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In this paper, a new algorithm is proposed for cooperative beamforming in the multiple input multiple output (MIMO) orthogonal frequency division multiple access (OFDMA) cognitive radio (CR) systems. The objective is to maximize the signal to interference plus noise ratio (SINR) of the selected secondary users subject to guarantee the primary user's quality of service over all subchannels. In each...
In this paper, we propose a channel aware fast utility-based algorithm for allocating power and subcarrier to the users in Orthogonal Frequency Division Multiple Access (OFDMA) networks. Utility function is a proven approach for fair and efficient radio resource allocation. Most of the proposed schemes in the related literature consider continuous rate adaptation. However, our proposed algorithm utilizes...
In this study, the problem of blind channel estimation for single-input single-output (SISO) orthogonal frequency-division multiplexing (OFDM) systems, is considered. Based on auto-correlation matrix, we develop a precoding-assisted blind channel estimation algorithm which is suitable for practical SISO-OFDM applications. Compared to the popular subspace-based blind channel estimation methods, the...
In this paper, a new companding transform for reduction in peak to average power ratio of OFDM signals is proposed. Linearity and existence of inflection points, which are key features of two previous works, are maintained in the proposed transform. However, unlike the previous works, the proposed transform does not cause abrupt jumps in the signal, hence leads to better spectral characteristics....
Orthogonal frequency division multiplexing (OFDM) systems may confront significant intercarrier interference (ICI) when applied in doubly selective channels. Furthermore, the insufficient cyclic prefix (CP) leads to interblock interference (IBI) which again results in ICI. These interferences cause an early error floor in conventional receivers. In this paper, we characterize the doubly selective...
In this paper, a new fast algorithm is proposed to suppress inter-carrier interference (ICI) in SISO-OFDM systems. Previous algorithms, due to high computation time, are impractical for OFDM systems especially with large number of subcarriers. To overcome this problem, our proposed algorithm computes rather than K2 elements of carrier frequency offset (CFO) matrix used by previous algorithms, only...
A precise method for calculating the bit error probability (BEP) of an iterative equalization-based oversampled OFDM system on fading channels in the presence of spectral nulls is derived. Several signaling formats, such as binary phase-shift keying, quaternary phase-shift keying, and M-ary quadrature amplitude modulation are considered.
Filtered orthogonal frequency division multiplexing (filtered-OFDM) and wavelet-OFDM are two modulation methods that have been proposed by the IEEE P1901 working group for data transmission over power lines. The filtered-OFDM is a modified version of the conventional OFDM that is designed to avoid the AM and amateur radio bands effectively. Although OFDM is a matured technology and thus it might be...
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