In an orthogonal frequency division multiplexing (OFDM) system, carrier frequency offset (CFO) causes intercarrier interference (ICI) which significantly degrades the system error performance. In this paper we provide a closed-form expression to evaluate the exact error probabilities of arbitrary 2-D modulation OFDM systems with CFO, and analyze the effect of CFO on error performance.

Deploying a group of mobile sensor (MS) nodes to monitor a moving phenomenon in an unknown and open area includes a lot of challenges if the phenomenon moves quickly and due to the limited capabilities of MS nodes in terms of mobility, sensing and communication ranges. To address these challenges and achieve a high weighted sensing coverage, in this paper, we propose a new algorithm for moving-phenomenon monitoring, namely VirFID-MP (Virtual Force (VF)-based Interest-Driven phenomenon monitoring with Mobility Prediction). In VirFID-MP, the future movement of the phenomenon is first predicted using the MS nodes' movement history data. Then, the prediction information is used to calculate a virtual force, which is utilized to speed up MS nodes toward the moving phenomenon. In addition, a prediction-based oscillation-avoidance algorithm is incorporated with VirFID-MP movement control to reduce the nodes' energy consumption. Our simulation results show that VirFID-MP outperforms original VirFID schemes in terms of weighted coverage efficiency and energy consumption.

In mobile ad hoc networks, a malicious node can respond with a faked route reply (RREP) message to a source that explores a route in order to make the source establish a false route leading to the malicious node. Then, the malicious node can absorb all transmitted packets like a black hole. This paper proposes a totally secure defense against the black hole attack with low control overhead and high reliability. The proposed approach, named a bullet-proof verification (BPV) method, consists of a detection phase, in which a node detects a suspicious node by analyzing the data routing information of its neighbors and a verification phase, in which a node initiates the verification of a suspicious node conditionally only if it receives RREP from the suspicious node. The crux of this approach lies in using an encrypted verification message that goes straight to the destination through the path that may include some malicious nodes and also in using both destination sequence number and hop distance for verification. In addition, a distributed watchdog mechanism is employed to track down any malicious nodes. Simulation results show that the BPV approach reduces control overhead significantly and defends against black hole attack reliably.

We introduce a high-level synthesis framework to automatically synthesize asynchronous circuits, especially speed-independent circuits, from a concurrent programming language called ALPEH. ALPEH is a high-level concurrent algorithmic specification that can model complex concurrent control flows, logical and arithmetic computations, and communications in easy way. This specification language has been developed to be translated into a Petri net. The major contribution of this paper is the generation of globally optimized control circuits during preserving neat formalism in the specification.

Information-Centric Networking (ICN) technology has recently been attracting substantial interest in the research community as one of the most promising future Internet architectures. The Named Data Networking (NDN) approach, which is one of the most recent instantiations of the ICN approach, would be a good choice for multimedia services, because NDN utilizes in-network storage embedded in NDN routers by caching recently or frequently requested contents. It is important to determine which data to cache at which NDN routers in order to achieve high performance, by considering not only the popularity of contents but also the inter-chunk popularity of a content item. This paper presents a chunk-block-based incremental caching scheme that considers both content and inter-chunk popularity. Our proposed scheme employs an incremental cache populating mechanism, which utilizes not only core-side but also edge-side NDN routers according to the request rate of the content item. Through simulations, we show that the proposed scheme achieves less delay, reduced redundant network traffic, and a higher cache hit ratio than legacy schemes.

In this letter, we analyze the effect of the size of observed data on the performance of time delay estimation (TDE) in the chirp spread spectrum (CSS) system. By adjusting the size of observed data, we reduce the effect of DC offsets, which would otherwise degrade the performance of TDE based on CSS, and we optimize the performance of TDE in CSS system. Finally, we derive the optimal size of observed data of TDE in CSS system.