The SC-FDMA (single carrier-frequency division multiple access) using DFT spread OFDM was adopted as the uplink standard of the 3GPP L TE (3 rd generation partnership project long term evolution). SC-FDMA has very low PAPR (peak to average power ratio) but is sensitive to the ICI (inter carrier interference) by phase noise. In this paper, we analyze the effect of phase noise considering the back-off amount of HP A (high power amplifier). And we propose the equalizer of advanced PNS (phase noise suppressing) algorithm to remove the ICI component effectively. This equalizer has similar form of SC-FDE (frequency domain equalization) and the equalization process is based on PNS algorithm, which removes the ICI interference by phase noise.
Performance of multi-user SC-FDMA (single carrier-frequency division multiple access) system varies according to the user allocation and adaptive bit assignment to the subcarriers because each user experiences different channel characteristics. If any specific user suffers from poor channel characteristics in the conventional method of the distributed and localized user mapping, the total communication performance will be degraded. So, in this paper, we like to propose a user allocation method to improve the system performance in the frequency selective fading channel. We allocate users first who have best channel condition in comparison with all users to each subcarrier according to the channel state information. And we increase bandwidth efficiency by improving the modulation level to high order because most users have good channel condition through subcarrier allocation method. Therefore, we improve system performance like the BER performance and throughput effectively. Through the computer simulations, the performance of proposed system is analyzed and compared with existing method.
Index Terms-multi-user SC-FDMA, adaptive subcarrier allocation, maximum throughput
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