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V. Aue,
G. Fettweis,
A. Finger,
E. Frster,
J. Hbner,
H. Kaluzni,
K. Kojucharow,
R. Lehnert,
W. Nowak,
H. Nuszkowski,
F. Poegel,
M. Riedel,
M Sauer, B. Stantchev,
J. Voigt,
J. Wagner,
S. Zimmermann
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ABSTRACT: The paper presents a wireless integrated services communications system for indoor and campus use. Whereas most current indoor wireless systems are distinct solutions for different services, our network, WISCS, covers the entire range from low-rate mobiles to high-speed portables. The system employs a picocellular structure in the 60 GHz band to provide capacity demanded by broadband services. The system concept and the employment of simple transponders connected via an optical fibre to a central base station allow a cost effective implementation. Virtual clustering of different number of cells is applied to allow coexistance of low rate mobile users and high rate portable users in one common system. WISCS uses adaptive modulation to yield an optimised performance in both the mobile and portable environment. The project is carried out at Communications Laboratory at Dresden University of Technology. Research includes new optical devices, flexible, efficient and error protected transmitting schemes, mm-wave circuits, antennas, and protocols. A demonstrator is currently under development.
04/2002;
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ABSTRACT: We analyze the degradation of orthogonal frequency division multiplexing (OFDM) signals from time-variant distortions like carrier and sampling frequency offset, Doppler spread and oscillator phase noise. We propose a novel analytical framework in the discrete-time domain based on the FFT demodulation of a single OFDM symbol and unify previous methods with some new results. Exact definitions of the signal-to-subcarrier-interference ratio (SIR) and the effective signal-to-noise ratio (SNR) are given and evaluated for a HIPERLAN/2 system.
IEEE Communications Letters 11/2000; · 0.98 Impact Factor
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ABSTRACT: An optimum and sub-optimum maximum likelihood (ML) rule for joint
frame and carrier frequency offset estimation are derived, which rely on
the transmission of a periodic pattern signal with an arbitrary number
of periods and period length, embedded in the random data signal of a
single user. Ad-hoc modification of the ML rule yields a robust metric
for pattern search in a multi-user signal in a time division multiple
access and time division duplex (TDMA/TDD) system, and a receiver with
automatic gain control keeping constant average signal power at the
synchronizer input. The mean, variance and Cramer-Rao Bound of the
frequency offset estimate as well as the mean and variance of the frame
estimate are theoretically evaluated and verified by simulation. The
presented material proposes a unified framework for synchronization by
periodic pattern signals and provides some new results, which are
compared to known references
Communications, 2000. ICC 2000. 2000 IEEE International Conference on; 02/2000
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ABSTRACT: We derive a maximum likelihood (ML) rule for one-shot frame
synchronization of a random data burst with non-coherent orthogonal
M-FSK signaling in a flat fading or AWGN channel. It uses a known frame
synchronization pattern and, optionally, channel state information at
the receiver. High SNR approximations are developed that are well suited
for a low-cost implementation. A burst synchronizer structure is
proposed with an ML frame synchronizer as the last processing stage.
Simulations reveal the performance gain of the ML rules over
conventional correlation rules for a 2-CPFSK modulated separate
signaling channel in an OFDM FTDMA broadband cellular system
Wireless Communications and Networking Conference, 1999. WCNC. 1999 IEEE; 02/1999
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ABSTRACT: A novel burst synchronization scheme suitable for a high rate
OFDM/TDMA/TDD (pico)cellular system with a centralized dynamic slot
allocation MAC protocol is presented. The physical layer may have an
optional low-rate separate signaling channel (SSC) used in the standby
mode and implemented on a subset of OFDM subcarriers. A one-shot
feedforward synchronization concept for the OFDM-based active
transmission mode is designed using the functionality of the SSC and a
special periodical OFDM preamble. Joint symbol and frequency
synchronization as well as channel estimation can be achieved
simultaneously. The synchronizer features low complexity and low
processing delay. Simulations verify its robust operation for indoor
channel power delay profiles at 5 GHz
Vehicular Technology Conference, 1998. VTC 98. 48th IEEE; 06/1998
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ABSTRACT: Future broadband picocellular networks demand powerful modulation
and coding methods under the tight constraints of affordable modem
complexity and low power consumption for the mobile terminal (MT). In
order to increase battery life and allow low-cost mobile equipment to be
effectively integrated in such a broadband system we propose the use of
a separate low-rate signaling channel (SSC) on the physical layer. This
additional channel has the primary function of power saving. For this
purpose it takes on connection and mobility control functions as well as
further tasks on broadcasting and synchronization. A new concept of a
broadband TDMA system is presented, incorporating OFDM for the physical
high rate data channel (D-channel) and CPFSK modulation with
non-coherent detection for the low-rate SSC, whereby both channels are
separated in frequency. Modem and system design issues are discussed and
evaluated by simulation
Vehicular Technology Conference, 1997, IEEE 47th; 06/1997
