A novel iterative algorithm for transmitter (TX) precoding for a Orthogonal Frequency Division Multiplexing - (OFDM-) Multiple Input Single Output (MISO) system with nonlinear Power Amplifiers (PAs) is proposed. Having a plurality of PAs at the TX, it is possible to synthesize peak power limited signals, transmitted at each TX branch, such that the total distortions seen at the receiver (RX) will be minimal. Two versions of the algorithm are proposed. The first one reduces nonlinear distortions seen at the RX antenna without considering the spectral purity requirements. The second one reduces nonlinear distortions at the RX and also keeps the out-of-band radiation of the TX signals at a low level in order to satisfy spectral purity requirements. For a low Back-Off (BO) scenario, where the nonlinear distortions are strong, the proposed algorithms show a much lower Symbol Error Rate (SER) and much higher power efficiency than the well known Maximum Ratio Transmission approach.

A communication system with non-linear power amplifier (PA) is considered. We introduce three major performance criteria of the system: (i) power efficiency of the PA, (ii) spectral purity of the transmitted signal expressed by adjacent channel interference, and (iii) transmission performance expressed by mutual information or symbol error rate. In order to fulfill the first two criteria it is proposed to use iterative clipping and filtering (ICF) at the transmitter together with low input back-off, while the third criterion is obtained by modified iterative receiver (MIR). The proposed MIR is based on the well-known iterative receiver, but with ICF in the feedback path. The obtained results show that the proposed system is better than its competitors when considering the three performance criteria together. The analysis and results are focused on OFDM; however, the proposed approach may be applied to single carrier.

In this paper we propose to use a so-called “Slave” power amplifier (PA) to remove the distortions caused by the non-linear “Master” high power amplifier (HPA) in multicarrier systems. We derive the mutual information (MI) expressions for the proposed scheme and perform simulations to obtain the spectral mask. It is shown that by adding an additional “Slave” PA we increase the MI and improve the spectral mask, while maintaining the same supplied power as in regular multicarrier system with a single “Master” HPA.

This paper investigates the statistical distribution of instantaneous power (IP) in pulse-shaped single-carrier (SC) modulation with independent I/Q components. Such knowledge is required due to the nonlinearities that may appear in the whole communication track, especially that of the power amplifier (PA). Exact analytical derivation of the distribution is an open problem. The existing works rely on Monte-Carlo simulations or on complex numerical analysis. In this paper we propose a straightforward method, based on numerical integration, to evaluate the complementary cumulative distribution function (CCDF) of IP by using characteristic function approach. Error analysis of the proposed numerical approach is given. It is shown that by investing relatively small computation power in the proposed numerical solution we can derive the CCDF of IP with high and controlled accuracy.

We propose and analyze two strategies for efficient use of linear power amplifiers in single carrier systems. The first strategy maximizes the mutual information for a given limited power supply by applying variable gain pre- amplification to the transmitted signal before it is fed to the power amplifier. The second strategy minimizes the required power supply while maintaining a fixed power output by adjusting the power amplifier's linear dynamic range using adaptive-biasing. Pre- amplification results in an increase of up to 1.4 times in average mutual information regardless of the power amplifier class while the adaptive- biasing results in a decrease of up to 7 dB in the required power supply for class A and up to 3 dB for class B power amplifiers.

This paper investigates the statistical distribution of instantaneous power (IP) in pulse-shaped single-carrier (SC) modulation. Such knowledge is required due to the nonlinearity of the power amplifier (PA). Exact analytical derivation of the distribution is an open problem. The existing works rely on Monte-Carlo simulations or on an approximated numerical analysis. In this paper we propose a straightforward method, based on numerical integration, to evaluate the complementary cumulative distribution function (CCDF) of IP by using characteristic function approach. Error analysis of the proposed numerical approach is given. It is shown that by investing relatively small computation power in the proposed numerical solution we can derive the CCDF of IP with high and controlled accuracy.