We propose a robust multi-mode linear precoder based on minimum bit error rate (MBER) selection criterion for multi-input-multi-output (MIMO) systems when transmitter only acquires the fading correlations of antennas....
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ISBN:
(纸本)9780780393912
We propose a robust multi-mode linear precoder based on minimum bit error rate (MBER) selection criterion for multi-input-multi-output (MIMO) systems when transmitter only acquires the fading correlations of antennas. The key point of the scheme is that the number of substreams and modulation mode change adaptively to minimize the mean of BER by using channel correlation matrix. In addition, we analyze two special cases with very high or low correlation coefficients. Simulation results state that the proposed scheme selects the most powerful spatial mode and improves the system performance significantly.
This paper considers the employment of linear transceivers for communication through multiple-input multiple-output (MIMO) channels with channel state information (CSI) at both sides of the link. The design of linear ...
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This paper considers the employment of linear transceivers for communication through multiple-input multiple-output (MIMO) channels with channel state information (CSI) at both sides of the link. The design of linear MIMO transceivers has been studied since the 1970s by optimizing simple measures of the quality of the system, such as the trace of the mean-square error matrix, subject to a power constraint. Recent results showed how to solve the problem in an optimal way for the family of Schur-concave and Schur-convex cost functions. In particular, when the constellations used on the different transmit dimensions are equal, the bit-error rate (BER) averaged over these dimensions happens to be a Schur-convex function, and therefore, it can be optimally solved. In a more general case, however, when different constellations are used, the average BER is not a Schur-convex function, and the optimal design in terms of minimum BER is an open problem. This paper solves the minimum BER problem with arbitrary constellations by first reformulating the problem in convex form and then proposing two solutions. One is a heuristic and suboptimal solution, which performs remarkably well in practice. The other one is the optimal solution obtained by decomposing the convex problem into several subproblems controlled by a master problem (a technique borrowed from optimization theory), for which extremely simple algorithms exist. Thus, the minimum BER problem can be optimally solved in practice with very simple algorithms.
The design of linear transceivers for multiple-input-multiple-output (MIMO) communication systems with channel state information is particularly challenging for two main reasons. First, since several substreams are es...
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The design of linear transceivers for multiple-input-multiple-output (MIMO) communication systems with channel state information is particularly challenging for two main reasons. First, since several substreams are established through the MIMO channel, it is not even clear how the quality of the system should be measured. Second, once a cost function has been chosen to measure the quality, the optimization of the system according to such criterion is generally difficult due to the nonconvexity of the problem. Recent results have solved the problem for the wide family of Schur-concave/convex functions, resulting in simple closed-form solutions when the system is modeled as a single MIMO channel. However, with several MIMO channels (such as in multi-antenna multicarrier systems), the solution is generally more involved, leading. in some cases to the need to employ general-purpose interior-point methods. This problem is specifically addressed in this paper by combining the closed-form solutions for single MIMO channels with a primal decomposition approach, resulting in a simple and efficient method for multiple MIMO channels. The extension to functions that are not Schur-concave/convex is also briefly considered, relating the present work with a recently proposed method to minimize the average bit error rate (BER) of the system.
作者：
Manton, JHUniv Melbourne
Dept Elect & Elect Engn ARC Special Res Ctr Ultra Broadband Informat Netw Melbourne Vic 3010 Australia
Channels with spectral nulls are sometimes dubbed bad channels because they can cause poor performance in communication systems. This correspondence investigates the validity of this intuition by studying the geometry...
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Channels with spectral nulls are sometimes dubbed bad channels because they can cause poor performance in communication systems. This correspondence investigates the validity of this intuition by studying the geometry of an orthogonal frequency-division multiplex (OFDM) system. It Is shown that the subchannel attenuation coefficients form a natural coordinate system for describing finite-impulse response (FIR) channels in an OFDM framework. It is also shown that channels with spectral nulls are geometrically significant;they form the faces of the convex set of all subchannel attenuation coefficients. This novel perspective makes it immediately clear why the worst performance of a linearly precoded OFDM system is achieved over a channel having the greatest number of spectral nulls. The practical implications of these results are discussed in the correspondence.
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