29,396 research outputs found
Spectral Efficiency of Multi-User Adaptive Cognitive Radio Networks
In this correspondence, the comprehensive problem of joint power, rate, and
subcarrier allocation have been investigated for enhancing the spectral
efficiency of multi-user orthogonal frequency-division multiple access (OFDMA)
cognitive radio (CR) networks subject to satisfying total average transmission
power and aggregate interference constraints. We propose novel optimal radio
resource allocation (RRA) algorithms under different scenarios with
deterministic and probabilistic interference violation limits based on a
perfect and imperfect availability of cross-link channel state information
(CSI). In particular, we propose a probabilistic approach to mitigate the total
imposed interference on the primary service under imperfect cross-link CSI. A
closed-form mathematical formulation of the cumulative density function (cdf)
for the received signal-to-interference-plus-noise ratio (SINR) is formulated
to evaluate the resultant average spectral efficiency (ASE). Dual decomposition
is utilized to obtain sub-optimal solutions for the non-convex optimization
problems. Through simulation results, we investigate the achievable performance
and the impact of parameters uncertainty on the overall system performance.
Furthermore, we present that the developed RRA algorithms can considerably
improve the cognitive performance whilst abide the imposed power constraints.
In particular, the performance under imperfect cross-link CSI knowledge for the
proposed `probabilistic case' is compared to the conventional scenarios to show
the potential gain in employing this scheme
Multi-User Diversity with Optimal Power Allocation in Spectrum Sharing under Average Interference Power Constraint
In this paper, we investigate the performance of multi-user diversity (MUD)
with optimal power allocation (OPA) in spectrum sharing (SS) under average
interference power (AIP) constraint. In particular, OPA through average
transmit power constraint in conjunction with the AIP constraint is assumed to
maximize the ergodic secondary capacity. The solution of this problem requires
the calculation of two Lagrange multipliers instead of one as obtained for the
peak interference power (PIP) constraint and calculated using the well known
water-filling algorithm. To this end, an algorithm based on bisection method is
devised in order to calculate both Lagrange multipliers iteratively. Moreover,
Rayleigh and Nakagami- fading channels with one and multiple primary users
are considered to derive the required end-to-end SNR analysis. Numerical
results are depicted to corroborate our performance analysis and compare it
with the PIP case highlighting hence, the impact of the AIP constraint compared
to the PIP constraint application
Co-primary inter-operator spectrum sharing over a limited spectrum pool using repeated games
We consider two small cell operators deployed in the same geographical area,
sharing spectrum resources from a common pool. A method is investigated to
coordinate the utilization of the spectrum pool without monetary transactions
and without revealing operator-specific information to other parties. For this,
we construct a protocol based on asking and receiving spectrum usage favors by
the operators, and keeping a book of the favors. A spectrum usage favor is
exchanged between the operators if one is asking for a permission to use some
of the resources from the pool on an exclusive basis, and the other is willing
to accept that. As a result, the proposed method does not force an operator to
take action. An operator with a high load may take spectrum usage favors from
an operator that has few users to serve, and it is likely to return these
favors in the future to show a cooperative spirit and maintain reciprocity. We
formulate the interactions between the operators as a repeated game and
determine rules to decide whether to ask or grant a favor at each stage game.
We illustrate that under frequent network load variations, which are expected
to be prominent in small cell deployments, both operators can attain higher
user rates as compared to the case of no coordination of the resource
utilization.Comment: To be published in proceedings of IEEE International Conference on
Communications (ICC) at London, Jun. 201
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