José Ramón Gállego

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.

Distributed resource allocation in cognitive radio networks with a game learning approach to improve aggregate system capacity

This paper presents a game theoretic solution for joint channel allocation and power control in cognitive radio networks analyzed under the physical interference model. The objective is to find a distributed solution that maximizes the network utility, defined with different criteria, with limited information. The problem is addressed through a non-cooperative game based on local information. Although the existence of a pure Nash Equilibrium cannot be assured for this game, simulation results show that it exists with high probability and with a performance similar to that of a potential game, where each player requires overall network information. The obtained results are compared with a centralized heuristic genetic algorithm to show the correctness of the proposals. From this point, utility functions for the local game are modified to restrict the transmitted power to drive the solution to a more cooperative approach. To overcome the convergence limitations of the local game, no-regret learning algorithms are used to perform the joint channel and power allocation. These algorithms provide stable mixed strategies in any scenario with even better global performance. This opens an interesting perspective to develop realistic protocols based on the modeled interactions and increases the adaptability to perform efficient opportunistic spectrum access.

Distributed Channel Allocation and Power Control in Cognitive Radio Networks Using Game Theory

This paper presents a game theoretic solution for joint channel allocation and power control in cognitive radio networks. The problem is analyzed under the physical interference model. The objective is to find a distributed solution that maximizes the network utility with limited information. We consider different criteria to define this network utility: capacity in bps and number of links fulfilling the SINR requirements. We propose a game with local information that provides similar performance to a potential game that requires global knowledge. The obtained results are compared with a heuristic genetic algorithm to show the correctness of the proposals.

Analysis of closed loop power control modes in UTRA-FDD under time varying multipath channels

Fast power control is perhaps the most important aspect in a WCDMA system like UTRA-FDD. In this paper, closed loop power control procedures in UTRA-FDD are studied. A physical layer simulator, which has been implemented in the C language from the standard of the UTRA-FDD mode, has been the tool to get the results included in this research. Simulations have been made for different mobile speeds (3, 30, 50 and 120 Km/h) getting very different results. Power control gets worse quickly as the mobile speed grows. The implementation of an adaptive algorithm to predict the received power to try to improve the power control has been studied, but large improvements have not been obtained. The probability distribution of the power control error and influence of SIR estimation error have also been studied.

On optimal resource allocation in virtual sensor networks

Sensor network virtualization is a promising paradigm to move away from highly-customized, application-specific wireless sensor network deployment by opening up to the possibility of dynamically assigning general purpose physical resources to multiple stakeholder applications. In this field, this paper introduces an optimization framework to perform the allocation of physical shared resources of wireless sensor networks to multiple requesting applications. The proposed optimization framework aims to maximize the total number of applications which can share a common physical network, while accounting for the distinguishing characteristics and limitations of the wireless sensor environment (limited storage, limited processing power, limited bandwidth, tight energy consumption requirements). Due to the complexity of the optimization problem, a heuristic algorithm is also proposed. The proposed framework is finally evaluated by simulation considering realistic parameters from actual sensor nodes and deployed applications to provide a detailed performance evaluation and to assess the gain involved in letting multiple applications share a common physical network with respect to one-application, one-network vertical design approaches.

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

Performance analysis of diversity transmission modes in UTRA FDD under time-varying multipath channels

This paper analyses the effect of the propagation environment on the theoretical performance of the downlink transmit diversity techniques specified in the standard of the UTRA FDD mode. These techniques are classified as open loop and closed loop modes. Simulation results, obtained via a C simulator of the physical layer of UMTS, show the negative effect of mobility. The diversity gain obtained with the closed loop techniques, which are the best ones, drops drastically when the Doppler frequency rises. In that case, the open loop mode of diversity performs well. Nevertheless, it is highly dependent on the correlation of the antennas, which reduces the theoretical improvement.

Game Theoretic Approach for End-to-End Resource Allocation in Multihop Cognitive Radio Networks

This paper presents a game theoretic solution for end-to-end channel and power allocation in multihop cognitive radio networks analyzed under the physical interference model. The objective is to find a distributed solution that maximizes the number of flows that can be established in the network. The problem is addressed through three different games: a local flow game which uses complete information about the links of the flow, a potential flow game requiring global network knowledge and a cooperative link game based on partial information regarding the links of the flow. Results show that the proposed link game highly decreases the complexity of the channel and power allocation problem in terms of computational load, reducing the information shared between the links forming each flow with a performance similar to that of the more complex flow games.

Joint route selection and resource allocation in multihop wireless networks based on a game theoretic approach

In this work we aim to design simple, distributed self-configuring solutions for the problem of route selection and channel and power allocation in multihop autonomous wireless systems using a game theoretic perspective. We propose and compare three games with different levels of complexity: a potential flow game where players need complete network knowledge, a local flow game requiring full information of the flow and a low complexity cooperative link game which works with partial information of the flow. All these games have been designed to always assure the convergence to a stable point in order to be implemented as distributed algorithms. To evaluate their quality, we also obtain the best achievable performance in the system using mathematical optimization. The system is modeled with the physical interference model and two different definitions of the network utility are considered: the number of active flows and the aggregated capacity in bps. Results show that the proposed games approach the centralized solution, and specially, that the simpler cooperative link game provides a performance close to that of the flow games.

An adaptive location management scheme for mobile broadband cellular systems

This paper presents an adaptive location management strategy that considers both location updating and paging by evaluating realistic mobility patterns. It proposes the design of an adaptive macro-location area based on multi-registration adapted to the terminals’ trajectory to reduce location updates. The solution includes an estimation of residence probabilities in the areas of the multi-registered list. This facilitates the design of a sequential paging scheme that reduces the average paging cost. Results show the capability of the solution to adapt to mobility patterns and traffic conditions in the network to minimize the overall location cost. Furthermore, the multi-registration approach and the reduced complexity in both network infrastructure and mobile terminals make the solution suitable for new packet-based broadband cellular systems.