Joint power and rate scheduling for cognitive multi-access networks with imperfect sensing

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. IntroductionOpportunistic spectrum access has been proposed to overcome the problem of spectrum scarcity. In this frame of work, an unlicensed secondary user attempts to opportunistically access a licensed primary channel in order to use the underutilized spectrum. This network is usually referred to as cognitive radio network. Although cognitive radio is a promising solution of spectrum scarcity problem, maintaining the performance of the licensed primary user unaffected is considered a challenge [1,2]. We consider a time-slotted cognitive network in which a secondary user can transmit simultaneously with an active primary user to a common receiver without adversely affecting the primary user's transmission. The secondary user senses the channel of the primary user at the beginning of each time slot to determine its state. Based on the sensing outcome and a feedback signal at the end of each time slot that indicates the success or failure of the transmission, the secondary user adapts its rate and power to maintain a certain quality of service level for the primary *Correspondence: ghada.hatem@nileu.edu.eg 1 Wireless Intelligent Networks Center (WINC), Nile University, Cairo, Egypt Full list of author information is available at the end of the article user. The adaptation is done via a cross-layer scheduling algorithm that aims to minimize the probability of packet loss of the secondary user under an average power constraint for the secondary user and a quality of service constraint for the primary user.In the last few years, the problem of scheduling for cooperative cognitive networks has been addressed by several authors. In [3], the authors considered a point to multipoint cognitive network in which they maximize the total throughput of the network while maintaining a required signal to interference plus noise ratio for the primary users. They investigated the uplink and downlink power control and channel assignment problem. The problem of power allocation was also investigated in [4] from a game theoretic point of vie...

Cross-layer transmission rate/power policy for cognitive multi-access networks with imperfect sensing

“…idle at time slot t where L(t) E {O,�, ... , (N -1)�} and N= .l..Hen 1� the probability of transmitting m packets using power policy p in model I and II can be written, respec tively, as gk7;'p ) = P r{ As( t +l) =m,P( t+l) = p �( t -l) =k ,,The probability of making a transition from state (k, i, j) to (I, s, q ) in model I can be written as (The derivation can be found in[8…”