We study joint rate control and resource allocation with a packet collision constraint that maximizes the total utility of secondary users in cognitive radio networks. We formulate and decouple the original optimization problem into separable subproblems and then develop an algorithm that converges to optimal rate control and resource allocation. The proposed algorithm can operate on different time-scales to reduce the amortized time complexity.

ITS (Intelligent Transport Systems) wireless communications system has been developing based on the leading edge ICT (Information Communication Technologies) in Japan. The comfort driving systems for example VICS (Vehicular Information Communication system), ETC (Electronic Toll Collection), Telematics has already become popular and the safety driving support systems, such as ASV (Advanced Safety Vehicle) and SMARTWAY have been scheduled for introduction in the near future. However, there are many residual issues in the comfort driving system because of the existence of the traffic jam and the interest of the economical cars in the world. Moreover, the acceleration of the development of the Smart Grid and EV (Electric Vehicle) would affect the future development of the ITS wireless communications system. In this paper, it is clarified that the future development should be advanced considering the one of the basic business rule of 'market-in and product-out'.

This letter studies a nesting discrete particle swarm optimizer for multi-solution problems. The algorithm operates in discrete search space and consists of two stages. The first stage is global search in rough lattice points for constructing local sub-regions each of which includes one target solution. The second stage is local search where the algorithm operates in parallel in fine lattice points of local subspaces and tires to find all the approximate solutions within a criterion. We then propose an application to finding multiple fixed points in nonlinear dynamical systems and investigate the algorithm efficiency.

Based on quadriphase perfect sequences and their cyclical shift versions, three families of almost perfect 16-QAM sequences are presented. When one of two time shifts chosen equals half a period of quadriphase sequence employed and another is zero, two of the proposed three sequence families possess the property that their out-of-phase autocorrelation function values vanish except one. At the same time, to the other time shifts, the nontrivial autocorrelation function values in three families are zero except two or four. In addition, two classes of periodic complementary sequence (PCS) pairs over the 16-QAM constellation, whose autocorrelation is similar to the one of conventional PCS pairs, are constructed as well.

We propose a novel channel model of satellite-to-ground optical transmission to achieve a global-scale high-capacity communication network. In addition, we compose an effective channel coding scheme based on low-density generator matrix (LDGM) code suitable for that channel. Because the first successful optical satellite communication demonstrations are quite recent, no practical channel model has been introduced. We analyze the results of optical transmission experiments between ground station and the Optical Inter-orbit Communications Engineering Test Satellite (OICETS) performed by NICT and JAXA in 2008 and propose a new Markov-based practical channel model. Furthermore, using this model we design an effective long erasure code (LEC) based on LDGM to achieve high-quality wireless optical transmissions.

Due to rapid growth of RFID system applications, the security and privacy problems become more and more important to guarantee the validity of RFID systems. Without introducing proper privacy protection mechanisms, widespread deployment of RFID could raise privacy concerns to both companies and individuals. As a fundamental issue for the design and analysis of secure RFID systems, some formal RFID privacy frameworks were proposed in recent years to give the principles for evaluating the security and privacy in RFID system. However, readers can be confused with so many proposed frameworks. In this paper, we make a comparative and survey study on the proposed RFID privacy frameworks. We mainly divide the existing models into three categories, the four-oracle framework, eight-oracle framework and Universal Composability framework. We give a brief review on the existing models and describe their abilities to model the adversarial behavior in RFID systems. We then analyze relations among those existing RFID privacy models and make some comparisons among their properties.

Using a single-site lightning location technique, a new portable lightning location system is developed. We incorporate an attitude detection technique using inertial sensors to detect an accurate electromagnetic field vector of sferics by palm-sized electromagnetic sensors which can have arbitrary attitude. The present paper describes the concept and the performance of the developed prototype of the portable system.

Recently, a novel approach to color image compression based on colorization has been presented. The conventional method for colorization-based image coding tends to lose the local oscillation of chrominance components that the original images had. A large number of color assignments is required to restore these oscillations. On the other hand, previous studies suggest that an oscillation of a chrominance component correlates with the oscillation of a corresponding luminance component. In this paper, we propose a new colorization-based image coding method that utilizes the local correlation between texture components of luminance and chrominance. These texture components are obtained by a total variation regularized energy minimization method. The local correlation relationships are approximated by linear functions, and their coefficients are extracted by an optimization method. This key idea enables us to represent the oscillations of chrominance components by using only a few pieces of information. Experimental results showed that our method can restore the local oscillation and code images more efficiently than the conventional method, JPEG, or JPEG2000 at a high compression rate.

Recently, social network services are rapidly growing and this trend is expected to continue in the future. Social network data can be published for various purposes such as statistical analysis and population studies. When social network data are published, however, the privacy of some people may be disclosed. The most straightforward manner to preserve privacy in social network data is to remove the identifiers of persons from the social network data. However, an adversary can infer the identity of a person in the social network by using his/her background knowledge, which consists of content information such as the age, sex, or address of the person and structural information such as the number of persons having a relationship with the person. In this paper, we propose a privacy protection method for social network data. The proposed method anonymizes social network data to prevent privacy attacks that use both content and structural information, while minimizing the information loss or distortion of the anonymized social network data. Through extensive experiments, we verify the effectiveness and applicability of the proposed method.

In multimedia communication, due to the limited computational capability of the personal information machine, a coder with low computational complexity is needed to integrate services from several media sources. This paper presents two efficient candidate schemes to simplify the most computationally demanding operation, the excitation codebook search procedure. For fast adaptive codebook search, we propose an algorithm that uses residual signals to predict the candidate gain-vectors of the adaptive codebook. For the fixed codebook, we propose a fast search algorithm using an energy function to predict the candidate pulses, and we redesign the codebook structure to twin multi-track positions architecture. Overall simulation results indicate that the average perceptual evaluation of speech quality (PESQ) score is degraded slightly, by 0.049, and our proposed methods can reduce total computational complexity by about 67% relative to the original G.723.1 encoder computation load, and with perceptually negligible degradation. Objective and subjective evaluations verify that the more efficient candidate schemes we propose can provide speech quality comparable to that using the original coder approach.

The use of IP addresses as host IDs and locators in the present day Internet protocols imposes constraints on designing efficient solutions for mobility, multihoming, renumbering, and security. To eliminate the constraints, different approaches of introducing ID/locator split into future network architectures have been discussed recently. HIMALIS is such an architecture, which uses distinct sets of values for identifiers and locators and allows the network layer to change locators without requiring the upper layers to change identifiers. One of the major challenges of HIMALIS is the design and implementation of a distributed ID-to-locator mapping database system to efficiently store, update and provide the up-to-date mapping data to the network elements. For this purpose, this paper discusses the application of the Domain Trusted Entity (DTE) infrastructure to the HIMALIS architecture. It provides a unified manner to get locators from high level identifiers (names) with enhanced security, privacy, and trust, while maintaining all capabilities and full compatibility with the previous DNR, HNR, and IDR infrastructures found in HIMALIS.

In this paper, we propose efficient sequential AES CCM architecture for the IEEE 802.16e. In the proposed architecture, only one AES encryption core is used and the operation of the CTR and the CBC-MAC is processed concurrently within one round. With this design approach, we can design sequential AES CCM architecture having 570 Mbps@102.4 MHz throughput and 1,397 slices at a Spartan3 3s5000 device.

Network structure has a great impact both on hazard spread and network immunization. The vulnerability of the network node is associated with each other, assortative or disassortative. Firstly, an algorithm for vulnerability relevance clustering is proposed to show that the vulnerability community phenomenon is obviously existent in complex networks. On this basis, next, a new indicator called network “hyper-betweenness” is given for evaluating the vulnerability of network node. Network hyper-betweenness can reflect the importance of network node in hazard spread better. Finally, the dynamic stochastic process of hazard spread is simulated based on Monte-Carlo sampling method and a two-player, non-cooperative, constant-sum game model is designed to obtain an equilibrated network immunization strategy.

In dense passive radio frequency identification (RFID) systems, code division multiple access (CDMA) techniques can be used to alleviate severe collisions and thus enhance the system performance. However, conventional CDMA techniques are challenging to implement, especially for passive tags due to cost and power constraints. In this paper, we design a CDMA-based multi-reader passive ultra high frequency (UHF) RFID system in which a reader detects only the strongest tag signal and a tag uses Gold codes only on the preamble and the data bits of RN16 without increasing its clock frequency. We present a new communication procedure based on dynamic framed slotted ALOHA (DFSA). In order to optimize the system, we theoretically analyze the system performance in terms of slot capacity and identification rate, and formally show how the code length and the number of readers affect the identification rate. Furthermore, we propose an effective method for tag estimation and frame size adjustment, and validate it via simulations. Through an example, we demonstrate how the analysis-based technique can be used to optimize the system configurations with respect to the number of readers and the number and length of Gold codes.

This paper discusses the task of human action detection. It requires not only classifying what type the action of interest is, but also finding actions' spatial-temporal locations in a video. The novelty of this paper lies on two significant aspects. One is to introduce a new graph based representation for the search space in a video. The other is to propose a novel sub-volume search method by Minimum Cycle detection. The proposed method has a low computation complexity while maintaining a high action detection accuracy. It is evaluated on two challenging datasets which are captured in cluttered backgrounds. The proposed approach outperforms other state-of-the-art methods in most situations in terms of both Precision-Recall values and running speeds.

This letter analyzes a resource chain trust model for P2P reputation-based systems. Many researchers have given a lot of efforts to reputation-based system area and some of them have made good theoretical models. Problems are to spread malicious contents whereas the remark that such models only concentrate on the relationship between the node and its direct neighbors is still controversial. To solve the problems, we introduced the RCM (Resource Chain Model) and the Enhanced RCM. In this letter, we analyze the models and then show usage of our models can help us to find the best and safest location efficiently and decrease the number of malicious transaction.

In Wireless Sensor Networks (WSNs), authentication is a crucial security requirement to avoid attacks against secure communication, and to mitigate against DoS attacks exploiting the limited resources of sensor nodes. Resource constraints of sensor nodes are hurdles in applying strong public key cryptographic based mechanisms in WSNs. To address the problem of authentication in WSNs, we propose an efficient and secure framework for authenticated broadcast/multicast by sensor nodes as well as for outside user authentication, which utilizes identity based cryptography and online/offline signature (OOS) schemes. The primary goals of this framework are to enable all sensor nodes in the network, firstly, to broadcast and/or multicast an authenticated message quickly; secondly, to verify the broadcast/multicast message sender and the message contents; and finally, to verify the legitimacy of an outside user. This paper reports the implementation and experimental evaluation of the previously proposed authenticated broadcast/multicast by sensor nodes scheme using online/offline signature on TinyOS and MICA2 sensor nodes.

Recently, numerous service discovery protocols have been introduced in the open literature. Unfortunately, many of them did not consider security issues, and for those that did, many security and privacy problems still remain. One important issue is to protect the privacy of a service provider while enabling an end-user to search an alternative service using multiple keywords. To deal with this issue, the existing protocols assumed that a directory server should be trusted or owned by each service provider. However, an adversary may compromise the directory server due to its openness property. In this paper, we suggest an efficient verification of service subscribers to resolve this issue and analyze its performance and security. Using this method, we propose an efficient and secure service discovery protocol protecting the privacy of a service provider while providing multiple keywords search to an end-user. Also, we provide performance and security analysis of our protocol.

Recently, Kang et al. discussed some security flaws of Wu et al.'s and Wei et al.'s authentication schemes that guarantee user anonymity in wireless communications and showed how to overcome the problems regarding anonymity and the forged login messages. However, we will show that Kang et al.'s improved scheme still did not provide user anonymity as they claimed.

A total-field/scattered-field (TF/SF) boundary for the constrained interpolation profile (CIP) method is proposed for multi-dimensional electromagnetic problems. Incident fields are added to or subtracted from update equations in order to satisfy advection equations into which Maxwell's equations are reduced by means of the directional splitting. Modified incident fields are introduced to take into account electromagnetic fields after advection. The developed TF/SF boundary is examined numerically, and the results show that it operates with good performance. Finally, we apply the proposed TF/SF boundary to a scattering problem, and it can be solved successfully.