The 5G mobile networks are expected to offer higher degrees of radio access heterogeneity across a wide range of technologies (LTE, WiFi, mmWave, etc.), which operate in both licensed and unlicensed spectrum providing dissimilar data rates and coverage. In light of the stringent requirements in terms of resource and energy efficiency, the performance optimization of such heterogeneous 5G systems becomes an involved task that demands abundant information on the states of users to solve a complex, large-scale optimization problem. However, the unpredictable mobility of communicating entities, including dual mobility of D2D partners, may lead to a rapid deviation from the initial, optimized system state and thus requires frequent re-optimizations of the entire network. In this article, we aim to deliver a comprehensive tutorial on the implications of system-wide energy and resource management with the emphasis on its time-dependent behavior. Proposing a novel network-centric 5G optimization framework, we employ insights from the random walk and Markov chain theories, and also confirm our findings with an extensive system-level simulation campaign. These results reveal an exponential performance degradation rate that primarily depends on the average user speeds. Together with reporting the divergence exponents for different 5G system configurations, we also provide practical insights into how to exploit them in order to non-incrementally improve the throughput and energy performance of the network.

The aggressive spatial reuse of radio resources is considered today as one of the most promising avenues to achieve significant cellular capacity improvements in future fifth-generation networks. Accordingly, device-to-device (D2D) communications are an emerging paradigm that promises to offer these much expected gains without the need for additional investments into the network infrastructure. However, before this attractive technology can be deployed ubiquitously, the research community has to fully understand the extent of its potential performance benefits across typical scenarios of interest. In this work, we consider one such use case of rectangular cells (common for offices, shopping malls, dormitories, etc.) and develop the corresponding analytical methodology for D2D performance evaluation. As our target metric, we employ the signal-to-interference (SIR) ratio experienced by a D2D user. To this end, we propose two relatively simple approximations for SIR distribution and hence capture the related parameters, including user throughput. Further, we carefully investigate the most interesting numerical results by making important conclusions on the envisioned operation of our chosen scenario. In particular, we demonstrate that under certain conditions, the SIR behaviour is insensitive to the dimensions of cells, while different propagation exponents 'scale' its density function thus allowing to simplify the characterisation of SIR in a wide range of input parameters. Copyright (C) 2015 John Wiley & Sons, Ltd.

The problem of channel quality estimation for devices in a wireless 5G network is formulated. As a performance metrics of interest we choose the signal-to-interference-plus-noise ratio, which depends essentially on the distance between the communicating devices. A model with a plurality of moving devices in a bounded three-dimensional space and a simulation algorithm to determine the distances between the devices for a given motion model are devised.

We suggest a convolution algorithm for calculating the normalization constant for stationary probabilities of a multiserver queuing system with random resource requirements. Our algorithm significantly reduces computing time of the stationary probabilities and system characteristics such as blocking probabilities and average number of occupied resources. The algorithm aims to avoid calculation of k-fold convolutions and reasonably use memory resources.

This paper explores so called "View-Upload Decoupling scheme" which strictly decouples data to what peer uploads and what it personally views. It is based on the split of downloaded user data streams into two types: the stream of the chosen TV channel and the stream (one or more) of the other TV channel, exclusively, to deliver it to other users. We developed a method for calculating one of the key QoS characteristics in P2P streaming network - the probability of universal streaming for each channel and a system-wide universal streaming across all channels. The statistical probability results of universal streaming for the VUD scheme compared to the traditional redistributing ISO scheme are presented.

In this paper an approach to analysis of dependence of Session Initiation Protocol server model with batch arrivals performance measures on batch size distribution is considered. Proposed approach employs non-parametric methods of statistical analysis. It is shown that there is statistical reliable dependence of performance measures, taken for signaling traffic analysis, on distance between distributions in definite norm. On the basis of proposed analysis elasticity coefficients were evaluated depending on distance between batch size distributions. This approach enables to get correction factors for estimation of these parameters in case distribution functions differ from uniform. © Springer International Publishing Switzerland 2016.

Growing popularity of cloud services is explained by many advantages of them. The accessibility, flexibility, scalability, ease of management, the relatively low cost of implementation can be listed among the main advantages. The demand for cloud services with the ability to change one cloud service provider to another one without any significant cost for a user result in a high competition between cloud providers. Due to this reason, it became important to find the optimal performance measures of cloud systems. These measures, on the one hand, must meet all the requirements of Service Level Agreement (SLA), on the other hand, do not lead to excessive costs for provider. The paper presents the evaluation of the main service quality characteristics of cloud systems, including formulas for variance of residence time in the synchronization buffer. For the analysis of a cloud system, fork-join queues with corresponding methods of its approximation were used.