Yulia V. Gaidamaka

Queuing Model for Loss-Based Overload Control in a SIP Server Using a Hysteretic Technique

In this paper, we develop a mathematical model of a load control mechanism for SIP server signaling networks based on a hysteretic technique developed for SS7 from ITU-T Recommendation Q.704. We investigate loss-based overload control, as proposed in recent IETF documents. The queuing model takes into account three types of system state – normal load, overload, and discard. The hysteretic control is made possible by introducing two thresholds in the buffer of total size B – the overload onset threshold H and the overload abatement threshold L. We denote the mathematical model using the modified Kendall notation as an \(M|G|1|\left\langle L,H\right\rangle |B\) queue with hysteretic load control. We also develop an analytical model for the case of an M|M|1 queue and a simulation model for an M|D|1 queue. We investigate the return time from an overload state as the target performance measure of overload control in a SIP server, and provide numerical examples in order to examine the difference between the M|M|1 and M|D|1 systems.

Modeling of Hysteretic Signaling Load Control in Next Generation Networks

In this paper we investigate traffic load control mechanisms for controlling congestion in signaling networks based on three types of thresholds. The goal of the paper is to analyze congestion controlling mechanisms and develop corresponding queuing models of SIP servers. The study is based on hysteretic congestion control, which has been developed for Signaling System 7 (SS7). Models for describing the hysteretic control are developed. The current state and problems of basic overload control mechanism proposed by Internet Engineering Task Force (IETF) for SIP signaling networks are investigated. Approaches to building mathematical models of SIP servers in the form of a queuing system with hysteretic control are proposed.

Mathematical theory of teletraffic and its application to the analysis of multiservice communication of next generation networks

This paper presents a survey of the authors results to discuss the model of a multiservice network with “triple play” (unicast, multicast, and elastic) traffic. The main results are given for the model with multicast traffic. Two service disciplines for multicast traffic are considered in the form of systems with transparent requests. An algorithm for the calculation of the blocking probabilities for models involving both unicast and multicast traffic is proposed. In conclusion, the lines of further research are outlined: the analysis of models of the session initiation protocol (SIP), including design problems to control overloads in SIP server networks, the planning of cross-layer interfaces for orthogonal frequency division multiplexing in mobile networks long term evolution (LTE), and the design of methods for the analysis of the quality factors of the file exchange and streaming in peer-to-peer (P2P) networks.

Model with threshold control for analyzing a server with an SIP protocol in the overload mode

The SIP protocol defines the Invite messages initiating the session and the nonInvite ones, which are sent on its stabilizing, being privileged since the resetting of these messages due to an overload leads to ceasing of the user’s session setting. The queueing system with polling, two queues of limited capacity, and threshold control of the load generated by nonpriority messages is studied in the present paper to be applied to a solution of the overload control problem in a server network with the SIP protocol. Under the simplest Markovian assumptions, the exhaustive and gated service disciplines are investigated, a method for calculating the transfer rate matrix of the Markovian process is proposed, formulas for calculating the basic probabilistic measures are obtained, and their numerical analysis is carried out.

SIR Analysis In Square-Shaped Indoor Premises.

The increased wireless network densification has resulted in availability of wireless access points (AP) in almost each and every indoor location (room, office, etc.). To provide complete in-building coverage very often an AP is deployed per room. In this paper we analyze signal-to-interference (SIR) ratio for wireless systems operating in neighboring rooms separated by walls of different materials by explicitly taking into account the propagation and wall penetration losses. Both AP and direct device-to-device (D2D) configurations are addressed. Our numerical results indicate that the performance of such system is characterized by both the loss exponent describing the propagation environment of interest and wall materials. We provide the numerical results for typical wall widths/materials and analyze them in detail. INTRODUCTION The predicted increase in the user traffic demands places extreme requirements on the future evaluation of mobile systems, often referred to as fifth generation (5G) networks [1], [2]. In addition to physical layer improvements including advanced modulation and coding and MIMO techniques, over the last decade researchers investigated a number of network solutions providing decisive performance improvements including the use of small (micro/pico/femto) cells [3], clientrelays [4], direct in-band and out-of-band device-to-device communications [5]. All these concepts target aggressive spatial reuse of frequencies promising substantial area capacity gains. With the adoption of novel mechanism the user devices are expected to take a more active part in 5G systems and, in some cases, even take on the role of the network infrastructure in providing wireless connectivity such as offering D2D-based data relaying, proximity services, etc. This shift from the classic cellular model is dictated by the progress in communications technologies: the user devices are augmenting their capabilities, whereas the base stations (BSs) are becoming smaller as a result of the ongoing network densification [6]. The networks densification, novel networking and service mechanisms as well as the trend to use multiple access technologies to serve the users, known as heterogeneous cellular system concept, altogether lead to increased randomness of the network, where the positions of servicing stations such as BSs, relays and D2D partners are random rather than deterministic. The signal-to-interference ratio (SIR) is a universal metric specifying performance of wireless systems [7]. Once SIR is known one could describe the Shannon rate of the channel and spectral efficiency of the system. In contrast to noise-limited systems, where the bit error rate (BER) decreases exponentially with signal-to-noise ratio (SNR), the heterogeneous mobile networks are interference-limited showing linear improvement of BER with respect to SIR. Thus, the increase of the emitted power does not improve the performance of these systems. Thus, the problem of finding SIR for typical network configurations is of special importance characterizing applicability and typical scenarios of modern and future wireless technologies. The SIR performance of wireless systems is often studied using the tools of stochastic geometry [8]. The basic approach is to specify the point process on the plane modeling positions of the stations and then derive the interference at the point of interest. The last step is rather complex as we need closed-form distribution of distance to the point of interest from at least several neighboring points. For this reason typical considered models are often limited to Poisson point process on the plane for which we immediately have closed-form expressions for distributions of distances to the i-th neighbor [9]. The constantly increasing need for wireless connectivity on-the-go [10] are gradually changing the way service is provisioned in wireless networks. Nowadays, one of the trends is to deploy small wireless stations including both IEEE 802.11 or micro-LTE access points (AP) in crowded areas to benefit from increased network densification [6] and shorter propagation distances. Examples include large shopping mall, office environment, where one of few adjacent rooms is served by an AP having relatively small coverage area. In this dense environment interference between neighboring APs is inevitable and may easily lead to degraded system performance. In this paper, using the tools of stochastic geometry, we analyze performance of wireless systems operating in neighboring rooms of rectangular configuration. We consider both direct device-to-device and AP configurations assuming that Proceedings 30th European Conference on Modelling and Simulation ©ECMS Thorsten Claus, Frank Herrmann, Michael Manitz, Oliver Rose (Editors) ISBN: 978-0-9932440-2-5 / ISBN: 978-0-9932440-3-2 (CD) the systems in adjacent rooms operate at the same frequency. The analytical results are compared to simulations showing adequate agreement. Numerical results for the set of input metrics demonstrate that the system performance is dictated by the interplay between path loss exponent typical for a given environment and type of the walls used between rooms. The rest of the paper is organized as follows. First, in the next section we introduce a system model. Further, we analytically study SIR for downlink scenario. The simulation models for both downlink and D2D scenarios are introduced next. Numerical results for different sets in input variables are illustrated. Conclusions are drawn in the last section. SYSTEM MODEL In this study we focus on an indoor scenario with grid aligned rooms, see Fig. 1 that are typical for shopping malls or office buildings. In these environments rooms are often of rectangular or square shapes. Each room is assumed to be equipped with an AP deployed in the geometrical center. To take advantage of the wireless network densification trend as a solution to upgrade the degree of spatial reuse, the devices in adjacent rooms are assigned the same set of communication channels [6]. The mobile terminals (users) operating over the same channel are assumed to be uniformly distributed over the room, one per room. We concentrate on the so-called tagged user in the central room, see Fig. 1(a) and Fig. 1(b). We assume both AP and users to be equipped with omnidirectional antennas. We do not focus on a particular radio technology addressing the general case. In addition to AP scenario we also address D2D configuration, sketched in Fig. 1(c). The principal difference compared to AP case is that both transmitter and receiver are assumed to be uniformly distributed within a room. Under this assumption the configuration is symmetric, i.e., we do not have to distinguish between uplink and downlink cases. Similarly, we concentrate on D2D pair located in the central room. Focusing on SIR, as a metric of interest, for both AP and D2D configurations we calculate it for a randomly chosen receiving device, taking into account the interference from a set of neighboring rooms. Using the commonly used propagation model, we add a correction factor, accounting for the attenuation of a signal when passing through a wall

Polling System with Threshold Control for Modeling of SIP Server under Overload

The main purpose of this research is the development of the methods for realizing an overload control mechanism on the Session Initiation Protocol servers by the application of polling systems with different service disciplines. The mathematical model is studied by means of numerical methods of the queuing theory and allows analyzing the behavior of different control parameters depending on the load in network of SIP servers. The polling system consists of two queues of finite capacity and implements the threshold control of loading by low-priority customers. The exhaustive and gated service disciplines are studied under Markov assumptions; formulas for calculation of the main probability measures of the polling system are derived. By performing simulations we demonstrate that the polling system with a threshold in the priority queue is a possible solution for loss-based overload control scheme at the SIP server. In some cases from the viewpoint of server utilization we found that the gated discipline is more preferable.

Analytical Modeling Of Rate-Based Overload Control With Token Bucket Traffic Shaping On Client Side.

Providing multimedia services to users assumes perfect quality of transfer and modern processing equipment that involves need of development of new methods of the analysis and forecasting of functioning of a communication network. In the paper we investigate the problem of the overload that occurs on a SIP (Session Initiation Protocol) server. SIP overload mitigation is based on RBOC (Rate-based overload control) schema, which was designed by IETF SIP overload control workgroup. The aim of RBOC schema is to restrict signaling message flow rate from the client side towards the server side. Hysteretic overload control algorithm is used to define trigger point for sending control information by the server to the client. Token bucket algorithm is applied to restrict the number of the tokens that the server grants the client. Simulation model for estimation main performance metrics is developed. Traffic with different type of distribution is used for investigation the behavior of the system with tandem servers. The optimization problem for maximization of processor utilization of SIP server on the dependence of threshold values and the number of token is formulated.

Analytical modeling of P2PTV network

To provide a live and on demand video services over the internet due scalability issue, P2P technology which proved to be more scalable is widely used today. Since most of the video streams presented in P2P live video streaming systems are television channels all over the world, we therefore referred them as P2PTV systems. The behavior of single user is presented in terms of exponential closed queuing network. Based on the model we construct a behavioral model of multiple users in P2PTV-network with multiple channels. The stationary probability distribution of P2PTV-network model is obtained in a product form in terms of the number of channels and the number of users present in the network. Given the popularity of television channels we obtained formulas for the analysis of some QoE parameter in P2PTV-network with finite and infinite number of viewers.

Design And Software Architecture Of Buffering Mechanism For Peer-To-Peer Streaming Network Simulation.

The rapid development of P2P technologies and appearing scope of applications involving it will help to solve a lot of optimization problems and improve the QoS for data delivery services. This paper is an extension of previous papers devoted to modelling P2P media streaming service and describes the design and simulation software architecture of P2P streaming network with buffering mechanism for a single media stream. We consider mathematical model in the form of discrete Markov chain taking into account the so-called lag – the time delay of data transfer between peers, download strategies and possible peer groups according to distances between them. Program algorithm is presented using UML activity diagram and the simulation results are shown.

Tractable Distance Distribution Approximations for Hardcore Processes

The Poisson point process (PPP) is widely used in performance analysis of wireless communications technologies as a basic model for random deployment of communicating entities. The reason behind widespread use of PPP is analytical tractability in terms of closed-form distributions of distances to the n-th neighbour needed for performance analysis. At the same time, the process allows for infinitesimally close distances between communicating stations not only contradicting the reality but presenting fundamental difficulties in analysis when used with power-law propagation models. As an alternative suggested in the literature ad free of abovementioned deficiencies are the hardcore processes where a certain separation distance between points is always presumed. Unfortunately, no closed-form expressions for distance distributions is available for these processes. We study distance distributions of Matern hardcore process and propose analytical approximations based on acyclic phase type distributions. The nature of approximation as a mixture of exponentials allows for their use in analytical performance analysis. Results for a range of process intensities are reported.