Kazuhiko Mitsuyama

Development of MMSE Macro-Diversity Receiver with Delay Difference Correction Technique

We have been developing a minimum mean square error macro-diversity (MMSE-MD) reception system using distributed remote antennas and radio-on-fiber (RoF) links for use in live broadcasts of road races. For the system to be feasible, we have to consider the propagation delay differences among diversity branches due to RoF links and radio propagation. This paper describes a hardware implementation of an MMSE-MD receiver embodying our delay difference correction (DDC) technique and indoor and outdoor performance evaluations. Our prototype receiver perfectly corrected the propagation delay difference among diversity branches in less than 11 symbols duration in a time-varying multipath fading environment, and it was capable of the MD reception without outage on an actual road race course.

Performance evaluation of iterative LDPC-coded MIMO OFDM system with time interleaving in mobile line-of-sight environments

Iterative low-density parity-check (LDPC) coded multiple-input multiple-output (MIMO) systems are known to be able to theoretically achieve excellent performance by computer simulation. If the systems can exploit time interleaving long enough to cover a fading cycle, excellent error rate performance should be obtained in mobile line-of-sight (LOS) environments. This paper describes an iterative LDPC minimum mean square error with soft interference cancellation (LDPC-MMSE-SIC) receiver with a time de-interleaver before the MMSE detector and evaluates it using channel state information (CSI) acquired in outdoor measurements. We show that the iterative receiver with time interleaving improves the error rate performance significantly in mobile LOS environments and outperforms an LDPC maximum likelihood detection (LDPC-MLD) receiver with the same error correction and interleaving.

Practical delay difference correction in distributed MIMO OFDM systems

We developed a practical delay difference correction (DDC) technique and confirmed that it could perfectly compensate for large delay differences due to the RoF link. Furthermore, we showed by a computer simulation of road race relay broadcasting that D-MIMO with DDC can achieve better coverage performance than C-MIMO due to low spatial correlation and good average received CNR.

Prototyping and performance evaluation of TDD-based 2×2 MIMO-OFDM transceiver

We have been developing a new wireless link that enables quick transmission of file-based video resources for news programmes. Since the transmission distance we assume ranges widely from less than 1 km to as far as 50 km, it is necessary to have efficient transmission timing control in duplex communication based on TDD. In order to enhance the transmission capacity in line-of-sight environments, it is useful to introduce a MIMO technique that exploits dual-polarized antennas and a multilevel modulation scheme such as 128 QAM and 256 QAM. In this paper, we describe the prototype TDD-based 2×2 MIMO-OFDM transceiver and its performance evaluation in wired and radio transmission experiments.

Performance of a 2×2 STTC-MIMO-OFDM in 800-MHz-band urban mobile environment

A 64-state 16-QAM space-time trellis code (STTC), which uses two transmitting antennas, is proposed and applied to a 2×2 MIMO-OFDM system for outdoor mobile transmission in the 800-MHz band. Although STTCs have been analyzed theoretically and the error performances have been simulated by many researchers, experimental results have rarely been reported. Therefore, we evaluated the performance of our 2×2 STTC-MIMO-OFDM in both a simulation and experiment in the 800-MHz-band urban mobile environment. As a result, excellent bit error rate (BER) performance obtained in the simulation was verified by the experiment.

PCI reduction method suitable for type-II HARQ with SR-ARQ

Hybrid automatic repeat request (HARQ) can make efficient and reliable transmission possible for radio communications. However, in the HARQ scheme, packet control information (PCI), such as HARQ block identifiers (HARQ block ids) in selective repeat ARQ (SR-ARQ), are required and the reduction of PCI overhead is an issue. In particular, type-II HARQ handles a large amount of PCI because it includes the HARQ block ids and sub-block ids. The sub-block id identifies the set of parity bits in the HARQ block of the corresponding sub-block, and is used to combine the sub-blocks. This report proposes a method of PCI reduction suitable for type-II HARQ with SR-ARQ. The method can inform the HARQ block id and sub-block id of each HARQ block by sending only the information on how many HARQ blocks are contained in each 1st, 2nd, 3rd, and 4th transmission group. The estimated size of reduced PCI and simulation results of our TDD communication system confirms that the proposed method greatly reduces PCI and improves data throughput compared to a conventional method.

Hardware Implementation of Proposed Antenna Selection Algorithm and Its Performance Evaluation Using Received Signals in Field Experiment

Multiple-input multiple-output (MIMO) systems with antenna selection are practical ones that can intuitively alleviate the computational complexity at the receiver and achieve good reception performance. Channel correlation, not just carrier-to-noise ratio (CNR), has a great impact on the reception performance in MIMO channels. We propose a simple antenna selection algorithm that exploits the condition number of the channel matrix and a predetermined threshold CNR. This paper describes the hardware implementation of the proposed algorithm and its performance evaluation, which was conducted in an indoor measurement using received signals obtained in the actual mobile outdoor experiment. The results confirm that our proposed method provides good bit error rate performance by setting a threshold CNR properly.

Development and Performance Evaluation of MMSE MacroDiversity Reception System With Delay Difference Correction

We have been developing a minimum-mean-square-error macrodiversity (MMSE-MD) reception system using distributed remote antennas and radio-on-fiber (RoF) links for use in live broadcasts of road races. The system selects remote antennas with good signal quality and combines their signals based on the MMSE algorithm to combat both small-scale and large-scale fading. For the system to be feasible, we have to consider propagation delay differences among diversity branches due to the RoF links and radio propagation. This paper describes a practical delay difference correction (DDC) technique that can keep signal continuity in any situation, the hardware implementation of an MMSE-MD receiver embodying the technique, and indoor and outdoor performance evaluations. Our prototype receiver perfectly corrected the propagation delay differences among diversity branches without losing signal continuity and maintained MD reception without signal outage across a wide area on an actual road-race course.