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In this paper we propose a game-theoretic approach for characterizing WiFi network performance in presence of intelligent nodes employing cognitive functionalities. We assume that a cognitive WiFi node is aware of its application requirements and is able to dynamically estimate the network status, in order to dynamically change its access strategy by tuning the contention window settings. We prove...
Underwater acoustic sensor networks are quite different from terrestrial wireless sensor networks. Localization for underwater applications is different due to the bandwidth limited acoustic communication, sparsely distributed network deployment, and more expensive and powerful sensor nodes. In this paper, we propose a new scheme to achieve better localization accuracy for underwater acoustic sensor...
This paper presents novel single-source localization techniques for a sensor network that is capable of obtaining both direction and range estimates by considering an optimization approach. Specifically, linear programming and non-linear programming techniques are developed and compared to a classic linear least squares technique. It is shown that the proposed techniques achieve superior results to...
In this paper, we propose a distributed contention resolution algorithm for multi-packet reception slotted ALOHA systems, which is based on backlog estimation. In the algorithm, a base station broadcasts a binary-valued collision indicator and the identifications of the packets successfully received, when some of packets simultaneously transmitted collide. Then, mobile terminals (MTs) estimate the...
We propose a no reference hybrid video-quality-estimation model for estimating video quality by using quality features derived from received packet headers and video signals. Our model is useful as a quality monitoring tool for estimating the video quality during use of an Internet protocol television service. It takes into account video quality dependence on video content and can estimate video quality...
The mean squared error (MSE) is commonly used to measure and compare the performance of various phase estimation techniques in communications and signal processing systems. When the received signal contains recursive nuisance parameters, the MSE is extremely difficult to obtain and even the conventional modified Cramer-Rao bound (MCRB) can not be readily applied. In this paper, a recursive MSE bound...
In this paper, we derive analytical expressions for the exact Cramer-Rao lower bounds (CRLBs) for the joint estimation of the carrier frequency, the carrier phase, the noise power and the signal amplitude of square quadrature amplitude (QAM) modulated signals. The channel is assumed to be slowly timevarying so that it can be assumed constant over the observation interval. The signal is assumed to...
Single carrier interleaved frequency division multiple access (SC-IFDMA) has been recently receiving much attention for uplink multiuser access in the next generation mobile systems because of its lower peak-to-average transmit power ratio. In this paper, we investigate the effect of carrier frequency offsets (CFO) on SC-IFDMA and propose a new low complexity time domain CFO compensation (TD-CC) scheme...
This paper studies fractional carrier frequency offset (CFO) estimation for orthogonal frequency-division multiplexing (OFDM) systems. In the IEEE 802.16 (WiMAX) standard, a training symbol structure with three highly correlated but not identical segments is specified. The existing CFO estimation methods require the segments in the training symbol to be identical, so cannot work for the generalized...
In this paper, we propose a semi-blind channel estimation algorithm for amplify-and-forward (AF) relay networks. The algorithm fits well for the recently developed space-time coding (STC) technique in AF relay network that serves for small size terminal and achieve the transmission diversity. Compared to the optimal training based estimators, e.g., maximum likelihood (ML) or linear minimum mean square...
The Voice over IP (VoIP) application utilizes the Internet to provide voice service; thus it is susceptible to various security issues common on the IP networks, such as the flooding attack. Moreover, VoIP uses the Session Initiation Protocol (SIP) for session control and management. The transactional nature of SIP makes flooding attack an even severer threat, which can consequentially lead to denial...
This paper studies large randomly spread direct-sequence code-division multiple-access system operating over a block fading multipath channel. Channel knowledge is obtained by a linear estimator whose initial decisions are iteratively refined by using a soft feedback from the single-user decoders. In addition to the traditional training symbol based signaling scheme, we study a novel method that utilizes...
Optical Burst Switching (OBS) has been developed as an efficient switching technique for the next generation optical Internet. A critical issue for OBS networks is the burst loss which could occur due to contention and/or insufficient offset time. Burst Loss Ratio (BLR) is used as the main performance parameter in bufferless OBS networks. This paper proposes a new TCP statistics based method to predict...
Many RFID systems use dynamic slotted ALOHA to identify the label information of the RFID tags. One of the key problems in the RFID system is how to estimate the number of RFID tags up to the desired level of accuracy. In this paper, we present the framework of tag estimation algorithm for the collision-oblivious (CO) reader which can only decide whether the tag response is successful or not. Thus,...
Anomaly detection in peer-to-peer (P2P) networks is generally difficult due to the large number of users in the network. Exhaustive probing on each user is extremely unrealistic. Besides, unlike hierarchical systems, the infrastructure of a P2P network is flat, which makes multi-casting based probing schemes impossible. Most P2P security research focus on proactive prevention schemes to secure the...
In this paper, the infrared optical wireless path loss inside an aircraft cabin is estimated. To this end, a Monte Carlo ray-tracing (MCRT) simulation is performed in a geometric computer-aided design (CAD) cabin model. Position, azimuth (AZ), elevation (EL) and field of view (FOV) properties of transmitters and receivers are defined. Key path loss parameters such as the path loss exponent and the...
This paper investigates the network performance loss of using only single-path routing when multiple paths are available. The performance metric is the aggregate utility achieved by the joint optimization of congestion control and routing. As computing the exact loss for a general network topology is NP-hard, we develop analytical bounds on this "cost of not splitting". Our bound is independent...
In this paper, we investigate the issue of vertical handoffs in heterogeneous wireless networks. A QoS-based vertical handoff scheme for WLAN and WiMAX interworking networks is proposed with aim to provide always best service to users. We also present a simple, yet efficient method to estimate the available bandwidth in WLAN and WiMAX networks to evaluate the real-time status of the overlay networks...
This paper proposes a novel spectrum sharing technique for an existing wireless local area network (LAN) system (primary user) based on IEEE 802.11a, and a new system (secondary user) equipped with the proposed spectrum sharing technique. Both systems are assumed to behave according to carrier sense multiple accesses with collision avoidance (CSMA/CA) protocol. An objective of spectrum sharing techniques...
In this paper we consider a network of distributed sensors that are trying to measure a parameter of interest cooperatively, by exchanging their acquired information repeatedly over fading channels. We consider different ways of using the available bandwidth, in terms of what each node can send to its neighbors. More specifically, we characterize the impact of local fusion and show how it is a suitable...
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