Questions regarding mobile communications are grouped separately from
those on fixed network communications due to a number of technical and
regulatory considerations. Since the need for regulation stems from the use of
radio frequency in the access portion of the network, we will begin with the
technical aspects.
Technical feature 1) Use of radio frequency
Radio spectrum is a limited resource that has traditionally been shared
between, for example, television and radio broadcasters, government, military
and private users (such as taxi operators) and mobile phone network operators.
In a technical sense, a mobile phone user is a two-way broadcaster, requiring
two radio channels, one from and the other to the other user/s.
Hence, the basic challenge to mobile phone technology is how to provide
services to as many users and at as high a data rate as possible using a
limited resource, i.e. the radio spectrum allocated to mobile communications.
Since each radio channel requires a frequency to be allocated to it, the
conventional way of solving the problem is to divide the frequency as much as
the technology allows and allocate separate channels to each active (talking)
mobile user. The technology in question is called Frequency Division Multiple
Access (FDMA).
In FDMA technology, the way to increase capacity, namely the number of
simultaneously active users, is to divide the frequencies further, thus
reducing the bandwidth assigned to each user. This results in poorer voice
quality and, in any case, a technological limit exists on the number of radio
channels that can be used for mobile communications.
Instead of dividing up frequencies, the cellular system divides up
geographical areas into separate cells. The size of a cell varies depending on
the user density in the area which is typically 2-5 km in radius. Each cell is
covered by a two-way antenna; one for transmission to and the other for
reception from the mobile users in the cell. This is normally called the
(radio) base station. The way to increase capacity is to allow the same
frequency to be used by different cells as long as they are not adjacent. If
the same frequency is used by adjacent cells, interference or jamming will
occur, especially at the periphery. This geographical reallocation of the same
radio frequency in non-adjacent cells is called 'frequency reuse'.
Another important technology that permits the use of the cellular
mobile network is the automatic 'hand-over' (or 'hand-off'). This enables a
mobile user to keep talking even when they move from one cell to an adjacent
cell, by handing over the radio channel from one cell to the next one.
Technical feature 2) Implications for regulation
Since the available radio spectrum is limited, there is also a limit to
the maximum number of mobile operators. However, the actual number of operators
to be given licences is more dependent on regulatory and business
considerations than technical limitations. Technology is flexible in this
sense. For example, depending on the density of users, the cell size can be
varied; the higher the density, the smaller the cell size. When users increase,
extra capacity can be added by breaking the cell up into smaller components or
by adding more, overlapping cells.
It seems that the regulators decide the number of operators on the
principle of 'small enough for each operator to have sufficient customers to be
profitable but large enough to stimulate competition'. Therefore, the number of
operators to be given licences varies from country to country and even from
time to time.
For example, in the UK, when 2nd generation (GSM) services were started
in 1991, there were only two operators, Cellnet and Vodafone, but in 1993 two
more licences were awarded to Orange and One2One. For 3rd generation services,
applications for which closed in January 2000, the government announced that
five licences would be given in March of that year, with a view to starting
operations in 2002. In Hong Kong, as many as seven operators were given
licences, although later one was acquired by another.
There are basically two methods of selection. One is through auction,
adopted, for example, by the US and the UK. The other is the so-called 'beauty
contest', where selection is made by the regulator on the basis of the contents
of applications. Each system has its own merits and demerits.
Technical feature 3) Small screen, low
power consumption
Mobile terminals must be portable in terms of size and weight,
i.e.easily carried in a pocket or handbag. Furthermore, their power consumption
must be low so that once their batteries are charged, they can last at least a
few hours in active use and a few days in waiting mode. Although for voice
calls these problems are almost solved, for access to the internet they still
pose a significant challenge and require new solutions. For example, because of
the smaller size screens of mobile terminals, web pages must be of a different
design from those for PC access. The current Windows operating system consumes
too much power even in waiting mode, requiring a new low energy operating
system designed for the smaller screen of mobile terminals.
These new challenges led to a range of technical initiatives geared to
mobile communications, such as Wireless Application Protocol (WAP) and EPOC.
WAP was first developed by Ericsson, Motorola, Nokia and Unwired Planet (now
Phone.com) and is a mobile equivalent of the Hyper Text Transfer Protocol
(HTTP), which enables mobile terminals to access web pages over the radio
channel.
EPOC is the name of an operating system developed by Symbian, a venture
led by Psion and involving Ericsson, Nokia, Motorola, NTT DoCoMo and others,
but with the notable exception of Microsoft. Microsoft, for its part, is
improving its Windows CE for mobile use. Recently, Ericsson also decided to
co-operate with Microsoft in this endeavour.
As far as mobile data terminals are concerned, Personal Digital
Assistants (PDAs) are designed with a focus on data applications. Meanwhile NTT
DoCoMo's 'i-mode' terminal is basically a mobile phone with a slightly bigger
screen. The 'i-mode' and its associated web services with some 3000 web sites
has been a great success. It was launched in February 1999 and by December of
that year had 2.5 million users, increasing to 6 million by April 2000.
Technical feature 4) Generation of systems
Mobile systems evolved from first generation analogue (1G) systems in
the 1980s to second generation digital (2G) systems in the1990s. The first
version of the third generation (3G) multimedia standards was completed in
1999, waiting for official approval by the ITU in mid-2000. Japanese operators
plan to start services in 2001, as the current radio spectrum allocated to the
2G system is quickly running out due to unexpected growth in demand.
The European Union (EU) has recommended that all its members finalise
the licensing of the Universal Mobile Telecommunication System (UMTS), the
European version of 3G standards, and that services are launched by 1st January
2002 - a challenging timetable to meet.
Finland was the first country to licence 3G operators, assigning four
licences in March 1999. The UK closed applications for five licences in January
2000 and the results will be announced later in the year. In addition to the
current four mobile network companies (BT Cellnet, Vodafone AirTouch, Orange
and One2One), the following operators also submitted applications:
- 3G - part of Eircom, the Irish telecoms group
- Crescent Wireless - organised by shareholders of Global Crossing
- Epsilon Tele.Com - a subsidiary of the Japanese finance house, Nomura
- NTL Mobile - a joint venture between the US-based cable group NTL and
France Telecom
- One.Tel Global Wireless - a subsidiary of One.Tel, the Australian
telecoms group
- SpectrumCo - a consortium led by Virgin and partners Tesco, EMI,
Sonera and others
- TIW UMTS - a subsidiary of TIW, the telecoms company listed in
Montreal and Atlanta
- Telefonica UK - a subsidiary of the Spanish and Latin American
telecoms company
- WorldCom Wireless (UK) - part of the US-based global telecoms
company.
In the US, the ITU's document
World Telecommunication Development
Report - Mobile Cellular World Telecommunication Indicators (1999) states
that:
"Since the United States only introduced digital wireless systems a
couple of years ago, it is not forecast to have 3G systems until 2003-2005. A
problem in the US market has been that no single digital standard has been
agreed, and carriers use different digital technologies that are often not
interoperable. However, it is a market with a potentially high demand for
professional mobile data services. The relative lack of success of
second-generation digital mobile systems in the United States leaves the field
open for 3G."
If you would like to add to the debate on technical aspects of mobile
communications go to the
Mobile Workshop.