Abstract-In cloud environments, resources can be requested on-demand when they are needed. A cloud management system is responsible for determining which physical machines are responsible for processing the requests. The problem of determining which servers are used for which services is referred to as the Cloud Application Placement Problem (CAPP), and multiple criteria such as cost and number of migrations must be taken into account. When applications are constructed as a collection of communicating services, such as in Service-Oriented Architectures, it becomes important to take the underlying network properties into account when these placement decisions are made. In this paper, we propose an Integer Linear Programming (ILP) formulation for the CAPP, which optimizes multiple criteria such as cost, latency and number of migrations between subsequent invocations by using multiple optimization criteria. We also present hierarchical algorithms based on particle swarm optimization and genetic algorithms to solve the CAPP. These algorithms are be executed within a management hierarchy, which reduces the amount of information needed for the algorithms to function, increasing scalability of the management system. Finally, we evaluate the hierarchical algorithms by comparing them to an optimal algorithm based on the ILP formulation.

This paper presents an analysis of the polarization characteristics of specular and dense multipath components (SMC & DMC) in a large industrial hall based on frequency-domain channel sounding experiments at 1.3 GHz with 22 MHz bandwidth. The RiMAX maximum-likelihood estimator is used to extract the full polarimetric SMC and DMC from the measurement data by taking into account the polarimetric radiating patterns of the dual-polarized antennas. Cross-polar discrimination (XPD) values are presented for the measured channels and for the SMC and DMC separately.

Abstract-The electromagnetic reverberation time characteristics of indoor environments are experimentally investigated from 2 to 10 GHz with bandwidths up to 900 MHz. At a given frequency, the reverberation time is observed to be approximately constant up to 900 MHz. Moreover, the reverberation time decreases for increasing frequencies. Based on the theory of electromagnetic fields in cavities, a model to predict the room quality factor, reverberation time value, and average absorption coefficient is developed for the first time in indoor environments for the investigated frequency range. The validity and robustness of the model is investigated with data obtained for various environments, central frequencies, and bandwidths. The model is applied to another room over the whole 2-10 GHz frequency band and a maximum and average relative error of 22.30% and 8.80% were obtained, respectively, with an rms error of 1.90 ns. Furthermore, good agreement is obtained with measurements reported in the literature with settings falling into the model range; scenarios for which relative errors smaller than 10% were computed. The results demonstrate that this approach is not only an accurate alternative to the reverberation time measurements and computations of indoor environments in the 2-10 GHz frequency range but also a viable route to link propagation mechanisms in indoor scenarios with reverberation chambers.

This work presents a novel localization framework based on Ultra-Wideband (UWB) channel sounding, employing a triangulation method using the geometrical properties of propagation paths, such as time of arrival, angle of departure, angle of arrival, and their estimated variances. In order to extract these parameters from the UWB sounding data, an extension to the high-resolution RiMAX algorithm was developed, facilitating the analysis of these frequency-dependent multipath parameters. This framework was then tested by performing indoor measurements with a vector network analyzer and virtual antenna arrays. The estimated means and variances of these geometrical parameters were utilized to generate multiple sample sets of input values for our localization framework. Next to that, we consider the existence of multiple possible target locations, which were subsequently clustered using a Kim-Parks algorithm, resulting in a more robust estimation of each target node. Measurements reveal that our newly proposed technique achieves an average accuracy of 0.26 m, 0.28 m and 0.90 m in Line-of-Sight (LoS), Obstructed-LoS (OLoS), and Non-LoS (NLoS) scenarios, respectively, and this with only one single beacon node. Moreover, utilizing the estimated variances of the multipath parameters proved to enhance the location estimation significantly compared to only utilizing their estimated mean values.

Abstract-This work presents a novel localization scheme based on Ultra-Wideband (UWB) channel sounding, employing a triangulation method that makes use of the geometrical properties of propagation paths, such as time of arrival (ToA), angle of departure (AoD) and angle of arrival (AoA). An extension to the high-resolution RiMAX algorithm was developed, facilitating the analysis of UWB frequency-dependent propagation parameters, allowing for the localization of a target node in Line-of-Sight (LoS), Obstructed-LoS (OLoS), and Non-LoS (NLoS) scenarios.

This work presents a measurement-based polarimetric analysis of the specular-and dense multipath components (SMCs and DMC) in a large industrial warehouse. MIMO channel sounding measurements were carried out in a flower auction warehouse, and were processed with the RiMAX multipath estimation framework. In the analysis, we investigate the behavior of the SMCs and the DMC power as a function of both the polarization and the transmitter-receiver distance for 1507 distinct positions of transmitter and receiver. The cross-polar discrimination of the transmitted V and H polarizations were analyzed statistically for this environment, as well as the relative power ratio of the DMC, and the DMC reverberation time.

This work presents an extension of the high-resolution RiMAX multipath estimation algorithm, enabling the analysis of frequency-dependent propagation parameters for ultra-wideband (UWB) channel modeling. Since RiMAX is a narrowband algorithm, it does not account for the frequency-dependency of the radio channel or the environment. As such, the impact of certain materials in which these systems operate can no longer be considered constant with respect to frequency, preventing an accurate estimation of multipath parameters for UWB communication. In order to track both the specular and dense multipath components (SMC and DMC) over frequency, an extension to the RiMAX algorithm was developed that can process UWB measurement data. The advantage of our approach is that geometrical propagation parameters do not appear or disappear from one sub-band onto the next. The UWB-RiMAX algorithm makes it possible to re-evaluate common radio channel parameters for DMC in the wideband scenario, and to extend the well-known deterministic propagation model comprising of SMC alone, towards a more hybrid model containing the stochastic contributions from the DMC’s distributed diffuse scattering as well.Our algorithm was tested with synthetic radio channel models in an indoor environment, which show that our algorithm can match up to 99% of the SMC parameters according to the multipath component distance (MCD) metric and that the DMC reverberation time known from the theory of room electromagnetics can be estimated on average with an error margin of less than 2 ns throughout the UWB frequency band. We also present some preliminary results in an indoor environment, which indicate a strong presence of DMC and thus diffuse scattering. The DMC power represents up to 50% of the total measured power for the lower UWB frequencies and reduces to around 30% for the higher UWB frequencies.

Abstract-Security is not taken into account by default in the Representational State Transfer (REST) architecture, but its layered architecture provides many opportunities for implementing it. In this paper, a security mechanism for Web service communication through mobile clients devices is proposed, that conforms to the REST architecture as much as possible. Results indicate that the custom security mechanism outperforms the Transport Layered Security (TLS) based system. Because of the genericness of REST, the proposed security mechanism can be adopted by a wide variety of other RESTful Web services.