In recent years, microwave wireless power transfer (WPT) has attracted considerable attention due to the increasing demand for various sensors and Internet of Things (IoT) applications. Microwave WPT requires technology that can detect and avoid human bodies in the transmission path. Using a phantom is essential for developing such technology in terms of standardization and human body protection from electromagnetic radiation. In this study, a simple and lightweight phantom was developed focusing on its radar cross-section (RCS) to evaluate human body avoidance technology for use in microwave WPT systems. The developed phantom's RCS is comparable to that of the human body.

In this study, we propose a mechanism called adaptive failsoft control to address peak traffic in mobile live streaming, using a chasing playback function. Although a cache system is avaliable to support the chasing playback function for live streaming in a base station and device-to-device communication, the request concentration by highlight scenes influences the traffic load owing to data unavailability. To avoid data unavailability, we adapted two live streaming features: (1) streaming data while switching the video quality, and (2) time variability of the number of requests. The second feature enables a fallback mechanism for the cache system by prioritizing cache eviction and terminating the transfer of cache-missed requests. This paper discusses the simulation results of the proposed mechanism, which adopts a request model appropriate for (a) avoiding peak traffic and (b) maintaining continuity of service.

We investigated the function in the Lateral Geniculate Nucleus of avoidance behavior due to the inconsistency between binocular retinal images due to blue from vergence eye movement based on avoidance behavior caused by the inconsistency of binocular retinal images when watching the rim of a blue-yellow equiluminance column.

The progress of immersive technology enables researchers and developers to construct work spaces that are freed from real-world constraints. This has motivated us to investigate the role of the human body. In this research, we examine human cognitive behaviors in obtaining an understanding of the width of their virtual body through simple yet meaningful experiments using virtual reality (VR). In the experiments, participants were modeled as an invisible board, and a spherical object was thrown at the participants to provide information for exploring the width of their invisible body. Audio and visual feedback were provided when the object came into contact with the board (body). We first explored how precisely the participants perceived the virtual body width. Next, we examined how the body perception was generated and changed as the trial proceeded when the participants tried to move right or left actively for the avoidance of collision with approaching objects. The results of the experiments indicated that the participants could become successful in avoiding collision within a limited number of trials (14 at most) under the experimental conditions. It was also found that they postponed deciding how much they should move at the beginning and then started taking evasive action earlier as they become aware of the virtual body.

On the Internet, end hosts and network nodes interdependently work to smoothly transfer traffic. Observed traffic dynamics are the result of those interactions among those entities. To manage Internet traffic to provide satisfactory quality services, such dynamics need to be well understood to predict traffic patterns. In particular, some nodes have a function that sends back-pressure signals to backward nodes to reduce their sending rate and mitigate congestion. Transmission Control Protocol (TCP) congestion control in end-hosts also mitigates traffic deviation to eliminate temporary congestion by reducing the TCP sending rate. How these congestion controls mitigate congestion has been extensively investigated. However, these controls only throttle their sending rate but do not reduce traffic volume. Such congestion control fails if congestion is persistent, e.g., for hours, because unsent traffic demand will infinitely accumulate. However, on the actual Internet, even with persistent congestion, such accumulation does not seem to occur. During congestion, users and/or applications tend to reduce their traffic demand in reaction to quality of service (QoS) degradation to avoid negative service experience. We previously estimated that 2% packet loss results in 23% traffic reduction because of this upper-layer reaction [1]. We view this reduction as an upper-layer congestion-avoidance mechanism and construct a closed-loop model of this mechanism, which we call the Upper-Layer Closed-Loop (ULCL) model. We also show that by using ULCL, we can predict the degree of QoS degradation and traffic reduction as an equilibrium of the feedback loop. We applied our model to traffic and packet-loss ratio time series data gathered in an actual network and demonstrate that it effectively estimates actual traffic and packet-loss ratio.

With the rapid increase in IoT (Internet of Things) applications, more sensor devices, generating periodic data flows whose packets are transmitted at regular intervals, are being incorporated into WSNs (Wireless Sensor Networks). However, packet collision caused by the hidden node problem is becoming serious, particularly in large-scale multi-hop WSNs. Moreover, focusing on periodic data flows, continuous packet collisions among periodic data flows occur if the periodic packet transmission phases become synchronized. In this paper, we tackle the compounded negative effect of the hidden node problem and the continuous collision problem among periodic data flows. As this is a complex variant of the hidden node problem, there is no simple and well-studied solution. To solve this problem, we propose a new MAC layer mechanism. The proposed method predicts a future risky duration during which a collision can be caused by hidden nodes by taking into account the periodic characteristics of data packet generation. In the risky duration, each sensor node stops transmitting data packets in order to avoid collisions. To the best of our knowledge, this is the first paper that considers the compounded effect of hidden nodes and continuous collisions among periodic data flows. Other advantages of the proposed method include eliminating the need for any new control packets and it can be implemented in widely-diffused IEEE 802.11 and IEEE 802.15.4 devices.

Several types of capacitive crosstalk avoidance codes have been devised in order to prevent capacitive crosstalk in on-chip buses. These codes are designed to prohibit transition patterns prone to capacitive crosstalk from any two consecutive words transmitted to on-chip buses. The present paper provides a rigorous analysis of the asymptotic rate for (p,q)-transition free word sequences under the assumption that coding is based on a stateful encoder and a stateless decoder. Here, p and q represent k-bit transition patterns that should not appear in any two consecutive words at the same adjacent k-bit positions. The maximum rate for the sequences is proven to be equal to the subgraph domatic number of the (p,q)-transition free graph. Based on the theoretical results for the subgraph domatic partition problem, lower and upper bounds on the asymptotic rate are derived. We also show that the asymptotic rate 0.8325 is achievable for p=01 and q=10 transition free word sequences.

Performance evaluation of an improved multiband impulse radio ultra-wideband (MIR UWB) system based on sub-band selection is proposed in this paper. In the improved scheme, a data mapping algorithm is introduced to a conventional MIR UWB system, and out of all the sub-bands, only partial ones are selected to transmit information data, which can improve the flexibility of sub-bands/spectrum allocation, avoid interference and provide a variety of data rates. Given diagrams of a transmitter and receiver, the exact bit error rate (BER) of the improved system is derived. A comparison of system performance between the improved MIR UWB system and the conventional MIR UWB system is presented in different channels. Simulation results show that the improved system can achieve the same data rate and better BER performance than the conventional MIR UWB system under additive white Gaussian noise (AWGN), multipath fading and interference coexistence channels. In addition, different data transmission rates and BER performances can be easily achieved by an appropriate choice of system parameters.

Network Coding-based Epidemic Routing (NCER) facilitates the reduction of data delivery delay in Delay Tolerant Networks (DTNs). The intrinsic reason lies in that the network coding paradigm avoids competitions for transmission opportunities between segmented packets of a large data file. In this paper, we focus on the impact of transmission competitions on the delay performance of NCER when multiple data files exist. We prove analytically that when competition occurs, transmitting the least propagated data file is optimal in the sense of minimizing the average data delivery delay. Based on such understanding, we propose a family of competition avoidance policies, namely the Least Propagated First (LPF) policies, which includes a centralized, a distributed, and a modified variants. Numerical results show that LPF policies can achieve at least 20% delay performance gain at different data traffic rates, compared with the policy currently available.

In this paper, we investigate the problems of the established congestion solution and then introduce a self-adjustable rate control that supports quality of service assurances over multi-hop wireless mesh networks. This scheme eliminates two phases of the established congestion solution and works on the MAC layer for congestion control. Each node performs rate control by itself so network congestion is eliminated after it independently collects its vector parameters and network status parameters for rate control. It decides its transmission rate based on a predication model which uses a rate function including a congestion risk level and a passing function. We prove that our scheme works efficiently without any negative effects between the network layer and the data link layer. Simulation results show that the proposed scheme is more effective and has better performance than the existing method.

Fault tolerant methods using dynamically reconfigurable devices have been studied to overcome wear-out failures. However, quantitative comparisons have not been sufficiently assessed on device lifetime enhancement with these methods, whereas they have mainly been evaluated individually from various viewpoints such as additional hardware overheads, performance, and downtime for fault recovery. This paper presents quantitative lifetime evaluations performed by simulating the fault-avoidance procedures of five representative methods under the same conditions in wear-out scenarios, applications, and device architecture. The simulation results indicated that improvements of up to 70% mean-time-to-failure (MTTF) in comparison with ideal fault avoidance could be achieved by using methods of fault avoidance with ‘row direction shift’ and ‘dynamic partial reconfiguration’. ‘Column shift’, on the other hand, attained a high degree of stability with moderate improvements in MTTF. The experimental results also revealed that spare basic elements (BEs) should be prevented from aging so that improvements in MTTF would not be adversely affected. Moreover, we found that the selection of initial mappings guided by wire utilization could increase the lifetimes of partial reconfiguration based fault avoidance.

Pattern-avoiding permutations are permutations where none of the subsequences matches the relative order of a given pattern. Pattern-avoiding permutations are related to practical and abstract mathematical problems and can provide simple representations for such problems. For example, some floorplans, which are used for optimizing very-large-scale integration (VLSI) circuit design, can be encoded into pattern-avoiding permutations. The generation of pattern-avoiding permutations is an important topic in efficient VLSI design and mathematical analysis of patten-avoiding permutations. In this paper, we present an algorithm for generating pattern-avoiding permutations, and extend this algorithm beyond classical patterns to generalized patterns with more restrictions. Our approach is based on the data structure πDDs, which can represent a permutation set compactly and has useful set operations. We demonstrate the efficiency of our algorithm by computational experiments.

A D2D (Device-to-Device) communication system needs to cope with inter-cell interference and other types of interferences between cellular network and D2D links. As a result, macro user equipments, particularly those located near a cell edge, will suffer from serious link performance degradation. We propose a novel interference avoidance mechanism assisted by the SRN (Shared Relay Node) in this letter. The SRN not only performs data re-transmission as a typical type-II relay, but has several newly defined features to avoid interference between cellular network and D2D links. The superb performance by the proposed scheme is evaluated through extensive system level simulations.

In P2P applications, networks are formed by devices belonging to independent users. Therefore, routing hotspots or routing congestions are typically created by an unanticipated new event that triggers an unanticipated surge of users to request streaming service from some particular nodes; and a challenging problem is how to provide incentive mechanisms to allocation bandwidth more fairly in order to avoid congestion and other short backs for P2P QoS. In this paper, we study P2P bandwidth game — the bandwidth allocation in P2P networks. Unlike previous works which focus either on routing or on forwarding, this paper investigates the game theoretic mechanism to incentivize node's real bandwidth demands and propose novel method that avoid congestion proactively, that is, prior to a congestion event. More specifically, we define an incentive-compatible pricing vector explicitly and give theoretical proofs to demonstrate that our mechanism can provide incentives for nodes to tell the true bandwidth demand. In order to apply this mechanism to the P2P distribution applications, we evaluate our mechanism by NS-2 simulations. The simulation results show that the incentive pricing mechanism can distribute the bandwidth fairly and effectively and can also avoid the routing hotspot and congestion effectively.

This paper proposes a procedure for avoiding delay faults in field with slack assessment during standby time. The proposed procedure performs path delay testing and checks if the slack is larger than a threshold value using selectable delay embedded in basic elements (BE). If the slack is smaller than the threshold, a pair of BEs to be replaced, which maximizes the path slack, is identified. Experimental results with two application circuits mapped on a coarse-grained architecture show that for aging-induced delay degradation a small threshold slack, which is less than 1 ps in a test case, is enough to ensure the delay fault prediction.

An ultra-wideband (UWB) system usually occupies a large frequency band, which may overlap with the spectrum of a narrow band system. The latter is referred to as a victim system. To effectively use frequency, a UWB system may create a notch in its spectrum to accommodate the victim signal for interference avoidance. Parameters of the notch such as the depth and the width of a notch need to be decided in accordance to victim systems. In this paper, we investigate the effective UWB avoidance by examining the suitable notch based on experimental evaluation. In the experiments, 3GPP LTE, Mobile WiMAX, as well as an IMT Advanced Test-bed are respectively employed to represent different types of victim systems. The UWB system is set up based on WiMedia specifications and operates at the UWB low band of 3.1–4.8 GHz. A notch is fabricated by nullifying the related subcarriers of the UWB signal. In addition, a filter or a window function is formed and employed to further smooth the notch. Bit error rate (BER) or packet error rate (PER) performances of victim systems are measured and used to evaluate the UWB interference. Our results show that when a notch is properly formed, the interference level introduced by UWB can be below the permitted level by regulations.

The paper presents capability of signal detection for realizing coexistence between broadband wireless access (BWA) systems and ultra wideband (UWB) devices. The capability is experimentally evaluated for baseband signals of downlink (DL) in both mobile WiMAX and 3GPP LTE. An UWB receiver based on fast Fourier transform (FFT) compliant with MB-OFDM standard is implemented as a detector of the BWA signals. The capability is evaluated in terms of elapsed time required to achieve signal detection with probability of 99% by the implemented FFT-based UWB receiver at different conditions of the receiver. Decisions on the signal detection are made by the simplest method which is by setting a threshold which is determined by noise floor of the receiver as reference. The experiments have been conducted though baseband signals for both AWGN and multipath fading channels without any synchronization between the DL signals and UWB receiver. In AWGN environment, results show that the elapsed time depends on the duty ratio of the DL signal to be detected, however, the correlation between the required time and duty ratio is not linear since their envelopes of the DL signals are not constant. In multipath fading environments based on channel models commonly employed as mobile radio environments, the required time for the signal detection becomes as 17 times longer than that in AWGN due to its signal attenuation. For robust signal detection in multipath fading environments, it has been revealed that the number of quantization bits at ADC is crucial through the experiments.

Due to universal frequency reuse, cell edge users in HSDPA suffer from serious inter-cell interference (ICI). In this letter we present a coordinated scheme for HSDPA which can mitigate ICI by interference avoidance in spatial domain. A system level simulation shows that our scheme can effectively improve the performance of the cell edge users.

We propose an interference avoidance architecture using uneven spreading as a media access mechanism for optical code division multiple access (OCDMA). While an equal-intensity pulse sequence encoded with the spreading sequence assigned to each node is transmitted for a “1” bit in conventional OCDMA with on-off keying (OOK), the proposed architecture creates an uneven-intensity pulse sequence where one of the pulses has higher intensity than the others. The high-intensity pulse allows source nodes to use increased sensing threshold for channel sensing, which leads to an increase in the number of chip offsets available for collision-free transmission. Our receiver with a hard limiter (HL) allows destination nodes to receive the transmission without false positives. Interference avoidance performance is examined by deriving the collision probability and comparing it with the conventional interference avoidance with equal-intensity spreading. Our numerical results show that our architecture has lower collision probability, shorter time required for channel sensing, higher throughput, higher bit rate, and supports more nodes than the conventional one for a fixed collision probability.

It is known that the optimal sensor coverage of a mission space is performed by a Voronoi partition, which is called a Voronoi coverage problem. We consider the case that the mission space has several obstacles where mobile sensors cannot be deployed and search an optimal deployment to maximize the sensing performance. Inspired by the potential field method, we introduce a repulsive potential for obstacle avoidance and define the objective function by a combination of two functions: one for evaluation of the sensing performance and the other for obstacle avoidance. We introduce a space where a sensor can move, called its moving space. In general, a moving space may not coincide with the mission space. We assume that the respective moving spaces of each sensor may differ from each other. By introducing a barycentric coordinate over the moving space, we show that the Voronoi coverage problem to maximize the objective function is transformed into a potential game. In potential games, local maximizers of a potential function are stable equilibrium points of the corresponding replicator dynamics. We propose a distributed sensor coverage control method based on the replicator dynamics to search a local maximizer of the objective function and a path to it. Using simulations, we also compare the proposed method with the Lloyd and TangentBug algorithm proposed by Breitenmoser et al.