This paper presents a GPU (Graphics Processing Units) implementation of dynamic programming for the optimal polygon triangulation. Recently, GPUs can be used for general purpose parallel computation. Users can develop parallel programs running on GPUs using programming architecture called CUDA (Compute Unified Device Architecture) provided by NVIDIA. The optimal polygon triangulation problem for a convex polygon is an optimization problem to find a triangulation with minimum total weight. It is known that this problem for a convex n-gon can be solved using the dynamic programming technique in O(n3) time using a work space of size O(n2). In this paper, we propose an efficient parallel implementation of this O(n3)-time algorithm on the GPU. In our implementation, we have used two new ideas to accelerate the dynamic programming. The first idea (adaptive granularity) is to partition the dynamic programming algorithm into many sequential kernel calls of CUDA, and to select the best parameters for the size and the number of blocks for each kernel call. The second idea (sliding and mirroring arrangements) is to arrange the working data for coalesced access of the global memory in the GPU to minimize the memory access overhead. Our implementation using these two ideas solves the optimal polygon triangulation problem for a convex 8192-gon in 5.57 seconds on the NVIDIA GeForce GTX 680, while a conventional CPU implementation runs in 1939.02 seconds. Thus, our GPU implementation attains a speedup factor of 348.02.

The effective bandwidth of the dynamic random-access memory (DRAM) for the alternate row-wise/column-wise matrix access (AR/CMA) mode, which is a basic characteristic in scientific and engineering applications, is very low. Therefore, we propose the window memory layout scheme (WMLS), which is a matrix layout scheme that does not require transposition, for AR/CMA applications. This scheme maps one row of a logical matrix into a rectangular memory window of the DRAM to balance the bandwidth of the row- and column-wise matrix access and to increase the DRAM IO bandwidth. The optimal window configuration is theoretically analyzed to minimize the total number of no-data-visit operations of the DRAM. Different WMLS implementationsare presented according to the memory structure of field-programmable gata array (FPGA), CPU, and GPU platforms. Experimental results show that the proposed WMLS can significantly improve DRAM bandwidth for AR/CMA applications. achieved speedup factors of 1.6× and 2.0× are achieved for the general-purpose CPU and GPU platforms, respectively. For the FPGA platform, the WMLS DRAM controller is custom. The maximum bandwidth for the AR/CMA mode reaches 5.94 GB/s, which is a 73.6% improvement compared with that of the traditional row-wise access mode. Finally, we apply WMLS scheme for Chirp Scaling SAR application, comparing with the traditional access approach, the maximum speedup factors of 4.73X, 1.33X and 1.56X can be achieved for FPGA, CPU and GPU platform, respectively.

Optical Code Division Multiplexing (OCDM) is a multiplexing technology for constructing future all-optical networks. Compared with other multiplexing technologies, it can be easily controlled and can establish lightpaths of smaller granularity. However, previous research has revealed that OCDM networks are vulnerable to cycle attacks. Cycle attacks are caused by multi-access interference (MAI), which is crosstalk noise on the same wavelength in OCDM networks. If cycle attacks occur, they disrupt all network services immediately. Previous research has proposed a logical topology design that is free of cycle attacks. However, this design assumes that path assignment is centrally controlled. It also does not consider the delay between each node and the centralized controller. In this paper, we propose novel logical topology designs that are free of cycle attacks and methods of establishing paths. The basic concepts underlying our methods are to autonomously construct a cycle-attack-free logical topology and to establish lightpaths by using a distributed controller. Our methods can construct a logical network and establish lightpaths more easily than the previous method can. In addition, they have network scalability because of their distributed control. Simulation results show that our methods have lower loss probabilities than the previous method and better mean hop counts than the centralized control approach.

With the diffusion of web services caused by the appearance of a new architecture known as cloud computing, a large number of websites have been used by attackers as hopping sites to attack other websites and user terminals because many vulnerable websites are constructed and managed by unskilled users. To construct hopping sites, many attackers force victims to download malware by using vulnerabilities in web applications. To protect websites from these malware infection attacks, conventional methods, such as using anti-virus software, filter files from attackers using pattern files generated by analyzing conventional malware files collected by security vendors. In addition, certain anti-virus software uses a behavior blocking approach, which monitors malicious file activities and modifications. These methods can detect malware files that are already known. However, it is difficult to detect malware that is different from known malware. It is also difficult to define malware since legitimate software files can become malicious depending on the situation. We previously proposed an access filtering method based on communication opponents, which are other servers or terminals that connect with our web honeypots, of attacks collected by web honeypots, which collect malware infection attacks to websites by using actual vulnerable web applications. In this blacklist-based method, URLs or IP addresses, which are used in malware infection attacks collected by web honeypots, are listed in a blacklist, and accesses to and from websites are filtered based on the blacklist. To reveal the effects in an actual attack situation on the Internet, we evaluated the detection ratio of anti-virus software, our method, and a composite of both methods. Our evaluation revealed that anti-virus software detected approximately 50% of malware files, our method detected approximately 98% of attacks, and the composite of the two methods could detect approximately 99% of attacks.

To solve the problems of the existing trusted network access protocols for Wireless Local Area Network (WLAN) mesh networks, we propose a new trusted network access protocol for WLAN mesh networks, which is abbreviated as WMN-TNAP. This protocol implements mutual user authentication and Platform-Authentication between the supplicant and Mesh Authenticator (MA), and between the supplicant and Authentication Server (AS) of a WLAN mesh network, establishes the key management system for the WLAN mesh network, and effectively prevents the platform configuration information of the supplicant, MA and AS from leaking out. Moreover, this protocol is proved secure based on the extended Strand Space Model (SSM) for trusted network access protocols.

Nowadays, with spreads of inexpensive small communication devices, a number of wireless local area networks (WLANs) have been deployed even in the same building for the Internet access services. Their wireless access-points (APs) are often independently installed and managed by different groups such as departments or laboratories in a university or a company. Then, a user host can access to multiple WLANs by detecting signals from their APs, which increases the energy consumption and the operational cost. It may also degrade the communication performance by increasing interferences. In this paper, we present an AP aggregation approach to solve these problems in multiple WLAN environments by aggregating deployed APs of different groups into limited ones using virtual APs. First, we formulate the AP aggregation problem as a combinatorial optimization problem and prove the NP-completeness of its decision problem. Then, we propose its heuristic algorithm composed of five phases. We verify the effectiveness through extensive simulations using the WIMNET simulator.

In communication networks, congestion control, routing, and multiple access schemes for scheduling transmissions are typically regulated by distributed algorithms. Engineers designed these algorithms using clever heuristics that they refined in the light of simulation results and experiments. Over the last two decades, a deeper understanding of these algorithms emerged through the work of researchers. This understanding has a real potential for improving the design of protocols for data centers, cloud computing, and even wireless networks. Since protocols tend to be standardized by engineers, it is important that they become familiar with the insights that emerged in research. We hope that this paper might appeal to practitioners and make the research results intuitive and useful. The methods that the paper describes may be useful for many other resource allocation problems such as in call centers, manufacturing lines, hospitals and the service industry.

Recently, many kinds of content are being circulated within a great many service-specific overlay networks. When the content is not extremely delay-sensitive, content circulation between wireless terminals can be realized without additional resources by using off-peak periods in wireless access links. In such content circulation, peer-to-peer content multicast is a promising approach to reduce the load on the centralized server. However, to minimize battery drain, each wireless terminal can only forward content to a restricted number of neighboring terminals once it has received the content. This paper proposes an efficient forwarding scheme for peer-to-peer content multicast between the wireless terminals intermittently connected with the backhaul network. In the proposed scheme, a restricted number of terminals with an earlier start time of off-peak periods are selected to forward the content when the number of forwarding hops from the source terminal is less than or equal to a predetermined threshold. In contrast, a restricted number of terminals are selected randomly when the number of forwarding hops exceeds the threshold. This paper clarifies that the proposed hybrid forwarding scheme can multicast the content to many terminals within an arbitrarily restricted period. A guideline to determine the optimum threshold for switching the terminal selection method in the proposed hybrid scheme is derived from simulation results.

Multiple access relay systems with network coding provide spatial diversity with fewer transmissions. However, errors generated at the relay can propagate to the destination and the system performance can be severely degraded. Although many techniques have been proposed to resolve the error propagation, these techniques require some special operations at the relay or complicated reception schemes at the destination unless the global channel state information is available at the destination. This paper proposes a simple cooperative demodulation scheme for multiple access relay systems with network coding assuming that the relay simply forwards the decoded data and the destination has only the local channel state information.

A wireless emergency communication network with a fixed allocation of spectrum resources cannot meet the tremendous demand for spectrum access when a crisis occurs. It is necessary to develop an effective spectrum access scheme to improve the performance of emergency communication systems. In this paper, we study a new emergency communication system combines cognitive radio technology and an emergency communication network. Emergency users can utility resources in a general network when traffic becomes congested in an emergency network. Non-reciprocal spectrum access scheme (NRA) and reciprocal spectrum access scheme (RA) for two heterogeneous cognitive networks, namely emergency network and general network are proposed to compare with traditional spectrum access scheme (TA). User behavior with each scheme is modeled by continuous-time Markov chains. Moreover, the blocking and dropping probabilities of users in two heterogeneous cognitive networks are derived as the performance metrics. In addition, the throughput and the spectrum utilization rate of the system are evaluated. Finally, we compare the performance of three dynamic spectrum access schemes. The simulation results show that the RA scheme is an effective scheme to enhance the performance of emergency systems.

This paper presents a hardware design of high throughput, low latency preamble detector for 3GPP LTE physical random access channel (PRACH) receiver. The presented PRACH receiver uses the pipelined structure to improve the throughput of power delay profile (PDP) generation which is executed multiple times during the preamble detection. In addition, to reduce detection latency, we propose an instantaneous preamble detection method for both restricted and unrestricted set. The proposed preamble detection method can detect all existing preambles directly and instantaneously from PDP output while conducting PDP combining for restricted set. The PDP combining enables the PRACH receiver to detect preambles robustly even in severe Doppler effect or frequency error exist. Using proposed method, the worst case preamble detection latency time can be less than 1 ms with 136 MHz clock and the proposed PRACH receiver can be implemented with approximately 237k equivalent ASIC gates count or occupying 30.2% of xc6vlx130t FPGA device.

We have investigated the impact of O2 annealing after SiOx deposition on the switching behavior to gain a better understanding of the resistance switching mechanism, especially the role of oxygen deficiency in the SiOx network. Although resistive random access memories (ReRAMs) with SiOx after 300 annealing sandwiched with Pt electrodes showed uni-polar type resistance switching characteristics, the switching behaviors were barely detectable for the samples after annealing at temperatures over 500. Taking into account of the average oxygen content in the SiOx films evaluated by XPS measurements, oxygen vacancies in SiOx play an important role in resistance switching. Also, the results of conductive AFM measurements suggest that the formation and disruption of a conducting filament path are mainly responsible for the resistance switching behavior of SiOx.

We have fabricated Pt/Si-rich oxide (SiOx)/TiN stacked MIM diodes and studied an impact of the structural asymmetry on their resistive switching characteristics. XPS analyses show that a TiON interfacial layer was formed during the SiOx deposition on TiN by RF-sputtering in an Ar + O2 gas mixture. After the fabrication of Pt top electrodes on the SiOx layer, and followed by an electro-forming process, distinct bi-polar type resistive switching was confirmed. For the resistive switching from high to low resistance states so called SET process, there is no need to set the current compliance. Considering higher dielectric constant of TiON than SiOx, the interfacial TiON layer can contribute to regulate the current flow through the diode. The clockwise resistive switching, in which the reduction and oxidation (Red-Ox) reactions can occur near the TiN bottom electrode, shows lower RESET voltages and better switching endurance than the counter-clockwise switching where the Red-Ox reaction can take place near the top Pt electrode. The result implies a good repeatable nature of Red-Ox reactions at the interface between SiOx and TiON/TiN in consideration of relatively high diffusibility of oxygen atoms through Pt.

Broadcast encryption scheme with personalized messages (BEPM) is a new primitive that allows a broadcaster to encrypt both a common message and individual messages. BEPM is necessary in applications where individual messages include information related to user's privacy. Recently, Fujii et al. suggested a BEPM that is extended from a public key broadcast encryption (PKBE) scheme by Boneh, Gentry, and Waters. In this paper, we point out that 1) Conditional Access System using Fujii et al.'s BEPM should be revised in a way that decryption algorithm takes as input public key as well, and 2) performance analysis of Fujii et al.'s BEPM should be done depending on whether the public key is transmitted along with ciphertext or stored into user's device. Finally, we propose a new BEPM that is transmission-efficient, while preserving O(1) user storage cost. Our construction is based on a PKBE scheme suggested by Park, Kim, Sung, and Lee, which is also considered as being one of the best PKBE schemes.

For opportunistic spectrum access (OSA), spectrum management is a key function to effectively utilize white space without causing harmful interference to incumbent receivers. Geo-location database approaches using radio propagation estimation have been regarded as practical spectrum management methods. However, propagation models inevitably fail to accurately estimate the path loss in actual radio environments, resulting in estimation error of carrier to interference ratio (CIR) of the incumbent receivers. This could prevent white space from being efficiently utilized, because the allowable transmit power of the opportunistic system has to be limited to keep the CIR at the required level. To improve the accuracy of CIR estimation, we propose the new concept of Interference Monitoring which works in combination with spectrum management. In this method, a monitoring node located near the incumbent receivers actually measures both the interference signals and the incumbent signals. Using the measurement results, the CIR estimates are corrected based on the minimum mean square error (MMSE) criterion. The proposed Interference Monitoring can be extended to establish cooperation among multiple monitoring nodes and thus spatial diversity. Analytical evaluations assuming a simple cellular system model show that Interference Monitoring can more accurately estimate CIR, and thus it can significantly increase the allowable transmit power. For an urban macro cell, Interference Monitoring with a single node achieved about a 6.5 dB increase in the transmit power; Cooperative Interference Monitoring with 4 nodes achieved about a 13.5 dB increase. Thus, Interference Monitoring-based spectrum management can maximize opportunities for white space utilization without imposing additional interference to the incumbent system.

In this paper, a novel interference suppression technique from added RoF (Radio-on-Fiber) system is proposed. In general RoF system, received RF (radio frequency) signal intensity is periodically varied depending on chromatic dispersion that is known as fading phenomenon. In proposed technique null points of this fading phenomenon are intentionally applied to minimize signal interferences. This technique can realize two types of multiplexing RoF signal. In the first configuration, a single optical carrier is modulated twice using two optical modulators connected in series. In second configuration, new RoF signal is added to the existing network using individual light source. Multiplexing RoF signals of 10 GHz-band with data of 30 Mbps 64QAM is experimentally demonstrated.

This paper describes mobile backhaul optical access network designs for future cellular systems, in particular, for those systems that exploit coordinated multipoints (CoMP) transmission/reception techniques. Wavelength-division-multiplexing passive optical networks (WDM-PON) are primarily considered and two proposals to enhance mobile backhaul capability of WDM-PONs for CoMP are presented. One is physical X2 links that support dedicated low latency and high capacity data exchange between base stations (BSs). The other is multicasting in WDM-PONs. It effectively reduces data/control transmission time from central node to multiple BSs joining CoMP. Evaluation results verify that the proposed X2 links and the multicasting enable more BSs to join CoMP by enhancing the mobile backhaul capability, which results in improved service quality for users.

Repairing embedded memories (e-memories) on an advanced system-on-chip (SoC) product is a key technique used to improve product yield. However, increasing the die area of SoC products equipped with various types of e-memories on the die is an issue. A fuse scheme can be used to resolve this issue. However, several fuse schemes that have been proposed to decrease the die area result in an increased repair time. Therefore, in this paper, we propose a novel fuse scheme that decreases both die area and repair time. Moreover, our approach is applied to a 65 nm SoC product. The results indicate that the proposed fuse scheme effectively decreases the die area and repair time of advanced SoC products.

This paper identifies a ripple effect problem (REP) that spreads interference to neighbors and proposes a novel channel localization mechanism to decrease the REP in a Wi-Fi system. The proposed mechanism has less blocking probability when compared to a random channel allocation mechanism and also has increased channel reusability. The proposed mechanism in simulation yields less channels BEm as the number of users and Tused increase.

A construction of shift sequence sets is proposed. Multiple distinct shift sequence sets are obtained by changing the parameters of the shift sequences. The shift sequences satisfy the conditions that P|L and P ≥ 2, where P is the length of the shift sequences, L is the length of the zero-correlation zone or low-correlation zone (ZCZ/LCZ). Then based on these shift sequence sets, many shift distinct ZCZ/LCZ sequence sets are constructed by using interleaving technique and complex Hadamard matrices. Furthermore, the new construction is optimal under the conditions proposed in this paper. Compared with previous constructions, the proposed construction extends the number of shift distinct ZCZ/LCZ sequence sets, so that more sequence sets are obtained for multi-cell quasi-synchronous code-division multiple access (QS-CDMA) systems.