15 research outputs found
Difference Antenna Selection and Power Allocation for Wireless Cognitive Systems
In this paper, we propose an antenna selection method in a wireless cognitive
radio (CR) system, namely difference selection, whereby a single transmit
antenna is selected at the secondary transmitter out of possible antennas
such that the weighted difference between the channel gains of the data link
and the interference link is maximized. We analyze mutual information and
outage probability of the secondary transmission in a CR system with difference
antenna selection, and propose a method of optimizing these performance metrics
of the secondary data link subject to practical constraints on the peak
secondary transmit power and the average interference power as seen by the
primary receiver. The optimization is performed over two parameters: the peak
secondary transmit power and the difference selection weight . We show that, difference selection using the optimized parameters
determined by the proposed method can be, in many cases of interest, superior
to a so called ratio selection method disclosed in the literature, although
ratio selection has been shown to be optimal, when impractically, the secondary
transmission power constraint is not applied. We address the effects that the
constraints have on mutual information and outage probability, and discuss the
practical implications of the results.Comment: 29 pages, 9 figures, to be submitted to IEEE Transactions on
Communication
Intelligent spectrum management techniques for wireless cognitive radio networks
PhD ThesisThis thesis addresses many of the unique spectrum management chal-
lenges in CR networks for the rst time. These challenges have a vital
e ect on the network performance and are particularly di cult to solve
due to the unique characteristics of CR networks. Speci cally, this thesis
proposes and investigates three intelligent spectrum management tech-
niques for CR networks. The issues investigated in this thesis have a
fundamental impact on the establishment, functionality and security of
CR networks.
First, an intelligent primary receiver-aware message exchange protocol
for CR ad hoc networks is proposed. It considers the problem of alleviat-
ing the interference collision risk to primary user communication, explic-
itly to protect primary receivers that are not detected during spectrum
sensing. The proposed protocol achieves a higher measure of safeguard-
ing. A practical scenario is considered where no global network topology
is known and no common control channel is assumed to exist.
Second, a novel CR broadcast protocol (CRBP) to reliably disseminate
the broadcast messages to all or most of the possible CR nodes in the
network is proposed. The CRBP formulates the broadcast problem as a
bipartite-graph problem. Thus, CRBP achieves a signi cant successful
delivery ratio by connecting di erent local topologies, which is a unique
feature in CR ad hoc networks.
Finally, a new defence strategy to defend against spectrum sensing data
falsi cation attacks in CR networks is proposed. In order to identify
malicious users, the proposed scheme performs multiple veri cations of
sensory data with the assistance of trusted nodes.Higher Committee For Education Devel-
opment in Iraq (HCED-Iraq