A Multiqueue Service Room MAC Protocol for Wireless Networks with Multipacket Reception Abstract-An adaptive medium-access control (MAC) protocol for heterogeneous networks with finite population is proposed. Referred to as the multiqueue service room (MQSR) protocol, this scheme is capable of handling users with different quality-of-service (QoS) constraints. By exploiting the multipacket reception (MPR) capability, the MQSR protocol adaptively grants access to the MPR channel to a number of users such that the expected number of successfully received packets is maximized in each slot. The optimal access protocol avoids unnecessary empty slots for light traffic and excessive collisions for heavy traffic. It has superior throughput and delay performance as compared to, for example, the slotted ALOHA with the optimal retransmission probability. This protocol can be applied to random-access networks with multimedia traffic.Index Terms-Medium-access control (MAC), multipacket reception (MPR), random-access network. In this paper, we have proposed a MQSR MAC protocol designed explicitly for multiaccess networks with MPR capability. By optimally exploiting all available information up to the current slot, the proposed MQSR protocol dynamically controls the size of the access set according to the traffic load and the channel MPR capability so that the expected number of successfully transmitted packets is maximized under a set of heterogeneous delay constraints. As a consequence, the channel MPR capability is efficiently exploited and the channel capacity is achieved at heavy traffic load.. A heuristic analysis on the packet delay provided by the MQSR protocol at any traffic load is given in Appendix B. While deriving an upper bound on the packet delay, we provide insights into the behavior of the MQSR protocol and answer the question whether it is possible that a user stays in the service room for an infinitely long period. Upper bounds on the expected number of slots that an active user (a user who enters the service room with a packet) and an idle user (a user who enters the service room without packet) spend in the service room during one visit are obtained.

O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Test Data Compression for Scan-Based BIST Aiming at 100x Compression Rate SUMMARY We developed test data compression scheme for scanbased BIST, aiming to compress test stimuli and responses by more than 100 times. As scan-BIST architecture, we adopt BIST-Aided Scan Test (BAST), and combines four techniques: the invert-and-shift operation, runlength compression, scan address partitioning, and LFSR pre-shifting. Our scheme achieved a 100x compression rate in environments where Xs do not occur without reducing the fault coverage of the original ATPG vectors. Furthermore, we enhanced the masking logic to reduce data for X-masking so that test data is still compressed to 1/100 in a practical environment where Xs occur. We applied our scheme to five real VLSI chips, and the technique compressed the test data by 100x for scan-based BIST. With advancements in semiconductor technology, the cost of testing VLSI chips has been increasing [1] . Testing them requires a large amount of test data and long testing time due to their increased scale, resulting in high costs. Therefore, the test data, including test stimuli and test responses, must be reduced.. One promising testing technique is the built-in self-test (BIST), in which a linear feedback shift register (LFSR) is used as a pseudo-random test generator and a multiple-input signature register (MISR) is used as a test response compactor [2] . BIST has been considered a practical solution to the difficulties with VLSI testing [3] , [4] . One of drawbacks of BIST is the difficulty to achieve the high fault coverage of the ATPG technique. Consequently, many hybrid BIST schemes (we use this term as its generalized meaning [5] , that is, the combinations of BIST and external testing) have been proposed to provide better test patterns to circuits under test (CUTs), still reducing test cost [5]- [9] . As the number of transistors being integrated into chips increases, more attention has been focused on SoC testing.. As a result, many commercial hybrid BIST The key technique for the hybrid BIST is significantly reducing stimuli and handling unknown (X) values. Circuits with hybrid BIST architectures use bit flipping circuits and/or broadcasters that propagate test stimuli into multiple scan chains. The techniques mentioned above have moderate compression rates (up to 25x) or have much higher rates in exchange for some limitation on the applicable test vectors, due to the arrangement of scan chains. For example, EDT achieves compression rates of 5x-25x [10]- [12] , and BAST achieves up to 22x [17] . While UltraScan enables more than 100x compression, 10x compression rate out of 100 is due to its faster ATE clock cycle [15] , [16] .. For tolerating Xs, on the other hand, coding-theorybased static masking logics such as X-Compact and Convolutional Compactor have been proposed, as well as filtering logics such as X-filter and Channel Masking that are controlled by an ATE [17]- [21] .. We developed test data compression scheme for scanbased BIST, aiming to compress test stimuli and responses by more than 100 times. The scheme combines four techniques: invert-and-shift operation, run-length compression, scan address partitioning, and LFSR pre-shifting. Our scheme achieved a 100x compression rate in environments where Xs do not occur without reducing the fault coverage of the original ATPG vectors. Furthermore, we enhanced the masking logic to reduce the amount of information for X-masking so that test data was still compressed to less than 1/100 in practical environments where Xs occur. We applied our scheme to five real VLSI chips. This paper is organized as follows. In Sect. 2, we present the proposed compression scheme, followed in Sect. 3 by the results of using it in the real circuits. In Sect. 4, we describe, the test response compression considering Xmasking and show some experimental results. Section 5 concludes the paper. We developed a scheme for scan-based BIST that can compress test stimuli and responses. The scheme combines the invert-and-shift operation, run-length compression, scan address partitioning, and LFSR pre-shifting. It achieved a 100x compression rate for environment in which X does not occur without reducing the fault coverage of the original ATPG. Experiments using five real VLSI chips showed that combining the four techniques enabled compression rates of 144x to 370x compared to an ATPG. Furthermore, we enhanced the masking logic to reduce data for X-masking. Experiments considering Xs showed that test data was still compressed by 101x to 312x while achieving more than 99% of fault coverage, of the ATPG.

B I I O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B


Integrating agile software development into stage-gate managed product development Abstract Agile methods have evolved as a bottom-up approach to software development. However, as the software in embedded products is only one part of development projects, agile methods must coexist with project management models typically of the stage-gate type. This paper presents a qualitative case study of two large independent software system projects that have used eXtreme Programming (XP) for software development within contexts of stage-gate project management models. The study is comprised of open ended interviews with managers as well as practitioners, followed by a structured, fully traceable, qualitative analysis. We conclude that it is possible to integrate XP in a gate model context. Key issues for success are the interfaces towards the agile subproject and management attitudes towards the agile approach. Agile methods have evolved as a new approach to developing software products (Agile Manifesto, 2001 ). The methods have been successfully implemented in small to medium sized projects, and the principles of the agile methods have inspired software developers in wide-ranging application domains (e.g., Vanhanen and Kä hkö nen, 2003; Fuqua and Hammer, 2003; Rasmussen, 2003; Schuh, 2001; Grenning, 2001; Poole and Huisman, 2001; Murru et al., 2003; Sharp and Robinson, 2004; Karlströ m, 2002) . The agile methodologies offer down-to-earth approaches to software development that focus on simplifying and improving the software development process, making the customers, the developers and the final product the most important (Agile Manifesto, 2001) . A summary of the main principles involved in the agile methods as formulated by the agile manifesto is given in Table 1. In real-life, however, software development projects are not isolated activities. They usually exist as sub-projects in an environment composed of hardware development, marketing, production planning etc. which all must be managed and coordinated concurrently (Cooper, 2001) . Furthermore, software development seldom starts from scratch; legacy software constitutes the core of new products to which new functionality and other types of customer value are added, or legacy software is moved to new platforms. The traditional approach when managing a complex development project situation is to use a project management model (PM) such as Cooper_s Stage-gate model (Cooper, 2001 ), see Fig. 1 . The PM gives support not only for the communication within the project, but also for decision makers sponsoring the project or acquiring the outcome of the project. The concepts of a PM are not connected to any specific domain; these models are sufficiently generic to be applied to any kind of project. However, PMs currently tend to have a basic sequential structure, i.e., distinct phases of pre-study, feasibility study, execution and conclusion. From a management point of view this is quite natural. Between each stage there is a decision gate at which the project must meet predetermined demands such as producing certain documents. The project sponsors can then make the decision whether the project is to proceed to the next phase, stay in the previous phase or be abolished.. Gate oriented PMs are compatible with maturity-oriented software process improvement work, using for instance the CMM framework (Paulk et al., 1993) . Both PMs and the maturity models aim at defining structures, roles and responsibilities within the organisation, but do not intend to actually dictate how the actual technical project work is to be performed. The agile methodologies can be considered a reaction to these maturity-oriented approaches within the software development process field, but we do not believe that the two schools are contradictive. Software projects using agile methods must be able to exist within Table 1 The agile manifesto (Agile Manifesto, 2001) 1. Individuals and interactions over processes and tools. 2. Working software over comprehensive documentation. 3. Customer collaboration over contract negotiation. 4. Responding to change over following a plan. Fig. 1 Stage-Gate modeli (Cooper, 2001) environments structured using gate oriented PM. Mature organizations add not only rigour and order to a chaotic environment, but also certain characteristics similar to a successful agile development project (Paulk et al., 1995; Paulk, 1999; Paulk, 2001) .. Gate oriented PM models have already been integrated with more iterative development models in general (Gilb, 1998) and the Rational Unified Process (RUP) in particular (Royce, 1998) . A proposal on how to integrate an instance of a gate model with various development methodologies, has been presented (Wallin et al., 2002) , although only at an overview level. The research presented by Wallin et al. presents the overall concepts and problems involved in combining a project management model with several different software development processes, including RUP and eXtreme Programming (XP). The presentation, however, is lacking in detail of how the interfaces are defined and how the different processes need to be modified.. Software projects using agile methods have indeed been executed in traditional PM environments, but the main characteristics of the PM are not originally designed for the management of software projects using agile methods, and their advantages are therefore not utilised in the management of the project. The agile development has in these cases had no effect on the project management and overall management of the project despite demonstrating success on the development level.. Rainer et al. present interesting work on Bbuy in'' for software development process improvement (Rainer et al., 2003) . This is an especially relevant issue for agile methods as these are often introduced bottom up in contrast to top down for most other software development processes. They present the importance of showing local effectiveness of the process to developers in contrast to metrics from other locations.. Boehm and Turner (Boehm and Turner, 2004) discuss contrasts between plan driven software development and agile approaches at length in their book. Gate models in general are a form of plan driven models, defined on a higher level of abstraction than those discussed. Those used by the companies involved in this study, however, are more specialised. Interestingly one of the conclusions drawn in the book is that future projects will need both agility and discipline, which can be implemented by containing the agile development methodology within the gate model. XP has been structured into values, principles and practices. Values are at a high level of abstraction and are not specific to software engineering or XP (Beck and Andres, 2004) . The fundamental values presented by Beck are Communication, Simplicity, Feedback, Courage and Respect, but it is also contended that a team needs further values to function. The principles are intended to bridge the gap between the abstract general values and the detailed specific practices. The principles, in contrast to the values will differ depending on the domain that you are in. The principles presented in XP are humanity, economics, mutual benefit, self similarity, improvement, diversity, reflection, flow, opportunity, redundancy, failure, quality, baby steps and accepted responsibility. For details on the specifics of the values, principles and practices of XP, please refer to Beck (Beck and Andres, 2004) .. XP is most frequently presented as the 12 detailed practices that are common knowledge in the Software Engineering community by now. Presenting XP as composed of 12 practices is similar to describing a car as composed of four wheels. While the description is true and the wheels really are an important part of the car, there are a many crucial details omitted. Simply quoting these practices might give an insight in what the team members were doing, but would not describe the major factors that make XP work.. In this paper we investigate the experiences from integrating agile teams in traditional project management models. Two cases are studied, both within large system development companies, comprising both software and hardware development. Ericsson Microwave Systems (EMW) is in the domain of airborne defence radar systems and ABB in industrial control systems. In both cases the agile method used was XP (Beck and Andres, 2004) while each company used their respective corporate variant of the gate model. We present and motivate a feasible approach for this investigation, using qualitative research methodology (Seaman, 1999) . As a result of this research approach, many interesting observations regarding the specific effects of Stage-Gate management as well as agile methodologies, and their combination are made. These are presented in the paper in an as structured fashion as the methodology allows. A shorter, more practice oriented presentation of the cases together with an additional case has recently been published (Karlströ m and Runeson, 2005) . This paper is organised as follows. In Section 2, the study scope is presented. In Section 3, background information about the companies and development teams involved is presented. The study design is presented in Section 4 and study validity in Section 5. Finally, the results are presented in Section 6 and a summary is provided together with the conclusions in Section 7. The results of the study show that it is indeed possible to successfully integrate project management models of the stage-gate type with XP projects. This has been achieved through complete isolation of the engineering teams and attempting to make these look as similar to a regular team as possible. Based on the results we identify certain key issues that are believed would make a more effective project management, involving agile methods. These include: An observed benefit due to the increased quality of the developed code was the lack of Bbig-bang'' integration problems, making the overall project much more predictable. The increased control felt both by the customers and developers is also considered to be an advantage in the cases studied. This is in contrast to the contradictive lack of control felt by the management.. In summary there are several interesting benefits of integrating agile teams into traditional stage-gate project management models and we have identified some key issues regarding these. There are also some key issues that must be addressed in order to be successful, some of which have been identified in this paper, in particular a clear customer interface, strategies for artefacts in the gate model, balance between micro and macro level planning, and management understanding of the agile principles.. Acknowledgments The authors would like to thank all the people that were available for interviews at ABB and EMW. This work is partially funded by the Swedish Research Council under grant 622-2004-552 for a senior researcher position in Software Engineering. The ABB model structure is more fixed than the EMW structure, but neither company managed to adapt the model to accommodate the agile teams. Customer ABB appointed a customer role to the TPM, while the customer was less clear in the EMW case.. Finish with a brief summary, thank the subject, and confirm that it is ok to come back to the subject with questions in retrospect. Inform about the feedback procedure. He has five years of industrial experience as a consulting expert in software engineering. Prof. Runeson's research interests concern methods and processes for software development, with special focus on verification and validation. He has published more than 70 papers in international journals and conferences and is the co-author of a book on experimentation in software engineering. He is member of the editorial board of Empirical Software Engineering. Following is a complete description and discussion of the analysis steps taken in the study, an overview of which is given in Fig. 2 .. During the course of the analysis, information takes on several forms at different levels of abstraction. The subjects act in and observe the reality within their organisation. Their reflections and observations on the area of research are discussed in the semi-structured interviews and recorded as an audio file. These recordings are then fully transcribed and interesting quotes are identified. Next, quotes are coded and grouped to support each other and finally individual results are identified from these groups. The grouping was conducted using plain tables in a word processing product.. The different forms that the information takes in this investigation are numbered 1 to 7 in Fig. 2 . The first form is the actual event in the study context. The second form is the subject's perception of the event, and so on as labelled in Fig. 2 . Each change in form is due to some kind of treatment and we refer to this change in form as a transition. The transitions are denoted ! through K in Fig. 2 and the subsequent tables. Each transition introduces additional validity threats to the results, depending on the treatment performed in the transition. Treatments and the validity threats introduced are summarised in Table 3 . Countermeasures to these validity threats are addressed in Section 5. These countermeasures can also be seen in part throughout the study design, as the one of the goals of a good study design is to minimise the effects of threats. Some of the transitions in the analysis were performed redundantly by two researchers independently of each other. The results of the individual analyses in these transitions were compared and aggregated into a common analysis result. This is indicated by a star next to transitions involving redundancy in Tables 3 and 5 . The analysis performed in the study is of the inductive type, implying that patterns, themes and categories of analysis come from the data itself in contrast to being imposed prior to the data collection, as is the case in deductive analysis. All approaches used in inductive analysis according to Patton have been considered in the analysis, except for the synthesising of studies (Patton, 2001) . This is however currently under preparation as further work is being planned. The main categories of analysis identified in the study were: The coded data were stored in tables together with references to the individual interview statement that the data was based on in order to ensure full traceability. These tables were then used to identify results across interview subjects and companies and draw the final conclusions.. In addition to the interview data, other information sources in the study include archival analysis of internal documents, including process description documents as well as experience documents, written by the teams to summarise their use of the new methodology, and informal information gained through conversations outside the interviews. This section presents the results identified in the case studies through the analysis procedure described in the paper. The results are presented individually and aggregated conclusions are presented in Section 7. We present the findings structured into five major groups in Section 6.1-6.5:. Further, among the observations, there are three contrasting perspectives on the observations; agile vs. non-agile teams, management vs. engineers, and EMW vs. ABB. The observations are discussed with respect to these perspectives in Section 6.6.

O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


A robust watermarking scheme using phase shift keying with the combination of amplitude boost and low amplitude block selection Watermarking is a potential method for copyright protection and authentication of multimedia data in the internet. The watermarking process can be viewed as a communication task, where the watermark acting like information is embedded into a host image acting like noise in a communication channel which is susceptible to all kinds of attacks acting like jamming. In a previous paper, we proposed a robust watermarking scheme using frequency shift keying (FSK). In the scheme, high-variance block selection (HVBS) is employed to enhance robustness. In this paper, a novel watermarking scheme using phase shift keying (PSK) modulation with amplitude boost (AB) and low amplitude block selection (LABS) is proposed. AB is hired to increase the robustness while LABS is employed to improve the imperceptibility. With proper combination of AB and LABS, the proposed scheme achieves superior performance in terms of robustness and imperceptibility.In order to demonstrate the effectiveness of the proposed scheme, simulations under various conditions were conducted. The empirical results showed that QPSK is the best choice among other PSKs and the proposed scheme can sustain most common attacks including JPEG compression, rotating, resizing, cropping, painting, noising and blurring etc. The empirical results also showed that the scheme with AB and LABS properly combined outperforms the scheme without. The gain of the former over the latter is more significant for host images with smooth characteristics than those with high-frequency characteristics. Simulation comparison with two other schemes (the Hsu's scheme and the Chen's scheme) showed that the proposed scheme is the most robust among the three. Because digital information is easy to transmit and duplicate unauthorized reproduction becomes a serious problem. While copyright and authentication gradually lose its security, the need for protecting intellectual property becomes more and more important. Recently, digital watermarking has been proposed as one solution to the problem of protecting the intellectual property [1] [2] [3] [4] [5] [6] [7] [8] [9] . Unlike the traditional visible watermark found on papers, a digital watermark does not change the perceived quality of the image content. It is a potential method to discourage unauthorized copying or attesting origin of the image. Generally, a digital watermark must fulfill the following requirements: imperceptible, robust and secure.. Watermarking techniques can be classified into two categories, one is processed in the spatial domain and the other is accomplished in the transform domain. In the spatial domain [1, 2] , the visual modes derived from data compression are very suitable for digital watermarking. Many excellent hiding methods published are based on just noticeable distortion (JND) [9] . Vector quantization is one of the widely used schemes to embedding watermarks. Lu and Sun [10] used codeword indices to carry the watermark information. However, the watermarks embedded in the spatial domain are not as robust as most of those embedded in the transform domain.. In the transform domain many approaches [3] [4] [5] [6] [7] are based on the Discrete Cosine Transform (DCT). Hsu and Wu [4] proposed a scheme by block-based image-dependent permutation of the watermarks in the middle band of the DCT coefficients and obtained good performance. Wu and Hsieh [6] used zerotree structure to embed watermark by rearranging the DCT coefficients in a way similar to the multiresolution analysis (MRA) of wavelet transforms. Moreover, Langelaar and Lagendijk [7] proposed a scheme that employs three parameters to guarantee the performance. That is, first use a large number of the DCT blocks to embed single information bit; next, use small JPEG quality factor to enhance the watermark robustness against re-encoding attacks; third, adopt the so-called minimal cutoff index in the zigzag scanned fashion of the DCT coefficients that can be removed from the watermarked image.. The discrete wavelet transform (DWT) is another effective transform-domain method for concealing watermarks. Tsia et al. [8] utilizes the wavelet multi-resolutional structure to decompose the image and scatter the two-dimensional watermark to select the location during the secret data embedding. Wei et al. [9] controlled the wavelet coefficients so that the watermark noises do not exceed the just-noticeable difference (JND) of wavelet coefficients during watermark insertion. More papers based on the DWT for watermarking can be found in Refs. [11, 12] .. Another method in the transform domain is to hide watermarks in the discrete Fourier transform (DFT) coefficients of the host image. Ruanaidh et al. [13] presented a phasebased method in the DFT domain and used an optimal detector for watermark recovery. Based on the Fourier-Mellin Transform Ruanaidh and Pun [14] presented a watermarking scheme that achieves rotation, scale and translation (RST) invariant. The scheme achieves robustness while sustains the RST attacks. Premaratne and Ko [15] proposed a new concept for embedding and detecting the watermark in the Discrete Fourier Transform. Since the embedding is independent of the image content, speedy embedding highly suitable for video streams can be achieved. Solachidis and Pitas [16] proposed a watermarking scheme which embeds a circularly symmetric watermark on a ring in the 2D DFT domain. The circularly symmetric watermark was used to solve the rotation invariance problem in the watermark detection in which a correlation operation was used.. In a previous paper [17] , we proposed a DCT domain watermarking scheme using the frequency shift keying (FSK). In the scheme, high-variance block selection (HVBS) is employed to enhance robustness. In this paper, we proposed a DFT domain watermarking scheme using the phase shift keying (PSK). In our proposed scheme, the watermark bits are first expanded by spread spectrum and then concealed by PSK modulation in the DFT coefficients of the host image. The PSK embedding is employed due to its superior noise immunity. In the PSK embedding, the watermark information is embedded in the phase part of the host image. Thus, the threshold effect in which the quality of the recovered watermark plunges when the amplitudes of the DFT coefficients used for embedding the secret bits are below a threshold value may occur [18] . In this paper, a novel idea combining amplitude boost (AB) and low-amplitude block selection (LABS) is proposed to curb the threshold effect raised by PSK. We demonstrated that by properly combining AB and LABS robustness can be enhanced without sacrificing imperceptibility. Meanwhile, in our scheme neither the original host image nor the original watermark is required during the watermark detection process.. The remainder of this paper is organized as follows. In Section 2, the proposed concealing algorithm is presented. The watermark extracting process is presented in Section 3. Empirical results are presented in Section 4. Finally, Section 5 concludes this paper. Digital watermarking is a potential method to discourage unauthorized copying or attest origin of digital data that includes audio, video and images. In this paper we present a robust watermarking scheme for still images using PSK with amplitude boost and low amplitude block selection. The amplitude boost strategy is used to enhance the robustness and the low amplitude block selection strategy is used to reduce the degradation of the host image caused by watermark concealing. Empirical results show that the proposed scheme can sustain attacks like JPEG lossy compression, Table 6 The performance comparison of the image manipulation attacks between the proposed scheme and the Hsu's scheme for Lena image rotation, resizing, cropping, painting, noising and blurring.. From the experiment results, we can see that the WABLABS scheme with AB and LABS properly combined is superior to the scheme without. Furthermore, the AB strategy is especially effective at encountering the resizing, noising and blurring attacks for which the WOAB scheme simply fails for the smooth images like Lena. The other advantage of our scheme is that the original host image and watermark are not needed during the watermark detection process.

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Language-based security on Android In this paper, we initiate a formal study of security on Android: Google's new open-source platform for mobile devices. Specifically, we present a core typed language to describe Android applications, and to reason about their dataflow security properties. Our operational semantics and type system provide some necessary foundations to help both users and developers of Android applications deal with their security concerns. Android [3] is Google's new open-source platform for mobile devices. Designed to be a complete software stack, it includes an operating system, middleware, and core applications. Furthermore, it comes with an SDK [1] that provides the tools and APIs necessary to develop new applications for the platform in Java. Interestingly, Android does not distinguish between its core applications and new applications developed with the SDK; in particular, all applications can potentially interact with the underlying mobile device and share their functionality with other applications. This design is very encouraging for developers and users of new applications, as witnessed by the growing Android "market" [2] . At the same time, it can be a source of concern-what do we understand about security on Android?. Indeed, suppose that Alice downloads and installs a new application, developed by Bob, on her Android-based phone.. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Say this application, wikinotes, interacts with a core application, notes, to publish some notes from the phone to a wiki, and to sync edits back from the wiki to the phone. Of course, Alice would not like all her notes to be published, and would not like all her published notes to be edited; for instance, her notes may include intermediate results of her ongoing lab experiments. How does she know whether it is safe to run the application? Can she trust the application to safely access her data? If she cannot, is there still a way to safely run the application? These concerns are important for Alice, because she realizes that running a malicious application on her phone can be disastrous; for instance, it may compromise the records of her experiments. Conversely, it is Bob's concern to be able to convince Alice that his application can be run safely on her phone. This paper initiates an effort to help Alice and Bob deal with these related concerns, through a unified formal understanding of security on Android. To this end, we envision a recipe inspired by PCC [11] : Bob constructs a safety proof for his application by some conservative analysis of the associated Java code, and Alice verifies the proof before installing the application. Such a recipe requires (at least) two ingredients: (1) a formal operational semantics for application code in an Android environment-this includes, in particular, formal specifications of the APIs provided by the SDK; (2) a static safety analysis for application code based on this semantics-in particular, this analysis may be formalized as a security type system for applications, and a soundness proof for such a system should provide the necessary safety proofs for well-typed applications. We take some initial steps towards composing such a recipe in this paper.. • We design a core formal language to describe and reason about Android applications abstractly. For now, we focus only on constructs that are unique to Android, while ignoring the other usual Java constructs that may appear in Android applications. This simplification allows us to study Android-specific features in isolation. Still, to reason about actual Android applications we must consider the usual Java features in combination with these features, and we plan to extend our language to include those features in the future.. • We present an operational semantics for our language. Our semantics exposes the sophisticated control flows that underlie Android's constructs. Indeed, while the official documentation provides only a vague idea of what these constructs mean, a formal understanding of their semantics is crucial for reasoning correctly about the behavior of Android applications. We test our semantics by running our own applications on an Android emulator (included in the SDK).. • We present a type system for security in this language. Our system exploits the access control mechanisms already provided by Android, and enforces "best practices" for developing secure applications with these mechanisms. We develop some new technical concepts, including a special notion of stack types, for this purpose.. The resulting guarantees include standard data-flow security properties for well-typed applications described in our language. We expect that these guarantees can be preserved without significant difficulty by extending our type system to handle other usual Java constructs.. As future work, we plan to extend our analysis so that it can handle application code in Java, and implement it using existing static analysis tools [10, 12, 7] . As envisioned above, certified installation of Android applications based on such an implementation should help both users and developers deal with their security concerns. More ambitiously, we believe that this setting provides an ideal opportunity to bring language-based security to the mainstream. Indeed, Android applications are usually small and structured, so we expect type inference to scale well on such applications; furthermore, the idea of certified installation should certainly be attractive to a growing and diverse Android community.. The rest of the paper is organized as follows. In Section 2 we present an overview of Android, focusing on the application model and security mechanisms. In Section 3 we present our formal language for Android applications. In Section 4, we present our security type system for this language, and outline key properties of typing. Finally, in Section 5, we discuss some related work and conclude. In Section 1, we point out several possible security concerns of users (such as Alice) and developers (such as Bob) of Android applications. We now outline how our approach can quell those concerns. Indeed, Alice can safely run any well-typed application on her phone. By Theorem 4.2, any such application is guaranteed to preserve the secrecy and integrity of her data. If such an application does not conform to our core discipline, it necessarily runs with permission ⊥, so Alice can still safely run such an application. Conversely, the only way Bob can convince Alice that his application is safe to run on her phone is by typechecking his application.. The only other study of Android security we are aware of is [9] . It reports a logic-based tool, Kirin, for determining whether the permissions declared by an application satisfy a certain global safety invariant. Typically, this invariant bans permissions that may result in data flows across applications. However, Kirin does not track data flows inside an application; thus, its analysis is necessarily less precise than ours. In particular, for an application that has several components, each of which require a disjoint set of permissions, Kirin conservatively considers the union of those permissions when deciding the safety of the application. In contrast, we track precise dependencies among the components, and thus may recognize the application to be safe even if Kirin cannot. This precision is important in the presence of signatures, which allow possibly unrelated applications to share the same set of permissions.. The approach in this paper is similar to our previous work on formalizing security on Windows Vista [8] . However, while in [8] we merely aim for a formal understanding of Windows Vista's security design, in this setting we can be much more ambitious, as discussed in Section 1. We plan to extend our analysis to application code in Java, and implement a certified installer for Android applications based on our analysis; we expect existing static analysis tools for Java, such as ESC/Java [10] , Soot [12] , and WALA [7] to provide a convenient foundation for such an implementation. Furthermore, our project bears several similarities with other existing projects for mobile code security, such as Mobius [5], Jif [4] , and S2MS [6] . We expect that as we begin implementing our analysis, we will benefit from tools and techniques developed in the context of such projects.. In conclusion, we initiate a formal language-based study of security on Android in this paper. We believe that it is worthwhile to put in the necessary effort into bringing language-based security to the mainstream via this setting.

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Supporting mobile payment QOS by data mining GSM network traffic In mobile commerce, short-message-service (SMS) is an important technique for delivering payment instruction. A payment model "SMS Credit" was proposed earlier [1]. Such payment service or similar relies on the transmission of SMS; it is needed to reduce the occurrence of packet losses and delay, to improve the quality of packet transmission services (QOS) in the network .This paper discusses how the payment service operates in a configurable radio resource environment via data mining. A Radio Resource Management and Prediction Server equipped with data mining algorithms will optimize the radio resources for both voice and data services in order to provide an optimized QOS. Specifically, data mining techniques are applied to define traffic policy and to calculate optimization result through traffic profile analysis. Nowadays, mobile networks need to support a high density of user population and multimedia services. In particular, mobile commerce that leverages on SMS has a stringent set of performance requirements on the delivery of messages, such as loss and latency [2] .. Given a limited capacity of resources by the fixed hardware infrastructure, mobile network is statistically allowed to relocate the radio resource based on the predication of the radio resource or traffic profile. Some problem of radio resource management and congestion that needs to be solved includes the concentration of large number of users or requests in a hot spot area causing an upsurge.. Radio resource mobility prediction hence has become an important topic in mobile network management [3] . In this paper, we show that data mining algorithms applied for predicting and managing the radio resource movement of cell. Cell usage and performance are mined from the historical data, and then the prediction rules are extracted from these patterns. That follows radio resource management and reconfiguration is accomplished by using these rules.. The radio resource management in the mobile network covers the methods for storing and updating the usage and the traffic profile of the mobile users who are served by the system. Radio resource prediction can be defined as the prediction of a cell next usage movement, where the cell is serving for different mobile user traveling in and out [4] . The predicated movement can then be used to increase the efficiency and utilization of mobile network.. By using the predicted and relocation scheme, the system can effectively allocate resources in the cell neighborhood of a mobile user. Effective relocation of resources to mobile users would improve resource utilization and reduce the latency in accessing the resources. Accurate prediction and relocation is also crucial in processing the queries of mobile payment service, especially in the m-payment model of SMS Credit [1] . When a user submits a payment service request or query, the response or processing liability will depend on the current cell resource at which the user is located. With effective predication and relocation, it is also possible to transfer the queries of the payment service from one cell to the other cell which has sufficient resource.. The paper is organized in this way. Section 2 introduces the disadvantages of the current GOS measure to mobile payment service. It shows the deficiency mainly come from the manual setting of a fixed GOS that results under-or over-utilization of radio resources. In section 3 we proposed a data-mining solution Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. for resolving the problems. Section 4 showcases some results of mining GSM network data. A conclusion is draw at the end.

O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O


A PTAS for the minimization of polynomials of fixed degree over the simplex Abstract. We consider the problem of computing the minimum value p min taken by a polynomial p(x) of degree d over the standard simplex ∆. This is an NP-hard problem already for degree d = 2. For any integer k ≥ 1, by minimizing p(x) over the set of rational points in ∆ with denominator k, one obtains a hierarchy of upper bounds p ∆(k) converging to p min as k −→ ∞. These upper approximations are intimately linked to a hierarchy of lower bounds for p min constructed via Pólya's theorem about representations of positive forms on the simplex. Revisiting the proof of Pólya's theorem allows us to give estimates on the quality of these upper and lower approximations for p min . Moreover, we show that the bounds p ∆(k) yield a polynomial time approximation scheme for the minimization of polynomials of fixed degree d on the simplex, extending an earlier result of Bomze and De Klerk for degree d = 2.

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Group attention control for communication robots with wizard of OZ approach This paper describes a group attention control (GAC) system that enables a communication robot to simultaneously interact with many people. GAC is based on controlling social situations and indicating explicit control to unify all purposes of attention. We implemented a semi-autonomous GAC system into a communication robot that guides visitors to exhibits in a science museum and engages in free-play interactions with them. The GAC system's effectiveness was demonstrated in a two-week experiment in the museum. We believe these results will allow us to develop interactive humanoid robots that can interact effectively with groups of people. The development of robots is entering a new stage whose focus is placed on interaction with people in daily environments. The concept of communication robot continues to rapidly evolve. A robot will act as a peer providing mental, communication, and physical support. For example, pet-type robots such as AIBO [1] and PARO [2] have been developed to provide mental care. Humanoid robots have also been developed for the research of Human-Robot Interaction. These robots investigate how humanlike body movements or facial expressions contribute to interaction with people [3] [4] [5] . In addition, robots have operated in such daily environments as elementary schools and museums [6] [7] [8] [9] . We received 120 questionnaires from visitors for both operating conditions. Figure 8 shows the results and the averages of the items to evaluate the effectiveness of creating a social situation. The t-test results of "Crowdedness" showed a significant difference under the GAC condition (p<.05), which visitors felt was less crowded than the no-GAC condition. Figure 9 shows the total number of visitors and the average time they stayed. This time average showed no significant differences between conditions (p = .14). The total number did not significantly differ between conditions (p = .54). These results indicate that the crowdedness of the GAC condition equals the crowdedness of the no-GAC condition.. The above two results indicate that better control of social situations solved the crowded situation around the robot. But "Approachability" and "Opportunity" results did not show a significant difference between conditions. Figure 10 shows the results and their averages for the items that evaluated the effectiveness of indicating explicit context. These results suggest that indicating explicit communication control might attract visitors to the robot because "Explanation" and "Naturalness" results showed a significant difference under the GAC condition (p<.05). Moreover, "Intention" results showed a significant trend under the GAC condition (p<.1). On the other hand, "Interest" results did not show a significant difference between conditions. Figure 11 shows the results of the item to investigate impressions of the robot. In the GAC condition, visitors evaluated the robot higher than the no-GAC condition (p<.05). In addition, results indicate that visitors had good impressions of the robot for each condition.

B I I O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Protecting source privacy in federated search Many information sources contain information that can only be accessed through search-specific search engines. Federated search provides search solutions of this type of hidden information that cannot be searched by conventional search engines. In many scenarios of federated search, such as the search among health care providers or among intelligence agencies, an individual information source does not want to disclose the source of the search results to users or other sources. Therefore, this paper proposes a two-step federated search protocol that protects the privacy of information sources. As far as we know, this is the first attempt to address the research problem of protecting source privacy in federated text search. Information plays crucial roles in today's fast pace-driven environment. How to find relevant information has been investigated in the field of information retrieval. Information can be copied (or crawled) and accessed by conventional search engines like Google or Yahoo!. When information is hidden from conventional engines, techniques applied to conventional search engine cannot be utilized directly. Federated search [1] has emerged as an answer to this problem.. Imagine the following two scenarios: 1) For better understanding of the spread of a specific disease, researchers may want to know if it has been reported by some health monitoring agencies. Due to possible liability, the agencies may not be willing to disclose their identities to the researchers. 2) Surgical accidents often occur across hospitals and health care centers. Reports are kept for the occurrences of such events. Some researchers may be interested in analyzing common mistakes among hospitals in a specific region so that more effective means to prevent these mistakes could Copyright is held by the author/owner(s). SIGIR'07, July 23-27, 2007, Amsterdam, The Netherlands. ACM 978-1-59593-597-7/07/0007. be developed. However, some hospitals may not be willing to share their reports because of possible damage on their reputations and obligations to the public. In order to benefit from these information, source privacy needs to be protected in the federated search environment, while traditional federated search techniques are not applicable here. We next investigate how to achieve this objective. Anonymization protocols proposed in [3, 5] are not suitable to achieve our objective. First of all, in our problem domain, the user identity needs not to be protected. As a result, we do not need to anonymize the communication from the user to the sources. Secondly, the source privacy needs to be preserved when they collaboratively produce the global ranked list. Since anonymizing the communication among the sources alone does not prevent a source from observing the contents of other sources' local ranked lists, source privacy is violated. Nevertheless, if preventing the disclosure of sources' IP addresses is a part of our objective, the aforementioned anonymization protocols could be utilized together with our proposed protocols.

O B I O B I O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O B I O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Analysing spatio-temporal autocorrelation with LISTA-Viz Many interesting analysis problems (e.g. disease surveillance) would become more tractable if their spatio-temporal structure was better understood. Specifically, it would be helpful to be able to identify autocorrelation in space and time simultaneously. Some of the most commonly used measures of spatial association are LISA statistics, such as the Local Moran's I or the Getis-Ord Gi*; however, these have not been applied to the spatio-temporal case (including many time steps) because of computational limitations. We have implemented a spatio-temporal version of the Local Moran's I and claimed two advances: first, we exploit the fact that there are a limited number of topological relationships present in the data to make Monte Carlo's estimation of probability densities computationally practical, and thereby bypass the 'curse of dimensionality'. We term this approach 'spatial memoization'. Second, we developed a tool (LISTA-Viz) for interacting with the spatio-temporal structure uncovered by the statistics that contains a novel coordination strategy. The potential usefulness of the method and the associated tool are illustrated by an analysis of the 2009 H1N1 pandemic, with the finding that there was a critical spatio-temporal 'inflection point' at which the pandemic changed its character in the United States. Effective methods for exploring space-time structure are needed to make sense of phenomena that contain both spatial and temporal referents (Andrienko et al. 2001) . There is a particular need for methods that can not only represent spatio-temporal data visually and interactively but also offer analytic judgements, by finding which spatio-temporal patterns in the data are significant in the statistical sense (Andrienko et al. 2007) , also known as geovisual analytics (Kraak 2008 ). An example of a pressing spatio-temporal problem that could benefit from a geovisual analytics approach is that of understanding the spread of infectious disease.. We have therefore created a method for exploring spatio-temporal structure using an extension to one of the most popular statistical methods for spatial autocorrelation, the local Moran's I (Anselin 1995) . This could be thought of as one of a class of LISTA statistics (for Local Indicators of Spatio-Temporal Association, after Anselin's LISA). We suggest that to make the computational problem of finding significance levels practical for larger datasets, the topology of the relations between the places be exploited.. We implemented this method in Java and created an interactive tool, called LISTA-Viz, which exposes the statistical method in a manner that makes it easy to use, and which offers tight integration with many other tools in the GeoViz Toolkit (Hardisty 2005, Hardisty et al. accepted) application. The user interface for LISTA-Viz is shown in Figure 1 . This integration means that the spatio-temporal structures uncovered by LISTA-Viz can be analysed visually and computationally by many other views and methods offered in the GeoViz Toolkit.. The computational strategy described here is one of enumerating topological relationships and estimating the probability density function for each one, and using those with the observed patterns. This allows for much better performance, with a speed-up of two orders of magnitude or more for many common analysis cases. This increased efficiency allows the LISTA-Viz tool to offer visual analytic capability, whereby the analyst can interactively explore the data, and receive feedback on the statistical significance of observed spatiotemporal patterns. Fortunately, this increased performance does not carry any penalty in terms of accuracy; the results are functionally identical to the results using the 'naive' Monte Carlo approach. This is true because the method is essentially a caching one: it stores the results of intermediate computations and uses them where the same result is called for, thereby reducing the number of steps needed to calculate a result at the cost of increasing memory usage. We call this approach 'spatial memoization', after the memoization optimization strategy that is employed in computing (particularly functional computing). In the remainder of this article, we describe some related work, the methods we used, our results and then conclusions and future research. Considering the capabilities of this method and its associated tool, some logical extensions are evident. These include using the spatial memoization strategy with other spatial analysis methods, evaluating these methods for use in disease surveillance, trying alternative weight structures and other topologies of coordination. Applying the newly developed LISTA-Viz method and tool allows us to show progress towards our goal of interactive exploration of spatio-temporal structure. We were able to reduce computational time (compared with the naive Monte Carlo approach) so that it is feasible to use the Local Moran's I statistics with large datasets. To create an interactive environment, fast computational methods are required. LISTA-Viz performance has been increased to allow for visual analytics, whereby the software user can interactively identify the data of interest, and the tools can respond by identifying which parts of spatio-temporal structures in the data are statistically significant. In addition, LISTA-Viz was able to identify interesting space-time clusters of influenza-like illnesses (ILI) or flu outbreaks. We describe these two outcomes in more detail below. There is a substantial body of work both on formal methods for delineating spatio-temporal structure and on interactive visual methods for examining space-time. Some of the more important statistical methods are spatial statistics (Cliff and Ord 2009) , scan statistics (Kulldorff and Nagarwalla 1995) , geographically weighted regression (GWR) (Brunsdon et al. 1998) , Markov chain Monte Carlo (Brooks 1998) as well as Bayesian methods (Lawson 2006) . Influential theory on visual analytics for spatio temporal problems includes the analyses of how software can support these analytic tasks (Andrienko et al. 2008b) . The contribution of LISTA-Viz consists of two parts, which we describe in turn. First we describe the LISTA-Viz computational methods and then how the interactive tool was realized in Java. The computational methods and the interactive tool could be realized separately in other environments, but they have advantages when used together, as described below. The computational method is described by first relating the steps in the method in detail, and then relating why this method will produce identical results at a computational saving, when compared with the naive Monte Carlo approach. The tool implementation is described by relating the programming architecture of both the LISTA-Viz tool and how it can fit into a larger computational ecosystem.. Using topology to overcome the 'curse of dimensionality' The core computational advance that we present here is a method for making Monte Carlo calculation of significance values practical for large numbers of observations and for large numbers of time slices. First, we describe the 'naive' Monte Carlo procedure and then the alternative that we are proposing which exploits topology. Our approach enables saving up to orders of magnitude of computational time, with a cost of slightly increased memory usage. We contend that using topology will not only enable analysis of space-time Moran's I but also be a viable strategy to render computationally practical other analysis methods that use Monte Carlo estimation of probability density functions for lattice data (commonly, data for enumerated units such as states or provinces).. We call this approach 'spatial memoization'. In computing, the term 'memoization' refers to an optimization strategy whereby the results of calling functions are stored and then used when identical inputs are presented. It is related to caching but is more specific in that it excludes techniques like page replacement and buffering. Spatial memoization refers to tailoring a memoization strategy for spatial inputs.. The naive approach to Monte Carlo calculation of local Moran's I values is as follows. (1) Create a list of each datum in the lattice (e.g. census districts) and normalize it into standard deviation units, and a list for each time step. values and report what proportion of the Monte Carlo values were larger than the given value. This is the equivalent of a P-value.. The difficulty with this method is the time required for calculation, as well as the amount of memory needed. The calculation time exponentially increases with the number of time steps. There is also the implicit difference that many time slices are likely to be examined (each with temporal neighbours) when looking for space-time structure, which implies that the calculations need to be repeated for each time step, whereas in the traditional spatial case only a single variable at a time is examined. The need to evaluate many variables in turn makes it even more desirable to find performant methods of analysis. The spatial memoization approach (which uses topology) is as follows:. (1) Create a list of each datum in the lattice (e.g. census districts) and normalize it to standard deviation units, and a list for each time step (this step is identical to that in the previously described procedure). (2) Enumerate the topological spatial relationships present in the dataset. For example, it may be found that there are observations with no neighbours, with one neighbour and so on. (3) For each observed spatial relationship found in Step 2 (number of neighbours), perform a Monte Carlo simulation with the normalized data by randomly picking (without replacement) from the lists created in Step 1 n times. Record the probability density for that relationship. (4) Compare each observed space-time local Moran's I value with the appropriate probability density and calculate a probability value (or P-value) from it.. This approach requires Monte Carlo repetitions to be performed for each topological relationship, rather than for each observation. Therefore, the advantage of this method should increase with the size of the dataset because the number of different spatial relationships (or topologies) is not likely to increase at the same rate that the number of observations does.. The numerical results of the LISTA-Viz approach are the same as those obtained following the traditional approach (within the limits of Monte Carlo simulation). This is true because the naive approach is essentially performing the same calculation repeatedly. The LISTA-Viz approach records, or caches, the results of calculations and stores them as an estimated probability density function that can be quickly called. We test the validity of this claim in the 'Results' section below. The cost is that the estimated probability density functions must be stored, and therefore more space in memory is required. For the most common analysis cases, the increased performance would make the memory cost well worth paying.. The LISTA-Viz software component The computational methods are realized using the standard Java libraries. The code for the methods is publicly available from the GeoViz Toolkit source code repository and is released under the Library General Public License (LGPL). These methods are referenced from a component that leverages the map and histogram components of the GeoViz Toolkit. Also, the coordination strategies are used so that the results of the space-time Moran's I are able to be broadcast to all other components of the GeoViz Toolkit (see Figure 2) . Note that a different coordination strategy was used internally within the LISTA-Viz component. This forms a part of the novel visual analytics strategy used by the LISTA-Viz component: the use of the introspective observer coordination (Hardisty et al. accepted) both internally to the visualization component and externally to automatically connect it to a larger visual analysis environment.. The introspective observer coordination strategy uses automatic interrogation of a component's capabilities and matches that with the coordinator software design pattern. This allows components to be flexibly combined, which is essential to visual analytics, in which both humans and computers are creating relevant changes in the analysis system.. In the case of the LISTA-Viz component, we created two coordinators: one internal and one external. The internal coordinator allows the map-histogram pairs to receive the appropriate spatial and numerical data from external sources and manages common visual and computational settings. The external coordinator is inside the GeoViz Toolkit, and it enables the space-time structures identified by the LISTA-Viz component to be broadcast to all other visual and computational components.. We describe here the process of how the realized LISTA-Viz component works in the hand of the user. The software can be used either as a stand-alone tool or as part of the GeoViz Toolkit. In the case of LISTA-Viz being used alone, the spatial data must be supplied as a command-line argument, whereas if it is being used as a part of the GeoViz Toolkit, the data-reading facilities provided by the GeoViz Toolkit can be used.. After the data are loaded, the system calculates the space-time Moran's I statistic and selects those observations that meet the significance level that has been selected. At that point, each map-scatterplot pair will have a different set of observations selected, as seen in Figure 2 . The user can then broadcast the set of selected observations associated with a particular map-scatterplot pair, which have been found to be part of a space-time cluster, to all listening components. In this manner these observations can be analysed in other tools and views.. We combine the LISTA-Viz computational approach, using spatial memoization, and the LISTA-Viz software component, with its novel coordination strategy, because the two better enable geovisual analytics than either would alone. One of the goals of developing the computational approach was to allow for interactive detection of space-time structures in data, such as clusters. Interactivity demands a flexible coordination strategy that allows users to start computational processes and interact with their results, without interfering with other simultaneous computational and visual processes. Multi-threading allows this, but it is difficult to create multi-threaded programmes in a robust, extensible manner. The LISTAViz coordination strategy allows the computational processes to proceed independently, and extensibly, thus contributing to interactivity and to the geovisual analytic process.

O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Bisimulation and cocongruence for probabilistic systems We introduce a new notion of bisimulation, called event bisimulation on labelled Markov processes and compare it with the, now standard, notion of probabilistic bisimulation, originally due to Larsen and Skou. Event bisimulation uses a sub -algebra as the basic carrier of information rather than an equivalence relation. The resulting notion is thus based on measurable subsets rather than on points: hence the name. Event bisimulation applies smoothly for general measure spaces; bisimulation, on the other hand, is known only to work satisfactorily for analytic spaces. We prove the logical characterization theorem for event bisimulation without having to invoke any of the subtle aspects of analytic spaces that feature prominently in the corresponding proof for ordinary bisimulation. These complexities only arise when we show that on analytic spaces the two concepts coincide. We show that the concept of event bisimulation arises naturally from taking the cocongruence point of view for probabilistic systems. We show that the theory can be given a pleasing categorical treatment in line with general coalgebraic principles. As an easy application of these ideas we develop a notion of "almost sure" bisimulation; the theory comes almost "for free" once we modify Giry's monad appropriately. The main point of this paper is to argue that one should work with probabilistic cocongruence rather than with probabilistic bisimulation. The theory works smoothly for LMPs on general measure spaces: one need not work with analytic spaces. The proof of the logical characterization of cocongruence is much simpler and more general than the proof of the logical characterization of bisimulation. One only needs to invoke the theory of analytic spaces to show that cocongruence and bisimulation coincide: which they indeed do on analytic spaces.. Indeed, it seems to us that bisimulation defined categorically is a historical anomaly. In the discrete case, bisimulation and cocongruence coincide and one can argue that it makes no difference. However, transition systems are coalgebras and cospans should fit the theory better than spans; as indeed is our experience in the probabilistic case. It would be interesting to reformulate the general theory in terms of cocongruences. Other people have also been thinking in terms of cocongruences. An interesting paper by Bartels et al. [1] was pointed out to us recently.. In the case of probabilistic systems, it has been argued that one should use metrics rather than equivalence relations [8, 12] . In the present context, a pressing problem is to understand the metric analogue of the theory of probabilistic cocongruence.

O O B O O O O O O O O O O O O O O B I I O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B I O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B


Reliable broadcasting in wormhole-routed hypercube-connected networks using local safety information Abstract-This paper presents a method to cope with reliable broadcasting in faulty hypercubes using local safety information. A new definition, broadcast subcube, is introduced, with which various techniques are proposed to improve performance of the broadcast algorithm. Local safety information is well used in the fault-tolerant broadcast algorithm by considering only safety of the broadcast subcube. An unsafe hypercube can be split into a set of maximal safe subcubes. If these maximal safe subcubes meet certain requirements (listed in this paper), then broadcasting can still be done successfully and, in some cases, optimal broadcast is still possible. The sufficient condition for optimal broadcast of a message is presented in an unsafe hypercube. Extensive simulation results show that the proposed method outperforms previous methods, in all cases.Index Terms-Broadcast subcube, fault-tolerant broadcasting, hypercube, local safety, maximal safe subcube.

O O O O O O O B I O O O O O O O O O O O O O O O B I O O O O B I O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O B I O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B I B B I B I I