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In this letter, we consider hierarchical cooperative spectrum sensing based on two-threshold energy detection in cognitive radio networks. In order to solve the sensing failure problem in conventional two-threshold energy detection, soft combination of the observed energy value from different cognitive radio users is investigated. Encouraged by the(More)
This paper presents a new class of multi-stub loaded resonators with flexibly controlled resonance modes, which are suitable for both tunable and nontunable filter applications. The proposed resonators, modified from a basic tri-mode resonator, include two quad-mode ones and a six-mode one. One of the quad-mode resonators is utilized to design a(More)
Long Term Evolution (LTE) is a main mobile communication technology in the future. For the reason that different kinds of multimedia applications have different quality of service (QoS) requirements, especially for Real Time (RT) traffics, it is necessary to design an effective scheduling algorithm to satisfy the various kinds of QoS needs. In this paper we(More)
This paper presents the design of novel tunable bandpass filters with constant absolute bandwidth. A novel mixed electric and magnetic coupling scheme is utilized. Theoretical analysis indicates that it is able to achieve desired coupling coefficients between the proposed resonators at various frequencies so as to obtain constant absolute bandwidth. For(More)
This paper presents a novel approach to design frequency-agile bandpass filters with constant absolute bandwidth and passband shape, as well as a suppressed second harmonic. A novel mixed electric and magnetic coupling scheme is proposed to control the coupling coefficient variation. Theoretical analysis indicates that it is able to achieve desired coupling(More)
This paper presents a novel method for designing Gysel power dividers with arbitrary power-division ratios as well as filtering responses. A coupling structure is utilized to replace the quarter-wavelength microstrip line in the power divider. By altering the coupling strength, the power ratio can be arbitrarily controlled with the highest ratio of 10:1.(More)
A novel broadband UHF RFID tag antenna mountable on metallic surface is presented. The structures of T-matching network and double symmetrical radiating patches shorted to ground plane are employed. The proposed antenna has a half power bandwidth of 11.4% when placed in free air and covers two major segments of the UHF RFID band when mounted on metallic(More)
This paper presents a novel approach to design RF tunable bandstop filters with constant absolute bandwidth. The filters are based on a doublet configuration which is attractive for high-order filter designs. In the doublet, two varactor-tuned resonators, arranged in a mirror-symmetrical manner, are coupled to a main transmission line. A novel coupling(More)
RFID technology is gaining much attention for indoor localization because of its advantages such as non-contact and non-line-of-sight nature. In this paper, we study two typical approaches using active RFID for indoor location sensing: LANDMARC and VIRE, and point out that the latter approach with a fixed threshold of Received Signal Strength Indication(More)