Ángela Hernández-Solana

Performance analysis of multiplexed medical data transmission for mobile emergency care over the UMTS channel

In this paper, a third-generation universal mobile telecommunications system (UMTS) solution for the delivery of biomedical information from an ambulance to a hospital is presented. The joint transmission of voice, real-time video, electrocardiogram signals, and medical scans in a realistic cellular multiuser simulation environment is considered, taking into account the advantages and particularities of UMTS technology for such transmission. The accomplishment of quality of service constraints for different services is investigated and quantitative results are provided in order to demonstrate the feasibility of using UMTS technology for emergency care services on high-speed moving ambulance vehicles.

Comparison of Algorithms for UWB Indoor Location and Tracking Systems

With the popularity of navigation applications and the integration of GPS in user devices, location-awareness is becoming an essential feature demanded by users. Nevertheless, location-awareness in indoor environments is still limited by the inability of GPS to operate indoors. With a centimeter-level ranging resolution, Ultra-Wideband (UWB) is one of the most promising technologies to provide indoor location. Several location & tracking algorithms have been proposed in the literature to compute users position according to the estimated distances to some reference nodes, each one providing the best performance in certain conditions. Nevertheless, most of these proposals are evaluated under too specific or simplistic conditions that do not account realistically for the specific implications of the UWB-based distance estimation and the indoor environment. This paper aims to evaluate the performance of different location and tracking algorithms on a realistic indoor scenario and with a specific UWB indoor ranging model, analyzing their advantages and drawbacks in relation to different conditions and system design parameters.

Cross-Layer Routing for QoS Provision in Multiservice Mobile Ad Hoc Networks

The high development that mobile networks and the provided services have experienced in the last few years has involved a great scientific and technical effort in order to support quality of service mechanisms for mobile users. In the case of mobile ad hoc networks (MANETs) this effort is even more noticeable due to the complexity of the dynamic environment of these networks. An appropriate resource allocation capable of integrating multimedia services with different requirements implies the design of efficient call admission control (CAC) techniques that in this ad hoc scenario require a distributed operation. This operation can be performed through a QoS routing process based on a cross-layer design. The interlayer cooperation allows to define new QoS metrics that reflect the network resource utilization and a bandwidth reservation carried out according to the different service demands during the path discovery guarantees the quality of the admitted connections

Radio resource strategies for uplink inter-cell interference fluctuation reduction in SC-FDMA cellular systems

In this paper we propose three different frequency resource management strategies that, working together with FFR and open-loop Fractional Power Control (PFC), succeed on mitigating both uplink inter-cell interference (ICI) and ICI fluctuations, that usually reduce the performance of SC-FDMA cell-based systems. Simulations are carried out with real-time traffic patterns at different loading scenarios, showing that our strategies outperform a typical FFR scheme suggested to coordinate frequency assignments among neighboring cells.

Evaluation of algorithms for UWB indoor tracking

Ultra-Wideband (UWB) stands out as one of the most promising technologies for the development of indoor location & tracking systems, providing very precise time of arrival measurement and consequently centimeter-level resolution in distance estimation. Once the distances to multiple reference nodes are estimated, several location & tracking algorithms can be used to compute users position. Position calculation is a widely studied topic, and many different methods have been proposed in the literature and evaluated under different conditions. Nevertheless, evaluation scenarios are usually generic and too simplistic. The rigorous evaluation of location & tracking algorithms should take into account the specific error distribution of UWB-based distance estimation and the implications of indoor tracking scenarios, such as users mobility, the number of reference nodes and the distance between them. The objective of this paper is to provide a realistic evaluation of the performance of different location & tracking algorithms (trilateration, least square — multidimensional scaling, extended Kalman filter and particle filter) in indoor environments using a specific UWB-based ranging model to characterize the distribution of distance estimation error.

Coexistence of MB-OFDM UWB with Impulse Radio UWB and other radio systems

The level of interference caused by Ultra-Wideband (UWB) systems in current radio services has been widely studied, both theoretically and with measurement campaigns, although most of them focus on pulse-based UWB systems. This paper presents experimental results on the coexistence of Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB systems when they are working in close proximity to other radio technologies such as UMTS, WiMAX, LTE, WiFi, Bluetooth and ZigBee. As restrictive spectrum masks have been imposed to UWB, no degradation is detected on those systems except for WiMAX as it operates in the same frequency band. On the other hand, MB-OFDM may be disturbed even by systems operating in a different frequency band due to spurious out-of-band emissions. The coexistence between MB-OFDM and Impulse Radio (IR) UWB systems is also addressed and experimental results are presented showing that IR UWB may interfere with MB-OFDM UWB systems causing a degradation on Packet Error Rate, which is limited due to the low activity factor of IR UWB.

An adaptive location management scheme for mobile broadband cellular systems

In this paper, we propose and evaluate under realistic mobility patters an adaptive location management strategy that jointly considers location update and paging. It requires little involvement of the terminal, and a non excessive computational load in the network. The location update scheme is based on the definition of an adaptive macro-location area, adapted to the mobility pattern of the terminals. In addition, we propose a sequential paging strategy that takes advantage of the multi-register in the macro-location area to characterize the residence probabilities in each location area of a generic macro area. Results show the viability of the proposal and its applicability to new packet-based broadband cellular systems.

Adaptive paging schemes for group calls in mobile broadband cellular systems

In this paper, we analyze the problem of efficient paging for group call searches under realistic mobility patterns. Taking as a basis a location update scheme, based on the definition of an adaptive macro-location area, adapted to the mobility pattern of the terminals, we characterize the residence probabilities in each location area of a generic macro-area. With this information, we propose and evaluate different sequential group paging strategies, also taking into account their computational cost. Results show the suitability of some of the proposals (semiadaptive and hybrid schemes) and its applicability to new packet-based broadband cellular systems.

Performance evaluation of cross-layer routing for qos support in mobile ad hoc networks

Mobile ad hoc networks (MANETs) appear nowadays as one of the most promising architectures to flexibly provide multimedia services in multiple wireless scenarios. However, the dynamic nature of this environment complicates the supporting of the heavily demanded QoS. Since cooperation in MANETs is required to establish multihop communications, designing efficient QoS Routing algorithms mainly concentrates the technical efforts to guarantee QoS. This work presents a cross-layer architecture that performs a practical solution to solve the trade-off between the QoS provision and the efficient resource utilization thanks to different layers sharing network status information to cooperate in the network resource management. The cooperation between Routing and MAC levels allows to select End-to-End QoS paths according to the bandwidth availability measured in a realistic interference scenario, and appropriately react to mobility in a QoS context.

Interference-aware routing with bandwidth requirements in mobile ad hoc networks

Mobile ad hoc networks are expected to deal with diverse multimedia applications demanding heavily QoS requirements. Several QoS routing algorithms have been proposed. However, most of these solutions do not take into account bandwidth demands and the quality of the selected paths in the routing process itself. We present an interference-aware QoS routing which considers the bandwidth demand based on a proposed QoS metric. A cross-layer design allows to perform this metric taking into account updated information of the interference and bandwidth environment. A multipath operation is performed so multiple paths with available bandwidth are formed during the route discovery process. By using the proposed metric it is possible to choose the best QoS route among several paths therefore performing a more appropriate resources allocation - distributed Call Admission Control (CAC) Nowadays, mobile ad hoc networks are expected to deal with diverse multimedia applications demanding QoS. In order to provide quality delivery to these applications, several QoS routing approaches (1) - (4) have been proposed, but it is still a challenging task due to the complexity of the dynamic environment of these networks. In order to facilitate QoS support in ad hoc networks, it is very important to solve the tradeoff between guaranteeing the requirements for the QoS provision with the best efficiency in the use of the networks resources. A cross-layer design tries to combine the functionality of the Routing layer with Medium Access Control (MAC) information and physical layer parameters to provide the routing algorithm with the more accurate information about the current status of the links in order to find the more appropriate path that is able to guarantee the QoS requirements during the whole connection. The proposed QoS routing includes a multipath approach to evaluate the possible available paths for a new connection differentiating them through a QoS metric, considered as a measurement of the bandwidth availability and the interference scenario. The operation of the proposed interference-aware routing algorithm in conjunction with an effective resource allocation in the MAC layer works as a distributed admission control (CAC) so that new QoS demanding applications can be efficiently allocated resources at the expense of the least QoS constrained connections, without disrupting the already QoS active ones. The remaining of the paper is organized as follows. Section II provides an introduction to the proposed QoS routing algorithm. Section III summarizes the effects of considering an interference-aware scenario. Simulation results are evaluated in Section IV and finally, some conclusions are provided in Section V. II. THE QOS ROUTING ALGORITHM