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Merayo N.,University of Valladolid | Gonzalez R.,University of Valladolid | De Miguel I.,University of Valladolid | Jimenez T.,Center for the Development of Telecommunications | And 5 more authors.
Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering | Year: 2010

A novel bandwidth assignment algorithm in WDM Ethernet Passive Optical Networks, called DyWaS-SLA, is proposed not only to provide service differentiation but also to offer subscriber differentiation. Simulation results show that DyWaS-SLA outperforms other bandwidth allocation algorithms in WDM-EPONs as it makes fairer bandwidth distribution than those methods. Consequently, it always insures a guaranteed bandwidth for every priority subscriber. Furthermore, DyWaS-SLA obtains lower mean packet delay and packet loss rate for the highest priority subscribers when compared with other bandwidth distribution schemes in WDM-EPONs. © Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering 2010.


Bahillo A.,Center for the Development of Telecommunications | Mazuelas S.,Center for the Development of Telecommunications | Lorenzo R.M.,University of Valladolid | Fernandez P.,University of Valladolid | And 3 more authors.
Eurasip Journal on Advances in Signal Processing | Year: 2010

Nowadays, a variety of information related to the distance between two wireless devices can be easily obtained. This paper presents a hybrid localization scheme that combines received signal strength (RSS) and round-trip time (RTT) information with the aim of improving the previous localization schemes. The hybrid localization scheme is based on an RSS ranging technique that uses RTT ranging estimates as constraints among other heuristic constraints. Once distances have been well estimated, the position of the mobile station (MS) to be located is estimated using a new robust least-squared multilateration (RLSM) technique that combines the RSS and RTT ranging estimates mitigating the negative effect of outliers. The hybrid localization scheme coupled with simulations and measurements demonstrates that it outperforms the conventional RSS-based and RTT-based localization schemes, without using either a tracking technique or a previous calibration stage of the environment. Copyright © 2010 A. Bahillo et al.


Bahillo A.,Center for the Development of Telecommunications | Mazuelas S.,Center for the Development of Telecommunications | Lorenzo R.M.,University of Valladolid | Fernandez P.,University of Valladolid | And 3 more authors.
Eurasip Journal on Wireless Communications and Networking | Year: 2010

The presence of (Non line of Sight) NLOS propagation paths has been considered the main drawback for localization schemes to estimate the position of a (Mobile User) MU in an indoor environment. This paper presents a comprehensive wireless localization system based on (Round-Trip Time) RTT measurements in an unmodified IEEE 802.11 wireless network. It overcomes the NLOS impairment by implementing the (Prior NLOS Measurements Correction) PNMC technique. At first, the RTT measurements are performed with a novel electronic circuit avoiding the need for time synchronization between wireless nodes. At second, the distance between the MU and each reference device is estimated by using a simple linear regression function that best relates the RTT to the distance in (Line of Sight) LOS. Assuming that LOS in an indoor environment is a simplification of reality hence, the PNMC technique is applied to correct the NLOS effect. At third, assuming known the position of the reference devices, a multilateration technique is implemented to obtain the MU position. Finally, the localization system coupled with measurements demonstrates that the system outperforms the conventional time-based indoor localization schemes without using any tracking technique such as Kalman filters or Bayesian methods. Copyright © 2010 Alfonso Bahillo et al.


Mazuelas S.,Center for the Development of Telecommunications | Lago F.A.,University of Valladolid | Fernandez P.,University of Valladolid | Bahillo A.,Center for the Development of Telecommunications | And 3 more authors.
Wireless Personal Communications | Year: 2010

The presence of non-line-of-sight (NLOS) propagation is a key issue that limits the accuracy of wireless location systems. The lack of direct sight causes the measurements obtained by location systems to be so unpredictable that they can produce high inaccuracies in the estimation of the mobile station location. In this paper we propose a novel technique to improve location reliability and accuracy in cases where NLOS propagation is present. For that, in registers of time of arrival (TOA) measurements taken from each base station (BS) in view, we detect the presence of NLOS propagation and estimate the ratio of the measurements coming from NLOS propagation. With this estimate we can assess how much is NLOS propagation affecting the measurements taken from each BS and then we can identify the best measurements and BSs to achieve the highest accuracies in location. © 2009 Springer Science+Business Media, LLC.


Merayo N.,University of Valladolid | Jimenez T.,Center for the Development of Telecommunications | Duran R.J.,University of Valladolid | Fernandez P.,University of Valladolid | And 3 more authors.
Photonic Network Communications | Year: 2010

A novel interleaved polling algorithm for Long-Reach EPONs is proposed in order to simultaneously provide subscriber and class of service differentiation. It is demonstrated that the new polling algorithm applied to a typical 100km Long-Reach EPON performs better than centralized methods, where bandwidth prediction is needed to overcome the higher round trip time in which ONUs cannot transmit. As polling methods in Long-Reach EPONs do not require prediction, they are much simpler and show less computational complexity than centralized schemes, avoiding the inaccuracy of bandwidth prediction. Simulation results show that the new algorithm increases the achieved throughput when compared to centralized algorithms with traffic prediction, obtaining a significant reduction of both mean packet delay and packet loss ratio for the highest priority service level profiles. © Springer Science+Business Media, LLC 2009.


Mazuelas S.,Center for the Development of Telecommunications | Lorenzo R.M.,University of Valladolid | Bahillo A.,Center for the Development of Telecommunications | Fernandez P.,University of Valladolid | And 2 more authors.
IEEE Transactions on Signal Processing | Year: 2010

In wireless location systems deployed in open areas, the statistical distributions of the range estimates are very tractable. However, due to the nature of the wireless propagation in urban and indoor environments, the behavior of the range estimates in such environments is very different. Therefore, the performance assessment results obtained for the systems operating in open areas cannot be transferred to the ones deployed in realistic urban and indoor environments. In this paper, the systematic and random errors (accuracy and precision) and the dilution-of-precision (DOP) in harsh environments are derived for the two most common multilateration algorithms, as well as the performance theoretical benchmark. We show that these quantities are determined by geometric parameters that we call topology-assessment-weighted-barycentric- parameters (TAWBAP), which are the norm of weighted barycenters obtained from the positions of anchors and target. These parameters manage the performance of the multilateration process showing the influence of the geometric configuration in connection with the specific characteristics of each range estimate. The improvement in performance obtained by using the TAWBAP parameters as a network design rule is demonstrated by means of simulations as well as by measurements taken in a real indoor environment. This improvement outperforms at least 25% the one achieved by topology deployments that have been considered as optimal in the literature. © 2010 IEEE.


Bahillo A.,University of Valladolid | Prieto J.,University of Valladolid | Mazuelas S.,Center for the Development of Telecommunications | Lorenzo R.M.,University of Valladolid | And 2 more authors.
IEEE Vehicular Technology Conference | Year: 2010

Due to their availability and cost, Received Signal Strength (RSS) based techniques are the most spread localization schemes when a person who carries an RSS meter is going to be located. However, this techniques are subject to errors associated with perturbations of the fields by the presence of the human body. Although these alterations are complex they are not completely unpredictable. This paper presents a few simple case studies to assess the E-field strength errors caused by the presence of the human body on RSS based localization schemes in a theoretical and experimental approach. It can be concluded that in a common but conservative worst case scenario this error could reach up to 15 dB and therefore it is of concern for analysis. Also, useful insights into the overall problem based on finite-difference time-domain (FDTD) simulations are given. © 2010 IEEE.

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