Ing-Yi Chen

Resource Allocation with Interference Avoidance in OFDMA Femtocell Networks

Interference control and quality-of-service (QoS) awareness are the major challenges for resource management in orthogonal frequency-division multiple access femtocell networks. This paper investigates a self-organization strategy for physical resource block (PRB) allocation with QoS constraints to avoid the co-channel and co-tiered interference. Femtocell self-organization including self-configuration and self-optimization is proposed to manage the large femtocell networks. We formulate the optimization problem for PRB assignments where multiple QoS classes for different services can be supported, and interference between femtocells can be completely avoided. The proposed formulation pursues the maximization of PRB efficiency. A greedy algorithm is developed to solve the resource allocation formulation. In the simulations, the proposed approach is observed to increase the system throughput by over 13% without femtocell interference. Simulations also demonstrate that the rejection ratios of all QoS classes are low and mostly below 10%. Moreover, the proposed approach improves the PRB efficiency by over 82% in low-loading scenario and 13% in high-loading scenario.

Analysis of a software reliability growth model with logistic testing-effort function

We investigate a software reliability growth model (SRGM) based on the Non Homogeneous Poisson Process (NHPP) which incorporates a logistic testing effort function. Software reliability growth models proposed in the literature incorporate the amount of testing effort spent on software testing which can be described by an exponential curve, a Rayleigh curve, or a Weibull curve. However it may not be reasonable to represent the consumption curve for testing effort only by an exponential, a Rayleigh or a Weibull curve in various software development environments. Therefore, we show that a logistic testing effort function can be expressed as a software development/test effort curve and give a reasonable predictive capability for the real failure data. Parameters are estimated and experiments on three actual test/debug data sets are illustrated. The results show that the software reliability growth model with logistic testing effort function can estimate the number of initial faults better than the model with Weibull type consumption curve. In addition, the optimal release policy of this model based on cost reliability criterion is discussed.

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Storage nodes are expected to be placed as an intermediate tier of large scale sensor networks for caching the collected sensor readings and responding to queries with benefits of power and storage saving for ordinary sensors. Nevertheless, an important issue is that the compromised storage node may not only cause the privacy problem, but also return fake/incomplete query results. We propose a simple yet effective dummy reading-based anonymization framework, under which the query result integrity can be guaranteed by our proposed verifiable top- k query (VQ) schemes. Compared with existing works, the VQ schemes have a fundamentally different design philosophy and achieve the lower communication complexity at the cost of slight detection capability degradation. Analytical studies, numerical simulations, and prototype implementations are conducted to demonstrate the practicality of our proposed methods.

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The complexity that telecommunications companies are faced with in their business processes and their information technology (IT) systems is especially apparent in their billing systems. These systems are required not only to handle large volumes of data and frequent changes in business rules, but also to ensure that the billing be done accurately and on time. This paper describes a solution that was developed to address this problem. It consists of an operations support system that is compliant with NGOSS (Next Generation Operations System and Software) and it implements a service-oriented architecture (SOA) that relies on an enhanced enterprise service bus (ESB). This enhanced ESB, referred to here as an adaptable service bus (ASB), makes it possible to carry out changes to business rules at runtime, thus avoiding costly shutdowns to the billing application. An implementation of this system has been operational in ChungHwa Telecom Company, Taiwan, since January 2008 and provides complete support to its billing application. As a result, the billing process cycle time has been reduced from 10–16 days to 3–4 days, which cleared the way for further growth of the business.

Query Result Completeness Verification in Tiered Sensor Networks

Telemedicine applications are evolving quickly as information technologies improve. New requirements from users and changes in business processes make it necessary to frequently alter applications. Developers are responsible for redesigning the applications on both the user and server sides to meet the latest requirements. This is both time consuming and expensive. A new approach is needed to improve the support of application construction and to reduce the costs involved. In this paper, we use OSGi as a platform, on which to combine components in order to form new functionalities used pervasively in different devices on the user side. Examples include cell phones, PDAs, and home gateways. For server side applications, we divided the health care system into several layers and combined the services provided by these modules using a loose-coupling mechanism - process choreography. When the requirements or system flows of the telemedicine server are changed, the proposed system can adapt to meet new needs by replacing the bundles on the edge server and reconfiguring the business process used in the health care system.

A runtime-adaptable service bus design for telecom operations support systems

In this paper, a simple codec algorithm, based on Reed-Solomon (RS) codes, is proposed for erasure correcting in RAID (redundant array of independent disks) level 6 systems. Unlike conventional RS codes, this scheme, with a mathematical reduction method, called reduced static-checksum table approach, could improve coding performance, including encoding and decoding procedures. This scheme uses current industrial RAID-5 controllers as well as the regular hardware, and is without extra cost in adding any new equipment. Moreover, our algorithm is able to expand to correct multiple failed-disks while others, EvenOdd codes for example, cannot do so. Also, this scheme performs all computations with only simple exclusive-OR (XOR) operators, the same as EvenOdd codes. For most RAID architectures, this new XOR-based RS code could adapt to implementation in terms of reliability, flexibility and lower cost.

Pervasive Digital Monitoring and Transmission of Pre-Care Patient Biostatics with an OSGi, MOM and SOA Based Remote Health Care System

In this paper, we propose an algorithm to construct the ordered binary decision diagram (OBDD) representing the cut function of a terminal-pair network. The algorithm recognizes isomorphic sub-problems and thus avoids redundant computations. The system reliability could be efficiently computed by the OBDD. Finally, we propose an approach to compute the importance measures for multiple components by traversing the OBDD only once. The correctness and the effectiveness of our approach are demonstrated by experiments on 30 benchmark networks. The experimental results on a 2-by-100 lattice network, which has 2/sup 99/ paths or 10,000 cuts, show an impressive improvement compared to the previous works using the sum of disjoint products method that have exponential complexity. The CPU time of our method, including the calculation of not only the reliability but also the importance measures, for a 100-stage lattice network is only about 0.24 seconds. Thus, this approach is very helpful for the reliability and sensitivity analysis of large networks.

An XOR based Reed-Solomon algorithm for advanced RAID systems

As checking spam became part of our daily life, unsolicited bulk e-mails (UBE) have become unmanageable and intolerable. Bulk volume of spam e-mails delivering to mail transfer agents (MTAs) is similar to the effect of denial of services (DDoS) attacks as it dramatically reduces the dependability and efficiency of networking systems and e-mail servers. Spam mails may also be used to carry viruses and worms which could significantly affect the availability of computer systems and networks. There have been many solutions proposed to filter spam in the past. Unfortunately there is no silver bullet to deter spammers and eliminate spam mails. That is, in isolation, each of existing spam protection mechanisms has its own advantages and disadvantages. In this paper, we analyze the shortcomings of existing anti-spam solutions and propose a multi-faceted approach using the spam-resistible mail agent (SRMA), which provides the most advantages and the least disadvantages of existing anti-spam solutions. Our experiments show that the proposed SRMA is immune to existing spambots and the prototype proves to be effective, feasible and deployable.

A cut-based algorithm for reliability analysis of terminal-pair network using OBDD

In large scale sensor networks, storage nodes may be placed as an intermediate tier for caching the sensor readings and respond to queries, resulting in reduced power consumption and storage savings for sensors. However if a storage node is compromised, it will create privacy issues and may return fake/incomplete results. Thus we suggest a simple yet effective dummy reading-based anonymization framework, whereby query result integrity can be guaranteed by our proposed Verifiable top-k Query (VQ) scheme. Compared to existing work, VQ schemes have a different design philosophy and achieve the lowest communication complexity, with only constant overhead, at with a small degradation of detection capability. Analysis and numerical examples demonstrate the practicality of our proposed approach.

A multi-faceted approach towards spam-resistible mail

Memory repair by using spare rows/columns to replace faulty rows/columns has been proved to be NP-complete. Traditional perfect algorithms are comparison-based exhaustive search algorithms and are not efficient enough for complex problems. To overcome the deficiency of performance, a new algorithm has been devised and presented in this paper. The algorithm transforms a memory repair problem into Boolean function operations. By using BDD (binary decision diagram) to manipulate Boolean functions, a repair function which encodes all repair solutions of a memory repair problem can be constructed. The optimal solution, if it exists, can be found efficiently by traversing the BDD of a repair function only once. The algorithm is very efficient due to the fact that BDD can remove redundant nodes, combine isomorphic subgraphs together, and have very compact representations of Boolean functions if a good variable ordering is chosen. The remarkable performance of the algorithm can be demonstrated by experimental results. Because a memory repair problem can be modeled as a bipartite graph, the algorithm may be useful for researchers in other fields such as graph theory.