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Amidst conflicting views about whether soft cooperative energy detection scheme (SCEDS) outperforms hard cooperative energy detection scheme (HCEDS) greatly in cognitive radio, we establish the bridge that mathematically connects SCEDS and HCEDS by closed approximations. Through this bridge, it is demonstrate that, if the number of detectors of HCEDS is 1.6(More)
A novel hybrid coupler with nonstandard phase difference has been reported recently by Wong <etal/> in 2012, which shows promising potentials in applications like the feeding networks for phased array antenna. However, it is found that the design equations of Wong <etal/> are incomplete because of the neglect of an interrelated constrain between the design(More)
—A new carrier frequency offset estimation scheme in orthogonal frequency-division multiplexing (OFDM) system is proposed. The carrier frequency offset estimation includes acquisition and tracking, and the acquisition range is as large as one half of overall signal bandwidth. The proposed tracking estimator is a maximum-likelihood estimator, and in AWGN(More)
The maximum-likelihood detection (MLD) algorithm is the optimal detection scheme for vertical Bell Laboratories layered space-time (V-BLAST) systems. However, it is generally infeasible to implement the MLD algorithm in practical systems because of its high computational complexity. In this paper, we used two parallel interference cancellation techniques,(More)
This paper presents an unequal Wilkinson power divider operating at arbitrary dual band without reactive components (such as inductors and capacitors). To satisfy the unequal characteristic, a novel structure is proposed with two groups of transmission lines and two parallel stubs. Closed-form equations containing all parameters of this structure are(More)
In this paper, a slot-based MAC protocol is proposed for cognitive radio wireless networks. This protocol makes cognitive users sense licensed channels periodically, and each period consists of a fixed number of slots. When cognitive users identify un-used licensed channels, they use IEEE 802.11 distribution coordination function (DCF) to contend the spare(More)