Vassilios G. Vassilakis

Call-Level Performance Modelling of Elastic and Adaptive Service-Classes with Finite Population

The call-level performance modelling is a challenge in the highly heterogeneous environment of modern telecom networks, due to the presence of elastic traffic. In this paper, we review existing teletraffic loss models and propose a model for elastic traffic of service-classes with finite population (quasi-random call arrival process). Upon arrival, calls have contingency alternative bandwidth requirements that depend on thresholds which indicate the available/occupied link bandwidth (state dependent model). Calls are admitted under the complete sharing policy, and can tolerate bandwidth compression, while in-service. We prove a recurrent formula for the efficient calculation of the link occupancy distribution and consequently the call blocking probabilities and link utilization. The accuracy of the proposed model is verified by simulation and is found to be quite satisfactory. Comparative results with other existing models show the necessity and the effectiveness of the proposed model. Its potential applications are mainly in the environment of wireless networks.

The Wireless Engset Multi-Rate Loss Model for the Handoff traffic analysis in W-CDMA networks

The call-level performance modelling and evaluation of 3G cellular networks is important for the proper network dimensioning and efficient use of the network resources, such as bandwidth and power. In the case of the wideband code division multiple access (W-CDMA) cellular networks, this task is complicated, not only because of the so called soft blocking, the multiple access interference (MAI) and the heterogeneous traffic, but also due to the handoff process. In this paper, we propose a new teletraffic model for the call-level analysis of handoff traffic in the uplink of W-CDMA networks where multiple services with finite number of traffic sources are accommodated. Parameters related to the soft blocking and MAI are included into the model. The proposed model is described by a discrete time Markov chain. An efficient recurrent formula for the calculation of the system state probabilities is derived. Based on this formula, blocking probabilities of both new and handoff calls are determined. The accuracy of the proposed model is evaluated through simulation and is found to be very satisfactory. Moreover, we show the necessity of distinguishing the handoff traffic from the new traffic, in respect of blocking probabilities.

The extended connection-dependent threshold model for call-level performance analysis of multi-rate loss systems under the bandwidth reservation policy

Firstly, we reviewed two extensions of the Erlang multi-rate loss model, whereby we can assess the call-level QoS of telecom networks supporting elastic traffic: (i) the extended Erlang multi-rate loss model, where random arriving calls of certain bandwidth requirements at call setup can tolerate bandwidth compression while in service; and (ii) the connection-dependent threshold model, where arriving calls may have several contingency bandwidth requirements, whereas in-service calls cannot tolerate bandwidth compression. Secondly, we proposed a new model, the extended connection-dependent threshold model. Calls may have alternative bandwidth requirements at call setup and can tolerate bandwidth compression while in service. We proposed a recurrent formula for the efficient calculation of link occupancy distribution and consequently call blocking probabilities, link utilization, and throughput per service class. Furthermore, in the proposed model, we incorporated the bandwidth reservation policy, whereby we can (i) equalize the call blocking probabilities of different service classes, (ii) guarantee specific QoS per service class, and (iii) implement different maximum bandwidth compression/expansion rate per service class so that the network supports both elastic and stream traffic. The accuracy of the new model is verified by simulation. Moreover, the proposed model performs better than the existing models. Finally, we generalize the proposed model by incorporating service classes with either random or quasi-random arrivals. Copyright

Call Blocking Probabilities in a W-CDMA cell with fixed number of channels and finite number of traffic sources

This paper focuses on the call blocking probabilities calculation in a W-CDMA cell with fixed number of channels and finite number of traffic sources. To this end, the use of the Engset multirate loss model (EnMLM) is proposed in the uplink direction. To apply the EnMLM we need to extend it by incorporating the so called local blockings. Arriving calls compete for their successful admission to a W-CDMA cell. The call admission depends on the availability of the required channels. To analyze the system, we formulate an aggregate one-dimensional Markov chain, and based on it, we determine the system state probabilities by an efficient recurrent formula. Consequently, we determine the call blocking probabilities in the uplink direction. Although the proposed model is approximate, its accuracy is found to be quite satisfactory. The evaluation is done through simulation. Moreover, the model performs better than the existing model which assumes infinite number of traffic sources in the cell.

Scalability of information centric networking using mediated topology management

Information centric networking is a new concept that places emphasis on the information items themselves rather than on where the information items are stored. Consequently, routing decisions can be made based on the information items rather than on simply destination addresses. There are a number of models proposed for information centric networking and it is important that these models are investigated for their scalability if we are to move from early prototypes towards proposing that these models are used for networks operating at the scale of the current Internet. This paper investigates the scalability of an ICN system that uses mediation between information providers and information consumers using a publish/subscribe delivery mechanism. The scalability is investigated by extrapolating current IP traffic models for a typical national-scale network provider in the UK to estimate mediation workload. The investigation demonstrates that the mediation workload for route determination is on a scale that is comparable to, or less than, that of current IP routing while using a forwarding mechanism with considerably smaller tables than current IP routing tables. Additionally, the work shows that this can be achieved using a security mechanism that mitigates against maliciously injected packets thus stopping attacks such as denial of service that is common with the current IP infrastructure.

The Wireless Engset Multi-Rate Loss Model for the Call-Level Analysis of W-CDMA Networks

We propose a new teletraffic model, named Wireless Engset Multi-rate Loss Model (W-EnMLM) for the call-level analysis of W-CDMA networks, supporting heterogeneous service-classes of finite population of traffic sources. Quasi- random arriving calls (generated by mobile users), compete for their admission to a W-CDMA cell under the Complete bandwidth Sharing (CS) policy. We present an approximate but recurrent formula for the efficient calculation of the system state probabilities and the call blocking probabilities in the uplink direction. The accuracy of the proposed model is verified by simulation results and found to be completely satisfactory. Moreover, the proposed model performs much better than the corresponding model of infinite number of traffic sources.

Call-Level Analysis of W-CDMA Networks Supporting Elastic Services of Finite Population

We present a new model, named Wireless Finite Connection-Dependent Threshold Model, for the call-level analysis of W-CDMA networks that support both elastic and stream traffic. Calls generated by service-classes of finite source population (quasi-random call arrival process) compete for their acceptance to a W-CDMA cell, under the complete sharing policy. An arriving call can be accepted with one of several contingency Quality-of-Service (QoS) requirements, depending on the resource availability in the cell; the latter is indicated by thresholds. We present an approximate but recurrent formula for the efficient calculation of the system state probabilities; consequently, the call blocking (time congestion) probabilities and other performance metrics in the uplink direction are provided. The models accuracy is verified by simulation and found to be quite satisfactory. Moreover, the proposed model performs much better than the corresponding model of infinite number of sources.

A software-defined architecture for next-generation cellular networks

In the recent years, mobile cellular networks are undergoing fundamental changes and many established concepts are being revisited. New emerging paradigms, such as Software-Defined Networking (SDN), Mobile Cloud Computing (MCC), Network Function Virtualization (NFV), Internet of Things (IoT), and Mobile Social Networking (MSN), bring challenges in the design of cellular networks architectures. Current Long-Term Evolution (LTE) networks are not able to accommodate these new trends in a scalable and efficient way. In this paper, first we discuss the limitations of the current LTE architecture. Second, driven by the new communication needs and by the advances in aforementioned areas, we propose a new architecture for next-generation cellular networks. Some of its characteristics include support for distributed content routing, Heterogeneous Networks (HetNets) and multiple Radio Access Technologies (RATs). Finally, we present simulation results which show that significant backhaul traffic savings can be achieved by implementing caching and routing functions at the network edge.

CAINE: a context-aware information-centric network ecosystem

Information-centric networking (ICN) is an emerging networking paradigm that places content identifiers rather than host identifiers at the core of the mechanisms and protocols used to deliver content to end users. Such a paradigm allows routers enhanced with content-awareness to play a direct role in the routing and resolution of content requests from users, without any knowledge of the specific locations of hosted content. However, to facilitate good network traffic engineering and satisfactory user QoS, content routers need to exchange advanced network knowledge to assist them with their resolution decisions. In order to maintain the location-independency tenet of ICNs, such knowledge (known as context information) needs to be independent of the locations of servers. To this end, we propose CAINE - Context-Aware Information-centric Network Ecosystem - which enables context-based operations to be intrinsically supported by the underlying ICN routing and resolution functions. Our approach has been designed to maintain the location-independence philosophy of ICNs by associating context information directly to content rather than to the physical entities such as servers and network elements in the content ecosystem, while ensuring scalability. Through simulation, we show that based on such location-independent context information, CAINE is able to facilitate traffic engineering in the network, while not posing a significant control signalling burden on the network.

A distributed in-network caching scheme for P2P-like content chunk delivery

In-network content caching has recently emerged in the context of information-centric networking (ICN), which allows content objects to be cached at the intermediate router side. In this paper, we specifically focus on in-network caching of peer-to-peer (P2P)-like content objects for improving both service and operation efficiencies. We propose a fully distributed in-network caching protocol for P2P-like content chunks, aiming to reduce P2P based content traffic load and also to achieve improved content distribution performances. Toward this end, the proposed holistic decision-making logic takes into account context information of both the underlying network and the P2P characteristics, such as chunk availability, popularity and peer distances. In addition, we also analyse the benefit of coordination between neighbouring content routers when making caching decisions in order to avoid duplicated P2P chunk caching nearby. An analytical modelling framework is developed to quantitatively evaluate the efficiency of the proposed in-network caching scheme. Extensive experiments are also conducted to validate the analytical results.