39 research outputs found
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
Interference Cancellation trough Interference Alignment for Downlink of Cognitive Cellular Networks
In this letter, we propose the interference cancellation through interference
alignment at the downlink of cognitive cellular networks. Interference
alignment helps the spatial resources to be shared among primary and secondary
cells and thus, it can provide higher degrees of freedom through interference
cancellation. We derive and depict the achievable degrees of freedom. We also
analyse and calculate the achievable sum rates applying water-filling optimal
power allocation
Resource Allocation for Licensed/Unlicensed Carrier Aggregation MIMO Systems
In this paper a novel Carrier Aggregation (CA)
scheme is proposed for downlink MIMO LTE-A Systems. The
proposed approach achieves increased transmission rates by
establishing the communication links via both licensed and
unlicensed bands without generating or experiencing interference
to/from the users of the latter bands. To that end, a rate
optimization problem is defined and solved subject to the previous
zero interference constraints, a total power constraint and a
maximum number of aggregated bands constraint. It turns
out that the previous problem is a Mixed Integer Non Linear
Programming (MINLP) one that requires an exhaustive search
procedure in order to be solved. To tackle this, an optimal low
complexity method is proposed based on the Lagrange dual
decomposition. The performance of the original (MINLP) and
the low-complexity proposed techniques is verified via indicative
simulation
Resource allocation for licensed/unlicensed carrier aggregation MIMO systems
In this paper a novel Carrier Aggregation (CA) scheme is proposed for downlink MIMO LTE-A Systems. The proposed approach achieves increased transmission rates by establishing the communication links via both licensed and unlicensed bands without generating or experiencing interference to/from the users of the latter bands. To that end, a rate optimization problem is defined and solved subject to the previous zero interference constraints, a total power constraint and a maximum number of aggregated bands constraint