Abstract
A cognitive multi-access network in which a primary user and a secondary user transmit to a common receiver is considered. The secondary user senses the channel at the beginning of each time slot to determine whether the primary user is active or idle. The sensing is not perfect; hence, the secondary user can miss the detection of an active primary user or erroneously declare an idle primary user as active. The secondary user can vary its transmission rate and power from a time slot to the other. A joint rate and power scheduling algorithm is proposed that minimizes the probability of packet loss of the secondary user under a maximum probability of collision constraint at the primary user and a constraint on the average power transmitted by the secondary user. The case in which no retransmissions are allowed and the cases in which one or both users retransmit the collided packets are also considered. The problem is posed as a linear optimization problem that can be solved efficiently.
Highlights
Opportunistic spectrum access has been proposed to overcome the problem of spectrum scarcity
This signal will be denoted as F(t), and in each time slot, it has three possible outcomes, i.e., Case 1: F(t) = 0 A negative acknowledgment (NACK) signal is transmitted at the end of time slot t which means that the primary user was sensed as idle when its true state was active, and the secondary user transmits As(t) = m ≥ 1 packets which resulted in a collision
2 Conclusion In this paper, we have proposed a scheduling algorithm that designs the transmission probabilities of a secondary user transmitting over a primary user channel to a common receiver
Summary
1.1 Introduction Opportunistic spectrum access has been proposed to overcome the problem of spectrum scarcity. A joint coding and scheduling algorithm for cognitive multiple-access networks was proposed in [9], where the primary and secondary users can transmit only one packet per time slot. In [15], authors considered a downlink cognitive radio network in which an OFDMA-based secondary system share the primary users’ spectrum They designed a joint cross-layer and sensing algorithm that optimizes a system utility, which adapts the power allocation and the sub-carrier assignment across the secondary users and proposed a distributed implementation of the algorithm. We design a cross-layer scheduling algorithm that minimizes the probability of packet loss of the secondary user under an average power constraint and a quality of service constraint at the primary user.
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