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Cognitive Cooperative Networks in Dual-Hop Asymmetric Fading Channels
"... Abstract—Previous works on cognitive relay networks (CRNs) considered only symmetric fading channels. However, in practical wireless propagation scenarios, it is likely that the channels of the secondary user (SU) and primary user (PU) may undergo different fading characteristics. In this paper, we ..."
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Abstract—Previous works on cognitive relay networks (CRNs) considered only symmetric fading channels. However, in practical wireless propagation scenarios, it is likely that the channels of the secondary user (SU) and primary user (PU) may undergo different fading characteristics. In this paper, we assume that the channels of the secondary network (SU-source→SU-relay→SU-destination) are subject to Rician fading, whereas the channels of the link from the SU to the PU experience Rayleigh fading. Based on this framework, the end-to-end outage probability (OP) of CRNs is investigated for two different relaying schemes: i) in the absence of the direct link with decode-and-forward (DF) protocol and ii) in the presence of the direct link with incremental DF protocol. In particular, we derive both exact and asymptotic OP expressions for the considered CRNs. Our analysis reveals important insights into the impact of fading parameters on the CRN performance under distinct fading distributions. I.
Overlay Spectrum Reuse in a Broadcast Network: Covering the Whole Grayscale of Spaces
"... Abstract—In this paper we address the problem of allowing secondary access to the spectrum assigned to a broadcast op-erator. We assume that the secondary transmitter knows of the primary message but is not able to apply interference cancellation techniques due to the lack of channel state informati ..."
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Abstract—In this paper we address the problem of allowing secondary access to the spectrum assigned to a broadcast op-erator. We assume that the secondary transmitter knows of the primary message but is not able to apply interference cancellation techniques due to the lack of channel state information. Thus, interference cancellation can only be performed at the secondary receivers, provided they are able to decode the primary message. Unlike previous approaches, which study the particular cases of secondary access in a white space (far away from the influence of the primary transmitter) or a black space (inside the primary coverage zone), we present an analysis which is valid for any position of the secondary operation area. An interesting result arises from the study of gray spaces (a region which is near the primary coverage area), where the optimum power allocation for the secondary transmitter can increment the primary coverage area, thus benefiting the primary system.
IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 1 Overlay Cognitive Transmission in a Multicarrier Broadcast Network with Dominant Line of Sight Reception
"... Abstract—The insertion of a secondary transmitter in a multicarrier broadcast single frequency network is studied. The secondary information is overlaid on top of the primary waveform, which is also reinforced by the secondary transmitter. The degradation of the primary service due to the presence o ..."
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Abstract—The insertion of a secondary transmitter in a multicarrier broadcast single frequency network is studied. The secondary information is overlaid on top of the primary waveform, which is also reinforced by the secondary transmitter. The degradation of the primary service due to the presence of echoes in a strong line of sight environment is taken into account, and mitigated with an appropriate filtering at the secondary transmitter. The transmit rate of the secondary system is maximized while keeping the original primary coverage area, defined as a function of a BER bound. The analytical results are verified by means of software simulations and hardware tests, where the importance of the proposed filtering is clearly shown.
Ergodic Capacity of Cognitive Radio under Imperfect Channel State Information
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RESEARCH Open Access Adaptive power allocation
"... Since the electromagnetic spectrum is becoming more and more scarce, improving spectrum efficiency is becoming extremely important for the sustainable development of wireless communication systems and ..."
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Since the electromagnetic spectrum is becoming more and more scarce, improving spectrum efficiency is becoming extremely important for the sustainable development of wireless communication systems and
