Spatial SINR Games of Base Station Placement and Mobile Association

We study the question of determining locations of base stations that may belong to the same or to competing service providers. We take into account the impact of these decisions on the behavior of intelligent mobile terminals who can connect to the base station that offers the best utility. The signal to interference and noise ratio is used as the quantity that determines the association. We first study the SINR association-game: we determine the cells corresponding to each base stations, i.e., the locations at which mobile terminals prefer to connect to a given base station than to others. We make some surprising observations: (i) displacing a base station a little in one direction may result in a displacement of the boundary of the corresponding cell to the opposite direction; (ii) A cell corresponding to a BS may be the union of disconnected sub-cells. We then study the hierarchical equilibrium in the combined BS location and mobile association problem: we determine where to locate the BSs so as to maximize the revenues obtained at the induced SINR mobile association game. We consider the cases of single frequency band and two frequency bands of operation. Finally, we also consider hierarchical equilibria in two frequency systems with successive interference cancellation

Investigations on Fe3+ doped polyvinyl alcohol films with and without gamma (γ)-irradiation

This paper deals with the preparation of pure and ferric chloride (FeCl3) doped polyvinyl alcohol (PVA) films by solution casting method. Optical and electrical properties were systematically investigated. We have found the decrease in optical band gap energy of PVA films on doping FeCl3. The optical band gap energy values in the present work are found to be 3.10 eV for pure PVA, 2 eV for PVA:Fe3+ (5 mol%), 1.91 eV for PVA:Fe3+(15 mol%) and 1.8 eV for PVA:Fe3+(25 mol%). Direct current electrical conductivity (σ) of pure, FeCl3 doped PVA films in the temperature range 70–127 °C has been studied. At 387 K dc electrical conductivity of pure PVA film is 5.5795 μ Ω−1 cm−1, PVA:Fe3+ (5 mol%) film is 10.0936 μ Ω−1 cm−1 and γ-Irradiated PVA:Fe3+ (5 mol%) film for 900 CGY/min is 22.1950 μ Ω−1 cm−1. The result reveals the enhancement of the electrical conductivity with γ-irradiation. FT-IR study signifies the intermolecular hydrogen bonding between Fe3+ ions of FeCl3 with OH group of PVA

Temperature dependence of pure quadrupole resonance of 35Cl in α-CH2ClCOOH

Measurements of the pure quadrupole resonance frequency of 35Cl in CH2ClCOOH have been made over a wide range of temperature (77K to 300K). Two resonance lines due to chemically inequivalent sites have been observed throughout the above temperature range

Thermoluminescence, optical absorption and ESR studies in (KCl)1-x(KBr)x mixed alkali halide crystals doped with gold

Mixed crystals of KCl–KBr of different compositions were grown with Czochralski technique. Crystals were doped with gold. Both the undoped and gold doped crystals were γ γ -irradiated using 60 Co 60 Co source. All the irradiated samples were subjected to thermoluminescence, optical absorption and ESR studies. The present study shows the composition dependence of the parameters and enhancement in the luminescence intensity as well as the absorption coefficient with gold doping. Non-linear variation of color center peak position and half band width of F-center with composition has been observed. The results of the above studies are presented in this paper

Caching Contents with Varying Popularity using Restless Bandits

We study content caching in a wireless network in which the users are connected through a base station that is equipped with a finite-capacity cache. We assume a fixed set of contents whose popularity varies with time. Users' requests for the content depend on their instantaneous popularity levels. Proactively caching contents at the base station incurs a cost but not having requested contents at the base station also incurs a cost. We propose to proactively cache contents at the base station so as to minimize content missing and caching costs. We formulate the problem as a discounted cost Markov decision problem that is a restless multi-armed bandit problem. We provide conditions under which the problem is indexable and also propose a novel approach to maneuver a few parameters to render the problem indexable. We demonstrate the efficacy of the Whittle index policy via numerical evaluation

Modelling the hydromechanical response in the vicinity of the Koyna reservoir (India): results for the initial filling period

International audienceThe seismic activity in the Koyna area is clearly related to the water impoundment of the Koyna dam in 1962, and has reached a remarkable level with the occurrence of a major event of magnitude 6.3 in 1967 December 10. We present a homogeneous poroelastic model based on analysis of the first eight years of seismicity, which aims to link the water-level fluctuations of the reservoir with the seismicity. Starting from a discretized lake,we calculate the stress field resulting from the water-level fluctuations and the pore pressure changes due to the undrained and the diffusive responses of the medium. Then, we compare the Coulomb stress variations with a set of relocated seismic events. We find that more than 80 per cent of the relocated events before the M6.3 event are well described by this poroelastic model, leading us to derive a suitable diffusivity cp = 0.2m2 s-1. Then, we model the response of the system after the M6.3 event of 1967 December 10, by comparing the variation of the Coulomb stress field with the spatio-temporal characteristics of the relocated post-seismic events and the decay of aftershocks with time. We find that compared to before the main event a tenfold increase in hydraulic diffusivity is required to satisfactorily describe the aftershock decay with the appropriate Omori exponent. Although this increase in diffusivity may be physically related to the main shock we also note that events later than 9 months after the main shock are not well explained. We therefore propose an alternative hydrological model, which involves two compartments of contrasting diffusivities

A coalitional game model for spectrum pooling in wireless data access networks

We consider a setting in which several operators offer downlink wireless data access services in a certain geographical region. Each operator deploys several base stations or access points, and registers some subscribers. In such a situation, if operators pool their infrastructure, and permit the possibility of subscribers being served by any of the cooperating operators, then there can be overall better user satisfaction, and increased operator revenue. We use coalitional game theory to investigate such resource pooling and cooperation between operators.We use utility functions to model user satisfaction, and show that the resulting coalitional game has the property that if all operators cooperate (i.e., form a grand coalition) then there is an operating point that maximizes the sum utility over the operators while providing the operators revenues such that no subset of operators has an incentive to break away from the coalition. We investigate whether such operating points can result in utility unfairness between users of the various operators. We also study other revenue sharing concepts, namely, the nucleolus and the Shapely value. Such investigations throw light on criteria for operators to accept or reject subscribers, based on the service level agreements proposed by them. We also investigate the situation in which only certain subsets of operators may be willing to cooperate