Riichiro Nagareda

OFDM mobile packet transmission system with multiuser detection and metric combining ARQ

This paper proposes an OFDM mobile packet transmission scheme that employs both non-linear multiuser detection (MUD) and automatic repeat request (ARQ) with metric combining for improving throughput performance. The scheme identifies users by detecting user identification (ID) symbols located at the head of a packet, and can separate the packets by MUD when the packets collide. Furthermore, it forces the respective transmitters to retransmit the same packets so as to reproduce the collision if the cyclic redundancy check (CRC) detects some errors, and employs metric combining for decreasing the number of retransmissions. In order to verify the throughput performance, computer simulations are conducted. The simulation results show that the proposed scheme can achieve much greater throughput than the conventional ones.

Implementation and Evaluation of 4×4 MIMO Fading Simulator Considering Antenna Characteristics

A 4 times 4 MIMO fading simulator (MIMO-FS) was constructed for the development of MIMO products. This MIMO-FS consists of multi-port up/down converters for 2.4/5.2GHz bands and baseband reconfigurable digital signal processors which allows the implementation of various MIMO channel models. In this paper, extended IEEE802.11n channel model including antenna characteristics and its hardware implementation are given as well as the system evaluation results.

An MMSE based calibration of LINC transmitter

This paper proposes a new correction technique for the LInear amplification with Nonlinear Components (LINC) transmitters. The technique, which is based on the minimum mean squared error (MMSE) criterion, estimates the gain and phase imbalance between the two amplifier branches. With information on the estimation, the imbalance is compensated by controlling the amplitude and phase of the input signal that is fed into one of the two amplifiers. Computer simulations with the QPSK modulation demonstrate that this method can calibrate the balance and sufficiently suppress the out-of-band distortion spectra.

Efficient OFDM mobile radio packet system employing LLR combining multiuser detection for ARQ with adaptive modulation and coding scheme

This paper proposes an OFDM mobile radio packet system that employs a new protocol of automatic repeat request (ARQ) for nonlinear multiuser detection (MUD) with log likelihood ratio combining (LC) on the appropriate bits. The conventional metric combining (MC) MUD separates collided packets by using nonlinear MUD, accumulates the Euclidian distance metrics of the received subcarrier symbols in the packets, and then achieves throughput improvement. However, when MC-MUD detects a packet error, it makes user terminals retransmit the same packets so as to reproduce the collision of the same packets. The proposed LC-MUD scheme simplifies the ARQ protocol and requires no reproduction of the same packet collision. The computer simulations demonstrate the superior throughput of LC-MUD to that of MC-MUD, and further improvement due to adaptive modulation and coding (AMC) optimized for the nonlinear MUD in LC-MUD.

OFDM Mobile Packet Transmission System with Multiuser Detection and Metric Combining ARQ

This paper proposes an OFDM mobile packet transmission scheme that employs both non-linear multiuser detection (MUD) and automatic repeat request (ARQ) with metric combining for improving throughput performance. The scheme identifies users by detecting user identification (ID) symbols located at the head of a packet, and can separate the packets by MUD when the packets collide. Furthermore, it forces the respective transmitters to retransmit the same packets so as to reproduce the collision if the cyclic redundancy check (CRC) detects some errors, and employs metric combining for decreasing the number of retransmissions. In order to verify the throughput performance, computer simulations are conducted. The simulation results show that the proposed scheme can achieve much greater throughput than the conventional ones.