GPUs have become the dominant computing units to meet the need of high performance in various computational fields. But the long operation latency causes the underutilization of on-chip computing resources, resulting in performance degradation when running parallel tasks on GPUs. A good warp scheduling strategy is an effective solution to hide latency and improve resource utilization. However, most current warp scheduling algorithms on GPUs ignore the ability of long operations to hide latency. In this paper, we propose a long-operation-first warp scheduling algorithm, LFWS, for GPU platforms. The LFWS filters warps in the ready state to a ready queue and updates the queue in time according to changes in the status of the warp. The LFWS divides the warps in the ready queue into long and short operation groups based on the type of operations in their instruction buffers, and it gives higher priority to the long-operating warp in the ready queue. This can effectively use the long operations to hide some of the latency from each other and enhance the system's ability to hide the latency. To verify the effectiveness of the LFWS, we implement the LFWS algorithm on a simulation platform GPGPU-Sim. Experiments are conducted over various CUDA applications to evaluate the performance of LFWS algorithm, compared with other five warp scheduling algorithms. The results show that the LFWS algorithm achieves an average performance improvement of 8.01% and 5.09%, respectively, over three traditional and two novel warp scheduling algorithms, effectively improving computational resource utilization on GPU.

Utilization data (a kind of incomplete data) is defined as the fraction of a fixed period in which the system is busy. In computer systems, utilization data is very common and easily observable, such as CPU utilization. Unlike inter-arrival times and waiting times, it is more significant to consider the parameter estimation of transaction-based systems with utilization data. In our previous work [7], a novel parameter estimation method using utilization data for an Mt/M/1/K queueing system was presented to estimate the parameters of a non-homogeneous Poisson process (NHPP). Since NHPP is classified as a simple counting process, it may not fit actual arrival streams very well. As a generalization of NHPP, Markovian arrival process (MAP) takes account of the dependency between consecutive arrivals and is often used to model complex, bursty, and correlated traffic streams. In this paper, we concentrate on the parameter estimation of an MAP/M/1/K queueing system using utilization data. In particular, the parameters are estimated by using maximum likelihood estimation (MLE) method. Numerical experiments on real utilization data validate the proposed approach and evaluate the effective traffic intensity of the arrival stream of MAP/M/1/K queueing system. Besides, three kinds of utilization datasets are created from a simulation to assess the effects of observed time intervals on both estimation accuracy and computational cost. The numerical results show that MAP-based approach outperforms the exiting method in terms of both the estimation accuracy and computational cost.

A spectrum suppressed transmission that increases the frequency utilization efficiency, defined as throughput/bandwidth, by suppressing the required bandwidth has been proposed. This is one of the most effective schemes to solve the exhaustion problem of frequency bandwidths. However, in spectrum suppressed transmission, its transmission quality potentially degrades due to the ISI making the bandwidth narrower than the Nyquist bandwidth. In this paper, in order to improve the transmission quality degradation, we propose the spectrum suppressed transmission applying both FEC (forward error correction) and LE (linear equalization). Moreover, we also propose a new channel allocation scheme for the spectrum suppressed transmission, in multi-channel environments over a satellite transponder. From our computer simulation results, we clarify that the proposed schemes are more effective at increasing the system throughput than the scheme without spectrum suppression.

Because of its high throughput potentiality on short-range communications and inherent superiority of high precision on ranging and localization, ultra-wideband (UWB) technology has been attracting attention continuously in research and development (R&D) as well as in commercialization. The first domestic regulation admitting indoor UWB in Japan was released by the Ministry of Internal Affairs and Communications (MIC) in 2006. Since then, several revisions have been made in conjunction with UWB commercial penetration, emerging new trends of industrial demands, and coexistence evaluation with other wireless systems. However, it was not until May 2019 that MIC released a new revision to admit outdoor UWB. Meanwhile, the IEEE 802 LAN/MAN Standards Committee has been developing several UWB related standards or amendments accordingly for supporting different use cases. At the time when this paper is submitted, a new amendment known as IEEE 802.15.4z is undergoing drafting procedure which is expected to enhance ranging ability for impulse radio UWB (IR-UWB). In this paper, we first review the domestic UWB regulation and some of its revisions to get a picture of the domestic regulation transition from indoor to outdoor. We also foresee some anticipating changes in future revisions. Then, we overview several published IEEE 802 standards or amendments that are related to IR-UWB. Some features of IEEE 802.15.4z in drafting are also extracted from open materials. Finally, we show with our recent research results that time bias internal a transceiver becomes important for increasing localization accuracy.

Emerging solid state drives (SSDs) based on a next-generation memory technology have been recently released in market. In this work, we call them low-latency SSDs because the device latency of them is an order of magnitude lower than that of conventional NAND flash SSDs. Although low-latency SSDs can drastically reduce an I/O latency perceived by an application, the overhead of OS processing included in the I/O latency has become noticeable because of the very low device latency. Since the OS processing is executed on a CPU core, its operating frequency should be maximized for reducing the OS overhead. However, a higher core frequency causes the higher CPU power consumption during I/O accesses to low-latency SSDs. Therefore, we propose the device utilization-aware DVFS (DU-DVFS) technique that periodically monitors the utilization of a target block device and applies dynamic voltage and frequency scaling (DVFS) to CPU cores executing I/O-intensive processes only when the block device is fully utilized. In this case, DU-DVFS can reduce the CPU power consumption without hurting performance because the delay of OS processing incurred by decreasing the core frequency can be hidden. Our evaluation with 28 I/O-intensive workloads on a real server containing an Intel® Optane™ SSD demonstrates that DU-DVFS reduces the CPU power consumption by 41.4% on average (up to 53.8%) with a negligible performance degradation, compared to a standard DVFS governor on Linux. Moreover, the evaluation with multiprogrammed workloads composed of I/O-intensive and non-I/O-intensive programs shows that DU-DVFS is also effective for them because it can apply DVFS only to CPU cores executing I/O-intensive processes.

Applying Software Defined Network (SDN) technology to wireless networks are attracting much attention. Our previous study proposed a channel utilization method based on SDN/OpenFlow technology to improve the channel utilization efficiency of the multi-channel wireless backhaul network (WBN). However, since control messages are inherently transmitted with data traffic on a same channel in WBN, it inevitably degrades the network capacity. Specifically, the amount of control messages for collecting statistical information of each flow (FlowStats) linearly increases with the number of ongoing flows, thereby being the dominant overhead for backhaul networks. In this paper, we propose a new method that prevents the increase of control traffic while retaining the network performance of the previous method. Our proposed method uses statistical information of each interface (PortStats) instead of per-flow information (FlowStats), and handles multiple flows on the interface together if possible. Otherwise, to handle individual flow, we propose a way to estimate per-flow information without introducing extra control messages. Finally, we show that the proposed method offers the same performance with the previous method, while greatly reducing the amount of control traffic.

Cloud computing, which enables users to enjoy various Internet services provided by data centers (DCs) at anytime and anywhere, has attracted much attention. In cloud computing, however, service quality degrades with user distance from the DC, which is unfair. In this study, we propose a bandwidth allocation scheme based on collectable information to improve fairness and link utilization in DC networks. We have confirmed the effectiveness of this approach through simulation evaluations.

Wireless Ad hoc networks have been rapidly developed in recent years since they promise a wide range of applications. However, their structures, which are based on the IEEE 802.11 standard, cause a severe unfairness problem in bandwidth sharing among different users. This is an extreme drawback because in wireless ad hoc networks, all users need to be treated fairly regardless of their geographical positions. In this paper, we propose a method to improve the fairness among flows by sensing channel access of other nodes based on the information obtained at the link layer and then, controlling the packet sending rate from the link layer to the MAC layer and the dequeue rate from the queue. Simulation results show that the proposed method achieves a better fairness with a good total throughput compared to conventional methods.

Service chaining (SC) is a method for realizing a service by transferring flows among several service functions (SFs) that process packets. A route among SFs is called a service path (SP). Service chaining is being developed to reduce costs, increase flexibility, and shorten time-to-market. SC technologies are expected to be applied to carrier networks so that large communication carriers benefit from them. We assume that SPs process the traffic of services that treat all users in the same way such as an Internet access service for home users. An SP processes flows from several users. We do not assume that each SP is assigned to a user. Because a carrier network accommodates many users, each service will be heavily utilized. Therefore, it is assumed that the amount of traffic of a service is larger than the resource of an SF apparatus. Several SPs are required to process the traffic. SPs are supposed to meet two requirements. One is guaranteeing minimum bandwidth. The other is reducing the number of SF apparatuses, i.e., high resource utilization. Resource utilization depends on the combination of the resource quantities of SF apparatuses. Network operators have to determine the bandwidth of each SP within the range from the minimum bandwidth to the resource quantities of SF apparatuses to maximize resource utilization. Methods for determining the bandwidth of each SP have not been proposed for meeting the two requirements. Therefore, we propose a resource allocation method for this purpose. The proposed method determines the bandwidth of each SP on the basis of the combination of the resource quantities of SF apparatuses for guaranteeing the minimum bandwidth and maximizing resource utilization and allocates necessary resources to each SP. We also evaluate the proposed method and confirm that it can guarantee the minimum bandwidth of SPs and achieve high resource utilization regardless of the combination of the resource quantities of SF apparatuses. Although SF apparatuses are generally produced without considering the combinations of resource quantities of SF apparatuses in SPs, the proposed method can provide more options for selecting SF apparatuses.

Low pin-count testing is an effective method to reduce test cost. Based on this method multi-site testing, i.e., where multiple devices are tested concurrently, can be supported under the limitation on the number of channels provided by ATE. In this work we propose a scalable test module (called STM) design that can support multi-site testing more efficiently when compared with previous work. In the previous work, the total number of devices that can be tested concurrently is usually fixed when the design for testability hardware is designed. For our STM, each STM can deal with a number of circuits to be tested at the same time. Moreover, STM is scalable, i.e., multiple STMs can work collaboratively while the ATE bandwidth still remains the same to further increase the degree of test parallelism. Our STM will be integrated with ATE and serve as an interface between ATE and circuits under test (CUT). Only four pins are required by STM to communicate with ATE, and IEEE 1149.1 Std. ports are employed to transfer test data to/from CUTs. STM has been verified via silicon proof, which contains only about 2,768 logic gates. Experiments results for a number of ISCAS and IWLS'05 benchmark circuits also demonstrate that by making good use of the scalable feature of STM, test efficiency can be enhanced significantly.

Our society has been getting more privacy-sensitive. Diverse information is given by users to information and communications technology (ICT) systems such as IC cards benefiting them. The information is stored as so-called big data, and there is concern over privacy violation. Visual information such as images and videos is also considered privacy-sensitive. The growing deployment of surveillance cameras and social network services has caused a privacy problem of information given from various sensors. To protect privacy of subjects presented in visual information, their face or figure is processed by means of pixelization or blurring. As image analysis technologies have made considerable progress, many attempts to automatically process flexible privacy protection have been made since 2000, and utilization of privacy information under some restrictions has been taken into account in recent years. This paper addresses the recent progress of privacy protection for visual information, showing our research projects: PriSurv, Digital Diorama (DD), and Mobile Privacy Protection (MPP). Furthermore, we discuss Harmonized Information Field (HIFI) for appropriate utilization of protected privacy information in a specific area.

Cognitive radio ad hoc networks can be used to solve the problems of limited available spectrum and inefficient spectrum usage by adaptively changing their transmission parameters. Routing protocol design has a significant impact on the network performance. However, an efficient protocol that takes account of primary user flows and the long-term channel assignment issue in route selection is still missing. In this paper, we propose AODV-cog, a cognitive routing protocol for CSMA/CA ad hoc networks based on AODV. AODV-cog chooses a route by considering the effect on the primary users, available channel bandwidth and link reliability. AODV-cog also takes account of future channel utilization which is an important but underexplored issue. AODV-cog switches channels for secondary user flows when network congestion occurs. We use theoretical analysis and computer simulations to show the advantage of AODV-cog over existing alternatives.

This paper proposes a reduced-complexity multiband multiple-input multiple-output (MIMO) receiver that can be used in cognitive radios. The proposed receiver uses heterodyne reception implemented with a wide-passband band-pass filter in the radio frequency (RF) stage. When an RF Hilbert transformer is utilized in the receiver, image-band interference occurs because of the transformer's imperfections. Thus, the imperfection of the Hilbert transformer is corrected in the intermediate frequency (IF) stage to reduce the hardware complexity. First, the proposed receiver estimates the channel impulse response in the presence of the strong image-band interference signals. Next, the coefficients are calculated for the correction of the imperfection at the IF stage, and are fed back to the IF stage through a feedback loop. However, the imperfection caused by the digital-to-analog (D/A) converter and the baseband amplifier in the feedback loop corrupts the coefficients on the way back to the IF stage. Therefore, the proposed receiver corrects the imperfection of the analog devices in the feedback loop. The performance of the proposed receiver is verified by using computer simulations. The proposed receiver can maintain its performance even in the presence of strong image-band interference signals and imperfection of the analog devices in the feedback loop. In addition, this paper also reveals the condition for rapid convergence.

This paper proposes a dynamic bandwidth allocation algorithm that improves the network performance and bandwidth sharing efficiency in the upstream channels of a hybrid passive optical network (PON) that combines a fiber-to-the-home (FTTH) access network and wireless sensor networks (WSNs). The algorithm is called the adaptive limited dynamic bandwidth allocation (ALDBA) algorithm. Unlike existing algorithms, the ALDBA algorithm is not limited to controlling just FTTH access networks, it also supports WSNs. For the proposed algorithm, we investigate the difference in the lengths of generated data packets between the FTTH terminals and sensor nodes of WSN to effectively evaluate the end-to-end average packet delay, bandwidth utilization, time jitter, and upstream efficiency. Two variants of the proposed algorithm and a limited service (LS) scheme, which is an existing well-known algorithm, are compared under non-uniform traffic conditions without taking into consideration priority scheduling. We demonstrate the proposed scheme through simulation by generating a realistic network traffic model, called self-similar network traffic. We conducted a detailed simulation using several performance parameters to validate the effectiveness of the proposed scheme. The results of the simulation showed that both ALDBA variants outperformed the existing LS scheme in terms of average packet delay, bandwidth utilization, jitter, and upstream efficiency for both low and high traffic loads.

Heterogeneous resources such as configurable logic blocks (CLBs), multiplier blocks (MULs) and RAM blocks (RAMs) where millions of logic gates are included have been added to field programmable gate arrays (FPGAs). The fixed-outline floorplanning used by the existing methods always has a big penalty item in the objective function to ensure all the modules are placed in the specified chip region, which maybe greatly degrade the wirelength. This paper presents a three-phase floorplanning method for heterogeneous FPGAs. First, a non-slicing free-outline floorplanning method is used to optimize the wirelength, however, in this phase, the satisfaction of resource requirements from functional modules might fail. Second, a min-cost-max-flow algorithm is used to tune the assignment of CLBs to functional modules, and assign contiguous regions to each module so that all the functional modules satisfy CLB requirements. Finally, the MULs and RAMs are allocated to modules by a network flow model. CLBs hold the maximum quantity among all the resources. Therefore, making a high utilization of them means an enhancement of the FPGA densities. The proposed method can improve the utilization of CLBs, hence, much larger circuits could be mapped to the same FPGA chip. The results show that about 7–85% wirelength reduction is obtained, and CLB utilization is improved by about 25%.

TCP Reno is not fully utilized in under-buffered links. We propose a new TCP congestion control algorithm that can utilize the link almost up to 100% except the first congestion avoidance cycle. Our scheme estimates the minimum congestion window size for full link utilization in every congestion avoidance cycle and sends extra packets without touching TCP Reno congestion control. It has the same RTT fairness and the same saw-tooth wave as TCP Reno does. Our scheme does not affect competing TCP Reno flows since it uses only unused link capacity. We provide a simple mathematical modeling as well as ns-2 simulation results which show that the link utilization is improved by up to 19.88% for k=1/8 against TCP Reno when the buffer is k times the optimal buffer size. We claim that our scheme is useful for transmitting large amount of data in under-buffered links.

TCP Friendly Rate Control (TFRC) has been widely used in the Internet multimedia streaming applications. However, performance of traditional TFRC algorithm degrades significantly when deployed over wireless networks. Although numerous TFRC variants have been proposed to improve the performance of TFRC over wireless networks, designing a TFRC algorithm with graceful performance both in throughput and fairness still remains a great challenge. In this paper, a novel TFRC algorithm, named TFRC-FIT, is proposed to improve the performance of TFRC over wireless environments. In the proposed approach, the behavior of multiple TFRC flows is simulated in single connection, while the number of simulated flows is adjusted by the network queuing delay. Through this mechanism, TFRC-FIT can fully utilize the capacity of wireless networks, while maintaining good fairness and TCP friendliness. Both theoretical analysis and extensive experiments over hardware network emulator, Planetlab test bed as well as commercial 3G wireless networks are carried out to characterize and validate the performance of our proposed approach.

This letter proposes a new scheduling method to improve scheduling efficiency of EPON. The proposed method uses a credit pool for each optical network unit (ONU) and for each service class. For high scheduling efficiency, the credit pool of an ONU can be negative amount to utilize the unused ONU credits. Also the proposed method dynamically excludes the lowest service class from scheduling to decrease a transmission cycle length. Using simulations, we show that the proposed method is better than the existing methods in mean delay.

The challenge in resource utilization under dynamic environment is how to utilize appropriate resources to the right users at the right time and the right location. In conventional system, centralized management system is applied but it tends to congest when user requests increase or resources rapidly move. Therefore, this paper proposes Autonomous Coordination Technology (ACT) through community organization for resource utilization. In ACT, a node which has surplus resources autonomously constructs community with a surplus-level based size and distributes resources to members which are deficient in resources. ACT consists of autonomous coordination within community and among communities. According to community organization, online property and flexibility can be satisfied. However, it is difficult to achieve service provision timeliness and resource allocation operatability in the mean time. Thus, ACT includes successive transportation method, and autonomous resource allocation which dynamic decision is made by a tradeoff between timeliness and operatability. As a result, the service assurance in terms of timeliness and operatability can be assured. The effectiveness of proposed technology is affirmed through the simulation of taxi dispatching application in terms of response time and standard deviation versus user rates.

The IEEE 802.11 MAC standard for wireless ad hoc networks adopts Binary Exponential Back-off (BEB) mechanism to resolve bandwidth contention between stations. BEB mechanism controls the bandwidth allocation for each station by choosing a back-off value from one to CW according to the uniform random distribution, where CW is the contention window size. However, in asymmetric multi-hop networks, some stations are disadvantaged in opportunity of access to the shared channel and may suffer severe throughput degradation when the traffic load is large. Then, the network performance is degraded in terms of throughput and fairness. In this paper, we propose a new cross-layer scheme aiming to solve the per-flow unfairness problem and achieve good throughput performance in IEEE 802.11 multi-hop ad hoc networks. Our cross-layer scheme collects useful information from the physical, MAC and link layers of own station. This information is used to determine the optimal Contention Window (CW) size for per-station fairness. We also use this information to adjust CW size for each flow in the station in order to achieve per-flow fairness. Performance of our cross-layer scheme is examined on various asymmetric multi-hop network topologies by using Network Simulator (NS-2).