Ergodic capacity of multiuser scheduling in cognitive radio networks: analysis and comparison

Abstract

This paper analyzes the ergodic capacity of secondary point‐to‐multipoint communications under the outage constraint of multiple primary user receivers (PU‐Rxs) and the secondary user (SU) maximum transmit power limit. We first derive analytical expressions of the ergodic capacity for three scheduling schemes, that is, round robin, Max‐signal‐to‐interference‐plus‐noise‐ratio (Max‐SINR) and Min‐SINR, and compare their performance. Numerical examples show that when the number of SU receivers (SU‐Rxs) increases in the presence of a single PU‐Rx and at high SINR, the Min‐SINR outperforms the Max‐SINR scheme. As the number of PU‐Rxs increases, the Max‐SINR performs better than the Min‐SINR scheduling. When the number of SU‐Rxs becomes large, the system capacity is enhanced but so is the feedback load. To exploit the Max‐SINR transmission while reducing the feedback load, we assume a threshold based on the channel quality where the SU‐Rxs with the instantaneous SINR above the threshold participate in the Max‐SINR scheduling; otherwise, an SU‐Rx is selected randomly. Then, an analytical expression of the average capacity is derived. Numerical results illustrate that the capacity with limited feedback is approximately the same as for the case of Max‐SINR with full feedback when the SU threshold for feedback condition is set to low and medium values. Copyright © 2016 John Wiley & Sons, Ltd.

Transmit Power Policy and Ergodic Multicast Rate Analysis of Cognitive Radio Networks in Generalized Fading

“…The PU's target rate is chosen to be R 0 = log(1+γ 0 ) = 0.03 bps/Hz for all the simulations. This is to match the performance target for the operational long-term evolution (LTE) network, which requires the cell edge user throughput to be higher than 0.02 bps/Hz/cell/user [18], [64], [65]. Furthermore, all the results are generated for the choice of P s,max = 20 dB, (κ p = 2, µ p = 3, m p = 1), (κ p,s = 2, µ p,s = 2, m p,s = 1), (κ s = 1, µ s = 1, m s = 1) and (κ s,p = 1, µ s,p = 2, m s,p = 1) unless mentioned otherwise.…”

“…Therefore, the SU-Tx must transmit at a power that keeps the outage at each of the PU-Rx below a predetermined level. Thus, transmit power policy at the SU-Tx can be mathematically formulated as follows [18], [19],…”

“…Similarly, recent contributions [18], [19] have also considered the performance of an interferencelimited underlay CRN relying on continuous power adaptation at the SU. In [19], the secondary transmitter is assumed to transmit information to the specific SU, having the kth highest signalto-interference ratio (SIR).…”

“…In [16], different-power adaptive transmit antenna selection (TAS) schemes were analyzed for the underlay CRN. Furthermore, the authors of [17] have determined the optimal rate sharing parameters for both the SU and the PU, so that the achievable rates were maximized.Similarly, recent contributions [18], [19] have also considered the performance of an interferencelimited underlay CRN relying on continuous power adaptation at the SU. In [19], the secondary transmitter is assumed to transmit information to the specific SU, having the kth highest signalto-interference ratio (SIR).…”

“…In [19], the secondary transmitter is assumed to transmit information to the specific SU, having the kth highest signalto-interference ratio (SIR). The authors of [18] have also investigated the ergodic capacity of the secondary network in an underlay CRNs contaminated by the interference arriving from the primary network in conjunction with various scheduling schemes, including a multicast scheduling (MS) scheme designed for enhancing the fairness among the users. In Table I, we provide a bold summary and comparison of the seminal literature relying on system models similar to our scenario.…”