Abstract-This paper proposes a new approach to simplify the two-dimensional random walk models capturing the movement of mobile users in Personal Communications Services (PCS) networks. Analytical models are proposed for the new random walks. For a PCS network with hexagonal configuration, our approach reduces the states of the two-dimensional random walk from (3 2 + 3 5) to ( + 1) 2, where is the layers of a cluster. For a mesh configuration, our approach reduces the states from (2 2 2 + 1) to ( 2 + 2 + 4) 4 if is even and to ( 2 + 2 + 5) 4 if is odd. Simulation experiments are conducted to validate the analytical models. The results indicate that the errors between the analytical and simulation models are within 1%. Three applications (i.e., microcell/macrocell configuration, distance-based location update, and GPRS mobility management for data routing) are used to show how our new model can be used to investigate the performance of PCS networks.

The star graph, though an attractive alternative to the hypercube, has a major drawback in that the number of nodes for an n-star graph must be n!, and thus considerably limits the choice of the number of nodes in the graph. In order to alleviate this drawback, the arrangement graph was recently proposed as a generalization of the star graph topology. The arrangement graph provides more flexibility than the star graph in choosing the number of nodes, but the degree of the resulting network may be very high. To overcome that disadvantage, this paper presents another generalization of the star graph, called the (n,fc)-star graph. We examine some topological properties of the (n, fc)-star graph from the graph-theory point of view. It is shown that two different types of edges in the (n,fc)-star graph prevent it from being edge-symmetric, but edges in each class are essentially symmetric with respect to each other. Also, the diameter and the exact average distance of the (n, fc)-star graph are derived. In addition, the fault-diameter for the (n,fc)-star graph is shown to be at most the fault-free diameter plus three.

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Adoption of Personal Health Record (PHR) applications has been slow due to consumers' concerns in security, privacy and trust, and the challenges in interoperability and integration with other Electronic Medical Record (EMR) systems. This paper proposes the design for a secure interoperable cloud-based PHR service. To enhance the portability and interoperability, we use the Continuity of Care Document (CCD) for both storing and exchanging the PHR information for an individual. To provide self-protecting security for each CCD instance, we apply a broad spectrum of security mechanisms -including access control, encryption, and digital signature -in an integrated, embedded, and finegrained manner, based on open standards such as eXtensible Access Control Markup Language, XML Encryption, XML Signature, and XML Key Management Specification. To support patient-controlled encryption and privacy-preserving keyword search, we use ciphertext-policy attribute-based encryption and public-key encryption with keyword search schemes, again in an integrated, embedded, and fine-grained manner.