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Information flow analysis is a powerful technique for reasoning about the sensitive information exposed by a program during its execution. While past work has proposed information theoretic metrics (e.g., Shannon entropy, min-entropy, guessing entropy, etc.) to quantify such information leakage, we argue that some of these measures not only result in counter-intuitive measures of leakage, but also...
The social behavior in cognitive radio networks is studied using analysis tools in social networks. A recommendation system is proposed for cognitive radio, thus incurring the channel preference propagation in the corresponding random geometric network. A mean field based ordinary differential equation is used to describe the dynamics of the channel preference propagation in cognitive radio networks...
Cognitive radio nodes of a dynamic spectrum access network monitor the spectrum around them in order to detect and opportunistically exploit temporarily unoccupied spectrum gaps. The overall behavior of the whole network depends on the spectrum occupancy perceived by each node at its local environment. An appropriate understanding of the local perception of cognitive radio nodes in various scenarios...
We address the problem of downlink multiuser scheduling in practical wireless networks under a desired fairness constraint. Wireless networks such as LTE, WiMAX and WiFi provide partial channel knowledge at the base station/access point by means of quantized user equipment feedback. Specifically in 3GPP's LTE, the Channel Quality Indicator (CQI) feedback provides time-frequency selective information...
Multiuser (MU) - multiple input multiple output (MIMO) techniques are attractive to increase the downlink spectrum efficiency since they allow a small number of antennas at each user station (STA). In MU-MIMO systems, the transmission performance is affected by the STA combination that is spatially multiplexed in the same frequency and same time slot. Thus, the AP needs to determine the optimum STA...
In this paper, we deal with channel estimation and intercarrier interference mitigation for very high mobility OFDM systems, the communication is between a BS and a train traveling at a speed of 500km/hr. The scheme proposed here uses piece-wise polynomial expansion to approximate time-variations of multipath channels. Two adjacent symbols are utilized to estimate the first and second-order parameters...
In this paper, we address the problem of efficient routing in delay tolerant network. We propose a new routing protocol dubbed as ORION. In ORION, only a single copy of a data packet is kept in the network and transmitted, contact by contact, towards the destination. The aim of the ORION routing protocol is twofold: on one hand, it enhances the delivery ratio in networks where an end-to-end path does...
Location information of nodes is the basis for many applications in wireless sensor networks (WSNs). However, most previous localization methods make the unrealistic assumption: (i) all nodes in WSN are always awake and (ii) the radio range of nodes is an ideal circle. This overlooks the common scenario that sensor nodes are duty-cycled to save energy and the radio range of nodes is irregular. In...
We propose a robust optimization framework for the multiple-access problem in a hospital environment. The users of e-Health applications (referred to as secondary users) coexist with active and passive medical devices (referred to as primary and protected users, respectively) under uncertainty in the channel (i.e. propagation) conditions. In particular, we design robust transmission scheduling and...
In this paper, we study the performance of a Radio over Free-Space Optical (RoFSO) system for transmitting Code Division Multiple Access (CDMA) signals using aperture averaging (AA) technique, in terms of Carrier-to-Noise-plus- Interference Ratio (CNIR) and outage probability. We propose a modified analytical model for AA, taking into consideration the intermodulation distortion term due to the laser...
In this paper, we develop a general reduced-rate orthogonal frequency division multiplexing (OFDM) transmission scheme for inter-subchannel interference (ICI) mitigation in a high-mobility environment. By transmit and receive preprocessing, we transform the original N-subcarrier OFDM system into an equivalent K-subcarrier one with significantly reduced ICI. In particular, we develop a general structure...
In this paper we investigate the benefits of placing optimal number of sinks for a wireless sensor network (WSN) to prolong the network lifetime, provided that the number of hops from each sensor to its nearest sink is no more than h>=1 and the sink location space is given in advance. We first formulate this problem as a joint optimization problem, which consists of finding the optimal number of...
The association policy in current IEEE 802.11 networks usually considers Received Signal Strength Indication (RSSI) to be the only metric to capture access link quality. However, when a Mesh Client (MC) in IEEE 802.11-based Wireless Mesh Network (WMN) needs to be associated with the most appropriate Mesh Access Point (MAP), the quality of both the access link and the routing path in mesh backhaul...
Cognitive radio systems allow secondary users to operate on underutilized licensed spectrum. When considering highly congested communication channels, however, opportunities for channel access based on time or frequency division can be limited for secondary user networks. In this research, we consider leveraging enhanced spatial diversity through directional steerable antennas to allow secondary user...
Ensuring a high customer satisfaction by monitoring Quality of Experience (QoE) aspects has become common practice for service providers. Such monitoring solutions, together with underlying QoE models, are mostly limited to measures captured in the core or access network and may thus neglect the QoE impact of recovery mechanisms deployed at client-side, e.g., FEC or ARQ. This limitation makes QoE...
In this paper, we investigate the capacity of Gaussian multiple access channels (MAC) with finite input alphabet and `quantized output'. With finite input alphabet and an unquantized receiver, the two-user Gaussian MAC rate region was studied in \cite{harsh08}. In most high throughput communication systems based on digital signal processing, the analog received signal is quantized using a low precision...
Relay-based cooperative transmission in cellular wireless networks has been an area of tremendous research recently. Since MIMO technique has been shown to increase the spectral efficiency significantly, relays with MIMO antennas seem to be potential candidate for future cooperative cellular system in order to achieve reliable transmission, high system throughput and extended network coverage. In...
We consider the joint optimization of relay station (RS) placement and RS sleep/active probability to enhance the energy efficiency of a one-dimensional cellular network. When the RSs are always active, conditions for optimal RS placement that minimizes transmission power are derived, based on which closed-form solution is obtained with path-loss exponent being two, and a simple numerical method for...
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