2,054 research outputs found
Dynamic Power Splitting Policies for AF Relay Networks with Wireless Energy Harvesting
Wireless energy harvesting (WEH) provides an exciting way to supply energy
for relay nodes to forward information for the source-destination pairs. In
this paper, we investigate the problem on how the relay node dynamically
adjusts the power splitting ratio of information transmission (IT) and energy
harvesting (EH) in order to achieve the optimal outage performance. According
to the knowledge of channel state information (CSI) at the relay, optimal
dynamic power splitting policy with full CSI and partial CSI are both provided.
Finally, through simulations, the proposed power splitting policies can improve
the outage performances and the policy with full CSI achieves the best
performance. It is also shown that the policy with partial CSI can approach the
policy with full CSI closely and incurs far less system overhead.Comment: accepted by IEEE ICC 2015 - Workshop on Green Communications and
Networks with Energy Harvesting, Smart Grids, and Renewable Energie
Protecting 802.11-Based Wireless Networks From SCTS and JACK Attacks
The convenience of IEEE 802.11-based wireless access networks has led to widespread deployment. However, these applications are predicated on the assumption of availability and confidentiality. Error-prone wireless networks afford an attacker considerable flexibility to exploit the vulnerabilities of 802.11-based mechanism. Two of most famous misbehaviors are selfish and malicious attacks. In this thesis we investigate two attacks: Spurious CTS attack (SCTS) and Jamming ACK attack (JACK). In the SCTS, malicious nodes may send periodic Spurious CTS packets to force other nodes to update their NAV values and prevent them from using the channel. In the JACK, an attacker ruins legitimate ACK packets for the intention of disrupting the traffic flow and draining the battery energy of victim nodes quickly. Correspondingly, we propose solutions: termed Carrier Sensing based Discarding (CSD), and Extended Network Allocation Vector (ENAV) scheme. We further demonstrate the performance of our proposed schemes through analysis and NS2 simulations
Faster Random Walks By Rewiring Online Social Networks On-The-Fly
Many online social networks feature restrictive web interfaces which only
allow the query of a user's local neighborhood through the interface. To enable
analytics over such an online social network through its restrictive web
interface, many recent efforts reuse the existing Markov Chain Monte Carlo
methods such as random walks to sample the social network and support analytics
based on the samples. The problem with such an approach, however, is the large
amount of queries often required (i.e., a long "mixing time") for a random walk
to reach a desired (stationary) sampling distribution.
In this paper, we consider a novel problem of enabling a faster random walk
over online social networks by "rewiring" the social network on-the-fly.
Specifically, we develop Modified TOpology (MTO)-Sampler which, by using only
information exposed by the restrictive web interface, constructs a "virtual"
overlay topology of the social network while performing a random walk, and
ensures that the random walk follows the modified overlay topology rather than
the original one. We show that MTO-Sampler not only provably enhances the
efficiency of sampling, but also achieves significant savings on query cost
over real-world online social networks such as Google Plus, Epinion etc.Comment: 15 pages, 14 figure, technical report for ICDE2013 paper. Appendix
has all the theorems' proofs; ICDE'201
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