Earticle

This paper proposes a novel censor-based scheme for cooperative spectrum sensing in Cognitive Radio Networks. A Takagi-Sugeno’s fuzzy system is proposed to make the decision on the presence of the licensed user’s signal based on the observed energy at each cognitive node. The local spectrum sensing results are aggregated to make the final sensing decision at the fusion center after being censored to reduce transmission energy and reporting time. Simulation results show that significant improvements of saving energy as well as reporting time are achieved by our scheme whereas the sensing accuracy is guaranteed.

An adaptive algorithm for reducing the hardware complexity is presented. This paper proposes a modified LMS algorithm for the adaptive system and analyzes its convergence characteristics mathematically. An objective of the proposed algorithm is to reduce the hardware complexity. In order to test the performances, it is applied to the echo canceller, and a program is described. The results from simulations show that the echo canceller adopting the proposed algorithm achieves almost the same performances as one adopting the NLMS algorithm. If an echo canceller is implemented with this algorithm, its computation quantities are reduced to the one third as many as the one that is implemented with the NLMS algorithm, without so much degradation of performances.

An uplink structure of convolution coded V-BLAST MC-CDMA system was analysed. The adaptive modulation techniques were applied to the system. The effective of adaptive modulation were set by simulation. The expected bit error rate (BER) were settled first, and then according to the BER simulation results, the conversion thresholds of modulation types of the system were determined. The BER performance of the adaptive modulation V-BLAST MC-CDMA system for a given various number of users was simulated. Simulation results show that adaptive modulation improves the spectrum efficiency of the system without sacrificing the expected BER performance.

This paper address the scheme to develop Radio Access Network System for mobile network. This system can save the cost of transmission link between base station and central office in mobile communication network. As this system can reduce the number of transmission links by sharing the transmission link that mobile communication base stations of several generation uses separately, and separates the traffics non-sensitive to delay time, and then transmits the traffics through IP network, it can reduce Capex and Opex of RAN network by using IP/MPLS network or Ethernet wireless bridge as RAN transmission network.

Optical filtering characteristics of planar distributed feedback (DFB) guiding structures which have L/4 phase-shift region, are evaluated by using the equivalent network based on a newly developed concept of Floquet’s theorem and bisection principle (Babinet’s theorem). The numerical results reveal that this method offers a simple and convenient algorithm to analyze the filtering and oscillating characteristics of L/4 phase-shifted DFB configurations as well as decreases dramatically the computational time.