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The receiver performance is degraded by nonlinear memory problem in communication system. The pre-distorter techniques are an effective technique to compensate for the nonlinear distortion of the HPA without memory effects. However, memory effect of HPA can no longer be ignored when data signal is transmitted in high speed. Many adaptive pre-distorter schemes have been studied to compensate for memory effect problem of HPA in transmitter. The complexity and cost of satellite will increase when using adaptive pre-distorter in satellite communication system. In this paper, we propose receiver feedback closed loop pre-distortion technique in order to compensate for nonlinear problem of HPA with memory problem. The purpose of this paper is to reduce complexity and cost of satellite design by using only pre-distorter at terrestrial station.

In this paper, we analyze the relationship between energy per bit and the data rate with the variation of the system bandwidth. A existing power model is mathematical model to express power consumption of each device. In this paper, we have to investigate the system level energy model for the RF front-end of a wireless transceiver. Also, the effects of the signal bandwidth, PAR, date rate, modulation level, transmission distance, specific attenuation of frequency band, and the signal center frequency on the RF front-end energy consumption and system capacity are considered. Eventually, we analyze the relationship between energy per bit and the data rate with the variation of the system bandwidth so that we simulate the minimum energy per bit in the several Gbps data rate using Shannon capacity theory.

It is very important to estimate the Signal to Noise Ratio(SNR) of received signal in time varying channel state. Most SNR estimation techniques derive the SNR estimates solely from the samples of the received signal after the matched filter. In the severe distorted wireless channel, the performance of these estimators become unstable and degraded. LP-based SNR estimator which can operate on data samples collected at the front-end of a receiver shows more stable performance than other SNR estimator. In this paper, we study an efficient SNR estimation algorithm based on LP and propose a new estimation method to decrease the computation complexity. Proposed algorithm accomplishes the SNR estimation process efficiently because it uses the forward prediction error and its conjugate value during the linear prediction error update. Via the computer simulation, the performance of this proposed estimation method is compared and discussed with other conventional SNR estimators in digital communication channels.

FH system is very robust to the jamming interference. OFDM system is very good for the high speed communication system. But, it has high PAPR. SC-FDMA system based on OFT-spread OFDM was proposed to reduce high PAPR. Therefore, in this paper, we like to introduce the FH system into SC-FDMA system, which can be best solution to the jamming hostile environment and for the high power efficiency. Also, OFDM is very sensitive to ICI. Especially, ICI generated by frequency offset and phase noise breaks the orthogonality among sub-carriers, which seriously degrades the system performance. We analyze the performance of the FH SC-FDMA system in the PBJ and MTJ channel. In this paper, the ICI effects caused by phase noise, frequency offset and Doppler effects are analyzed and we like to propose the PNFS algorithm in the equalizer to compensate the ICI influences. Through the computer simulations, we can confirm the performance improvement.

Single carrier M-APSK modulation technique is well used in satellite communication system due to the low PAPR so that the we can expect more resistance to the non-linear distortion. Although TWTA has high amplification efficiency, it may produce serious non-linear distortion. Memory effect that can be observed in the very high speed data rate would be another harmful effect. In this paper, to compensate non-linear distortion efficiently in case of HPA model with the memory effect, we design adaptive pre-distorter using NLMS (normalized least mean square) algorithm. Through the simulation, we confirm that the pre-distorter using NLMS algorithm is able to improve the BER performance than existing pre-distorter.

2-dimensional antenna beamforming is studied in this paper. Beamforming technique can reduce interferences signals to increase SNR. Because of this advantage, beamforming technique was adapted for WPAN (wireless personal area network) using 60GHz band. Since this 60GHz band signal has a characteristic of low diffraction, it is good for indoor communication environment. In this paper, we analyze 60GHz frequency band characteristics such as reflection coefficient, path loss. Also, we propose a 3-dimensional tracking system with MUSIC algorithm. After simulation, one result shows that this system can track DOA (direction of arrival) using proposed method. Another result shows how many antenna numbers are suitable for indoor communication environment. As those two results, it can be adapted in 60GHz frequency band indoor communication.

In this paper, we propose a wireless repeater with DFE (decision feedback equalizer) based on LDPC (Low Density Parity Check) codes. So as to meet ever increasing requirements on higher wireless access data rate and better quality of service (QoS), the wireless repeater system studied. In the wireless repeater, the feedback channel and RF impairments such as phase noise, carrier frequency offset, and more has caused performance degradation. In order to remove feedback channel and phase noise, we suggest a novel equalizer for wireless repeater. LDPC codes are well known as forward error correction codes which are very good performance. LDPC codes have a good performance in error correction along with Turbo codes. The proposed equalizer helps to compensate RF impairments and improve better performance than used independently. In addition, proposed equalizer has less iterative number of LDPC codes. So, the proposed equalizer system has low complexity. Therefore, we propose system model of proposed equalizer for wireless repeater and evaluate BER performance in feedback channel and phase noise based on OFDM system by using MATLAB Simulink.