Abstract—Existing performance comparisons of single-carrier (SC) and multicarrier transmission are mainly based on simulations. In this letter, we present a framework to compare the performance of cyclic prefix (CP)-based SC block transmission and orthogonal frequency-division multiplexing (OFDM) in frequency-selective fading channels. Minimum mean-squared error, equal-gain, and approximate minimum bit-error rate power-allocation schemes for CP-OFDM are considered. Performance of these methods is compared analytically and verified by simulations. Index Terms—Cyclic prefix (CP), frequency-selective fading, orthogonal frequency-division multiplexing (OFDM), single-carrier (SC), power allocation. I.

Abstract — Power allocation for multiple-input multiple-output (MIMO) spatial multiplexing systems is investigated. Minimization of bit error rate (MBER) is employed as the optimization criterion. MBER power allocation schemes for a variety of receiver structures, including zero-forcing (ZF), successive interference cancellation (SIC), and ordered SIC (OSIC), are proposed. It is shown that the newly proposed MBER power allocation schemes improve error rate performance. Simulation results indicate that SIC and OSIC with MBER power allocation outperform MBER precoding for ZF equalization as well as minimum mean squared-error (MMSE) precoding/decoding. Performance under noisy channels and power feedback is analyzed. A modified algorithm that mitigates error propagation in interference cancellation is developed. Compared to existing precoding methods, the proposed schemes significantly reduce both processing complexity and feedback overhead, and improve error rate performance. I.

Abstract — A two-input multiple-output (TIMO) system represents an important special case of multiple-input multipleoutput (MIMO) systems and occurs in practical scenarios where there are limitations on cost and/or space to install more antennas, in MIMO with transmit antenna selection which selects two out of multiple transmit antennas and turns MIMO into TIMO, or in cooperative communications with two singleantenna mobiles sharing their antennas. In this paper, minimum bit error rate (MBER) transmit optimization for TIMO spatial multiplexing systems is investigated. Approximate MBER transmit power allocation for a variety of receiver structures is proposed. Transmit beamforming schemes using 4-ary Pulse-Amplitude-Modulation (4-PAM) and Quaternary Phase-Shift-Keying (QPSK) pre-mixing are also proposed, which eliminate error floors in ill-conditioned TIMO channels. It is shown both analytically and by numerical simulations that the proposed schemes offer superior performance over existing schemes. Essentially, the proposed transmit optimization provides a simple and efficient means to utilize partial channel state information at the transmitter. I.

Transmit optimization for two-input multiple-output (TIMO) spatial multiplexing systems is investigated. Minimization of bit error rate (MBER) is employed as the optimization criterion. MBER transmit power allocation for a variety of receiver structures is proposed. An approximate MBER transmit beamforming scheme is also proposed, which eliminates error floors in ill-conditioned TIMO channels. It is shown that the newly proposed transmit optimization schemes together with interference cancellation and detection ordering offer superior performance over existing general precoding methods, with reduced complexity as well as feedback overhead. 1.

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