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Publications in Scientific Journals:

C. Mehlführer, S. Caban, M. Rupp:
"Cellular System Physical Layer Throughput: How Far Off Are We From The Shannon Bound?";
IEEE Wireless Communications, 18 (2011), 6; 54 - 63.



English abstract:
Cellular wireless systems have made impressive
progress over the past two decades. They
currently connect more than five billion people
worldwide. With the advent of turbo decoders in
the 1990s, the design of optimal decoders very
close to the Shannon bound became possible in
AWGN channels. Nowadays many researchers
believe that this is true for entire wireless systems
and that therefore there is not much left to
investigate. In this contribution, we take a closer
look at WiMAX and HSDPA, two successful
cellular systems being operated currently in
many countries, and check their truly achievable
performance. We have measured the physical
layer throughput of WiMAX and HSDPA in
various realistic environments (urban and mountainous)
with high-quality equipment and different
antenna configurations. We furthermore
compared the throughput measured to the Shannon
bound. Based on our measurements, we
analyze the losses in design and implementation
(e.g., pilots, guard carriers, coding, equalization,
and channel estimation) and report our findings.
Surprisingly, we are currently only utilizing 40
percent of the available channel capacity; or
roughly equivalently, we are up to 10 dB off the
Shannon bound at typical operational points,
thus providing a lot of potential improvement
for future 4G systems. In advanced four transmit
antenna configurations of HSDPA, the losses
are even more pronounced, showing that our
current standards are not well suited to take
advantage of the much higher capacity provided.

German abstract:
Cellular wireless systems have made impressive
progress over the past two decades. They
currently connect more than five billion people
worldwide. With the advent of turbo decoders in
the 1990s, the design of optimal decoders very
close to the Shannon bound became possible in
AWGN channels. Nowadays many researchers
believe that this is true for entire wireless systems
and that therefore there is not much left to
investigate. In this contribution, we take a closer
look at WiMAX and HSDPA, two successful
cellular systems being operated currently in
many countries, and check their truly achievable
performance. We have measured the physical
layer throughput of WiMAX and HSDPA in
various realistic environments (urban and mountainous)
with high-quality equipment and different
antenna configurations. We furthermore
compared the throughput measured to the Shannon
bound. Based on our measurements, we
analyze the losses in design and implementation
(e.g., pilots, guard carriers, coding, equalization,
and channel estimation) and report our findings.
Surprisingly, we are currently only utilizing 40
percent of the available channel capacity; or
roughly equivalently, we are up to 10 dB off the
Shannon bound at typical operational points,
thus providing a lot of potential improvement
for future 4G systems. In advanced four transmit
antenna configurations of HSDPA, the losses
are even more pronounced, showing that our
current standards are not well suited to take
advantage of the much higher capacity provided.

Keywords:
WiMAX, HSDPA, throughput


Electronic version of the publication:
http://publik.tuwien.ac.at/files/PubDat_200964.pdf



Related Projects:
Project Head Christoph Mecklenbräuker:
Christian Doppler Lab "Funktechnologien für nachhaltige Mobilität"

Project Head Markus Rupp:
Mobilkom


Created from the Publication Database of the Vienna University of Technology.