A main drawback of frequency division multiplexing (OFDM) system is the high peak-to-aver-age power ratio (PAPR). High PAPR leads to amplifier nonlinearity, inter-modulation and low inefficiency. As a simplest approach, traditional clipping method can reduce PAPR of OFDM signals, but it causes large unwanted out-of-band radiation. In this paper, a new clipping method is proposed, which can reduce PAPR without out-of-band radiation. It is based on the traditional clipping to generate the error signal. Zero out-of-band radiation is achieved by filtering the error signal. Although the proposed method produces more inband noise, by using noise cancel algorithm, the ideal unclipped signal′s BER performance can be achieved.

New OFDM peak-to-average power reduction scheme

Uplink resource allocation in SC-FDMA wireless networks

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

In mobile communication systems, the received signal power varies due to fading, shadowing and path loss, resulting in the transmission performance degradation. Transmit antenna diversity is a promising technique to improve the transmission performance. For the downlink transmission, the outage probability in a service area can be improved by distributing the transmit antennas over the service area instead of using all of them at the same location (i.e., a base station). This is because the slowly varying local average received signal power due to the shadowing and distance-dependent path losses can be mitigated. In this paper, we evaluate the channel capacity distribution obtainable a distributed antenna system (DAS) using maximal ratio transmission (MRT) diversity. We discuss the effects of the number of antennas, path loss exponent, and shadowing loss standard deviation on the distribution of channel capacity. Keywords-Maximal ratio transmission, distributed antenna systems, channel capacity

A Study on Channel Capacity of Distributed Antenna System Using Maximal Ratio Transmission

In this paper, we propose a joint transmit/receive frequency-domain equalization (FDE) based on minimum mean square error (MMSE) criterion for multi-input multi-output (MIMO) analog network coding (ANC) in single-carrier (SC) bi-directional relay communications. In the proposed scheme, the relay station (RS) equipped with multiple antennas carries out antenna diversity and one-tap transmit FDE, and the base station (BS) and mobile terminal (MT) receivers, both equipped with single antenna, carry out one-tap receive FDE only. The FDE weights at RS, BS and MT are jointly optimized so as to minimize the end-to-end mean square error (MSE). We evaluate, by computer simulations, the bit error rate (BER) performance when using the proposed scheme, and discuss how the transmit FDE at RS operates and affects the BER performance.

https://www.mobile.ecei.tohoku.ac.jp/paper/pdf/rcs_2012/10_rcs_2012_miyazaki.pdf

Joint Transmit/Receive MMSE-FDE for MIMO Analog Network Coding in Single-Carrier Bi-Directional Relay Communications

Single-carrier (SC) transmission using frequency-domain space-time block coded joint transmit/receive diversity (FD-STBC-JTRD) combined with transmit frequency-domain equalization (FDE) obtains full spatial diversity gain and frequency diversity gain. Channel state information (CSI) is required only at transmitter for transmit FDE. In our previous study of SC FD-STBC-JTRD, single transmit FDE weight matrix was used. In this paper, noting that a sequence of data blocks is STBC encoded into a code-word composed of a new sequence of coded data blocks, we derive the optimal transmit FDE weight design. Multiple transmit FDE weight matrices, each associated with each coded block in a STBC code-word, are used unlike our previous transmit FDE weight design. Transmit FDE weight matrices are jointly optimized based on the minimization of the mean square error (MSE) between the transmitted signal before STBC encoding and the received signal after STBC decoding. We show by theoretical analysis that the optimal transmit FDE weight design can achieve 1/RSTBC times higher signal-to-interference plus noise power ratio (SINR) than our previous design (single transmit FDE weight matrix), where RSTBC denotes the STBC coding rate. And then, we show, by computer simulation, the optimal transmit FDE weight design achieves better bit error rate (BER) performance than our previous design.

Transmit FDE weight design for single-carrier space-time block coded joint transmit/receive diversity

SUMMARY 2-time slot cooperative relay can be used to increase the cell-edge throughput. Adaptive data modulation further improves the throughput. In this paper, we introduce adaptive modulation to singlecarrier (SC) cooperative decode-and-forward (DF) relay. The best modulation combination for mobile-terminal (MT)-relay station (RS) and RS-base station (BS) links is determined for the given local average signal-to-noise power ratios (SNRs) of MT-BS, MT-RS and RS-BS links. According to the modulation combination, the ratio of time slot length of the MT-RS link (first time slot) and the RS-BS link (second time slot) is changed. It is shown by computer simulation that the use of adaptive modulation can achieve higher throughput than fixed modulation and reduces by about 9 dB the required normalized total transmit SNR for a 10%-outage throughput of 0.8 bps/Hz compared to direct transmission.

https://www.mobile.ecei.tohoku.ac.jp/paper/pdf/inter_2011/14_in_2011_kazuhiro.pdf

Signal-Carrier Cooperative DF Relay Using Adaptive Modulation

Broadband data services are demanded even under high mobility environment, such as high-speed railway. In this paper, we consider single-carrier (SC) linearly distributed antenna network (DAN). The distributed antenna-mobile terminal (MT) link will be a line-of-sight link and therefore, fading can be characterized as the frequency-selective Nakagami-Rice fading. Distributed antenna diversity using single frequency network (SFN) can mitigate the impacts of path and shadowing losses as well as the frequency-selective fading. In this paper, frequency-domain space-time block coded-joint transmit/receive diversity (FD-STBC-JTRD) is employed as SFN linearly distributed antenna diversity. It is confirmed by computer simulation that FD-STBC-JTRD is a powerful diversity to improve the transmission performance under a high mobility environment.

Hiroyuki Miyazaki

Papers

Cooperative Distributed Antenna Transmission for 5G Mobile Communications Network

Joint Transmit/Receive MMSE-FDE for MIMO Analog Network Coding in Single-Carrier Bi-Directional Relay Communications

Transmit FDE weight design for single-carrier space-time block coded joint transmit/receive diversity

Signal-Carrier Cooperative DF Relay Using Adaptive Modulation

Linearly distributed antenna diversity using single frequency network for high-speed railway communications