Section: New Results

Agile Radio Resource Sharing

The contributions of the axis in agile radio resource sharing can be gathered in three groups: (a) green communications; (b) performance analysis; and (c) scheduling and power allocation techniques.

The main contributions in the subject of green communications focus on the problem of increasing the energy efficiency of Orthogonal Frequency-Division Multiple Access (OFDMA) wireless networks. In particular, Tsilimantos et al. in [21] and Hasan et al. in [15] studied different techniques to strategically switch off some of the base stations in cellular systems while guaranteeing a given quality of service (QoS). In [21] , the authors use methods from stochastic geometry to determine the number of active cells that can be switched off while the outage probability, or equivalently the signal to interference plus noise ratio (SINR), remains the same. In [15] , this problem is studied from a decentralized point of view using methods from coalitional game theory.

The contributions in performance analysis are mainly oriented to the field of body area networks (BANs), [17] indoor adaptive OFDM wireless networks and relay channels.

In [17] , Lauzier et al. presented the results of a measurement campaign whose primary objective was to characterize the complete mesh of a BAN and analyze the quality of every radio link between the different nodes. In [18] , [19] , the Multi-Resolution Frequency Domain ParFlow (MRFDPF) model is used to calculate the bit error rate (BER) and study the feasibility of adaptive modulation in OFDM systems.

In the context of relay channels, Ferrand et al. [32] studied the asymptotic coding gain of the packet error rate of relay channels in which the radio links are subject to both fading and log-normal shadowing effects simultaneously.

Power allocation techniques and scheduling were studied by Ferrand et al. [33] and Wang et al. [9] . More specifically, advances in the study of the achievable rate region of relay channels in the case of global power constraints were reported in [33] . Cooperative scheduling techniques in the context of BAN were proposed in [9] to reduce inter-BAN interference using tools from game theory.