  In this paper, we study and analyze cooperative cognitive radio networks with
arbitrary number of secondary users (SUs). Each SU is considered a prospective
relay for the primary user (PU) besides having its own data transmission
demand. We consider a multi-packet transmission framework which allows multiple
SUs to transmit simultaneously thanks to dirty-paper coding. We propose power
allocation and scheduling policies that optimize the throughput for both PU and
SU with minimum energy expenditure. The performance of the system is evaluated
in terms of throughput and delay under different opportunistic relay selection
policies. Towards this objective, we present a mathematical framework for
deriving stability conditions for all queues in the system. Consequently, the
throughput of both primary and secondary links is quantified. Furthermore, a
moment generating function (MGF) approach is employed to derive a closed-form
expression for the average delay encountered by the PU packets. Results reveal
that we achieve better performance in terms of throughput and delay at lower
energy cost as compared to equal power allocation schemes proposed earlier in
literature. Extensive simulations are conducted to validate our theoretical
findings.
