J. Singh, Christopher Rose · 2004
We investigate practical methods of distributed interference avoidance where users iteratively adapt their codewords in response to global feedback from the receiver. In turn, the receiver adaptively tracks user codewords and offers a reasonable alternative to feeding back codewords. We introduce variants of standard interference avoidance procedures which produce more easily tracked incremental codewords and study the response of the system to abrupt changes in the interference background as might be encountered in a practical system. Furthermore, the methods we propose are strongly reminiscent of adaptive equalization for which a large body of knowledge and hardware expertise exist.
Cited by 10
Jasvinder Singh Christopher · 2007
We investigate practical methods of distributed interference avoidance where users iteratively adapt their codewords in response to global feedback from the receiver. In turn, the receiver adaptively tracks user codewords and offers a reasonable alternative to feeding back codewords. We introduce variants of standard interference avoidance procedures which produce more easily tracked incremental codewords and study the response of the system to abrupt changes in the interference background as might be encountered in a practical system. Furthermore, the methods we propose are strongly reminiscent of adaptive equalization for which a large body of knowledge and hardware expertise exist.
Cited by 0
Valeria D’Amico, Carmen Botella, Jochen Giese et al. · Chalmers Publication Library (Chalmers University of Technology) · 2010
This paper gives an overview of the objectives and current research activities on interference avoidance in the EC funded research project ARTIST4G. It is the main objective of the ARTIST4G Work Package 1 (WP1), to build forward on the 3GPP LTE Release 8 baseline, proposing a novel fair mobile broadband technological framework in which to design innovative, practical, scalable and cost-effective interference avoidance solutions. This paper provides an overview of the fundamental classes of innovations studied in ARTIST4G Work Package 1 (WP1) and presents some performance results obtained by means of numerical simulations and test-bed measurements run in the field.
Cited by 11
Ashish Kulkarni, D.V. Thombre · 2011
Cited by 5
Christopher Rose, Sennur Ulukus, Roy Yates · 1999
Motivated by the emergence of programmable radios, we seek to understand a class of communication system where pairs of transmitters and receivers can adapt their modulation/demodulation method in the presence of interference to achieve better performance. Using signal to interference ratio as a metric, we present a class of iterative distributed algorithms for synchronous systems which results in an ensemble of optimal waveforms for multiple users connected to a common receiver (or co-located independent receivers). That is, the waveform ensemble meets the Welch Bound with equality and therefore achieves minimum average interference over the ensemble of signature waveforms. We provide convergence results for a number of scenarios and propose further research to help develop a theory and practice of interference avoidance for future licensed and unlicensed band systems.
Cited by 0
Christopher Rose, Roy D. Yates · 1998
Since radios are becoming ever more sophisticated, we consider a waveform-agile scenario where the transmitting radio may be instructed to vary its waveform or signature in response to interference conditions. Using classical Karhunen-Loeve methods, we derive the optimal waveform for a single user under given interference and then and provide an iterative distributed algorithm which results in an ensemble of optimal waveforms for multiple users connected to a common receiver (or co-located independent receivers). That is, the waveform ensemble provides minimum average interference over the ensemble. Furthermore, this optimum is achievable at the receiver with simple matched filters. 1 Introduction Wireless communications is a shared medium method. Thus, from its inception wireless system designers have had to consider interference from both natural sources and other users of the medium. The usual radio communications design cycle consists of measuring or predicting channel impairmen...
Cited by 0
Solà Colom, Marc · RECERCAT (Consorci de Serveis Universitaris de Catalunya)
This project aims to design and implement a method to make possible IEEE 802.15.4 fair coexistence with other ISM band widespread technologies. This method is intended to provide interference robustness on packet-loss critical applications such as Wireless Actuator Control (WAC) for assisted living at home and medical applications.
Cited by 0Open access
Laurenz Wiskott, Malte J. Rasch, Gerd Kempermann · 2008
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Dimitrie C. Popescu, Christopher Rose · International Journal of Satellite Communications and Networking · 2003
Abstract We apply interference avoidance methods to multiuser systems with multiple inputs and multiple outputs (MIMO) such as would be used on the uplink (or in overlapping downlink footprints) for satellite systems with multiple antennas. An arbitrary signal space can be used and the method can be applied to any MIMO system model regardless of the choice signal basis functions. Information is transmitted via multicode CDMA where symbols that comprise the data frame from a given user are ‘spread’ over the available dimensions using a precoding matrix. Optimal precoding matrices that maximize signal‐to‐interference plus noise‐ratio for all symbols/users are then obtained by application of distributed greedy interference avoidance methods. In general, algorithms based on greedy interference avoidance are different from water filling schemes. However, the codeword ensembles obtained provide similar simultaneous water filling solutions and thus maximize sum capacity. Numerical simulations have been performed and the signal‐to‐noise ratio distribution for receiver antennas and complementary cumulative distribution functions for sum capacity with optimal precoding matrices are also presented. Copyright © 2003 John Wiley & Sons, Ltd.
Cited by 7
Marc Solà Colom · 2008
Cited by 0
Karama Hamdi · 2007
Cited by 0
Rare & Special e-Zone (The Hong Kong University of Science and Technology) · 2007
Interference avoidance in cognitive radio networks by Karama Hamdi thesis 2007 xiii, 82 leaves : ill. ; 30 cm Today's wireless networks are characterized by a fixed spectrum assignment policy. However, a large portion of the assigned spectrum is used…Read more ›
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Hass, Harold, McLaughlin, Stephen, Foutekova, Ellina P · OpenGrey (Institut de l'Information Scientifique et Technique) · 2009
In recent years, cellular systems based on orthogonal frequency division multiple access – time division duplex (OFDMA-TDD) have gained considerable popularity. Two of the major reasons for this are, on the one hand, that OFDMA enables the receiver to effectively cope with multipath propagation while keeping the complexity low. On the other hand, TDD offers efficient support for cell-specific uplink (UL)/downlink (DL) asymmetry demands by allowing each cell to independently set its UL/DL switching point (SP). However, cell-independent SP gives rise to crossed slots. In particular, crossed slots arise when neighbouring cells use the same slot in opposing link directions, resulting in base station (BS)-to-BS interference and mobile station (MS)-to-MS interference. BS-to-BS interference, in particular, can be quite detrimental due to the exposed location of BSs, which leads to high probability of line-of-sight (LOS) conditions. The aim of this thesis is to address the BS-to-BS interference problem in OFDMA-TDDcellular networks. A simulation-based approach is used to demonstrate the severity of BS-to-BS interference and a signal-to-interference-plus-noise ratio (SINR) equation for OFDMA is formulated to aid system performance analysis. The detrimental effects of crossed slot interference in OFDMA-TDD cellular networks are highlighted by comparing methods specifically targeting the crossed slots interference problem. In particular, the interference avoidance method fixed slot allocation (FSA) is compared against state of the art interference mitigation approaches, viz: random time slot opposing (RTSO) and zone division (ZD). The comparison is done based on Monte Carlo simulations and the main comparison metric is spectral efficiency calculated using the SINR equation formulated in this thesis. The simulation results demonstrate that when LOS conditions among BSs are present, both RTSO and ZD perform worse than FSA for all considered performance metrics. It is concluded from the results that current interference mitigation techniques do not offer an effective solution to the BS-to-BS interference problem. Hence, new interference avoidance methods, which unlike FSA, do not sacrifice the advantages of TDD are open research issues addressed in this thesis. The major contribution of this thesis is a novel cooperative resource balancing technique that offers a solution to the crossed slot problem. The novel concept, termed asymmetry balancing, is targeted towards next-generation cellular systems, envisaged to have ad hoc and multi-hop capabilities. Asymmetry balancing completely avoids crossed slots by keeping the TDD SPs synchronised among BSs. At the same time, the advantages of TDD are retained, which is enabled by introducing cooperation among the entities in the network. If a cell faces resource shortage in one link direction, while having free resources in the opposite link direction, the free resources can be used to support the overloaded link direction. In particular, traffic can be offloaded to near-by mobile stations at neighbouring cells that have available resources. To model the gains attained with asymmetry balancing, a mathematical framework is developed which is verified by Monte Carlo simulations. In addition, asymmetry balancing is compared against both ZD and FSA based on simulations and the results demonstrate the superior performance of asymmetry balancing. It can be concluded that the novel interference avoidance approach is a very promising candidate to.
Cited by 0Open access
Ellina Foutekova · ERA · 2009
In recent years, cellular systems based on orthogonal frequency division multiple access – time division duplex (OFDMA-TDD) have gained considerable popularity. Two of the major reasons for this are, on the one hand, that OFDMA enables the receiver to effectively cope with multipath propagation while keeping the complexity low. On the other hand, TDD offers efficient support for cell-specific uplink (UL)/downlink (DL) asymmetry demands by allowing each cell to independently set its UL/DL switching point (SP). However, cell-independent SP gives rise to crossed slots. In particular, crossed slots arise when neighbouring cells use the same slot in opposing link directions, resulting in base station (BS)-to-BS interference and mobile station (MS)-to-MS interference. BS-to-BS interference, in particular, can be quite detrimental due to the exposed location of BSs, which leads to high probability of line-of-sight (LOS) conditions. The aim of this thesis is to address the BS-to-BS interference problem in OFDMA-TDDcellular networks. A simulation-based approach is used to demonstrate the severity of BS-to-BS interference and a signal-to-interference-plus-noise ratio (SINR) equation for OFDMA is formulated to aid system performance analysis. The detrimental effects of crossed slot interference in OFDMA-TDD cellular networks are highlighted by comparing methods specifically targeting the crossed slots interference problem. In particular, the interference avoidance method fixed slot allocation (FSA) is compared against state of the art interference mitigation approaches, viz: random time slot opposing (RTSO) and zone division (ZD). The comparison is done based on Monte Carlo simulations and the main comparison metric is spectral efficiency calculated using the SINR equation formulated in this thesis. The simulation results demonstrate that when LOS conditions among BSs are present, both RTSO and ZD perform worse than FSA for all considered performance metrics. It is concluded from the results that current interference mitigation techniques do not offer an effective solution to the BS-to-BS interference problem. Hence, new interference avoidance methods, which unlike FSA, do not sacrifice the advantages of TDD are open research issues addressed in this thesis. The major contribution of this thesis is a novel cooperative resource balancing technique that offers a solution to the crossed slot problem. The novel concept, termed asymmetry balancing, is targeted towards next-generation cellular systems, envisaged to have ad hoc and multi-hop capabilities. Asymmetry balancing completely avoids crossed slots by keeping the TDD SPs synchronised among BSs. At the same time, the advantages of TDD are retained, which is enabled by introducing cooperation among the entities in the network. If a cell faces resource shortage in one link direction, while having free resources in the opposite link direction, the free resources can be used to support the overloaded link direction. In particular, traffic can be offloaded to near-by mobile stations at neighbouring cells that have available resources. To model the gains attained with asymmetry balancing, a mathematical framework is developed which is verified by Monte Carlo simulations. In addition, asymmetry balancing is compared against both ZD and FSA based on simulations and the results demonstrate the superior performance of asymmetry balancing. It can be concluded that the novel interference avoidance approach is a very promising candidate to
Cited by 0Open access
Oghenekome Oteri, A. Paulraj · 2006
We study performance tradeoffs for joint diversity enhancement and interference mitigation in multi-cell networks with multiple antennas at the transmitter. Our transmitter combines a space time coding block followed by a multimode beamformer. We assume that the transmitter knows the channel covariance for its own and the interfered user. The coding techniques maximize link performance via diversity gain for its own user while constraining the interference power to the interfered (or other) user. We examine strategies for choosing this interference constraint based on greedy or co-operative methods for a symmetric two cell scenario where each link interferes with the other. In the greedy algorithm, each user selfishly maximizes diversity to its own user without regard to the interference it generates to the other user. Both users account for the incoming interference and they eventually iteratively reach the Nash equilibrium (NE). In the co-operative algorithm, each user balances the diversity to its own user but co-operates by limiting the amount of interference to the other user. We show that in the co-operative case, it is possible to find Pareto dominant solutions where the users either maintain or improve their symbol error rate performance
Cited by 1
L Weichert · Journal of Physics E Scientific Instruments · 1983
Various types of interfering signals are outlined and measures which can be adapted in order to suppress their effects are described. It is shown that by balancing the whole system including the signal source, the leads and the instrument, as well as twisting and correct screening of signal leads, the susceptibility to external electric, magnetic or electromagnetic fields and coupling to interfering sources can be substantially reduced. A crucial question is finding and constructing a design which avoids ground loops. They are a serious problem in a measuring system. For optimum efficiency, the user of an instrument should take care in matching his arrangement of sensors, leads, instrument and grounding with the design concept of reducing interference susceptibility.
Cited by 5
Huimin Deng, Kai Ying, Daquan Feng et al. · IEEE Journal on Selected Areas in Communications · 2024
The deployment of low earth orbit (LEO) satellites megaconstellations presents a promising way for achieving global coverage and service, attributed to their comparatively low round-trip latency and launch costs. However, this surge in LEO satellite launches exacerbates the scarcity of the limited spectrum resources. Spectrum sharing between satellite constellations and terrestrial networks and beam hopping (BH) technology emerge as viable strategies to mitigate this spectrum shortage. To enhance spectrum efficiency and avoid serious inter-system interference, we investigate the beam hopping scheduling of satellites for interference avoidance. The beam hopping scheduling of the integrated satellite-terrestrial wireless networks system is formulated as throughput-driven beam hopping (TDBH) problem and satisfaction-rate-driven beam hopping (SDBH) problem, respectively. In particular, we decompose the TDBH problem into two sub-problems by relaxation, and a genetic algorithm (GA) is introduced to handle the SDBH problem. The impact of channel conditions and traffic load intensity on the satellite system throughput is analyzed in TDBH simulation. As for SDBH optimization problem, the simulation results show that the proposed GA algorithm improves the average traffic satisfaction rate by 16.96% at least, compared with other benchmarks and suits to scenarios with different traffic demands and fading channel conditions.
Cited by 18
John Paffett · OpenGrey (Institut de l'Information Scientifique et Technique) · 2000
Cited by 0
Kluwer Academic Publishers eBooks · 2006
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Bette M. Wirier, Paul Manning, E. Michael Geyer et al. · 1997
Due to the planned high reliance on GPS for aviation
applications, if a radio frequency interference (RFI)
incident does occur, the rapid location and removal
of the source will be essential. Such rapid response
capability requires widespread deployment of the
field detection instrumentation. Achieving wide-
spread deployment at reasonable costs requires the
development of new approaches to source location.
When a rare report of interference is received, these
systems must be operable by non-specialists with
minimal training. The U.S. DOT Volpe National
Transpoitation Systems Center (Volpe Center),
under the sponsorship of the Federal Aviation
Administration, is currently developing two
innovative instruments for locating sources of RF1 to
GPS.
A GPS Interference Locator System (GILS) is
intended primarily for use by personnel on the
ground; it uses the traditional RF1 localization
technique involving a directional antenna and signal
detection electronics. However, achieving low-cost
and simplicity of operation while still being able to
sense the low signal levels that can disrupt GPS
necessarily entails compromises. This paper
describes the four design approaches formulated for
GILS, discusses the tradeoffs, and presents the
results of tests performed on a system prototype.
The fundamental “instruments” for measuring the
direction of a GPS interference source from an
aircraft (ARLAS -- Aircraft RI?1 Localization and
Avoidance System) is the vertical (elevstion) pattern
of the aircraft’s top-mounted GPS antenna, the
signal-to-noise ratio (SNR) that can be calculated by
every GPS receiver and the values of roll, pitch and
heading from aircraft gyros. When the aircraft is
bank& the antenna illuminates some areas on the
ground (low SNR if interferer is present) while
obscuring others (higher SNR even if intetierer is
present). By flying in a tight circle, the aircraft
effectively “scans” the ground and obtains data
sufficient to estimate the direction of an RF1 source.
The design approach is demonstrated using data
from the 1994 St. Louis GPS anomaly.
The ARLAS system being developed for the FM
would use data from equipment already deployed on
FAA aircraB, merely adding a software module to
the flight management system. In this way, every
FAA aircraft can be used to locate RF1 sources at
minimal cost. If added to GPS receiver software, it
could assist non-FAA aircraft to provide the FAA
with more precise reports of RF1 events and to avoid
airspace effected by RF1 (should it occur). It will
also distinguish between RF1 from environmental or
on-site sources.
Cited by 2