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39
Position Estimation via Ultra-Wideband Signals
, 2008
"... The high time resolution of ultra-wideband (UWB) signals facilitates very precise position estimation in many scenarios, which makes a variety applications possible. This paper reviews the problem of position estimation in UWB systems, beginning with an overview of the basic structure of UWB signals ..."
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Cited by 25 (1 self)
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The high time resolution of ultra-wideband (UWB) signals facilitates very precise position estimation in many scenarios, which makes a variety applications possible. This paper reviews the problem of position estimation in UWB systems, beginning with an overview of the basic structure of UWB signals and their positioning applications. This overview is followed by a discussion of various position estimation techniques, with an emphasis on time-based approaches, which are particularly suitable for UWB positioning systems. Practical issues arising in UWB signal design and hardware implementation are also discussed.
Ranging energy optimization for robust sensor positioning based on semidefinite programming
- IEEE Trans. Signal Process
, 2009
"... Abstract—Sensor positioning is an important task of loca-tion-aware wireless sensor networks. In most sensor positioning systems, sensors and beacons need to emit ranging signals to each other. Sensor ranging energy should be low to prolong system lifetime, but sufficiently high to fulfill prescribe ..."
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Cited by 12 (4 self)
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Abstract—Sensor positioning is an important task of loca-tion-aware wireless sensor networks. In most sensor positioning systems, sensors and beacons need to emit ranging signals to each other. Sensor ranging energy should be low to prolong system lifetime, but sufficiently high to fulfill prescribed accuracy requirements. This motivates us to investigate ranging energy optimization problems. We address ranging energy optimization for an unsynchronized positioning system, which features robust sensor positioning (RSP) in the sense that a specific accuracy re-quirement is fulfilled within a prescribed service area. We assume a line-of-sight (LOS) channel exists between the sensor and each beacon. The positioning is implemented by time-of-arrival (TOA) based two-way ranging between a sensor and beacons, followed by a location estimation at a central processing unit. To establish a dependency between positioning accuracy and ranging energy, we assume the adopted TOA and location estimators are unbiased and attain the associated Cramér–Rao bound. The accuracy re-quirement has the same form as the one defined by the Federal Communication Commission (FCC), and we present two con-straints with linear-matrix-inequality form for the RSP. Ranging energy optimization problems, as well as a practical algorithm based on semidefinite programming are proposed. The effective-ness of the algorithm is illustrated by numerical experiments. Index Terms—Cramér–Rao bound, localization, semidefinite programming, wireless sensor networks.
Molisch, “A two-step time of arrival estimation algorithm for impulse radio ultrawideband systems
- in Proc. 13th European Signal Processing Conference (EUSIPCO
, 2005
"... High time resolution of ultra wideband (UWB) signals facilitates very precise positioning capabilities based on time-ofarrival (TOA) measurements. Although the theoretical lower bound for TOA estimation can be achieved by the maximum likelihood principle, it is impractical due to the need for extrem ..."
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Cited by 9 (5 self)
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High time resolution of ultra wideband (UWB) signals facilitates very precise positioning capabilities based on time-ofarrival (TOA) measurements. Although the theoretical lower bound for TOA estimation can be achieved by the maximum likelihood principle, it is impractical due to the need for extremely high-rate sampling and the presence of large number of multipath components. On the other hand, the conventional correlation-based algorithm, which serially searches possible signal delays, takes a very long time to estimate the TOA of a received UWB signal. Moreover, the first signal path does not always have the strongest correlation output. Therefore, first path detection algorithms need to be considered. In this paper, a data-aided two-step TOA estimation algorithm is proposed. In order to speed up the estimation process, the first step estimates the rough TOA of the received signal based on received signal energy. Then, in the second step, the arrival time of the first signal path is estimated by considering a hypothesis testing approach. The proposed scheme uses low-rate correlation outputs, and is able to perform accurate TOA estimation in reasonable time intervals. The simulation results are presented to analyze the performance of the estimator. Index Terms — Ultra-wideband (UWB), impulse radio (IR), time of arrival (TOA) estimation, statistical change detection, method of moments (MM).
Potential of UWB technology for the next generation wireless communications
- in Proc. IEEE Int. Symp. Spread Spectrum Techniques and Applicat. (ISSSTA
, 2006
"... Abstract — This paper discusses the potential deployment of ultra-wideband (UWB) radio technology for next generation wireless communications. Firstly, the state-of-art in UWB technology is reviewed. Then, the current status of worldwide regulatory efforts and industrial standardization activities i ..."
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Cited by 7 (1 self)
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Abstract — This paper discusses the potential deployment of ultra-wideband (UWB) radio technology for next generation wireless communications. Firstly, the state-of-art in UWB technology is reviewed. Then, the current status of worldwide regulatory efforts and industrial standardization activities is discussed. Various technical challenges that remain to be solved prior to the successful deployment of UWB systems as well as the possible technical approaches are also reported. Specifically, we envisioned the potential of location awareness capabilities to provide new applications and usage models for future mobile terminals. An overview of the existing ranging and localization techniques is presented and some technical aspects as well as design trade-offs in terms of device complexity and ranging accuracy are highlighted. Finally, since UWB systems operate as overlay systems, issues of coexistence and interference with existing narrowband systems are presented. I.
A compressed sensing receiver for UWB impulse radio in bursty applications like wireless sensor networks
- Elsevier Physical Commun
, 2009
"... We propose a novel receiver for Ultra-Wide-band Impulse-Radio communica-tion in Wireless Sensor Networks, which are characterized by bursty traffic and severe power constraints. The receiver is based on the principle of Compressed Sensing, and exploits the sparsity of the transmitted signal to achie ..."
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Cited by 7 (2 self)
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We propose a novel receiver for Ultra-Wide-band Impulse-Radio communica-tion in Wireless Sensor Networks, which are characterized by bursty traffic and severe power constraints. The receiver is based on the principle of Compressed Sensing, and exploits the sparsity of the transmitted signal to achieve reliable demodulation from a relatively small number of projections. The projections are implemented in an analog front-end as correlations with tractable test-functions, and a joint decoding of the time of arrival and the data bits is done by a DSP back-end using an efficient quadratic program. The proposed receiver differs from extant schemes in the following respects: (i) It needs neither a high-rate analog-to-digital converter nor wide-band analog delay lines, and can operate in a significantly under-sampled regime. (ii) It is robust to large timing uncertainty and hence the transmitter need not waste power on explicit training headers for timing synchronization. (iii) It can operate in a regime of heavy inter-symbol in-terference (ISI), and therefore allows a very high baud rate (close to the Nyquist rate). (iv) It has a built-in capability to blindly acquire and track the channel response irrespective of line-of-sight/non-line-of-sight conditions. We demon-strate that the receiver’s performance remains close to the maximum likelihood receiver under every scenario of under-sampling, timing uncertainty, ISI, and channel delay spread. Key words: ultra-wide-band, low power physical layer, compressed sensing, maximum likelihood sequence estimation, inter-symbol interference, timing uncertainty, wireless sensor networks ∗Corresponding author.
Noncoherent Ultra-Wideband (De)Modulation
, 2007
"... Ultra-wideband (UWB) radios have received increasing attention recently for their potential to overlay legacy systems, their low-power consumption and low-complexity implementation. Because of the pulsed or duty-cycled nature of the ultra-short transmitted waveforms, timing synchronization and chann ..."
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Cited by 4 (0 self)
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Ultra-wideband (UWB) radios have received increasing attention recently for their potential to overlay legacy systems, their low-power consumption and low-complexity implementation. Because of the pulsed or duty-cycled nature of the ultra-short transmitted waveforms, timing synchronization and channel estimation pose major, and often conflicting, challenges and requirements. In order to address (or in fact bypass) both tasks, we design and test noncoherent UWB (de)modulation schemes, which remain operational even without timing and channel information. Relying on integrate-and-dump operations of what we term “dirty templates, ” we first derive a maximum likelihood (ML) optimal noncoherent UWB demodulator. We further establish a conditional ML demodulator with lower complexity. Analysis and simulations show that both can also be applied after (possibly imperfect) timing acquisition. Under the assumption of perfect timing, our noncoherent UWB scheme reduces to a differential UWB system. Our approach can also be adapted to a transmitted reference (TR) UWB system. We show that the resultant robust-to-timing TR (RTTR) approach considerably improves performance of the original TR system in the presence of timing offsets or residual timing acquisition errors.
Precise timing for multiband OFDM in a UWB system
- IEEE Trans. Commun
"... Abstract — Precise positioning is one attractive application of ultra wideband (UWB) systems. Its enormous bandwidth has generated high expectation on the spatial resolution that it could achieve. However, synchronization in the presence of dense multipath is challenging, since the first arrival is ..."
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Cited by 4 (4 self)
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Abstract — Precise positioning is one attractive application of ultra wideband (UWB) systems. Its enormous bandwidth has generated high expectation on the spatial resolution that it could achieve. However, synchronization in the presence of dense multipath is challenging, since the first arrival is not necessarily the strongest one due to channel fading. It is unclear how high a spatial resolution can be realized in practical implementation, and how reliable it will be. We in this paper address practical synchronization algorithms for multiband OFDM UWB transmission, and analyze the performance of a maximum likelihood (ML) joint timing/channel estimation algorithm. We show that the probability of mis-timing in single band OFDM has only diversity order one. Most timing errors lie closely around the right timing, as we show that the probability of timing error equal to or greater than Δ having diversity order of min(Δ,L), where L the number of channel taps. We reveal the benefit of frequency hopping across multiple subbands that enables an NBfold diversity increase in timing performance, where NB is the number of subbands used. I.
Two-step time of arrival estimation for pulse-based ultra-wideband systems
- 2008, Article ID 529134
"... In cooperative localization systems, wireless nodes need to exchange accurate position-related information such as time-of-arrival (TOA) and angle-of-arrival (AOA), in order to obtain accurate location information. One alternative for providing accurate position-related information is to use ultra-w ..."
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Cited by 3 (0 self)
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In cooperative localization systems, wireless nodes need to exchange accurate position-related information such as time-of-arrival (TOA) and angle-of-arrival (AOA), in order to obtain accurate location information. One alternative for providing accurate position-related information is to use ultra-wideband (UWB) signals. The high time resolution of UWB signals presents a potential for very accurate positioning based on TOA estimation. However, it is challenging to realize very accurate positioning systems in practical scenarios, due to both complexity / cost constraints and adverse channel conditions such as multipath propagation. In this paper, a twostep TOA estimation algorithm is proposed for UWB systems in order to provide accurate TOA estimation under practical constraints. In order to speed up the estimation process, the first step estimates a coarse TOA of the received signal based on received signal energy. Then, in the second step, the arrival time of the first signal path is estimated by considering a hypothesis testing approach. The proposed scheme uses low-rate correlation outputs and is able to perform accurate TOA estimation in reasonable time intervals. The simulation results are presented to analyze the performance of the estimator.
Non–coherent receiver with fractional sampling for impulsive UWB systems
- IEEE Int. Commun. Conf
, 2009
"... Abstract—We propose a low complexity noncoherent receiver operating at twice the symbol-rate for systems where each data symbol consists of multiple frames/chips. The receiver does not require explicit timing and channel estimation. It implements simple delayed-autocorrelation, followed by sampling ..."
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Cited by 1 (0 self)
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Abstract—We propose a low complexity noncoherent receiver operating at twice the symbol-rate for systems where each data symbol consists of multiple frames/chips. The receiver does not require explicit timing and channel estimation. It implements simple delayed-autocorrelation, followed by sampling at twice the symbol-rate. Simulation results show the receiver achieves performance close to a conventional one with perfect timing. I.
