Konstantin Samouylov

Time-Dependent SIR Modeling For D2D Communications In Indoor Deployments.

Device-to-device (D2D) communications is expected to become an integral part of the future 5G cellular systems. The connectivity performance of D2D sessions is heavily affected by the dynamic changes in the signal-to-interference ratio (SIR) caused by random movement of communicating pairs over a certain bounded area of interest. In this paper, taking into account the recent findings on the movement of users over a landscape, we characterize the probability density function (pdf) of SIR under stochastic motion of communicating D2D pairs on planar fractals. We demonstarte that the pdf of SIR depends on the fractal dimension and the spatial density of trajectories. The proposed model can be further used to investigate timedependent user-centric performance metrics including the link data rate and the outage time.

Busy Period Analysis of a Queueing System with Breakdowns and Its Application to Wireless Network Under Licensed Shared Access Regime

Licensed shared access (LSA) framework is becoming one of the promising trends for future 5G wireless networks. Two main parties are involved in the process of sharing the frequency band – the primarily user (owner) and the secondary user (licensee). From the LSA licensee’s perspective, who has access to the band when the owner does not need it, the band is unreliable and its customers (e.g. users of wireless network) suffer from possible service interruptions. This can only occur when there is at least one customer in service (i.e. in busy period). The aim of this paper is to estimate the impact of the LSA band unreliability to the LSA licensee within the period when some interruptions are possible. The metric is the relation between the number of service interruptions and the number of customers served during a busy period. We model the occupancy of the LSA band as a multi-server homogeneous queueing system with finite and infinite buffer size and deal with the busy period analysis. The system is analyzed in steady state by deriving expressions in terms of the Laplace-Stiltjes transforms for the continuous time distributions and in terms of the probability generating functions for the number of customers served during a busy period and number of failures which occur in a busy period. The non-monotonic nature of some probabilistic measures is identified. Some illustrative examples are added to the paper.

Queuing Model with Unreliable Servers for Limit Power Policy Within Licensed Shared Access Framework

Shared access to spectrum by several parties seems to become one of the most promising approaches to solve the problem of radio spectrum shortage. The framework proposed by ETSI, licensed shared access (LSA), gives the owner absolute priority in spectrum access, to the detriment of the secondary user, LSA licensee. The latter can access the spectrum only if the owner’s QoS is not violated. If the users of both parties need continuous service without interruptions, the rules of shared access should guarantee the possibility of simultaneous access. Balancing the radio resource occupation between parties could take quite a long time compared to the dynamics of the system due to the coordination process by the national regulation authority (NRA). We examine a scheme of the simultaneous access to spectrum by the owner and the LSA licensee that minimizes the coordination activities via NRA. According to this scheme, when the owner needs the spectrum, the power of the LSA licensee’s eNB/UEs is limited. From the LSA licensee’s perspective, the scheme is described in the form of a queuing system with reliable (single-tenant band) and unreliable (multi-tenant band) servers. We show that the infinitesimal generator of the system has a block tridiagonal form. The results are illustrated numerically by estimating the average bit rate of viral videos, which varies due to aeronautical telemetry corresponding to the owner’s traffic.

Analysis of Business Process Execution Time with Queueing Theory Models

In the paper an approach to the analysis of business process efficiency is proposed. A method for the estimation of a business process execution time as an important performance measure of business processes efficiency is developed. It represents a combination of queuing networks modelling and simplex algorithm of linear programming. The method allows the calculating of the minimum business processes execution time. A method of optimizing activity of the telecommunication company at a predetermined threshold for the business processes execution time is given. The developed technique was illustrated with an end-to-end business process flow “Request-to-Answer” with initial data close to reality.

SIR Distribution In D2D Environment With Non-Stationary Mobility Of Users.

Fifth generation (5G) cellular systems are expected to rely on the set of advanced networking techniques to further enhance the spatial frequency reuse. Device-todevice (D2D) communications is one of them allowing users to establish opportunitic direct connections. The use of direct communications is primarily determined by the signal-to-interference ratio (SIR). However, depending on the users movement, the SIR of an ative connection is expected to drastically fluctuate. In this work we develop an analytical framework allowing to predict the channel quality between two moving entities in a filed of moving interfering stations. Assuming users movement driven by Fokker-Planck equation we obtain the empirical probability density function of SIR. The proposed methodology can be used to solve problems in the area of stochastic control of D2D communications in cellular networks. INTRODUCTION The need for higher capacity at the air interface in next generation mobile cellular systems calls for efficient ways of utilizing available frequency bands. Together with widening the bands itselves by moving upper in the frequency band to millimeter wave spectrum, one of the trends nowadays is developing of new techniques improving the use of available spectrum, e.g., increasing the base stations density via using the micro-, picoand femto-cells, and enabling user devices to communicate directly with one another by establishing direct deviceto-device (D2D) connections. The latter is the focus of this work. The contemprorary cellular systems, such as GSM and LTE, are interference-limited in anture, implying that the link quality between two nodes highly depends on other nearby nodes using the same frequency, as their signal will literally interfere with the link of interest. As a result, the critical metric of interest for such systems characterizing the link quality is the signal-tointerference (SIR) ratio. A given level of SIR upper bounds the maximum capacity of a link. Furthermore, whenever SIR downcrosses some threshold it becomes impossible to maintain stable connection. In this paper, we study the evolution of SIR for a pair of devices as a function of mobility, assuming that all the devices, including those of interest and interfering ones, are mobile. We formulate the framework that enables us to describe the analytical properties of SIR as a function of movement trajectories. The proposed methodology not only forms the basis for analysis of statistical properties of SIR but potentially allows for stochastic control SIR functional. The future cellular system may contain advanced functionality of advising users to move in a certain derection to improve the channel quality. In this case, the framework offers the prossibility of functional modeling on the moving bodies trajectories. The case when the trajectories depend on the functional is of particular interest. Proceedings 31st European Conference on Modelling and Simulation ©ECMS Zita Zoltay Paprika, Péter Horák, Kata Váradi, Péter Tamás Zwierczyk, Ágnes Vidovics-Dancs, János Péter Rádics (Editors) ISBN: 978-0-9932440-4-9/ ISBN: 978-0-9932440-5-6 (CD) GENERATING TRAJECTORIES OF NONSTATIONARY RANDOM WALKS Consider a process with a non-stationary probability distribution function (pdf) and a given evolution equation. The method for generating a trajectory of the random process with thse properties has been proposed in (Bosov et al. 2014). In (Orlov 2014, Orlov and Fedorov 2016) it has been extended to generating an trajectories, whose pdf is evolving according to a given kinetic equation. The software tool for generating an ensemble of random non-stationary trajectories and performing their statistical analysis has been introduced in (Orlov and Fedorov 2016, Fedorov and Orlov, 2016). Below, we describe the key points of the developed methodology. Let pdf ) , ( t x f be defined by a kinetic equation. Consider the Fokker-Plank equation, 0 2 ) ( ) ) , ( ( 2 2 uf03d uf0b6 uf0b6 uf02d uf0b6 uf0b6 uf02b uf0b6 uf0b6 x f t f t x u x t f uf06c . (1) This equation can be solved numerically for a given initial condition, ) ( ) , ( 0 x t x f t uf072 uf03d uf03d . The solution of (1) is based on the time horizon T . For the sake of simplicity, choose a unit time step. At each time instant T t ..., , 2 , 1 uf03d a random number is generated from the cumulative distribution function (CDF) uf028 uf029 uf0f2 uf03d x dy t y f t x F 0 ) , ( , . (2) When the solution of (1) is represented as a histogram ) (t f j , where j is the number of class intervals, the continuous strictly monotonic CDF has the form uf028 uf029 , ) ( ) ( ) , ( 1 1 uf0e5 uf03d uf02b uf02b uf0d7 uf02d uf03d j k k j t f t f j nx t x F (3) for ] / ; / ) 1 [( n j n j x uf02d uf0ce , n j ,.., 1 uf03d . The algorithm for generating a sequence of random numbers, forming a feasible trajectory of the time series for a predetermined time interval is as follows. First, generate a series of random numbers, } { k y , of length T having uniform distribution in ] 1 , 0 [ . The series with CDF ) , ( t x F is obtained by combining the numerical inverse transform method with sliding window of length T , that is, uf028 uf029 k x F y k N k , uf03d . (4) Generating a set of samples, we obtain the set of trajectories that can be considered as an ensemble of solutions of the kinetic equation. STATISTICAL ANALYSIS OF FUNCTIONAL ON THE ENSEMBLE OF TRAJECTORIES Consider SIR functional defined as a function of the distance between the moving points. The positions of these points form an ensemble of trajectories of a random process. Let uf061 i x be a position of point i in a certain region of a three-dimensional space, where the superscript uf061 labels (x,y,z) coordinates . The number of points in the system is 2 uf02b N . Let also ij r be the distance between the points, calculated in the Cartesian coordinate system as

Analysis of Resource Sharing Between MBB and MTC Sessions with Data Aggregation Using Matrix-Analytic Methods and Simulation

Mobile broadband (MBB) and ubiquitous machine type communications (MTC) appear essential in future 5G networks, however their requirements in terms of data rate, expected number of users, latency and reliability are largely contradictory, which constitutes a major challenge for 5G architecture design. MTC data aggregation via device clustering may prevent signaling congestion due to a massive number of MTC devices in the cell. Resource sharing between MBB and MTC sessions with MTC data aggregation can be modeled using a multi-service loss system, however its numerical analysis is impeded due to the considerable difference in scales of MBB and MTC parameters. In the paper, we use simulation to assess the performance measures of the loss system and its more realistic modification. Cases of light, moderate and heavy MTC loading and various parameters of the MMPP of MTC arrivals are considered.

Modeling End-to-End Business Processes of a Telecom Company with a BCMP Queueing Network

A thorough analysis of business processes allows a communication and digital service provider to reduce costs and to carry out digital transformation efficiently, which are important factors of the telecommunication business success. Massive numbers of randomly arriving customer requests, real-time service and standardized and highly automated procedures make telecommunication company business processes a good subject for analysis using queueing theory. Such an analysis is facilitated by the extensive body of standards, developed by the global telecommunication industry association TM Forum and addressing various service business management issues. We propose an approach to estimating certain important TM Forum business metrics and other business process measures using a BCMP network that combines stochastic models of several standard TM Forum end-to-end eTOM business flows. The steady-state probability distribution of the model is derived along with the expressions for a number of performance measures.

Modeling the Process of Dynamic Resource Sharing Between LTE and NB-IoT Services

The Internet of Things (IoT) undergoes fundamental changes, expanding its infrastructure with more advanced and mobile devices. As the IoT develops, the existing cellular communication technologies often do not provide sufficient coverage while modern IoT terminals are often expensive and characterized by a short battery life. To address these issues, in Release 13 (LTE Advanced Pro) published in 2016, 3GPP consortium has proposed the Narrow-Band IoT (NB-IoT) technology as an efficient way to provide a wide range of new capabilities and services in a wireless cellular network. Having specified three operational regimes, 3GPP did not provide guidelines on the way resource sharing has to be done between LTE and NB-IoT traffic. In this paper, the in-band NB-IoT service model is presented, where a certain amount of LTE radio resources are exclusively allocated to LTE and NB-IoT users while the rest are shared between them. We analyze the proposed system for performance metrics of interest including NB-IoT and LTE session drop probabilities and resource utilization.

Modelling Of Vertical Handover From Untrusted WLAN Network To LTE.

Nowadays, operators offer telecommunication services at a very high level. For the support of the best quality of service it would be reasonable to implement a handover to another radio access network cell in the same territory, a so-called vertical handover (VHO), by transferring the user connection and IP session from the current access network to a new network. In this paper, we analyze vertical handovers from an untrusted WLAN network to an LTE network. This type of handover from an untrusted WLAN network is the most difficult because of the many nodes of an LTE network related to authorization and resource allocation. The paper includes a synthesis of the basic procedures for the session setup and LTE resource allocation. Unlike other papers, we represent a complicated VHO procedure as a sequence of at least 40 signalling messages from the discovery of a new network for the VHO to its full completion at the target LTE network. We also propose a vertical handover time estimation method for the said VHO procedure. We perform numerical experiments on realistic data.

On Analyzing the Blocking Probability of M2M Transmissions for a CQI-Based RRM Scheme Model in 3GPP LTE

Machine type communications (MTC) or machine-to-machine (M2M) services become one of the drivers towards 5th generation (5G) wireless network. Various MTC devices such as smart meters and sensors form the basis of smart cites and homes. The question is how to efficiently transmit the information from MTC devices via a wireless network, which is primarily used for human-to-human (H2H) communications. Nevertheless, one of the important qualities of service (QoS) measure is still blocking probability. In the simplest case, the Erlang B formula is used to calculate the blocking probability. A more precise value can be obtained considering the MTC devices positons within a cell and applied radio resource management (RRM) mechanisms. First of all, it is expressed in the distances from the devices to eNodeB. In the paper, following the approach of including the stochastic distance in the queuing system, we propose formulas for calculating stationary probability distribution in product form considering a channel quality indicator (CQI) reported by MTC devices. Two RRM schedulers working according to the round robin policy (RRP) and full power policy (FPP) are considered. The former assumes full occupation of a time frame by all MTC devices and a variable devices’ power such that to achieve a needed uplink bit rate. The latter assumes a constant power and variable time frame occupation.