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Dynamic spectrum access has become a promising technique to fully utilize the scarce spectrum resources. However, spectrum allocation schemes with high efficiency and Quality of Service (QoS) guarantee for the primary users have yet to be designed. In this paper, two novel dynamic spectrum access schemes are proposed. The proposed schemes are based on continuous-time Markov chains (CTMC), through...
We concentrate on the sum power minimization problem for the uplink of wireless cellular systems in this paper. Given a certain quality-of-service (QoS) constraint per mobile station (MS), the optimal power control and receiver beamforming are jointly considered with adaptive multi base station set (MBS) selection for joint reception. An iterative optimization algorithm is proposed accordingly. Although...
In this paper, a new technique for dynamic spectrum management of a Wideband Code Division Multiple Access (WCDMA)/Digital Video Broadcasting (DVB) heterogeneous system is introduced. The solution is obtained using coloring theory, and significantly reduces the complexity of spectrum management.
Three dimensional beam prpopapagation method is used to analyze the performance of multimode interference coupler based on general interference and restricted interference mechanisms. Numerical results show that couplers based on general interference are more preferable.
This paper presents another look at the problem of frequency spectrum sensing based on energy detection in OFDM. OFDM is one of the most important techniques to improve the capacity of the channel in 3G and 4G. In order to detect the presence of the spectrum holes and utilize them efficiently without causing interference to primary users in OFDM, spatial spectrum estimation is considered as the key...
In this paper, the performance of an ultra-wideband (UWB) communication system employing orthogonal pulse position modulation (PPM) and non-orthogonal pulse position modulation (NPPM) is considered. Time hopping (TH) is used to decrease the effect of multiuser interference. It is shown that for a large number of users, NPPM provides better bit error rate (BER) performance than PPM. We also determine...
We consider the coupling between four photonic crystal waveguide as a multimode interference system and showed that the dispersion curves of the eigenmodes intersect or almost intersect. Degenerate modes appear in the system. At the crossing point, the multimode interference is deprived and power is confined to its input direction without observable transfering to other photonic crystal waveguides.
In this paper, a novel robust adaptive beamformer based on principal component regression (PCR) is derived. Unlike many existing methods, the proposed method is completely automatic (or so-called parameter-free), which means, it do not need the choice of user parameters. The performance of our approach is illustrated by numerical simulations and compared to other robust adaptive beamformers. The simulation...
The goal of this paper is to present an iterative robust adaptive beamformer using partial least squares (PLS) based on the generalized sidelobe canceller (GSC) parameterization of the minimum variance (MV) beamformer. The proposed method can be implemented simply as an iterative process and does not require the choice of a user parameter. The shrinkage properties and the relations among ridge regression...
Wireless mesh network (WMN) has become a popular access network architecture. But because of its multi-hop nature, co-channel interference and contention, the attainable capacity of a wireless node in a WMN is significantly less than the radio capacity. We propose a overlay architecture for a WMN, where a wireless-ring (WRing) is deployed over the regular mesh for carrying wireless mesh traffic only...
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