This paper presents a joint time-delay and channel estimator to assess the achievable positioning performance of the\nLong Term Evolution (LTE) system in multipath channels. LTE is a promising technology for localization in urban and\nindoor scenarios, but its performance is degraded due to the effect of multipath. In those challenging environments,\nLTE pilot signals are of special interest because they can be used to estimate the multipath channel and counteract its\neffect. For this purpose, a channel estimation model based on equi-spaced taps is combined with the time-delay\nestimation, leading to a low-complexity estimator. This model is enhanced with a novel channel parameterization\nable to characterize close-in multipath, by introducing an arbitrary tap with variable position between the first two\nequi-spaced taps. This new hybrid approach is adopted in the joint maximum likelihood (JML) time-delay estimator to\nimprove the ranging performance in the presence of short-delay multipath. The JML estimator is then compared with\nthe conventional correlation-based estimator in usual LTE conditions. These conditions are characterized by the\nextended typical urban (ETU) multipath channel model, additive white Gaussian noise (AWGN) and LTE signal\nbandwidths equal to 1.4, 5 and 10 MHz. The resulting time-delay estimation performance is assessed by computing\nthe cumulative density function (CDF) of the errors in the absence of noise and the root-mean-square error (RMSE)\nand bias for signal-to-noise ratio (SNR) values between -20 and 30 dB.
Loading....