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Random-access packet-based communication schemes are suitable for wireless sensor networks since medium access in their applications is often uncoordinated while sensor nodes communicate bursty flows of data. Preamble detection is an important task in packet-based communication protocols. The implementation of a previously proposed preamble detection scheme for low-power, wide-band, asynchronous packet...
This paper investigates the use of full duplex relaying (FDR) in cognitive radio systems. Cognitive FDR systems offer the advantage not only of increasing spectral efficiency by spectrum sharing but also of extending the coverage through the use of relays. Concurrent transmissions at the source and relay in FDR systems can overcome a loss of resource efficiency in a way that conventional half duplex...
In this paper, we investigate a path selection approach for wireless cooperative multihop communications with one source, one destination, and multiple intermediate relaying nodes, which are clustered linearly. Specifically, we adopt a cooperative maximum ratio combining (C-MRC) technique as a framework for the path selection approach, namely a C-MRC-based approach and a modified C-MRC-based approach...
Considering vehicles as sensors for traffic and pollution information is a new paradigm to monitor the environment and to open the way to an efficient smart navigation. In this work we focus on the uplink acquisition of traffic information from vehicles toward a remote control center. With the increase in the number of vehicles equipped with on board units (OBUs) enabling cellular transmissions, this...
As the regulation in wireless communications is moving toward a more flexible and efficient way of managing radio spectrum, it is envisaged that multiple small-sized cellular networks owned by different operators, e.g., facility owners or local operators, will operate in close vicinity on shared spectrum. In this environment, the networks may compete for their own utilities in a selfish manner with...
This work addresses the problem of optimized content distribution over wireless networks with cooperation among mobile terminals. The mobile terminals are optimally divided into groups where each group internally cooperates by downloading and exchanging a common content from the base station in order to minimize the total energy consumed by the mobile terminals. We assume unicasting transmissions...
Wireless Sensor Networks (WSNs) play a crucial role in this communication era because they have the ability to real time monitoring and controlling the physical environment from remote locations. Though networked sensors has the advantage to improve the accuracy of information obtained from the network by proper coordination and collaboration between sensors, communicating information between the...
In this paper a spectrum sharing scheme is proposed to maximize the successful transmission probability of a single-hop cognitive network coexisting with a random primary network. Both cognitive and primary networks exhibit randomness in topologies and endure imperfect wireless channel conditions. For a given primary outage probability bound, the maximum secondary transmit power is determined and...
Increasing the capacity of wireless cellular networks is a major concern for network operators. We address the problem of offloading the cellular network via assistance from the mobile terminals to receive an on-demand common content from the base station. The base station unicasts the content to selected mobile terminals that either unicast or multicast it to other mobile terminals over local ad...
An asymmetric resource allocation (ARA) scheme for the downlink wireless multi-destination relay systems with orthogonal frequency division multiplexing (OFDM) modulation is proposed. Unlike the previous work, the transmission durations at the source (base station) and the relay are designed to be asymmetric, which enhances the degree of freedom for transmission. Therefore, the proposed ARA scheme...
The time-varying feature of wireless channels usually makes the hard delay bound for data transmissions unrealistic to guarantee. In contrast, the statistically-bounded delay with a small violation probability has been widely used for delay quality-of-service (QoS) characterization and evaluation. While existing research on the statistical-delay control mainly focused on the single-hop links, in this...
In a cooperative system with an amplify-and-forward relay, the cascaded channel training protocol enables the destination to estimate the source-destination channel gain and the product of the source-relay (SR) and relay-destination (RD) channel gains using only two pilot transmissions from the source. Notably, the destination does not require a separate estimate of the SR channel. We develop a new...
This paper presents a solution that exploits changes in radio signal strength (RSSI) to detect a movement or presence of a person within a particular environment. The performance of the proposed scheme is experimentally evaluated. Based on the results, we belive that the proposed scheme is particularly suitable for application in the future intelligent home systems.
This paper considers the joint power allocation and subcarrier pairing problem in decode-and-forward (DF) relaying orthogonal-frequency-division multiplexing (OFDM) system, and proposes a strategy, called MW-RA, to maximize the weighted sum rate with total power constraint. MW-RA is formulated as a mixed integer programming problem and then transformed to a convex optimization problem by continuous...
We investigate asymmetric resource allocation (RA) for a dual-hop multi-relay decode-and-forward (DF) relay system based on the orthogonal frequency division multiplexing (OFDM) modulation, where given a fixed total transmit time duration, the time slot durations for the two hops via each of the K relays are designed to be asymmetric, and in general, all the 2K time slot durations may be different...
In this paper, we propose a cooperative MIMO beamforming scheme for secondary spectrum access, where the wireless network consists of one primary pair PT-PR (primary transmitter-primary receiver) and one secondary pair ST-SR (secondary transmitter-secondary receiver). To secondary spectrum access without performance degrading of the primary system, ST generates and transmits superposed signal which...
With the emergence of green communication as a central design issue in wireless networks, the need for energy-efficient transmission protocols has significantly increased. In this paper, we study the problem of cooperative energy-efficient content distribution among a number of mobile terminals that are seeking to receive a content from a common wireless access point, e.g., a base station. We model...
This paper enhances earlier work on random selection and forwarding, which is a probabilistic forwarding protocol for wireless relay networks. We have extended the system model to account for more realistic scenarios and we have applied the framework to the conventional first-in first-out forwarding technique, which we use as a reference for comparison. Most importantly, we have analyzed the asymptotic...
Multiple Input Multiple Output (MIMO) systems have recently emerged as a key technology in wireless communication systems for increasing both data rates and system performance. The Vertical Bell Labs Space-Time Architecture (V-BLAST) is one of the schemes, which can be applied to MIMO wireless system. This paper proposes signal detectors for V-BLAST architecture with Maximum Likelihood (ML), Zero-...
A new methodology of spatial index is studied under mobile geographic information system (GIS) environment based on smart phone. Key technologies are presented in the methodology, including R-tree structure, quad-tree structure, and mobile GIS. In order to deal with the problem between the limited processing speed and low memory of smart phone with the high speed inquire of mobile GIS, a new spatial...
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