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Even though emerging as a promising approach to increase road safety, efficiency and convenience, Vehicular Ad hoc Networks (VANETs) pose many new research challenges, especially on the aspect of location privacy. The existing literatures focus on preventive techniques to achieve location privacy protection, however the location privacy risk assessment receives less attention. In this paper, we introduce...
The issue of distributed channel selection in opportunistic spectrum access is investigated in this paper. We consider a practical scenario where the channel availability statistics and the number of competing secondary users are unknown to the secondary users. Furthermore, there is no information exchange between secondary users. We formulate the problem of distributed channel selection as a static...
Prior work in implementing spectrum sharing scenarios for cognitive radio networks has relied on the unlikely assumption of full cross-channel knowledge made available to the cognitive transmitter (CT) and/or the target primary receiver (PR). However, estimation of this cross-channel knowledge is not only important from a practical stand-point, but also in limiting the real interference power felt...
The resource allocation in cognitive radio networks is one of the key issues to improve the spectrum efficiency. In most previous work, only one type of the secondary user (SU) network architecture is considered, i.e., it is always assumed that all SUs are centralized, or all are distributed. However, in heterogeneous cognitive radio networks, which takes both the centralized and distributed architectures...
Spectrum leasing via cooperation refers to the possibility for primary users to lease part of the spectral resources to secondary users in exchange for cooperation. This paper proposes a novel implementation of this concept in which secondary cooperation aims at improving the secrecy of the primary link. In particular, a secondary transmission with multiple antennas creates interference on both primary...
In sensor networks, the adversaries can inject false data reports from compromising nodes. Previous approaches for filtering false reports share keys between the source node and its upstream nodes on the path to sink, and rely on intermediate nodes to verify the reports generated by downstream nodes in a probabilistic manner. As a result, false reports have to travel several hops before detected....
Ensuring timely delivery of event reports is a critical requirement in mobile sensor networks, as the effectiveness of area surveillance depends largely on the sensor network response delay. However, due to the sensor mobility and the energy limitation, fast report transportation is constrained by the intermittent wireless link connections between sensor nodes. We derive lower and upper analytical...
TDD multiuser downlink MIMO channels with delayed channel state information at the transmitter (CSIT) are considered. Block diagonalization is applied at the base station (BS). In order to cope with the inter-user interference caused by the delayed CSIT, we develop a novel capacity estimation method at first and then propose robust delayed CSIT aware multimode selection schemes based on the estimation...
Grids can efficiently deal with challenging computational and data processing tasks which cutting edge science is generating today. So-called e-Science grids cope with these complex task by deploying geographically distributed server infrastructure, interconnected by high speed networks. The latter benefit from optical technology, offering low latencies and high bandwidths, thus giving rise to so-called...
This paper proposes a scheme to increase possible patterns of wavelength-conversion for an optical packet switch (OPS) with parametric wavelength converters (PWCs) by obtaining additional converted wavelengths using the existing resources. It is called a recursive parametric wavelength conversion (RPWC) scheme. A PWC uses a pump wavelength to define the original and converted wavelengths, called wavelength...
Cooperative diversity is an emerging and powerful solution that can significantly improve the diversity order and link reliability over the harsh wireless fading channels. Although there has been a lot of work on achieving full diversity by using advanced space-time coding or signal processing schemes, how to increase the spectral efficiency or multiplexing gain with half-duplex relays has not received...
Multi-Packet Reception (MPR) enables simultaneous receptions from different transmitters to a single receiver, which has been demonstrated to bring capacity improvement in wireless network. However, MPR does not improve the transmission capability of intermediate relay nodes in a multi-hop routing and thus these nodes may become the bottlenecks for increasing throughput despite of great reception...
Data aggregation is one of the main methods to conserve energy in wireless sensor networks (WSN). Redundant data can be aggregated at intermediate nodes of a WSN reducing the number of messages exchanged and, consequently, reducing communication costs. Most data aggregation protocols are generally based on a static routing scheme. Although those protocols can save energy by eliminating data redundancy,...
With the soaring development cost of deep sub-micron silicon and the fast-growing diversity in wireless communications, software defined baseband becomes more and more important for handheld devices. However, most software defined receivers reported in previous literatures are still far away from fulfilling the requirement of emerging wireless standards such as the LTE-Advanced. The category-E User...
This paper addresses the downlink scheduling issue in drive-thru networks which is characterized by flow-level dynamics and user basis deadlines. Vehicular users requesting for data download service with variable file sizes regularly arrive at and depart from the limited coverage range of roadside access point. If the corresponding data queue at the access point cannot be serviced in a certain time...
Deploying energy harvesting nodes can significantly extend the lifetime of a battery powered wireless network. The nature of these systems calls for specific design principles to efficiently utilize the dynamic energy resources. In contrast to the conventional wireless networks, transmission policies for these systems should take into account the recharge process of the node as well as its battery...
Channel coding such as Reed-Solomon (RS) and convolutional codes has been widely used to protect video transmission in wireless networks. However, this type of channel coding can effectively correct error bits only if the error rate is smaller than a given threshold; when the bit error rate is underestimated, the effectiveness of channel coding drops dramatically and so does the decoded video quality...
IPTV multicasting is an important service for residential users. In this paper, we explore how to allocate resources to different layer-encoded IPTV programs using multicast services in relay-assisted centralized wireless access networks. We consider the scenario of two-hop relay stations, and the MAC protocol is OFDMA-based, as in IEEE 802.16m or Long Term Evolution-Advanced (LTE-A). We formulate...
Methods for transmit power control based on simple long-term channel prediction for the general body-area communications channel are presented. The power control methods are based on large sets of empirical every-day activity data. Numerous transmit-receive pair (Tx-Rx) locations on the human body, i.e. on-body, for a typical body-area-network (BAN) are considered. With the use of a simple prediction...
This paper proposes a dynamic primal-dual type scheduling algorithm in wireless networks, which achieves optimal throughput even with uncertain parameters. In wireless networks, such uncertain parameters are generated by complicated stochastic dynamics, such as random packet arrivals, channel fading, and node mobilities. The algorithm is a generalization of the well-known max-weight scheduling algorithm...
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