  This paper proposes efficient multiple-access schemes for large wireless
networks based on the transmitters' buffer state information and their
transceivers' duplex transmission capability. First, we investigate the case of
half-duplex nodes where a node can either transmit or receive in a given time
instant. The network is said to be naturally sparse if the number of
nonempty-queue transmitters in a given frame is much smaller than the number of
users, which is the case when the arrival rates to the queues are very small
and the number of users is large. If the network is not naturally sparse, we
design the user requests to be sparse such that only few requests are sent to
the destination. We refer to the detected nonempty-queue transmitters in a
given frame as frame owners. Our design goal is to minimize the nodes' total
transmit power in a given frame. In the case of unslotted-time data
transmission, the optimization problem is shown to be a convex optimization
program. We propose an approximate formulation to simplify the problem and
obtain a closed-form expression for the assigned time durations to the nodes.
The solution of the approximate optimization problem demonstrates that the time
duration assigned to a node in the set of frame owners is the ratio of the
square-root of the buffer occupancy of that node to the sum of the square-roots
of each occupancy of all the frame owners. We then investigate the slotted-time
data transmission scenario, where the time durations assigned for data
transmission are slotted. In addition, we show that the full-duplex capability
of a node increases the data transmission portion of the frame and enables a
distributed implementation of the proposed schemes.
