Switched parasitic capacitors of sleep blocks with a tri-mode power gating structure are implemented to reduce on-chip resonant supply noise in 1.2 V, 65 nm standard CMOS process. The tri-mode power gating structure makes it possible to store charge into the parasitic capacitance of the power gated blocks. The proposed method achieves 53.1% and 57.9% noise reduction for wake-up noise and 130 MHz periodic supply noise, respectively. It also realizes noise cancelling without discharging time before using parasitic capacitors of sleep blocks, and shows 8.4x boost of the effective capacitance value with 2.1% chip area overhead. The proposed method can save the chip area for reducing resonant supply noise more effectively.

In this letter, the amount of interference and an analytic methodology from a combination of Korea's LTE system and Japan's digital terrestrial TV broadcasting system using the 700 MHz frequency band are established when considering a practical deployment of both systems. We performed Monte-Carlo simulations on the throughput loss to evaluate how much interference radiating from Japan's DTV is imposed on the Korean LTE system. The results of the established methodology can be used as a guideline for allowing the deployed LTE system to avoid an unacceptable amount of interference.

In this letter, we propose a more secure modeling and simulation approach that can systematically detect state variable corruptions caused by buffer overflows in simulation models. Using our approach, developers may not consider secure coding practices related to the corruptions. We have implemented a prototype of the approach based on a modeling and simulation formalism and an open source simulator. Through optimization, the prototype could show better performance, compared to the original simulator, and detect state variable corruptions.

Fairness among uplink and downlink TCP flows can not be supported in infrastructure IEEE 802.11 Wireless LANs using the distributed coordination function (DCF). In order to resolve this problem, we propose the Distributed Access Time Control (DATC) scheme, in which each station controls the rates of its TCP flows based on channel access time. The DATC scheme can provide per-station fairness even when the number and direction of flows in each station are different. This scheme can be simply implemented in mobile stations without having to modify the access points. The properties of the proposed scheme are investigated and its effectiveness is verified through simulations.

Digital hearing aid users often complain of difficulty in understanding speech in the presence of background noise. To improve speech perception in a noisy environment, various speech enhancement algorithms have been applied in digital hearing aids. In this study, a speech enhancement algorithm using modified spectral subtraction and companding is proposed for digital hearing aids. We adjusted the biases of the estimated noise spectrum, based on a subtraction factor, to decrease the residual noise. Companding was applied to the channel of the formant frequency based on the speech presence indicator to enhance the formant. Noise suppression was achieved while retaining weak speech components and avoiding the residual noise phenomena. Objective and subjective evaluation under various environmental conditions confirmed the improvement due to the proposed algorithm. We tested segmental SNR and Log Likelihood Ratio (LLR), which have higher correlation with subjective measures. Segmental SNR has the highest and LLR the lowest correlation of the methods tested. In addition, we confirmed by spectrogram that the proposed method significantly reduced the residual noise and enhanced the formants. A mean opinion score that represented the global perception score was tested; this produced the highest quality speech using the proposed method. The results show that the proposed speech enhancement algorithm is beneficial for hearing aid users in noisy environments.

In this letter, an improved residual symbol timing offset (STO) estimation scheme is suggested in an orthogonal frequency division multiplexing (OFDM) based digital radio mondiale plus (DRM+) system with cyclic delay diversity (CDD). The robust residual STO estimator is derived by properly selecting the amount of cyclic delay and a pilot pattern in the presence of frequency selectivity. Via computer simulation, it is shown that the proposed STO estimation scheme is robust to the frequency selectivity of the channel, with a performance better than the conventional scheme.

A new matched-filter (MF) acquisition scheme with adaptive threshold is proposed for a frequency-hopped/spread-spectrum multiple-access (FH/SSMA) system. Detection and false alarm probabilities are derived for combined interference environments. The combined interference consists of partialband noise jamming or tone jamming, multiple access interference (MAI), multipath interference, and thermal noise. We use Gaussian approximation for modeling the MAI and multipath interference. Equal power assumption of the users is employed which is typically used in the SSMA system analysis. In the proposed scheme, MF output is compared to an adaptive threshold determined by the number of jammed frequency slots. It is shown that the proposed adaptive-threshold acquisition scheme achieves higher detection probability and lower false alarm probability than a conventional fixed-threshold scheme for each jammed fractional bandwidth, JSR, the number of multipaths, and the number of users. It is also shown that adaptive threshold achieves faster acquisition and higher packet throughput than fixed threshold in application to FH/SSMA packet radio system.

This paper discribes a shared medium access control protocol for residential home and small business customer ATM network application with distributed high-speed multimedia services. This protocol offers global fairness for the whole network with a CG (Centralized Grant) signal and, at the same time, offers local fairness between nodes with DG (Distributed Grant) signals. The DG signal is only meaningful to the next neighboring node. The local fairness is kept between two nodes in distributed way, but this distributed local fairness helps to keep the global fairness. Because the DG signal is related to the passed DG signal from the neighbor node. This protocol is rather simple but shows high performance than the already announced protocols.

In this paper, we evaluated performance of mobile exchange control network. Queueing network model is used for modeling of mobile exchange control network. We developed a call control processing and location registration scenario that has a message exchange function between processors in mobile exchange control network. The network symbols are used the simulation models that are composed of the initialization module, message generation module, message routing module, message processing module, message generation module, HIPC network processing module, output analysis module. As a result of computer simulation, we obtain the processor utilization, the mean queue length, the mean waiting time of control network based on call processing and location registration capacity. The call processing and location registration capacity are referred by the number of call attempts in the mobile exchange and must be satisfied with the quality of service (delay time).

PIN diodes for digital X-ray detection as a single photon counting sensor were fabricated on a floating-zone (FZ) n-type (111), high resistivity (5-10 kΩcm) silicon substrates (500 µm thickness). Its electrical properties such as the leakage current and the breakdown voltage were characterized. The size of pixels was 100 µm100 µm. The p+ guard-ring was formed around the active area to reduce the leakage current. After the p+ active area and guard-ring were fabricated by the ion-implantation, the extrinsic-gettering on the wafer backside was performed to reduce the leakage current by n+ ion-implantation. PECVD oxide was deposited as an IMD layer on front side and then, metal lines were formed on both sides of wafers. The leakage current of detectors was significantly reduced with a guard-ring when compared with that without a guard ring. The leakage current showed the strong dependency on the gap distance between the active area and the guard ring. It was possible to achieve the leakage current lower than 0.2 nA/cm2.

This paper presents an optimal load balancing algorithm based on both of the ANFIS (Adaptive Neuro-Fuzzy Inference System) modeling and the FIS (Fuzzy Inference System) for the local status of real servers. It also shows the substantial benefits such as the removal of load-scheduling overhead, QoS (Quality of Service) provisioning and providing highly available servers, provided by the suggested method.

This letter proposes a high precision ranging scheme based on the time of arrival estimation technique for the IEEE 802.15.4a chirp spread spectrum system. The proposed scheme consists of a linear channel impulse response estimation process with the zero forcing or minimum mean square error technique and the multipath delay estimation process with matrix pencil algorithm. The performance of the proposed scheme is compared with that of a well known MUSIC algorithm in terms of computational complexity and ranging precision. Simulation results demonstrate that the proposed scheme outperforms the MUSIC algorithm even though it has comparatively lower computational complexity.

In this paper, we propose an error-correction low-pass filter (EC-LPF) algorithm for estimating the wireless distance between devices. To measure this distance, the received signal strength indication (RSSI) is a popularly used method because the RSSI of a wireless signal, such as Wi-Fi and Bluetooth, can be measured easily without the need for additional hardware. However, estimating the wireless distance using an RSSI is known to be difficult owing to the occurrence of inaccuracies. To examine the inaccuracy characteristics of Bluetooth RSSI, we conduct a preliminary test to discover the relationship between the actual distance and Bluetooth RSSI under several different environments. The test results verify that the main reason for inaccuracy is the existence of measurement errors in the raw Bluetooth RSSI data. In this paper, the EC-LPF algorithm is proposed to reduce measurement errors by alleviating fluctuations in a Bluetooth signal with responsiveness for real-time applications. To evaluate the effectiveness of the EC-LPF algorithm, distance accuracies of different filtering algorithms are compared, namely, a low-pass filer (LPF), a Kalman filter, a particle filter, and the EC-LPF algorithm under two different environments: an electromagnetic compatibility (EMC) chamber and an indoor hall. The EC-LPF algorithm achieves the best performance in both environments in terms of the coefficient of determination, standard deviation, measurement range, and response time. In addition, we also implemented a meeting room application to verify the feasibility of the EC-LPF algorithm. The results prove that the EC-LPF algorithm distinguishes the inside and outside areas of a meeting room without error.

This paper describes the Differential Pass Transistor Pulsed Latch (DPTPL) which enhances D-Q delay and reduce power consumption using NMOS pass transistors and feedback PMOS transistors. The proposed flip-flop uses the characteristic of stronger drivability of NMOS transistor than that of transmission gate if the sum of total transistor width is the same. Positive feedback PMOS transistors enhance the speed of the latch as well as guarantee the full-swing of internal nodes. Also, the power consumption of proposed pulsed latch is reduced significantly due to the reduced clock load and smaller total transistor width compared to conventional differential flip-flops. DPTPL reduces ED by 45.5% over ep-SFF. The simulations were performed in a 0.1 µm CMOS technology at 1.2 V supply voltage with 1.25 GHz clock frequency.

This paper proposes T-CROM (Time-delayed Collaborative ROuting and MAC) protocol, that allows collaboration between network and MAC layers in order to extend the lifetime of MANETs in a resources-limited environment. T-CROM increases the probability of preventing energy-poor nodes from joining routes by using a time delay function that is inversely proportional to the residual battery capacity of intermediate nodes, making a delay in the route request (RREQ) packets transmission. The route along which the first-arrived RREQ packet traveled has the smallest time delay, and thus the destination node identifies the route with the maximum residual battery capacity. This protocol leads to a high probability of avoiding energy-poor nodes and promotes energy-rich nodes to join routes in the route establishment phase. In addition, T-CROM controls the congestion between neighbors and reduces the energy dissipation by providing an energy-efficient backoff time by considering both the residual battery capacity of the host itself and the total number of neighbor nodes. The energy-rich node with few neighbors has a short backoff time, and the energy-poor node with many neighbors gets assigned a large backoff time. Thus, T-CROM controls the channel access priority of each node in order to prohibit the energy-poor nodes from contending with the energy-rich nodes. T-CROM fairly distributes the energy consumption of each node, and thus extends the network lifetime collaboratively. Simulation results show that T-CROM reduces the number of total collisions, extends the network lifetime, decreases the energy consumption, and increases the packet delivery ratio, compared with AOMDV with IEEE 802.11 DCF and BLAM, a battery-aware energy efficient MAC protocol.

A subarray signal processing scheme is described for a large-scale two-dimensional analog-digital hybrid beamformer to be used in quasi-millimeter-wave-band mobile communication systems. Multiple analog phased arrays direct their respective beams to multiple users, enabling space-division multiple access (SDMA). An iterative soft-input soft-output (SISO) multi-user detector recovers multi-user signals from subarray output signals corrupted by inter-user interference (IUI). In addition, a phased-array directivity control algorithm is derived based on inter-subarray signal phase-difference estimation from inter-beam-interference (IBI)-cancelled subarray output signals. Simulation results demonstrate that our proposed scheme achieves reduced hardware complexity, IUI-resistant multi-user signal detection, and IBI-resistant multi-user-tracking phased-array directivity control.

We present transmission- and reflection-type measurement methods for the differential mode delay (DMD) of a multimode optical fiber (MMF) optimized for high-speed local area networks (LANs) for the 850-nm band. Compared with a previously reported transmission-type measurement method for the 1550-nm wavelength band, we demonstrate here high-resolution DMD measurement methods for MMFs in the 850-nm band. As the method is based on a Fourier-domain intermodal interference technique, the measurement sensitivity is ∼60-dB, and it requires a fiber only a few meters in length. The shorter wavelength also allows a threefold improvement in the measurement resolution. The reflection-type measurement technique is a more practical than the transmission-type measurement technique for the field testing of short MMFs already installed in networks. We believe that this method will be a practical tool not only for field testing of short-length MMFs already installed in networks but also for the development of new plastic optical fibers (POFs).

In the statistic en-route filtering, each report generation node must collect a certain number of endorsements from its neighboring nodes. However, at some point, a node may fail to collect an insufficient number of endorsements since some of its neighboring nodes may have dead batteries. This letter presents a report generation method that can enhance the generation process of sensing reports under such a situation. Simulation results show the effectiveness of the proposed method.