  We consider a cooperative relaying system which consists of a number of
source terminals, one shared relay, and a common destination with multi-packet
reception (MPR) capability. In this paper, we study the stability and delay
analysis for two cooperative relaying schemes; the sensing-based cooperative
(SBC) scheme and the decision-based cooperative (DBC) scheme. In the SBC
scheme, the relay senses the channel at the beginning of each time slot. In the
idle time slots, the relay transmits the packet at the head of its queue, while
in the busy one, the relay decides either to transmit simultaneously with the
source terminal or to listen to the source transmission. The SBC scheme is a
novel paradigm that utilizes the spectrum more efficiently than the other
cooperative schemes because the relay not only exploits the idle time slots,
but also has the capability to mildly interfere with the source terminal. On
the other hand, in the DBC scheme, the relay does not sense the channel and it
decides either to transmit or to listen according to certain probabilities.
Numerical results reveal that the two proposed schemes outperform existing
cooperative schemes that restrict the relay to send only in the idle time
slots. Moreover, we show how the MPR capability at the destination can
compensate for the sensing need at the relay, i.e., the DBC scheme achieves
almost the same stability region as that of the SBC scheme. Furthermore, we
derive the condition under which the two proposed schemes achieve the same
maximum stable throughput.
