Abstract
In this work, we study the cognitive decode-and-forward (DF) relaying, where a primary user (PU) communicates with an access point (AP), and in the same geographical region, a secondary source (SS) communicates to a secondary destination (SD) with assistance from a secondary relay (SR). Either SR or SD can decode the secondary data directly (DIR) or using the successive interference cancelation (SIC) technique. Based on the decoding methods of SR and SD, we proposed SR-DIR-SD-DIR, SR-DIR-SD-SIC, SR-SIC-SD-DIR, and SR-SIC-SD-SIC-based cognitive DF relaying schemes. The outage probabilities of both primary and secondary systems are analyzed for all the decoding manners. The transmit powers of SS and SR are further determined to minimize the outage probability of secondary system subject to the constraint that the outage performance loss of primary system should not exceed a certain percentage compared with the stand-alone primary network without spectrum sharing. Numerical results show that by using the SIC decoding, the outage probability of secondary system can be greatly decreased, especially when the interference from PU is strong or the transmission rate of primary data is low.
Highlights
Spectrum sharing schemes have been extensively studied to meet the ever-growing wireless transmission requirements using the licensed spectrum, which is often underutilized across time and space
Numerical results show that the outage performance of secondary system can be significantly improved by using the successive interference cancelation (SIC) technique, as the strong interference from primary user (PU) can be effectively suppressed, and the total network throughput can be greatly boosted compared with the none spectrum sharing scenario
We consider a cognitive decode-and-forward (DF) relaying system as shown in Fig. 1, where PU communicates to an access point (AP), and secondary source (SS) communicates to secondary destination (SD) with assistance from secondary relay (SR)
Summary
Spectrum sharing schemes have been extensively studied to meet the ever-growing wireless transmission requirements using the licensed spectrum, which is often underutilized across time and space. Primary users (PUs) own the licensed spectrum and have higher priorities of accessing it. Secondary users (SUs) can share the spectrum under the performance constraint of primary system [1]. If the spectrum is busy for a long time, SUs can rarely access it [2]. SUs can transmit concurrently with PUs, but they should carefully control their powers to avoid violating the performance constraint of primary system [3]. SUs can cooperatively transmit primary data to exchange some resources for the spectrum access [4]. In the multiple SU scenario, the primary data can be quickly delivered with assistance from a selected SU, so the secondary data can be transmitted in the remaining time over the spectrum [5].
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