An increasing number of distributed generators will penetrate into the distribution power system in future smart grid, thus a centralized control strategy cannot effectively optimize the power loss ...problem in real-time. This paper examines the idea of a fully distributed optimal power flow (OPF) approach, based on the alternating direction multiplier method, to optimize the power loss. The objectives are not only to effectively obtain the minimization of power loss, but also to analyze the effect of communication time-delay on optimization performance. Both synchronous and asynchronous iterative algorithms are proposed to solve the OPF problem. In addition, four different strategies are proposed to improve convergence speed when delay occurs. The proposed weighted autoregressive strategy can reduce the fluctuation effectively. In comparison with synchronous algorithm, simulation results show that the asynchronous algorithm has a better optimization result.
With the rapid growth in IC outsourcing in the semiconductors industry, concerns have increased about the weakening ICs security against hardware Trojan attacks. In this brief, an integrated hardware ...Trojan detection and localization methodology is presented by employing the proposed SAT-based test pattern generation scheme and the MUX-based debugging technique. The experimental results show that our methodology can effectively detect timing anomalies in the path-delays caused by hardware Trojans with node coverage around 97% as well as localizing all Trojan's gates with a localization resolution around 99.6%. Moreover, all timing error sites are successfully identified with zero False Negative and 0.56% False Positive rates.
Supporting data dissemination in vehicular networks is difficult due to high mobility of vehicle traffic, limited communication resources, and dynamic communication requirements. In this paper, we ...investigate data dissemination in hybrid vehicular networks, where messages generated at vehicles should be uploaded to the roadside unit (RSU) assisted by vehicle-to-vehicle (V2V) communications, using vehicles traveling in both directions as relays. The objective is to optimize the resource utilization and reduce the data delivery delay. We first analyze the data uploading capacity and delivery delay in hybrid vehicular networks with the store-carry-and-forward mechanism. Applying the analytical results and given the traffic and data information, a distributed multisource scheduling algorithm is proposed. Extensive simulations are conducted to verify the correctness of the analysis. It shows that the proposed algorithm significantly improves the data dissemination efficiency compared with the existing solutions.
In this work, we investigate a slotted-time relay assisted cooperative random access wireless network with multipacket (MPR) reception capabilities. MPR refers to the capability of a wireless node to ...successfully receive packets from more than two other modes that transmit simultaneously at the same slot. We consider a network of N saturated sources that transmit packets to a common destination node with the cooperation of two infinite capacity relay nodes. The relays assist the sources by forwarding the packets that failed to reach the destination. Moreover, the relays have also packets of their own to transmit to the destination. We further assume that the relays employ a state-dependent retransmission control mechanism. In particular, a relay node accordingly adapts its transmission probability based on the status of the other relay. Such a protocol is towards self-aware networks and leads to substantial performance gains in terms of delay. We investigate the stability region and the throughput performance for the full MPR model. Moreover, for the asymmetric two-sources, two-relay case we derive the generating function of the stationary joint queue-length distribution with the aid of the theory of boundary value problems. For the symmetric case, we obtain explicit expressions for the average queueing delay in a relay node without solving a boundary value problem. Extensive numerical examples are presented and provide insights on the system performance.
In order to meet the ever-increasing traffic demands, the combination of fiber and Millimeter Wave (mmWave) is expected to play a key role for 5G Centralized-Radio Access Networks (C-RANs). Due to ...the inefficiency of the Common Public Radio Interface for the Baseband Unit (BBU)-Remote Radio Head (RRH) communication, analog-Radio-over-Fiber (a-RoF) technology is considered a promising solution, mainly due to the RRH simplification and lower fronthaul requirements it imposes. In such mmWave a-RoF C-RANs, efficient Medium Transparent-Medium Access Control (MT-MAC) protocols are needed able to meet the challenging 5G requirements. To this end, in this paper, we propose a gated service MT-MAC protocol which authorizes each user to transmit the amount of data it requested. A detailed delay model is proposed, which is validated through simulations for different fiber lengths, network load conditions and number of available optical wavelengths. Moreover, the proposed protocol is compared with the state-of-the-art (SoA) and is shown to achieve up to 20 times higher throughput, 2 times lower delay with 100% lower blocking probability and 5 times higher data wavelength utilization, while being able to adapt to varying network traffic conditions. Our proposal also attains sub-ms latency in most cases, constituting it a promising candidate for 5G mmWave a-RoF C-RANs.
With the increase in the number of Electronic Control Units (ECUs) and future requirements for vehicle functions, two SR (Stream Reservation) traffic classes may not be sufficient to ensure ...fulfilment of constraints for multiple traffic types with individual timing requirements transmitted in the Ethernet-AVB (Audio Video Bridging) networks. The goal of this paper is to determine the worst-case delay for an additional SR traffic class under the CBS (Credit-Based Shaper) algorithm. Delay evaluation is based on the impact analysis of CBS on different priority flows, particularly depending on when the credits of both SR class A and B drain from the worst-case perspective. More specifically, both the impact of CBS and the evolution trends of credit on different priority class flows are first analyzed from the worst-case perspective. Then, for an additional SR class, two types of worst-case delay models are established with the CBS configuration suggestions. Finally, an approach to calculate the worst-case queuing delay is proposed. Moreover, the worst-case end-to-end delay is determined by the network calculus approach and simulation. Numerical results show that the delay bounds of our models are tighter than those of other models, which is beneficial to the development of Ethernet-AVB for in-vehicle networking.
Delays in construction result in a multitude of negative effects on project performance, and severe dismays among participating parties. This study aims to digitize the traditional process of ...recording and managing the construction delays using Building Information Modeling (BIM). Extensive literature review followed by semi-structure interviews of 21 industry experts were carried out to identify the issues faced by construction stakeholders in managing construction delays. To resolve these issues, a plugin named BIM-based Construction Delays Recorder (BIM-CDR) is developed using Application Programming Interface (API) of the most commonly used BIM software i.e. Autodesk Revit. BIM-CDR provides a centralized repository, encompassing detailed information related to delays, which can be retrieved and visualized to analyze their impact on delay claims. To assess the effectiveness of BIM-CDR, a feasibility study is conducted with the experts’ review panel. The results revealed that BIM-CDR can record wide-ranging information related to all the significant issues causing delays on construction sites, and can help in effectively managing their corresponding claims. The advantages of the developed prototype include visualization of delays’ location, facilitation of delay analysis and effective delays management. Moreover, it also promotes transparency and speedy settlement of delay related claims without any unwanted disputes.
Video cameras are increasingly used to provide real-time feedback in automatic control systems, such as autonomous driving and robotics systems. For such highly dynamic applications, the ...glass-to-glass (G2G) and glass-to-algorithm (G2A) latencies are critical. In this paper, we analyze the latencies in a point-to-point video transmission system and propose novel frame skipping and preemption approaches to reduce the G2G and G2A delays. We implement the proposed approaches in a prototype that shows significantly reduced G2G and G2A latencies as well as reduced transmission bitrate requirements compared with traditional video transmission schemes. In our low-delay video communication prototype, a VGA resolution video is transmitted with average G2G and G2A delays of 21.2 and 11.5 ms, respectively, with off-the-shelf hardware.
Caching at mobile devices and leveraging device-to-device (D2D) communication are two promising approaches to support massive content delivery over wireless networks. The analysis of cache-enabled ...wireless networks is usually carried out by assuming that devices are uniformly distributed, however, in social networks, mobile devices are intrinsically grouped into disjoint clusters. In this regards, this paper proposes a spatiotemporal mathematical model that tracks the service requests arrivals and account for the clustered devices geometry. Two kinds of devices are assumed, particularly, content clients and content providers. Content providers are assumed to have a surplus memory which is exploited to proactively cache contents from a known library, following a random probabilistic caching scheme. Content clients can retrieve a requested content from the nearest content provider in their proximity (cluster), or, as a last resort, the base station (BS). The developed spatiotemporal model is leveraged to formulate a joint optimization problem of the content caching and spectrum partitioning in order to minimize the average service delay. Due to the high complexity of the optimization problem, the caching and spectrum partitioning problems are decoupled and solved iteratively using the block coordinate descent (BCD) optimization technique. To this end, an optimal and suboptimal solutions are obtained for the bandwidth partitioning and probabilistic caching subproblems, respectively. Numerical results highlight the superiority of the proposed scheme over conventional caching schemes under equal and optimized bandwidth allocations. Particularly, it is shown that the average service delay is reduced by nearly 100% and 350%, compared to the Zipf and uniform caching schemes under equal bandwidth allocations, respectively.
This article reports on the extraction of the electron velocity as a function of gate bias from N-polar GaN deep recess high-electron-mobility transistors (HEMTs) designed for mm-wave power ...amplification. Bias-dependent small-signal S-parameter measurements are used to obtain small-signal equivalent circuit parameters, which are applied to a transit delay model. The model accounts for fringing capacitance to arrive at an electron velocity associated with the transit of the physical gate length. A peak electron velocity of <inline-formula> <tex-math notation="LaTeX">1.4\times 10^{{7}} </tex-math></inline-formula> cm/s was obtained at a drain current of 700 mA/mm corresponding to a channel charge density of <inline-formula> <tex-math notation="LaTeX">0.3\times 10^{{13}} </tex-math></inline-formula> cm −2 . At higher current, the velocity slowly decreased with the electron velocity crossing below <inline-formula> <tex-math notation="LaTeX">10^{{7}} </tex-math></inline-formula> cm/s at 1.8 A/mm. This behavior was found to be in good agreement with a previously proposed model based on optical phonon scattering at the source injection point. An analysis of the delay components is used to provide guidance for the factors influencing the device performance.
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