Mehmet Ufuk Çağlayan

Location area planning in cellular networks using simulated annealing

Location area (LA) planning plays an important role in cellular networks because of the trade-off caused by paging and registration signaling. The upper bound on the size of an LA is the service area of a mobile switching center (MSC). In that extreme case, the cost of paging is at its maximum, but no registration is needed. On the other hand, if each cell is an LA, the paging cost is minimal, but the registration cost is the largest. In general, the most important component of these costs is the load on the signaling resources. Between the extremes lie one or more partitions of the MSC service area that minimize the total cost of paging and registration. In this paper, we try to find an optimal method for determining the location areas. For that purpose, we use the available network information to formulate a realistic optimization problem. We propose an algorithm based on simulated annealing (SA) for the solution of the resulting problem. Then, we investigate the quality of the SA technique by comparing its results to greedy search and random generation methods.

Distributed Software System Design Representation Using Modified Petri Nets

A model for representing and analyzing the design of a distributed software system is presented. The model is based on a modified form of Petri net, and enables one to represent both the structure and the behavior of a distributed software system at a desired level of design. Behavioral properties of the design representation can be verified by translating the modified Petri net into an equivalent ordinary Petri net and then analyzing that resulting Petri net. The model emphasizes the unified representation of control and data flows, partially ordered software components, hierarchical component structure, abstract data types, data objects, local control, and distributed system state. At any design level, the distributed software system is viewed as a collection of software components. Software components are externally described in terms of their input and output control states, abstract data types, data objects, and a set of control and data transfer specifications. They are interconnected through the shared control states and through the shared data objects. A system component can be viewed internally as a collection of subcomponents, local control states, local abstract data types, and local data objects.

Location area planning and cell-to-switch assignment in cellular networks

Location area (LA) planning plays an important role in cellular networks because of the tradeoff caused by paging and registration signalling. The upper boundary for the size of an LA is the service area of a mobile services switching center (MSC). In that extreme case, the cost of paging is at its maximum but no registration is needed. On the other hand, if each cell is an LA, the paging cost is minimal but the cost of registration is the largest. Between these extremes lie one or more partitions of the MSC service area that minimize the total cost of paging and registration. In this paper, we seek to determine the location areas in an optimum fashion. Cell to switch assignments are also determined to achieve the minimization of the network cost. For that purpose, we use the available network information to formulate a realistic optimization problem, and propose an algorithm based on simulated annealing (SA) for its solution. Then, we investigate the quality of the SA-based technique by comparing it to greedy search, random generation methods, and a heuristic algorithm.

End-to-end reliable event transfer in wireless sensor networks

A new group of end-to-end reliable event transfer schemes is introduced for sensor networks. In these schemes, reliable event delivery is considered rather than reliable delivery of data packets, since the ultimate goal is the detection of events in sensor networks. Reliable event transfer is critical in many applications. Therefore, the need for transferring the events in a reliable way coerced us to introduce a new group of end-to-end event transfer schemes, in sensor networks end-to-end reliable event transfer schemes can be categorized into two broad classes, as acknowledgement based and non-acknowledgement based. Our new schemes introduced in this paper are in acknowledgement based class. The performance of the proposed schemes is also evaluated for various application areas by simulation.

Extracting trust information from security system of a service

The issue of trust is a research problem in emerging open environments, such as ubiquitous networks. Such environments are highly dynamic and they contain diverse number of services and autonomous entities. Entities in open environments have different security needs from services. Trust computations related to the security systems of services necessitate information that meets needs of each entity. Obtaining such information is a challenging issue for entities. In this paper, we propose a model for extracting trust information from the security system of a service based on the needs of an entity. We formally represent security policies and security systems to extract trust information according to needs of an entity. The formal representation ensures an entity to extract trust information about a security property of a service and trust information about whole security system of the service. The proposed model is applied to Dental Clinic Patient Service as a case study with two scenarios. The scenarios are analyzed experimentally with simulations. The experimental evaluation shows that the proposed model provides trust information related to the security system of a service based on the needs of an entity and it is applicable in emerging open environments.

Design and performance evaluation of a banyan network based interconnection structure for ATM switches

This paper presents a new self-routing packet network called the plane interconnected parallel network (PIPN). In the proposed design, the traffic arriving at the network is shaped and routed through two banyan network based interconnected planes. The interconnections between the planes distribute the incoming load more homogeneously over the network. The throughput of the network under uniform and heterogeneous traffic requirements is studied analytically and by simulation. The results are compared with the results of the baseline network and another banyan network based parallel interconnection network. It is shown that, for the proposed design, a higher degree of heterogeneity results in better performance.

Trust assessment of security for e-health systems

Abstract The expansive connectivity of emerging information systems has set the stage for pervasive access to healthcare services via e-health systems for selecting the best possible healthcare services. Emerging systems are expected to be highly dynamic open environments connecting diverse number of healthcare services and autonomous entities that are autonomous agents or software applications representing patients. Entities in such dynamic environments may have different security needs from e-health systems raising the challenge of trust computations regarding security. In this research, we proposed a trust assessment model of an e-health service from the viewpoint of an entity. The model contains a comprehensive architecture applicable to different types of entities, and a novel set of trust assessment metrics may be used to assess a specific property of a security system (i.e. partial metrics) or all properties (i.e. total metrics). The simulation based evaluation of proposed model in the context of a Hospital Online Appointment Service has shown that the proposed model provides better trust computation results than existing trust models for e-health systems. Furthermore, the entities are also able to assess the trust even with incomplete security information.

A formal role-based access control model for security policies in multi-domain mobile networks

Mobile users present challenges for security in multi-domain mobile networks. The actions of mobile users moving across security domains need to be specified and checked against domain and inter-domain policies. We propose a new formal security policy model for multi-domain mobile networks, called FPM-RBAC, Formal Policy Model for Mobility with Role Based Access Control. FPM-RBAC supports the specification of mobility and location constraints, role hierarchy mapping, inter-domain services, inter-domain access rights and separation of duty. Associated with FPM-RBAC, we also present a formal security policy constraint specification language for domain and inter-domain security policies. Formal policy constraint specifications are based on ambient logic and predicate logic. We also use ambient calculus to specify the current state of a mobile network and actions within security policies for evaluation of access requests according to security policies. A novel aspect of the proposed policy model is the support for formal and automated analysis of security policies related to mobility within multiple security domains.

A Model of Security Information Flow on Entities for Trust Computation

Service oriented environments are computer network systems that are highly dynamic and change with time. Entities in such environments have different security needs from services. Management of security information in dynamic environments with multiple entities, each with its own changing needs, is a complex task. The complexity mainly arises from a lack of trust to security information collected from entities and services. Therefore, the trust assessment about services, which is a crucial task, depends on the propagation of security information. In this paper, a new model of security information flow over entities is proposed for trust computation about services. The model is presented together with a simple scenario to clarify the proposed model.

Attacks and improvements to chaotic map-based RFID authentication protocol

Because of its low cost and ease of deployment, radio frequency identification RFID technology offers great potential for all applications that require identification. Main obstacle for wide adoption of this technology is the concerns about its security and privacy issues. Many RFID authentication protocols have been proposed to provide desired security and privacy level for RFID systems. Recently, Benssalah et al. have proposed a chaotic map-based RFID security protocol. In this paper, we analyze the security of this protocol and discover its vulnerabilities. We show that message generation arises some weaknesses, and this protocol is vulnerable to tracking, tag impersonation, and de-synchronization attacks. The success probabilities of the proposed attacks are significant, and their complexities are polynomial. Furthermore, we propose an RFID authentication protocol. Our protocol utilizes the Chebyshev chaotic map hard problem and conforms to the EPCglobal Class 1 Generation 2 EPC C1-G2 standard. Our protocol eliminates the weaknesses of the protocol of Benssalah et al. Copyright