  This paper deals with the problem of admission control/channel access in
power-controlled decentralized wireless networks, in which the
quality-of-service (QoS) is expressed in terms of the signal-to-interference
ratio (SIR). We analyze a previously proposed admission control algorithm,
which was designed to maintain the SIR of operational (active) links above some
given threshold at all times (protection of active links). This protection
property ensures that as new users attempt to join the network, the already
established links sustain their quality. The considered scheme may be thus
applicable in some cognitive radio networks, where the fundamental premise is
that secondary users may be granted channel access only if it does not cause
disturbance to primary users.
  The admission control algorithm was previously analyzed under the assumption
of affine interference functions. This paper extends all the previous results
to arbitrary standard interference functions, which capture many important
receiver designs, including optimal linear reception in the sense of maximizing
the SIR and the worst-case receiver design. Furthermore, we provide novel
conditions for protection of active users under the considered control scheme
when individual power constraints are imposed on each link. Finally, we
consider the possibility of a joint optimization of transmitters and receivers
in networks with linear transceivers, which includes linear beamforming in
multiple antenna systems. Transmitter optimization is performed alternately
with receiver optimization to generate non-decreasing sequences of SIRs.
Numerical evaluations show that additional transmitter side optimization has
potential for significant performance gains.
