some indication
as to what constitutes 4G.
The first point relates to mobility. Generally, low
mobility is a person walking. High mobility is usually around 100km/h or about 60mph; a typical
speed when traveling on a train or a car. Mobility also means that a person should be able to
move between base stations without losing a connection, so there is a handover component to
4G.

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The second part of the ITU report relates to throughput. There's no mention of throughput
specifically, as in "You'll have 1GB/sec throughput on the downlink." What it does have is the
spectral efficiency target for each speed and the likely throughput for this. The report does have
some concrete examples, which give an indicative level of the throughput. For instance, with
100MHz of bandwidth, a low mobility user should have a peak data rate of 1.5GBits/sec in the
downlink. Under the same conditions, the peak uplink speed should be 675Mbits/sec.
This is significantly higher than current 3G rates, both in the downlink and the uplink. This is
where you can quite definitely state that a network is 4G rather than 3G.
Other aspects
One of the other parts of 4G that sets it apart from its predecessor is that it's entirely packet
switched. IP is used in the network layer to route packets. This sets 4G apart from earlier 3G
technologies, which often use older circuit-switched networks for voice.
Wireless is more complicated in terms of transmission than a wired network. The inverse square
law applies to wireless propagation; in fact, it's often greater than the inverse square. The radio
signals can also take different paths to the receiver and interfere at the receiver end.
Then there's the limitation of spectrum. This can be very restrictive. The frequency bands
currently available are quite small. To further complicate matters, many of the spectrum
allocations around the world are in a somewhat fragmented state. Portions may be allocated to
2G, for example, and other parts to 3G — but these portions are often not in contiguous bands of
the spectrum, leading to fragmentation.
A way around the problem of fragmentation of spectrum is Carrier Aggregation. This idea was
probably meant more to increase potential throughput, but it has the side effect of also allowing
operators to be able to use non-contiguous slices of spectrum. Carrier aggregation is a feature of
both LTE-Advanced and WiMAX2 — it was not possible under earlier technologies.