Outage performance of cognitive radio networks with multiple decode‐and‐forward relays

Abstract

This paper considers the cognitive radio network with one primary user (PU), one secondary user (SU), and multiple decode-and-forward relays. We propose a relaying scheme to ensure the priority of primary transmission, where the relays are used to forward PU's message and sometimes also SU's message. First, SU is allowed to use the spectrum to transmit only when its transmission would not affect the decoding status of PU's message at all relays. Second, once the secondary transmission happens, the relays that successively decode SU's message are allowed to retransmit this message when it would not affect the decoding status of PU's message at primary receiver. The interference from PU to SU and the interference from SU to PU are both considered. By analyzing the decoding status of primary message and secondary message at different relays, we formulate the outage probabilities of both primary transmission and secondary transmission. When all channels follow Rayleigh distributions, we derive the analytical expressions for the general case of any number of relays, which are validated by means of Monte Carlo simulations. or improving PU's transmission by applying sophisticated signal processing and coding. In the interweave approach, SU utilizes the spectrum not currently being used by PU.A number of transmission schemes for CRN have emerged in literature. In particular, to improve the spatial diversity order, the technique of relaying has been introduced into CRN. Authors in [6-9] considered one-relay scenario, and authors in [10-13] considered multi-relay scenario, where in the latter only one appropriate relay node is selected to forward the received signals. However, in [14], multiple relays may be selected to forward SU's signals, and SU does not know which and how many secondary relays will be selected and participate in the second phase. In these papers, [7][8][9][10]12] analyzed the performance when considering the interference from PU to SU, and [12] is the first paper analyzing the outage probability in underlay cognitive networks with multiple relays when considering this interference.In the aforementioned works, that is, [6][7][8][9][10][11][12][13], the relays are only deployed for secondary transmission. Nevertheless, some other papers discussed the case when the relays may assist the primary or/and secondary transmission. In [15][16][17], the relays would forward PU's or SU's message depending on the decoding status in the first phase. In [18][19][20], a relay node could help simultaneously the primary and the secondary transmissions. Actually, primary system stands for the existing communication systems, which have been studied widely when deployed with multiple relays. All what we can do is the designs based on the existing framework; thus, it is reasonable to investigate the CRN when relays are deployed mainly for primary transmission. When the resources at the relays are redundant for primary system, the relays might also be used for secondary transmission on the premise that this operation would n...

Performance evaluation of cognitive relay networks for end user mobile over mixed realistic channels

“…Furthermore, the need for wireless and mobile data has increased due to the heavy use of personal digital assistants (PDAs), smart phones and tablets that allows the exchange of data either by voice or video through geographical and time boundaries. Therefore, it is necessary to introduce the CRN as an intelligent technology that can adapt to the time-varying radio frequency (RF) environment for covering the urgent demand for higher data rates and wider bandwidth [10,11]. This paper proposes an analytical paradigm fitting fast mobile environment to examine the performance analysis of vehicular dual-hop CRN with amplify and forward (AF) relay over Nakagami-𝑚 channels, with 𝑚 < 1 distribution model with intelligent resource management schemes that are designed for fixed, nomadic, and mobile communication.…”

“…Due to the limitation on the required transmission power and the shortage of the coverage area in cognitive radio network, the concept of cognitive relay network (CRN) had been introduced and defined as the combination of both, the cooperative relaying and cognitive radio network to enhance the performance of the communication system. In particular, it increases the capacity and throughput, reduces the power consumption, extends the lifetime of the network, and expands the covered area [11][12].…”