Charles Kabiri

Packet transmission time for cognitive radio networks considering interference from primary user

In this paper, we investigate a downlink model for underlay cognitive radio networks (CRNs). In particular, we assume that the secondary transmitter (SU-Tx) sends common packets to secondary receivers (SU-Rx) under the outage constraint of a single primary user (PU) and the peak transmit power constraint of the SU-Tx. All channels undergo Rayleigh fading. Given these settings, an adaptive transmit power policy for the SU-Tx is considered. Moreover, the cumulative distribution function (CDF) and probability density function (PDF) for packet transmission time are derived to analyze the timeout probability, the average packet transmission time and the average time a packet spends in the system for the SU-Rx having the best channel condition. Numerical results are provided to investigate the impact of the PU transmit power and channel mean powers on secondary network performance. The results show that when the number of SU-Rx becomes large, the timeout probability and the packet average time in the system decrease to a minimum.

On the performance of cognitive radio networks with DF relay assistance under primary outage constraint using SC and MRC

In this paper, we analyze the performance of a cognitive radio network (CRN) that is assisted by a single relay. In particular, the secondary user (SU) transmitter (SU-Tx) and the secondary relay (SR) utilize the licensed frequency band of the primary user (PU). To protect the PU from harmful interference, the SU-Tx and SR must regulate their transmit power to satisfy the outage probability constraint of the PU. System performance in terms of outage probability is analyzed for selection combining (SC) and maximal ratio combining (MRC). Specifically, a power allocation policy and analytical expressions for the outage probability with SC and MRC are derived. Our results show that the upper bound of the outage probability corresponding to MRC is equal to the exact expression for the outage probability for SC.

Outage probability and ergodic capacity of underlay cognitive radio systems with adaptive power transmission

In this paper, we consider a spectrum sharing system in which a primary transmission coexists with a secondary network composed of a secondary base station (SBS) and multiple secondary user receivers (SU-Rxs). The secondary user (SU) can access the spectrum licensed to the primary user (PU) as long as the SU does not cause any harmful interference to the PU. Among all available SU-Rxs, only the best SU-Rx with highest signal-to-interference-plus-noise ratio (SINR) is selected to receive the transmit signals from the SBS. We derive an analytical expression for the outage probability (OP) of the SU-Rx with highest SINR. Moreover, we derive an approximation of the ergodic capacity at the SU-Rx. In order to meet the requirements at the PU receiver (PU-Rx), at the same time, satisfying the quality of the SU link, an adaptive power allocation strategy is developed. The power allocation policy imposes the SU transmitter (SU-Tx) to adapt its transmit power in order to avoid harmful interference at the PU receiver (PU-Rx), with a PU predefined outage constraint.

A Framework for Packet Delay Analysis of Point-to-Multipoint Underlay Cognitive Radio Networks

This paper presents a queueing analytical framework for the performance evaluation of the secondary user (SU) packet transmission with service differentiation in a point-to-multipoint underlay cognitive radio network. The transmit power of the SU transmitter is subject to the joint outage constraint imposed by the primary user receivers (PU-Rxs) and the SU maximum transmit power limit. The analysis considers a queueing model for secondary traffic with multiple classes, and different types of arrival and service processes under a non-preemptive priority service discipline. The SU quality of service (QoS) is characterized by a packet timeout threshold and target bit error rate. Given these settings, analytical expressions of the packet timeout probability and average transmission time are derived for opportunistic and multicast scheduling. Moreover, expressions of the average packet waiting time in the queue and the total time in the system for each class of traffic are obtained. Numerical examples are provided to illustrate the secondary network performance with respect to various parameters such as number of PU-Rxs and SU receivers, SU packet arrival process, QoS requirements, and the impact of interference from the primary network to the secondary network.

Symbol error probability and effective capacity of an underlay CRN over α-μ fading channels

This paper analyses the performance of an underlay cognitive radio network (CRN) over α-μ fading channels in terms of symbol error probability (SEP) and effective capacity (EC). The α-μ distribution allows for a more general fading model with an increased level of generality compared to well-known models such as Nakagami-m and Rayleigh fading. The SEP and EC at the secondary user receiver are therefore evaluated for different fading parameters α and μ. In the considered underlay CRN, the secondary user transmit power is subject to a peak interference power constraint in order to limit the interference to the primary user receiver. Given this setting, analytical expressions for the SEP and EC are derived for the general case of α-μ fading channels. Numerical results are provided to illustrate the performance of the considered underlay CRN on different fading channels.

Outage analysis of cognitive relay networks over α-μ fading channels

In this paper, we investigate the performance of an underlay cognitive relay network over α-μ fading channels. In particular, we assume non-identical fading parameters and derive an analytical expression for the outage probability of a dual-hop underlay system subject to a peak interference power constraint. Numerical and simulation results are presented to evaluate the effect of fading parameters on the outage probability of the system.

Outage probability of a cognitive cooperative relay network with multiple primary users under primary outage constraint

In this paper, we consider a cognitive cooperative relay network (CCRN) that utilizes a decode-and-forward relay in the presence of multiple primary users. Given this system setting, we study the effect of multiple primary transmitters (PU-Txs) and multiple primary user receivers (PU-Rxs) on the outage probability of the considered CCRN. Specifically, power allocation policies for the secondary user transmitter (SU-Tx) and the secondary relay (SR) are formulated, subject to the outage constraint which is imposed by the PU-Rxs as well as the peak transmit power limits given at the SU-Tx and SR. On the basis of these power allocation policies for the SU-Tx and SR, an expression for the outage probability of the CCRN is derived. Numerical examples are presented to show the effect of different system parameters on the outage probability of the CCRN.

Effective capacity of cognitive cooperative relay networks over α-μ fading channels

In this paper, the effective capacity, a link-layer model supporting Quality of Service (QoS) metrics such as user data rate, packet loss rate and service delay, is analyzed. We consider an underlay cognitive cooperative relay network (CCRN) subject to independent non-identically distributed α-μ fading. An analytical expression of the effective capacity is derived by means of Fox H-functions and Meijer G-functions along with the Mellin transform of the product of two H-functions. The network performance is analyzed against the QoS exponent and the peak interference power constraint imposed by primary users.

Outage performance analysis of cognitive relay networks with BRS and MMRS

In this paper, we consider a spectrum sharing system where a secondary user (SU) transmitter (SU-Tx) communicates with an SU receiver (SU-Rx) with the help of multiple secondary relays (SRs) in the presence of a single primary network link. In particular, the SU-Tx and SR are subject to their maximum transmit power limits and the timeout constraint of the primary user (PU). Moreover, we assume that the relay selection is based on either best relay selection (BRS) or max-max relay selection (MMRS). In BRS, a single relay having the best end-to-end channel condition among the SRs is selected for cooperation between the source and the destination. However, the selected relay may not experience the best source-relay channel and relay-destination channel at the same time. To overcome the limitation of selecting the same relay for both reception and transmission, MMRS uses the best relay of the SU-Tx→SR link for reception at the relay and the best relay of the SR→SU-Rx link for transmission to the destination. Specifically, we compare the performance for BRS and MMRS in terms of the outage probability, and study the impact of the number of SRs, PU transmit power and different channel mean powers of interference links on the secondary network performance. Furthermore, based on the performance of the MMRS and assuming that automatic repeat request (ARQ) is implemented for packet retransmission, we investigate the outage probability for delay limited applications. The numerical results indicate that the MMRS outperforms BRS when more than one SRs are deployed. The secondary network outage probability is reduced when the number of SRs and the number of retransmissions become large. It is also shown that the interference from the PU has a significant impact on the secondary network performance.

Outage probability and ergodic capacity of a spectrum sharing system with multiuser diversity

In this paper, we derive analytical expressions for outage probability and ergodic capacity of a spectrum sharing system with multiuser diversity under Nakagami-m fading. In particular, multiuser diversity effects in such systems where several secondary users utilize the licensed spectrum of the primary user are considered. The best and worst channel quality scenarios are investigated for transmission from a number of secondary transmitters. Numerical analysis and simulations are shown to reveal the effects of multiusers and fading parameters on the considered system.