2018/2
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- ItemRobust Adaptive Beamforming Using k-means Clustering: A Solution to High Complexity of the Reconstruction-Based Algorithm(Společnost pro radioelektronické inženýrství, 2018-06) Tan, Zhihao; Jia, Weimin; Jin, WeiRecently, a new robust adaptive beamforming (RAB) algorithm has been proposed to reconstruct the interference-plus-noise covariance matrix (IPNCM) based on narrowing the interference angular domain and using an annular uncertainty set (NIAD-AUS). The method is robust against unknown arbitrary-type mismatches. However, its computational complexity will increase exponentially with the number of array sensors. In this paper, a novel method is proposed to solve this problem. First, k-means clustering (KMC) algorithm is utilized to estimate the annulus uncertainty set with fewer clustering weight points rather than whole sampling. Second, the KMC Capon spectrum is used to reconstruct the IPNCM. Compared with the previous reconstruction-based algorithms, the proposed approach can retain the high performance of the state-of-the-art NIAD-AUS algorithm. More importantly, it can also obtain the IPNCM more quickly. Lastly, simulation results demonstrate the effectiveness and robustness of the proposed algorithm.
- ItemA Fast Method for Blind Identification of Punctured Convolutional Codes(Společnost pro radioelektronické inženýrství, 2018-06) Han, Shu Nan; Zhang, Min; Li, Xin HaoThe existing method for blind identification of a punctured convolutional code involves searching for dual words and the puncturing pattern exhaustively. As the length of the dual words and the code rate increase, the computational complexity of this method expands exponentially. To address this problem, a fast scheme for blind identification of punctured convolutional codes is proposed. First, a recursive algorithm for solving the parity check equation set is proposed. The dual word and generator polynomial bases of the punctured convolutional code are estimated by using the recursive algorithm. After this, by using the structural properties of the generator matrix of the blocked code, possible generator matrices of the punctured convolutional code are obtained. Finally, since a generator polynomial of the parent convolutional code can be recovered from any column of its polycyclic pseudocirculant matrix, the corresponding generator matrix of the parent code and the puncturing pattern are reconstructed simultaneously from an estimation of the generator matrix of the punctured code. The reconstructed generator matrix of the parent code with a minimal constraint length is determined to be the identification result. Simulation experiments show the effectiveness of the proposed method. As there is no need to search for the dual word and puncturing pattern exhaustively, the method can achieve fast identification of punctured convolutional codes. Additionally, the method is robust to bit errors in the received sequence.
- ItemExpansion of Cell Range with Geometric Information of Pico Cell for Maximum Sum Rate in Heterogeneous Networks(Společnost pro radioelektronické inženýrství, 2018-06) Jung, Taesung; Song, Iickho; Lee, Seungwon; Jung, Seungjae; Yoon, Seokho; Kang, JoonhyukIn this paper, taking the positions of pico-cell base stations (PBSs) into consideration, a scheme of cell range expansion (CRE) for maximum sum rate is addressed in heterogeneous multi-input multi-output multi-user wireless networks. The optimal CRE bias obtained numerically by the proposed CRE scheme with inter-cell interference coordination (ICIC) allows us to maximize the sum rate while successfully maintaining the load balance between the macrocell base station and PBSs. Numerical results confirm that the proposed CRE scheme with ICIC can provide higher sum rate than conventional schemes and balanced load.
- ItemExtended Noise Analysis Model of CW-type Radar Sensors with IQ Down-Conversion(Společnost pro radioelektronické inženýrství, 2018-06) Jenik, Vojtech; Hudec, Premysl; Panek, PetrCW-type structures belong to the most frequently employed radars, especially in a form of small sensors used, for example, in security applications or automotive industry. Range and reliability of operation of these sensors strongly depend upon their noise parameters. This paper extends previously published works by considering all potential inner noise sources and creating complex noise model of the concerned radar family including often used IQ signal processing. The noise sources cover local oscillator amplitude-noise and phase-noise, noise of a RF signal path and noise of a low-frequency signal path. The resulting noise model was verified by practical measurements which included different local oscillator types, different low-frequency bandwidths and different time-delays of the cross-talked signals. In all cases, the agreement between theory and measurement was within estimated limits. The developed model is applicable for noise analysis and design of all common CW-type radars.
- ItemA First-Order Primal-Dual Method for Saddle Point Optimization of PAPR Problem in MU-MIMO-OFDM Systems(Společnost pro radioelektronické inženýrství, 2018-06) Singh, Davinder; Sarin, R. K.This paper investigates the use of a particular splitting-based optimization technique for constrained l∞-norm based peak-to-average power ratio (PAPR) reduction problem in multiuser orthogonal frequency-division multiplexing (OFDM) based multiple-input multi-output (MIMO) systems. PAPR reduction and multi-user interference (MUI) cancelation are considered in a saddle-point formulation on the downlink of a multi-user MIMO-OFDM system and an efficient primal-dual hybrid gradient (PDHG) inspired algorithm with easy-to-evaluate proximal operators is developed. The proposed algorithm converges significantly faster to satisfactory solutions with much improved asymptotical convergence rate than existing methods. Numerical results illustrate the superior performance of the proposed algorithm over existing methods in terms of PAPR reduction for different MIMO configurations.