In this paper, we consider an underlay cognitive radio network where the spectrum is shared with the primary network. Due to the coexistence of primary and secondary networks, primary users (PUs) are interfered with by the inter-network interference, at the same time secondary users (SUs) counteract the intra-network (inter-user) interference. Based on the cooperative feedback between the primary network and the secondary network, the secondary transmitter (ST) applies the cognitive beamforming to suppress the interference to PUs while improving the sum rate of SUs. We herein propose an adaptive feedback bits allocation among multiple PUs and SUs where the quantized channel direction information (CDI) for the interference channel is forwarded to the ST in order to utilize the beamforming. Moreover, based on the cognitive beamforming, we adjust the transmit power of the ST under the constraint of the average interference at PUs. To jointly solve the feedback bits allocation and the transmit power control problems, we formulate an optimization problem which requires a little iterations compared with the separated feedback bits allocation and the transmit power control problems. Numerical results show that the proposed scheme significantly improves the sum rate of SUs while satisfying the average interference constraint at PUs.

This study presents a strategy to remove tetracycline by using magnetite-activated persulfate. Magnetite (Fe3O4) was synthesized at high purity levels—as established via X-ray diffractometry, transmission electron microscopy, and N2 sorption analyses—and tetracycline was degraded within 60 min in the presence of both magnetite and persulfate (K2S2O8), while the use of either substance yielded limited degradation efficiency. The effects of magnetite and persulfate dosage, the initial concentration of tetracycline, and the initial pH on the oxidative degradation of tetracycline were interrogated. The results demonstrate that the efficiency of tetracycline removal increased in line with magnetite and persulfate dosage. However, the reaction rate increased only when increasing the magnetite dosage, not the persulfate dosage. This finding indicates that magnetite serves as a catalyst in converting persulfate species into sulfate radicals. Acidic conditions were favorable for tetracycline degradation. Moreover, the effects of using a water matrix were investigated by using wastewater treatment plant effluent. Comparably lower removal efficiencies were obtained in the effluent than in ultrapure water, most likely due to competitive reactions among the organic and inorganic species in the effluent. Increased concentrations of persulfate also enhanced removal efficiency in the effluent. The tetracycline degradation pathway through the magnetite/persulfate system was identified by using a liquid chromatograph-tandem mass spectrometer. Overall, this study demonstrates that heterogeneous Fenton reactions when using a mixture of magnetite and persulfate have a high potential to control micropollutants in wastewater.

and received the M.S. and Ph.D. degrees in Electrical Engineering from the Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea. From 2001 to 2005, he was with IP One, Seoul, Korea, where he led several research projects and developed Wi-Fi products and a seamless roaming solution among heterogeneous networks. From 2005 to 2007, he was a Senior Engineer at Samsung Electronics, Suwon, Korea, where he involved in the design, performance evaluation, and development of mobile WiMAX systems and 4G wireless systems.

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Abstract-This paper proposes a converged architecture for broadcast and multicast services in a heterogeneous network. To support the broadcast/multicast services in the long-term evolution (LTE) network, the standard enhances multimedia broadcast multicast service (MBMS). In the broadcast network, digital video broadcasting for handhelds (DVB-H) is the standard for broadcasting IP data services to user equipment (UE). Accordingly, the converged LTE and DVB-H network can be used to service the broadcast/multicast services. To employ the converged network, additional entities are required for the contents management, electronic service guide (ESG) management and resource management. Therefore, we propose several logical entities to fulfill functionality from the above mentioned issues. The proposed logical entities are as follows: an integrated contents server, an integrated ESG server and an integrated management server. We also present several scenarios for implementing the converged architecture and compare the advantage of each scenario. Service providers can exploit the converged architecture according to preference and equipped devices. This study is of particular interest to the service providers because it provides the service providers with an insight of the various scenarios to make the converged architecture for broadcast/multicast service. Index Terms-Broadcasting, converged architecture, digital video broadcasting for handhelds (DVB-H), multimedia broadcast multicast service (MBMS), long-term evolution (LTE).