다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

An OFDM transmitter spreads original data symbols with a complex-valued spreading matrix derived from a discrete Fourier transform. Spread data symbols are mapped to OFDM subcarriers. Spreading and mapping are configured to produce a transmitted spread-OFDM signal with a low peak-to-average power ratio (PAPR) and orthogonal code spaces. In MIMO systems, the complex-valued spreading matrix can comprise a MIMO precoding matrix, and the code spaces can comprise MIMO subspaces. In Cooperative-MIMO, a combination of low code-space cross correlation and low PAPR can be achieved.

Spreading and precoding in OFDM

Cooperative Distributed Antenna Transmission for 5G Mobile Communications Network

We started a new research project in the “advanced 5G” era that aims at accommodating various types of communications involving current and emerging services with different data flow-level quality requirements. In this paper, the objectives and the technical aspects of the research project are introduced. We propose an architecture based on a virtualized radio access network (vRAN) that enables adaptive control of equipment resources and location of functions in the vRAN environment in accordance with spatially and temporally changing communication demands. The seven planned research items that are essential for realizing the advanced 5G network are listed as follows: blockage prediction, new radio access technologies (RATs) and their implementations with software-defined radio (SDR), adaptive interference and resource control, integration of radio and fiber resource control, highly efficient access transmission control, adaptive placement of BS functions, and quality aware traffic pattern prediction.

Research Project to Realize Various High-reliability Communications in Advanced 5G Network

A new companding scheme for reducing the peak-to-average power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) systems is proposed in this study. It proceeds from speech signal processing similar to the earliest $\mu$ -law companding (MC) model. The proposed scheme compands (compresses and expands) the amplitudes of OFDM signals to a maximum of 1 V. Besides significantly reducing the PAPR, the proposed technique is also able to function as a limiter, thus reducing the system complexity and limiting the amplitudes of OFDM symbols to a unity maximum voltage, which does not exist in other companding PAPR techniques. Over frequency-selective fading channels with frequency domain equalization and using minimum mean square error (MMSE) to minimize the noise overhead, the proposed technique outperforms four other companding schemes over light and severe fading conditions. Finally, we demonstrate that PAPR reduction using companding can dispense with corresponding decompanding scheme at the receiver as it amplifies the distortion noise, thereby reducing the bit error ratio performance and increasing the receiver complexity. We investigate the out-of-band interference of the proposed scheme and also show that it outperforms the other existing techniques by up to 5 dB.

/pdf/enhanced-nonlinear-companding-scheme-for-reducing-papr-of-1jztdwhpyz.pdf

Enhanced Nonlinear Companding Scheme for Reducing PAPR of OFDM Systems

Single-carrier (SC) signals have a low peak-to-average power ratio (PAPR) property. However, the PAPR becomes higher as the modulation level increases. We have recently proposed a frequency-domain selected mapping (FD-SLM) which can effectively reduce PAPR of SC signal with high modulation level, but standard SLM technique requires the transmission of side-information to the receiver side. In this paper, a new FD-SLM with minimum mean-square error (MMSE) based blind signal detection is proposed, where there is no change on SLM algorithm at the transmitter and no necessity of side-information transmission. Simulation results show that the proposed blind FD-SLM technique reduces the PAPR of SC signals without significant degradation of bit-error rate (BER) performance.

http://www.mobile.ecei.tohoku.ac.jp/paper/pdf/inter_2015/13_in_2015_amnart.pdf

A blind selected mapping technique for low-PAPR single-carrier signal transmission

Single-carrier transmission is a promising transmission technique due to its low peak-to-average power ratio (PAPR) property compared to multicarrier transmission, and using frequency-domain equalization (FDE) at the receiving side also mitigate the adverse effect of channel frequency-selectivity. An introduction of transmit filter can improve the system performance in terms of either PAPR or error probability. In this paper, we focus on the transmit filter aiming to reduce PAPR by employing the minimization of variance of instantaneous transmit power. Filter roll-off factor is also considered in order to provide excess-bandwidth transmission. With a combination of an FDE and spectrum combining at the receiver, excess-bandwidth transmission inherits additional frequency diversity gain, and therefore improves error probability. Performance evaluation of the proposed filtering algorithm is done by computer simulation, while the PAPR and bit-error rate (BER) performance of proposed algorithm are compared with conventional square-root Nyquist filter.

Performance evaluation of Low-PAPR transmit filter for single-carrier transmission

Single-carrier (SC) signal has a low peak-to-average power ratio (PAPR) property. However, the PAPR of SC signal increases if transmit filtering and/or high-level modulation are applied. We have recently proposed a time-domain selected mapping (TD-SLM) which effectively reduces the PAPR of filtered SC signals by applying the binary phase rotation before transmit filtering, but the necessity of side-information decreases the spectrum efficiency (SE). In this paper, a blind TD-SLM which does not require side-information is proposed. Unlike the frequency-domain SLM (FD-SLM) and the original TD-SLM with side-information, polyphase rotations are used. Performance evaluation of the proposed blind TD-SLM is done by computer simulation assuming turbo-coded filtered SC block signal transmission in aspects of PAPR and bit-error rate (BER) to show that no significant BER performance degradation is occurred.

A Blind Polyphase Time-Domain Selected Mapping for Filtered Single-Carrier Signal Transmission

We have been studying cooperative distributed antenna transmission (CDAT) as a promising technique for realizing the 5th generation (5G) high-speed mobile communications. Assuming time division duplex (TDD), the macro-cell base station (MBS) and the user equipments (UEs) conduct the channel estimation independently to obtain the shared channel state information (CSI). In this paper, we introduce a TDD frame structure consisting of uplink pilot time slot and downlink pilot time slot followed by data time slots. MIMO channel estimation is done before the user data transmission. Also presented is the pilot signal design. The accuracy of the proposed MIMO channel estimation and achievable bit error rate (BER) performance of user data transmission are evaluated by computer simulation.

Amnart Boonkajay

Papers

Cooperative Distributed Antenna Transmission for 5G Mobile Communications Network

A blind selected mapping technique for low-PAPR single-carrier signal transmission

Performance evaluation of Low-PAPR transmit filter for single-carrier transmission

A Blind Polyphase Time-Domain Selected Mapping for Filtered Single-Carrier Signal Transmission

MIMO channel estimation for time-division duplex distributed antenna cooperative transmission