Malamati D. Louta

Proportional delay differentiation provision by bandwidth adaptation of class‐based queue scheduling

Supporting quality of service (QoS) over the Internet is a very important issue and many mechanisms have already been devised or are under way towards achieving this goal. One of the most important approaches is the so-called Differentiated Services (DiffServ) architecture, which provides a scalable mechanism for QoS support in a TCP/IP network. The main concept underlying DiffServ is the aggregation of traffic flows at an ingress (or egress) point of a network and the marking of the IP packets of each traffic flow according to several classification criteria. Diffserv is classified under two taxonomies: the absolute and the relative. In absolute DiffServ architecture, an admission control scheme is utilized to provide QoS as absolute bounds of specific QoS parameters. The relative DiffServ model offers also QoS guarantees per class but in reference to the guarantees given to the other classes defined. In this paper, relative proportional delay differentiation is achieved based on class-based queueing (CBQ) scheduler. Specifically, the service rates allocated to the classes of a CBQ scheduler are frequently adjusted in order to obtain relative delay spacing among them. The model presented can also be exploited in order to meet absolute delay constraints in conjunction with relative delay differentiation provision. Simulation experiments verify that our model can attain relative as well as absolute delay differentiation provided that the preconditions posed are satisfied. Copyright

Towards the Seamless Integration of Mobile Agents into Service Creation Practice

Mobile agent technology has been proposed to address complexity problems related with service creation and deployment in todays open telecommunications domain. However, the integration of mobility into the traditional service creation process should not be decided on an ad-hoc basis. Based on the specific benefits and drawbacks of mobility, careful consideration is required in order to achieve a seamless integration of mobile agents into service creation practice. This paper explains in detail the necessity of a careful introduction of mobility in traditional service creation practices and concludes with a guideline to maximize the temporal and spatial locality of invocations between distributed service components.

Towards an incentive-compatible, reputation-based framework for stimulating cooperation in opportunistic networks: a survey

In opportunistic networks (OppNets), routing and data forwarding among mobile devices are facilitated by relays or next-hop forwarders. To guarantee end-to-end data delivery it is important to provide participation. However, in sparsely connected OppNets, it is extremely challenging to monitor the behaviour of the relays and identify selfish/malicious relays cooperating with each other in order to forge routing information or drop useful data. Cooperation enforcement schemes are seen as a lightweight alternative to conventional secure forwarding techniques that involve cryptographically signed certificate exchanges, providing a ‘softer’ security layer to protect basic networking operations. In general, cooperation enforcement schemes fall into two broad categories: trust establishment via a reputation system and pricing or credit-based schemes. This study offers a comprehensive survey of representative cooperation enforcement schemes that exploit a reputation system. The authors analyse their distinct features, identify and discuss critical challenges that should be efficiently addressed when designing such mechanisms, indicating at the same time potential solutions and provide an informative table to display the authors’ findings. From this analysis, they examine issues and concerns surrounding the field of cooperation enforcement in OppNets, and provide guidelines and directions for future researchers.

Cost-Efficient Design of Future Broadband Fixed Wireless Access Systems

In future broadband fixed wireless access systems the overall design procedure is critical for their successful commercial deployment as well as their efficient operation and management. The problem addressed in this paper is twofold. Specifically, at a first phase the radio access network planning problem is addressed, which aims at finding the minimum-cost configuration of Access Point Transceivers (APTs) given thegeographical layout of the area to be covered. At the second phase, the interconnecting planning problem is addressed and aims at finding the minimum-cost configuration of the AccessPoint Controllers (APCs) and Inter-Working Units (IWUs) given the Access PointTransceivers layout. Both problems are formally defined, optimally formulated, and solved by computationally efficient heuristics. Finally, results are provided and subsequent conclusions are drawn.

Efficient internet search engine service provisioning exploiting a collaborative web result ranking mechanism

In the context of this paper, a meta-search third-party Web result ranking mechanism is proposed, which is capable of adapting over the continuous changes that occur on the Web, providing in parallel personalized information acquisition considering the users navigation behaviour. The designed meta search engine service rates, re-organises and combines the results acquired from search services for a specific user information resource request in accordance with a weighted combination of a performance related factor (tightly related to the ranking of the Web result as given by the search engine service) and a reliability related factor (corresponding to the users satisfaction stemming from the specific Web result that he/she browses), while the performance of each search engine with respect to adequately adapting to the Web evolution is taken into account. Assuming a group of users falling within the same category with respect to the information/resource needs, the Web result reliability rating system is collaborative in the sense that it considers both first-hand information (acquired from the users past experiences with the search engine services) and second-hand information (corresponding to other users experiences with search engine services), while the matching degrees of the users profiles have been taken into account. A set of results indicative of the efficiency of our proposed scheme is provided. Transparency is achieved for both personalization and Web evolution adaptation mechanisms, requiring virtually none effort from the users part.

An effective negotiation strategy for simple buyer response in e-commerce environment

Electronic commerce is expected to dominate the market if coupled with the appropriate technologies and mechanisms. Mobile agents are one of the means that may enhance the intelligence and improve the efficiency of systems in the e-marketplace. We propose a dynamic multilateral negotiation model and an efficient negotiation strategy that can be used to extend the functionality of autonomous agents, so that they reach to an agreement aiming to maximise their owners utility. The framework considers contract and decision issues, is based on real market conditions, adopts a light ranking mechanism that does not require a complicated rationale on behalf of the buyer agents, and has been empirically evaluated.

Retailer selection in future open competitive communications environments

The highly competitive communications markets of the future should encompass mechanisms for enabling users to find and associate with the most appropriate retailers, i.e. those offering at a certain time period adequate quality services in a cost efficient manner. This paper presents such mechanisms. Our starting point is the definition of a business case, through which the role of the best candidate-retailer selection problem is explained. In the sequel, the problem is analysed and the identified sub-problems are concisely defined, mathematically formulated and solved. The identified components of the best candidate-retailer selection problem involve the evaluation of the quality of a retailer offer and the reduction of the set of candidate retailers by exploiting learning from experience notions. In the final sections, results are provided and concluding remarks are made.

Personal mobility support in future service architectures

Support for personal mobility will be among the key factors for success in the competitive communications market of the future. This paper proposes enhancements to the personal mobility support capabilities of service architectures. The TINA service architecture is used as a reference, even though our approach is applicable to other models as well. Our starting point is a business case that falls into the realm of personal mobility. The aim of the business case is to enable users that are found outside their home domain to access services by choosing the best visited retailer, i.e. the one offering adequate quality services in the most cost-efficient manner. In the sequel the following key issues are addressed. First, the introduction of the additional functionality that is required for supporting the business case, and the realisation through appropriate service components. Second, the integration of the new service components in the standard TINA service architecture. Third, the detailed description of a version of the logic of the new components. In this last respect, we formally state, mathematically formulate and solve problems related to the visited retailer selection. Copyright

Design of the ATM-based interconnecting network of the access segment of future cellular systems

An important issue in future cellular communication systems is the design of the interconnecting network of their access segment. This problem aims at finding the minimum-cost configuration of cell site switches (CSSs) and local exchanges (LEs) given the base transceiver station (BTS) layout. An extended version of the problem may also comprise the deployment of mobility and service control points-access (MSCPs-A), based on the assumption that CSSs and LEs are not fully capable of handling the logic of the cellular system. In this paper we solve the extended problem, under the additional assumption that the communication among the network elements is based on the ATM technique. The problem is formally defined, optimally formulated, and solved by computationally efficient heuristics. Finally, results are provided and subsequent conclusions are drawn. Copyright

Implications of 3g licensing to mobile telecommunications market dynamics

Abslruct- In lhis paper, the implications of 3G licensing to lhc tclccommuiiication business roles involved in the 3G markct chain are exposed. The lraditional licensing models an described and compared, while the outcome of their adoplion over the tiorld is presented. An innrivative licrnsing scheme is proposcd, which aims to present the ndvanlnges of all existing methods used for the assignmcnl of thc 3G licences. This scheme claims to have lhc adaptability potenlial for any ohjectiw that the rcgulnlory aulhorilie~ may have. It is assessed tia a simulation example based on the 3C liccnsing procedure of the llniled Kingdom, the candidates nod IPSU~~S.