Maciej Sobieraj

Evaluation of traffic characteristics of UMTS with bandwidth reservation and handoff mechanism

The paper proposes an analytical method of blocking probability calculation in UMTS networks with bandwidth reservation and connection handover mechanism. The papers proposes also reservation algorithms for a group of cells, exploiting the effects of connection handoff between cells. The proposed analytical model is based on the generalized model of a limited-availability group. The results of analytical calculations of blocking probability in a group of UMTS cells with bandwidth reservation are compared with simulation data.

The Modified MSM Clos Switching Fabric with Efficient Packet Dispatching Scheme

Next generation switches/routers will have to use switching fabrics in order to achieve the desired capacity and speed to support growing Internet traffic. For high-performance switches and routers the Clos switching fabric is very attractive because of its modular architecture and scalability. A great many packet dispatching schemes for three-stage buffered and bufferless Clos switching fabrics were proposed in the literature. Some of them provide high throughput under uniform, others under nonuniform traffic distribution. In this paper the modified MSM Clos switching fabric and a very simple packet dispatching scheme, called Static Dispatching with Rapid Unload of Buffers (SDRUB), are proposed. We show via simulation that this modified switching fabric and the described scheduling deliver very good performance in terms of throughput, cell delay and input buffers size under different traffic distribution patterns.

Modeling switching networks with multi-service sources and point-to-group selection

The aim of this paper is the elaboration of a new analytical calculation method of the occupancy distribution and the blocking probability in multi-service switching networks with multi-service sources. The considered multi-stage switching networks operates according to point-to-group selection. The analytical results of the blocking probability in the switching networks with multi-service sources are compared with simulation data.

Point-to-Group Blocking Probability in Switching Networks with Threshold Mechanisms

The paper presents a new method for determining traffic characteristics of multi-stage switching networks with threshold mechanisms. The proposed method makes it possible to calculate point-to-group blocking probability in switching networks with multirate traffic. The basis of the proposed method is an effective availability conception. The results of analytical calculations are compared with simulation data.

Analytical modeling of multi-service systems with multi-service sources

The paper presents a new analytical model for performance evaluation of multi-service communication systems. The paper considers for the first time multi-service systems in which each single traffic source can generate calls of different traffic classes, i.e. the multi-service systems with multi-service sources. To date only the models assuming that a single source of given class generates always only calls of this class, i.e. the multi-service systems with single-service sources, have been considered in teletraffic literature. The proposed algorithm makes it possible to determine occupancy distribution as well as blocking and loss probability for calls of particular traffic classes. In order to assure completeness of considerations the systems with both finite and infinite traffic sources are considered. The results of analytical modeling of the systems with multi-service sources are compared with simulation data. The possible application of the proposed model is presented in the context of an exemplary cellular system with WCDMA (Wideband Code Division Multiple Access) radio interface.

Blocking probability calculation in UMTS networks with bandwidth reservation, handoff mechanism and finite source population

The paper proposes a new analytical approach to blocking probability calculation in wireless mobile networks with bandwidth reservation and connection handoff mechanisms, carrying a mixture of different traffic streams. This mixture can be composed of an arbitrary number of traffic classes, generated by a finite as well as an infinite population of traffic sources. The appropriate bandwidth reservation algorithm for a group of cells, exploiting the effects of connection handoff between cells, is also proposed. The results of analytical calculations of blocking probability in a group of UMTS cells with bandwidth reservation are compared with simulation data.

A full-availability group model with multi-service sources and threshold mechanisms

The aim of this paper is elaboration of a new analytical calculation method of the occupancy distribution and the blocking probability in full-availability systems with multi-service sources and threshold mechanisms. The paper considers the multi-service full-availability systems in which each single traffic source can generate calls of different traffic classes, i.e., the multi-service systems with multi-service sources. To date only the models of the threshold systems assuming that a single source of given class generates always only calls of this class, i.e., the multi-service threshold systems with single-service sources, have been considered in teletraffic literature. The results of analytical modeling of the considered multi-service threshold system with multi-service sources are compared with simulation data.

Modelling Limited-Availability Groups with BPP Traffic and Bandwidth Reservation

The article proposes a new method for calculating occupancy distribution and blocking/loss probability in the limited availability group with bandwidth reservation. The proposed method makes it possible to model groups servicing multi-service BPP traffic streams (Binomial--Poisson--Pascal). The proposed method is based on the analysis of the service process occurring in the considered system on the basis of the one-dimensional Markov chain. Significant increase in the accuracy and precision of the proposed method, in relation to other methods known from the literature, was obtained as the result of a modification of service streams within the reservation space. The accuracy of the proposed method has been verified by simulation studies.

Analytical Modeling of the Influence of Connection Handoff on UMTS Traffic Characteristics

The paper presents a model of a group of cells, exploiting the effects of connection handoff between cells, aimed at increasing the traffic capacity of a system. The analytical model proposed is based on the model of limited-availability group, which makes it possible to determine basic traffic characteristics in the system under consideration. The results of analytical calculations of blocking in a group of UMTS cells were compared with simulation data.

Model of the Threshold Mechanism with Double Hysteresis for Multi-service Networks

This paper presents a new generalized threshold model that can be used in cellular networks. In the proposed model, called Double Hysteresis Model (DHM), it is assumed that the amount of resources accessible for a new call of a given class can depend on three load areas of the system. The switching between areas is modulated by a three-state Markov chain that determines the average time the system spends in a particular load area. The results obtained for the discussed analytical model are compared with the results of the simulation of an exemplary WCDMA radio interface carrying a mixture of different multi-rate traffic streams. The research study confirms high accuracy of the proposed model.