Lately, spectrum sensing performance has been improved by using cooperate spectrum sensing which each results of sensing of several secondary users are reported to the fusion center. Using Cognitive Radio, secondary user is able to share a bandwidth allocated to primary user. In this paper, we propose a new decentralized cooperative spectrum sensing scheme which compensates the performance degradation of existing decentralized cooperative spectrum sensing considering the error probability of the channel which sensed result of the secondary user is delivered to the fusion center in decentralized cooperative spectrum sensing. In addition, a sensing threshold optimization of minimizing the error probability of decentralized cooperative spectrum sensing is introduced by deriving the equation and the optimal sensing threshold has been confirmed to maximize the decentralized cooperative spectrum sensing performance.※ 이 논문은 인천대학교 2014년도 자체연구비 지원에 의하여 연구되었음.

Recently, data traffic is significantly increased by high rate data service. As a result, radio spectrum is considered one of the most scarce and valuable resources for wireless communications. For the solution of this problem, cognitive radio(CR) has been proposed as an efficient means to opportunistic spectrum sharing between primary (licensed) users and cognitive radio users. In this paper, user selection scheme in CR networks is proposed for additional consideration of secondary system. The proposed user selection scheme mitigates interference to primary user by using orthogonal channel vectors while improves performance of secondary system. Simulation results show that the proposed scheme achieves 1.62bps/Hz higher average throughput of whole system than one of the existing scheme.주저자：인천대학교 전자공학과 통신신호처리 연구실,

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bols detection with LRAD and correction are explaAbstract ined, simulation results will be provided in Section 5. Some concluding remarks are offered in Section 6. MLD (Maximum Likelihood Detection) has shown optimum performance in MIMO systems. However, its 2. System model complexity generally makes it impractical. To solve this problem, various techniques were proposed. We consider the often used Rayleigh fading MIMO LRAD (Lattice-Reduction-Aided Detection) was also systems model proposed to improve the performance of MIMO systems[1]. In this paper, we suggest error symbol dete-YC = Hcxc + nc (1) ction and correction in symbols estimated by LRAD. In other words, the proposed system detects the first Where usually the vectors xc, nc, yc and the matrix symbols by LRAD and searches error terms in the first Hc are obtained from the equivalent baseband model, detection symbols. And correct the error symbols by and hence are complex-valued. Hc is the channel optimal or sub-optimal systems. As a result, its matrix, xc is the vector of transmitted symbols, each performance approaches more nearly to that of MLD chosen from some X and fnc is the additive white which shows optimum performance, but it has much Gaussian noise (AWGN) vector. We assume all less complexity than MLD[1]. vectors to be column vectors of dimension K, and Hc 1. Introduction is a Kx K matrix of complex transfer coefficients between transmitter and receiver. We can equivalently write MIMO (Multiple-Input Multiple-Output) systems have recently become very popular since it can improve link reliability without sacrificing bandwidth 9YC 9i-H, -KMc 91c, 9 n ( efficiency. For the system designer, the goal is toLyc LHC ]iR-3xc i n L2) achieve an attractive performance-complexity tradeoff. At one end of the spectrum, MLD (Maximum Like-(where the 9i and 3 prefix denote the real and imalihood Detection) is optimal, but its complexity generally makes it impractical. A variety of other detectors, ginary parts), which gives an equivalent 2K-dimenboth linear and nonlinear, require substantially less sional real model of the form complexity, but sacrifice performance significantly. Recently, Yao and Wornell [2] introduced the idea of y = Hx + n (3) LRAD (Lattice-Reduction-Aided Detection). The striking property of this scheme is that it results in error

In this paper, the scheme for designing optimal beamforming matrix for interference control is proposed. The optimal beamforming matrix is found though linear combination of interference alignment conditions and renewal of linear combination coefficient. The proposed scheme has advantages that the complexity is reduced and there is no multiplying operation in matrix calculations even if proposed scheme has the form similar to that of existing least square based scheme. The simulation results show that proposed scheme has about 4bps/Hz higher gain than existing least square scheme. Also there is no additional multiplying calculation and increase of matrix size when the number of transmit and receive antennas is increased. . 최근에는 구현 가능한 방법으로 간섭 정렬(interference alignment) 이 대두되고 있다 [6][7][8][9] . 간섭 정렬은 송수신단의 개수 에 상관없이 다른 사용자들의 간섭을 신호 공간의