Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Improved and weighted sum rate maximization for successive zero-forcing in multiuser MIMO systems | Elliott and Krzymien EURASIP Journal on Wireless Communications and Networking 2011 2011 133 http content 2011 1 133 Ũ EURASIP Journal on Wireless Communications and Networking a SpringerOpen Journal RESEARCH Open Access Improved and weighted sum rate maximization for successive zero-forcing in multiuser MIMO systems Robert C Elliott1 2 and Witold A Krzymien1 2 Abstract We propose an improved algorithm for optimizing the transmit covariance matrices for successive zero-forcing SZF precoding in multiple-input multiple-output systems. We use a conjugate gradient projection method to solve the optimization problem. Our algorithm improves upon the existing method twofold. First the existing covariance optimization method with higher SNRs or more simultaneously supported users can yield a lower sum rate than when using block diagonalization BD when theoretically SZF should never be inferior to BD. In comparison our method consistently provides a higher throughput than BD. Several simulations demonstrate our algorithm s enhanced performance which exceeds the existing method s sum rate by up to 12 in the examined cases. Second our proposed algorithm also supports the maximization of a weighted sum rate with SZF to incorporate quality of service QoS . To our knowledge no other work in the literature considers a weighted sum rate and or QoS with SZF. 1. Introduction The topic of multiple-input multiple-output MIMO broadcast channels has drawn much research interest for several years. MIMO spatial multiplexing is potentially a key enabling technique to achieve increased throughput and quality of service QoS in commercial fourth-generation cellular and other future broadband wireless networks. The downlink of a MIMO system can be modeled as a broadcast channel BC where a base station transmits different data streams simultaneously to several users. It is known that the capacity of a MIMO BC can be reached through the use of dirty paper coding DPC 1 2
