| 1. |
- Gezici, S., et al.
(författare)
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Jamming of Wireless Localization Systems
- 2016
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Ingår i: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 64:6, s. 2660-2676
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the optimal jamming of wireless localization systems is investigated. Two optimal power allocation schemes are proposed for jammer nodes in the presence of total and peak power constraints. In the first scheme, power is allocated to jammer nodes in order to maximize the average Cramér-Rao lower bound (CRLB) of target nodes, whereas in the second scheme, the power allocation is performed for the aim of maximizing the minimum CRLB of target nodes. Both the schemes are formulated as linear programs, and a closed-form solution is obtained for the first scheme. For the second scheme, under certain conditions, the property of full total power utilization is specified, and a closed-form solution is obtained when the total power is lower than a specific threshold. In addition, it is shown that non-zero power is allocated to at most NT jammer nodes according to the second scheme in the absence of peak power constraints, where NT is the number of target nodes. In the presence of parameter uncertainty, robust versions of the power allocation schemes are proposed. Simulation results are presented to investigate the performance of the proposed schemes and to illustrate the theoretical results.
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| 2. |
- Gezici, S., et al.
(författare)
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Optimal jammer placement in wireless localization networks
- 2015
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Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. - : IEEE conference proceedings. - 9781479919307 ; , s. 665-669
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Konferensbidrag (refereegranskat)abstract
- The optimal jammer placement problem is proposed for a wireless localization network, where the aim is to degrade the accuracy of locating target nodes as much as possible. In particular, the optimal location of a jammer node is obtained in order to maximize the minimum of the Cramér-Rao lower bounds for a number of target nodes under location related constraints for the jammer node. Theoretical results are derived to specify scenarios in which the jammer node should be located as close to a certain target node as possible, or the optimal location of the jammer node is determined by two or three of the target nodes. In addition, explicit expressions for the optimal location of the jammer node are derived in the presence of two target nodes. Numerical examples are presented to illustrate the theoretical results.
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| 3. |
- Molisch, Andreas, et al.
(författare)
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A low-cost time-hopping impulse radio system for high data rate transmission
- 2005
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Ingår i: Eurasip Journal on Applied Signal Processing. - 1110-8657. ; :3, s. 397-412
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Tidskriftsartikel (refereegranskat)abstract
- We present an efficient, low-cost implementation of time-hopping impulse radio that fulfills the spectral mask mandated by the FCC and is suitable for high-data-rate, short-range communications. Key features are (i) all-baseband implementation that obviates the need for passband components, (ii) symbol-rate (not chip rate) sampling, A/D conversion, and digital signal processing, (iii) fast acquisition due to novel search algorithms, and (iv) spectral shaping that can be adapted to accommodate different spectrum regulations and interference environments. Computer simulations show that this system can provide 110 Mbps at 7–10 m distance, as well as higher data rates at shorter distances under FCC emissions limits. Due to the spreading concept of time-hopping impulse radio, the system can sustain multiple simultaneous users, and can suppress narrowband interference effectively.
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| 4. |
- Molisch, Andreas, et al.
(författare)
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An efficient low-cost time-hopping impulse radio for high data rate transmission
- 2003
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Ingår i: Proceeding of the Sixth International Symposium on Wireless Personal Multimedia Communications.
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Konferensbidrag (refereegranskat)abstract
- We present an efficient, low-cost implementation of time-hopping impulse radio that fulfills the spectral mask mandated by the FCC and is suitable for high-data-rate, short-range communications. The system was proposed to the IEEE 802.15.3a group for standardization as high-datarate personal-area network (PAN). Key features are: (i) all-baseband implementation obviates the need for local oscillators and other passband components, (ii) all sampling and digital signal processing is done at 200MHz, (iii) fast acquisition is accomplished by novel search algorithms,(iv) the spectral can be shaped adaptively to accommodate different spectrum regulations and interference environments. We show that this system can provide 110Mbit/s at 7-10m distance, as well as higher data rates at shorter distances. Due to the spreading concept of time-hopping impulse radio, the system can sustain multiple piconets, and can suppress narrowband interference effectively.
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| 5. |
- Gezici, S, et al.
(författare)
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Localization via ultra-wideband radios: A look at positioning aspects of future sensor networks
- 2005
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Ingår i: IEEE Signal Processing Magazine. - 1053-5888. ; 22:4, s. 70-84
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Tidskriftsartikel (refereegranskat)abstract
- UWB technology provides an excellent means for wireless positioning due to its high resolution capability in the time domain. Its ability to resolve multipath components makes it possible to obtain accurate location estimates without the need for complex estimation algorithms. In this article, theoretical limits for TOA estimation and TOA-based location estimation for UWB systems have been considered. Due to the complexity of the optimal schemes, suboptimal but practical alternatives have been emphasized. Performance limits for hybrid TOA/SS and TDOA/SS schemes have also been considered. Although the fundamental mechanisms for localization, including AOA-, TOA-, TDOA-, and SS-based methods, apply to all radio air interface, some positioning techniques are favored by UWB-based systems using ultrawide bandwidths.
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| 6. |
- Gezici, S, et al.
(författare)
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On the performance of transmitted-reference impulse radio
- 2004
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Ingår i: GLOBECOM '04. IEEE Global Telecommunications Conference.
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Konferensbidrag (refereegranskat)abstract
- We consider a time-hopping impulse-radio system that uses transmitted-reference pulses for implicit channel estimation and equalization. A hybrid receiver structure first performs a filtering matched to the hopping sequence, and a subsequent correlation of the data pulses with the reference pulses. We analyze the performance of such a system both in AWGN and in multipath. For the AWGN case, we give exact expressions for the bit error probability that take into account the non-Gaussian nature of the noise-noise crossterms arising in the correlators. For the multipath case, we analyze inter-frame interference, as well as multipath interference from the reference pulse to the data pulse, providing dosed-form equations in the limit of a large number of multipath components.
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| 7. |
- Gezici, S, et al.
(författare)
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Optimal and Suboptimal Linear Receivers for Impulse Radio UWB Systems
- 2006
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Ingår i: The 2006 IEEE International Conference on Ultra-Wideband. - 1424401011 ; , s. 161-166
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Konferensbidrag (refereegranskat)abstract
- The high time resolution of ultra-wideband (UWB) signals results in a large number of multipath components (MPCs) arriving at the receiver, which presents a source of diversity. In addition to this multipath diversity, there is also repetition diversity inherent in impulse radio (IR) UWB systems, since a number of pulses are transmitted for each information symbol. In order to make optimal use of multipath and repetition diversity, the receiver needs to consider the optimal combination of contributions from both different frames and different MPCs. In this overview paper, the optimal linear receiver for a given user in a frequency-selective multiuser environment, which combines all the samples from the received signal according to the minimum mean square error (MMSE), criterion, is studied. Due to the complexity of this optimal receiver, two suboptimal receivers with lower complexity are considered, optimal frame combining (OFC) and optimal multipath combining (OMC) receivers, which reduce computational complexity by suboptimal combining in the multipath diversity and repetition diversity domains, respectively. Finally, a two-step MMSE algorithm which reduces complexity by performing MMSE combining in two steps is presented, and its optimality properties are discussed. Simulations are performed to compare the performance of different receivers
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| 8. |
- Gezici, S, et al.
(författare)
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Optimal and suboptimal linear receivers for time-hopping impulse radio systems
- 2004
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Ingår i: 2004 International Workshop on Ultra Wideband Systems, 2004. Joint with Conference on Ultrawideband Systems and Technologies. Joint UWBST & IWUWBS.. - 0780383737 ; , s. 11-15
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Konferensbidrag (refereegranskat)abstract
- In this paper, we consider optimal and suboptimal linear receivers for a given user in a frequency-selective multiuser environment. The optimal linear receiver combining all the samples from the frames and the multipath components, according to the MMSE criterion, is designed. Due to the complexity of this receiver, two suboptimal receivers are considered: (i) an optimal frame combining receiver, which optimally combines the samples from the frames, while combining different multipath components suboptimally; (ii) an optimal multipath combining receiver, which combines the samples from different multipath components optimally, while combining the samples from the frames suboptimally. In this paper, these optimal and suboptimal linear receivers are designed and their performance is evaluated via simulations.
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| 9. |
- Gezici, S, et al.
(författare)
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Performance evaluation of impulse radio UWB systems with pulse-based polarity randomization
- 2005
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 53:7, s. 2537-2549
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the performance of a binary phase shift keyed random time-hopping impulse radio system with pulse-based polarity randomization is analyzed. The effects of interframe interference and multiple-access interference on the performance of a generic Rake receiver are investigated for asynchronous systems in frequency-selective environments. A key step is to model the asynchronous system as a chip-synchronous system with uniformly distributed timing jitter for the transmitted pulses of interfering users. This model allows the analytical technique developed for the synchronous case to be extended to the asynchronous case and allows the derivation of closed-form equations for the bit error probability in various Rake receiver architectures. It is shown that a Gaussian approximation can be used for both multiple-access and interframe interference as long as the number of frames per symbols is large (typically, at least 5), whereas there is no minimum requirement for the number of users for the equations to hold. It is observed that under many circumstances, the chip-synchronous case shows a worse bit error probability performance than the asynchronous case; the amount of the,difference depends on the autocorrelation function of the ultra-wideband pulse and the signal-to-interference-plus-noise-ratio of the system. Simulations studies support the approximate analysis.
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| 10. |
- Gezici, S, et al.
(författare)
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Performance Evaluation of Impulse Radio UWB Systems with Pulse-Based Polarity Randomization in Asynchronous Multiuser Environments
- 2004
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Ingår i: IEEE Wireless Communications and Networking Conference, 2004. WCNC.. - 1558-2612 .- 1525-3511. - 0780383443 ; , s. 908-913
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Konferensbidrag (refereegranskat)abstract
- The performance of a binary phase shift keyed random time-hopping impulse radio system with pulse-based polarity randomization is analyzed. The effects of multiple access interference are investigated for both chip-synchronous and asynchronous systems. It is shown that the performance of a chip-synchronous system is the same as that for the symbol-synchronous case studied in E. Fisher and H. V. Poor (Oct. 2-4, 2002). The asynchronous system is modelled as a chip-synchronous system with uniformly distributed timing jitter on the transmitted pulses of interfering users. This extends the analytical technique developed for the chip-synchronous case to the asynchronous case. An approximate closed-form expression for the probability of error, expressed in terms of the autocorrelation function of the transmitted pulse, is derived for the asynchronous case. The analysis shows that the chip-synchronous assumption can result in over-estimating the error probability, and hence that the system design based on this approximation will he on the safe side. The degree of over-estimation mainly depends on the autocorrelation function of the UWB pulse and signal-to-interference-plus-noise-ratio (SIR) of the system. Simulations studies support this approximate analysis.
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