| 1. |
- Molisch, Andreas, et al.
(author)
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A low-cost time-hopping impulse radio system for high data rate transmission
- 2005
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In: Eurasip Journal on Applied Signal Processing. - 1110-8657. ; :3, s. 397-412
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Journal article (peer-reviewed)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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| 2. |
- Gezici, S, et al.
(author)
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Localization via ultra-wideband radios: A look at positioning aspects of future sensor networks
- 2005
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In: IEEE Signal Processing Magazine. - 1053-5888. ; 22:4, s. 70-84
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Journal article (peer-reviewed)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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| 3. |
- Gezici, S, et al.
(author)
-
Optimal and Suboptimal Linear Receivers for Impulse Radio UWB Systems
- 2006
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In: The 2006 IEEE International Conference on Ultra-Wideband. - 1424401011 ; , s. 161-166
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Conference paper (peer-reviewed)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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| 4. |
- Gezici, S, et al.
(author)
-
Performance evaluation of impulse radio UWB systems with pulse-based polarity randomization
- 2005
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In: IEEE Transactions on Signal Processing. - 1053-587X. ; 53:7, s. 2537-2549
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Journal article (peer-reviewed)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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