Some Trends in Mobile Communications and Related Activities at SINTEF
Telecom and Informatics
by Knut Grythe
SINTEF Telecom and Informatics has activities within the major signal
processing trends in mobile communications. These include adaptive and
smart antennas, radio access methods as Orthogonal Frequency Division Multiplexing
(OFDM) and Code Division Multiple Access (CDMA), and software radio solutions.
The work is carried out under different projects like the European ACTS
project SINUS on mobile satellite communication (1996-1998) and a national
research program called WIRAC on broadband radio access (1997-2001). In
addition there are internal projects aimed at supporting and supplementing
the external activities. The underlying goal is to participate and contribute
to the European activities and keep SINTEF Telecom and Informatics updated
in this import field for both Norwegian and European industry.
The statement "In contact anytime, anywhere, with any one"
leaves no room for misunderstanding of the ambitious goals of the mobile
communication industry. Observing the success of eg, the GSM system, the
struggle towards systems with even more and better multimedia capabilities
is carried out. An example of new systems emerging is the next generation
of cellular communication system in Europe denoted Universal Mobile Telecommunication
Systems (UMTS). UMTS will offer services like data, voice and video. In
micro cells the highest bitrate is 2 Mbit/sec, while in GSM type of cells
the maximum rate is 384 kbit/sec, still making multimedia available.
Making business from these new systems depends upon the potential number
of users. The offered capacity in terms of concurrent users is consequently
an important figure of merit for UMTS. To be able to obtain a highest possible
capacity various strategies and techniques are applied.
Adaptive antennas to obtain a spatial isolation of individuals or groups
of users enhances the capacity by reducing the interference between users
as the signals enter the receiver. Due to size and complexity, adaptive
antennas will be deployed at the basestations. A complete isolation is
normally not possible due to the higher number of users compared to the
number of antenna elements resulting in interference within a smaller group
of users. However, combined with a suitable radio access method like Time
Division Multiple Access (TDMA), Code Division Multiple Access (CDMA) or
Orthogonal Frequency Division Multiplexing (OFDM) these groups of users
can be successfully demodulated and the information extracted.
UMTS represents a system with a versatile set of terminals , supporting
applications like video and high speed access to Internet. However, the
already deployed systems like GSM and Digital European Cordless Telephone
(DECT) will continue to be in service for many years to come. Companies
producing user handsets and terminals have observed a market potential
in dual/multimode terminals. These are terminals which have the property
of eg, operating as a GSM terminal in one instant and in the next as a
DECT terminal or as an Iridium satellite terminal. When UMTS becomes a
reality around 2000, dual mode terminals for DECT and UMTS will be available.
To produce this kind of equipment at a lowest possible cost, the concept
software radio has been introduced. A true software radio is reconfigurable
through down-loading an appropriate software package into a signal processing
kernel. The down-loading may be done through eg the communication network,
if offered by the operator or from a SIM-card by the user himself. Much
work is currently carried out on software radios since it is not a well
established field. Questions under investigation are among others what
kind of hardware structure is most suitable for this kind of operations.
Carrying out all the operations in standard digital signal processors DSPs
is not feasible due to lack of speed and too high power consumption. Further,
there exists no standard for this kind of software.
SINTEF Telecom and Informatics has activities aimed at developing a
hardware structure for such a software reconfigurable radio, termed RealFAST.
RealFAST is composed of Field ProGrammable Arrays (FPGAs) and standard
DSPs in a highly flexible manner, reflecting the typical multi-rate processing
flow of a digital radio. SINTEF is planning to contribute with this concept
in both Norwegian and European projects.
SINTEF Telecom and Informatics has further contributed in the European
ACTS project SINUS on mobile satellite communication. The purpose of SINUS
is to demonstrate multimedia communication until 64 kbit/sec. To obtain
a multimedia capability, the radio access on the down link from the fixed
earth station to the mobile unit has a CDMA multicode structure. By selecting
a number of parallel orthogonal codes, a multirate operation is obtained.
In the reverse direction only one code with scaleable length is used to
obtain a multirate operation.
In cooperation with the Norwegian University of Science and Technology
(NTNU), SINTEF Telecom and Informatics has started a long term research
program financed by the Norwegian Research Council on WIdeband Radio ACcess
(WIRAC). Here, more advanced radio access concepts based upon OFDM and
CDMA will be studied. Also the influence of adaptive antennas is planned
to be investigated. Keywords are multi-user detection, interference cancellation,
multirate service multiplexing, Quality-of Service and multirate channel
coding. These areas will be studied from a theoretical point of view, as
well from the hardware side. Having a cross-disciplinary point of view
is import, meeting a variety of requirements.
Please contact:
Knut Grythe - SINTEF Telecom and Informatics
Tel: +47 73 592683
E-mail: knut.grythe@informatics.sintef.no
