Semi-blind channel estimation for joint communication and positioning

Abstract

In this contribution, semi-blind channel estimation for joint communication and positioning (JCAP) is proposed. The concept is based on a unified signal architecture. Within this framework channel estimation is the core part, since it links communication and positioning algorithms. Thus, channel estimation serves twofold purposes: Firstly, it is inherently required for data detection and secondly it is employed to estimate positioning relevant information like the time of arrival (TOA). JCAP aims at exploiting synergetic effects. Employing semi-blind channel estimation is beneficial in this context, since it allows to assimilate the estimated communication data as virtual training.

Direct ranging in multi-path channels using OFDM pilot signals

“…In the considered case, however, p(y|d) is unknown. Instead, estimator (14) may be approximated as in [4] and [7] via a two-step approach. These methods, however, require the knowledge of the number of path components, which is generally unknown and hard to estimate.…”

“…We omit the comparison with the energy detector, which is sensitive to the selected threshold value and provides inaccurate TOA estimates [3] [13]. We also omit the comparison with multidimensional search approach, because these estimators require access to L, which is assumed to be unknown in this work [4] [7]. We then report the performance of estimator (15) when there is a mismatch between the channel assumptions made for its derivation and the real channel conditions in which it is used.…”

“…In [4], Wang et al derived the Cramér-Rao bound (CRB) on the mean square error (MSE) of the range estimator and investigated how the OFDM signal parameters and the spacing between the multi-path components affect the bound. The CRB is a lower bound for the MSE of the estimator proposed in [7], which requires estimation of the delays of all separable multi-path components. The bound in [4] and the methods in [5] [6] [7] require the separability of the multi-path components and the knowledge of their exact number, which is generally difficult to estimate reliably.…”

“…The CRB is a lower bound for the MSE of the estimator proposed in [7], which requires estimation of the delays of all separable multi-path components. The bound in [4] and the methods in [5] [6] [7] require the separability of the multi-path components and the knowledge of their exact number, which is generally difficult to estimate reliably. Furthermore, the required multidimensional search is impractical for a realistic number of multi-path components.…”

Bayesian ranging for radio localization with and without line-of-sight detection

“…Using the prior distribution of the range, Bayesian estimators, including approximate maximum a posteriori (MAP) and minimum-mean-square-error (MMSE) estimators and a pth-order MMSE polynomial estimator, are proposed in [15]. In contrast to the methods in [16] [17], direct ranging operates without knowledge of the number of multipath components in the channel response and separability condition on these components. Although the methods in [14], [15] still rely on LOS state information, the principle of ranging without estimating intermediate parameters seems promising.…”