Browsing by Subject "Least-squares (LS) estimation"

Now showing 1 - 5 of 5

Open Access
Enhancements to linear least squares localization through reference selection and ML estimation
(IEEE, 2008-03-04) Güvenç, İsmail; Gezici, Sinan; Watanabe F.; Inamura, H.
Linear least squares (LLS) estimation is a low complexity but sub-optimum method for estimating the location of a mobile terminal (MT) from some distance measurements. It requires selecting one of the fixed terminals (FTs) as a reference FT for obtaining a linear set of expressions. However, selection of the reference FT is commonly performed arbitrarily in the literature. In this paper, a method for selection of the reference FT is proposed, which improves the location accuracy compared to a fixed selection of the reference FT. Moreover, a covariancematrix based LLS estimator is proposed in line of sight (LOS) and non-LOS (NLOS) environments which further improves accuracy since the correlations between the observations are exploited. Simulation results prove the effectiveness of the proposed techniques. © 2008 IEEE.
Open Access
On the performance of linear least-squares estimation in wireless positioning systems
(IEEE, 2008-05) Gezici, Sinan; Güvenç, İ.; Sahinoğlu, Z.
A common technique for wireless positioning is to estimate time-of-arrivals (TOAs) of signals traveling between a target node and a number of reference nodes, and then to determine the position of the target node based on those TOA parameters. In determining the position of the target node from TOA parameters, linear or nonlinear least-squares (LS) estimation techniques can be employed. Although the linear LS techniques are suboptimal in general, they facilitate low-complexity position estimation. In this paper, performance of various linear LS techniques are compared, and suboptimality of the linear approach is quantified in terms of the Cramer-Rao lower bound (CRLB). Simulations are performed to compare the performance of the linear LS approaches versus the CRLBs for linear and nonlinear techniques. ©2008 IEEE.
Open Access
Theoretical limits and a practical estimator for joint estimation of respiration and heartbeat rates using UWB impulse radio
(IEEE, 2007) Gezici, Sinan; Arıkan, Orhan
In this paper, Cramer-Rao lower bounds are derived fo r joint estimation of respiration and heartbeat rates via impulse radio ultra-wideband signals. Generic models are employed for displacement functions due to respiration and heartbeat, and the bounds are obtained for the cases of known and unknown channel coefficients. In addition, a two-step suboptimal estimator is proposed, which is based on joint time-delay estimation followed by a least-squares approach. It is shown that the proposed estimator is asymptotically optimal under mild conditions. Simulation studies are performed to evaluate the lower bounds and performance of the proposed estimator for realistic system parameters.
Open Access
Theoretical limits for estimation of periodic movements in pulse-based UWB systems
(Institute of Electrical and Electronics Engineers, 2007) Gezici, Sinan
In this paper, Cramer-Rao lower bounds (CRLBs) for estimation of signal parameters related to periodically moving objects in pulse-based ultra-wideband (UWB) systems are presented. The results also apply to estimation of vital parameters, such as respiration rate, using UWB signals. In addition to obtaining the CRLBs, suboptimal estimation algorithms are also presented. First, a single-path channel with additive white Gaussian noise is considered, and closed-form CRLB expressions are obtained for sinusoidal object movements. Also, a two-step suboptimal algorithm is proposed, which is based on time delay estimation via matched filtering followed by least-squares estimation, and its asymptotic optimality property is shown in the limit of certain system parameters. Then, a multipath environment is considered, and exact and approximate CRLB expressions are derived. Moreover, suboptimal schemes for parameter estimation are studied. Simulation studies are performed for the estimation of respiration rates in order to evaluate the lower bounds and performance of the suboptimal algorithms for realistic system parameters.
Open Access
Theoretical limits for estimation of vital signal parameters using impulse radio UWB
(IEEE, 2007) Gezici, Sinan; Şahinoğlu, Z.
In this paper, Cramer-Rao lower bounds (CRLBs) for estimation of vital signal parameters, such as respiration and heart-beat rates, using ultra-wideband (UWB) pulses are derived. In addition, a simple closed-form CRLB expression is obtained for sinusoidal displacement functions under certain conditions. Moreover, a two-step suboptimal solution is proposed, which is based on time-delay estimation via matched filtering followed by least-squares (LS) estimation. It is shown that the proposed solution is asymptotically optimal in the limit of certain system parameters. Simulation studies are performed to evaluate the lower bounds and performance of the proposed solution for realistic system parameters.