Cobalt-catalyzed aryl C-H activation and highly regioselective intermolecular annulation of sulfonamides with allenes

Herein we describe a cobalt-catalyzed C-H activation of aryl and heteroaryl sulfonamides and their intermolecular heteroannulation reaction with allenes, providing a convergent strategy for the synthesis of biologically interesting heterocyclic scaffolds. Carbometallation of allenes proceeds selectively through a Co-alkenyl pathway for a wide range of electron-poor and electron-rich allenes

Cobalt-Catalyzed Diastereoselective [4+2] Annulation of Phosphinamides with Heterobicyclic Alkenes at Room Temperature

Cobalt-catalyzed sp(2) C-H bond functionalization of diarylphosphinamides with heterobicyclic alkenes was demonstrated at room temperature employing commercially available cobalt(II)-salts. The effectiveness of this strategy was illustrated with the reaction of various 8-aminoquinoline derived phosphinic amides and 7-oxa/azabenzonorbornadienes. The reaction conditions exhibited excellent functional group tolerance and high diastereoselectivities. Furthermore, extension of this approach to the preparation of polyaryl cyclic phosphinamides was achieved through the dehydrative ring opening/aromatization sequence

Performance of MRC fusion-based cooperative spectrum sensing with censoring of cognitive radios in Rayleigh fading channels

In this paper, the performance of a cooperative spectrum sensing (CSS) is evaluated, considering maximal ratio combining (MRC) fusion in the presence of Rayleigh fading. A cognitive radio (CR) senses the primary users (PUs) using an energy detector (ED) in the sensing channel (S-channel). If a CR is selected to transmit its local decisions to a fusion centre (FC), it does so using a reporting (R)-channel with binary phase shift keying (BPSK) signaling. In the present work, we consider censoring of CRs based on a characterization of Rayleigh faded R-channels. In other words, CRs, whose estimated R-channel fading coefficients towards the FC exceed a predefined threshold (censoring threshold), are allowed to transmit. MRC fusion is considered at the FC to estimate the performance in terms of average missed detection and total error probabilities for various values of (i) the censoring threshold, (ii) the number of CRs, (iii) the average S-channel and R-channel signal-to-noise ratios (SNRs), under both perfect and imperfect channel estimations. The performance of CSS system with MRC fusion is also compared, for various values of the network parameters, with the performance with majority logic fusion

Cooperative spectrum sensing with censoring of cognitive radios with majority logic fusion in Hoyt fading

In this paper, the performance of cooperative spectrum sensing (CSS) is assessed in the presence of Hoyt fading. A cognitive radio (CR) user, which senses the primary users (PUs) using an energy detector (ED) in sensing channel (S-channel), is censored on the basis of the quality of the reporting channel (R-channel). A threshold-based censoring scheme is used: CR users, whose estimated R-channel fading coefficients towards the fusion center (FC) exceed a predefined threshold (denoted as censoring threshold), are allowed to transmit. Majority logic fusion is considered at the FC to estimate the performance in terms of average missed detection and total error probabilities for various values of the censoring threshold, the number of CRs, the false alarm probability, the average S-channel and R-channel signal-to-noise ratios (SNRs), under both perfect and imperfect channel coefficient estimations. The impact of the Hoyt fading parameter on the average missed detection probability is highlighted. Furthermore, an analytical expression for the probability of selection of CRs, in terms of the censoring threshold, is derived and validated with simulations

Cooperative spectrum sensing with censoring of cognitive radios in Rayleigh fading under majority logic fusion

In this paper, the performance of cooperative spectrum sensing (CSS) has been assessed in presence of Rayleigh fading. A cognitive radio (CR) senses the primary users (PUs) using an energy detector (ED) in sensing channel (S-channel). If a CR is selected to transmit its local decisions to a fusion centre (FC), it does so using a reporting (R)-channel with binary phase shift keying (BPSK) signaling. In the present work, we consider censoring of CRs based on a characterization of Rayleigh faded R-channels. In other words, CRs, whose estimated R-channel fading coefficient towards the FC exceeds a predefined threshold, are allowed to transmit. Majority logic fusion is considered at the FC to estimate the performance in terms of average missed detection and total error probabilities for various values of censoring threshold, number of CRs, false alarm probabilities, average S-channel and R-channel SNRs, under both perfect and imperfect channel estimations