Yoshikazu Kakura

Likelihood Function for QRM-MLD Suitable for Soft-Decision Turbo Decoding and Its Performance for OFCDM MIMO Multiplexing in Multipath Fading Channel

This paper proposes likelihood function generation of complexity-reduced Maximum Likelihood Detection with QR Decomposition and M-algorithm (QRM-MLD) suitable for soft-decision Turbo decoding and investigates the throughput performance using QRM-MLD with the proposed likelihood function in multipath Rayleigh fading channels for Orthogonal Frequency and Code Division Multiplexing (OFCDM) multiple-input multiple-output (MIMO) multiplexing. Simulation results show that by using the proposed likelihood function generation scheme for soft-decision Turbo decoding following QRM-MLD in 4-by-4 MIMO multiplexing, the required average received signal energy per bit-to-noise power spectrum density ratio (E b /N 0 ) at the average block error rate (BLER) of 10 -2 at a 1-Gbps data rate is significantly reduced compared to that using hard-decision decoding in OFCDM access with 16 QAM modulation, the coding rate of 8/9, and 8-code multiplexing with a spreading factor of 8 assuming a 100-MHz bandwidth. Furthermore, we show that by employing QRM-MLD associated with soft-decision Turbo decoding for 4-by-4 MIMO multiplexing, the throughput values of 500 Mbps and 1 Gbps are achieved at the average received E b /N 0 of approximately 4.5 and 9.3 dB by QPSK with the coding rate of R= 8/9 and 16QAM with R = 8/9, respectively, for OFCDM access assuming a 100-MHz bandwidth in a twelve-path Rayleigh fading channel.

Likelihood function for QRM-MLD suitable for soft-decision turbo decoding and its performance for OFCDM MIMO multiplexing in multipath fading channel

This paper proposes likelihood function generation of complexity-reduced maximum likelihood detection with QR decomposition and M-algorithm (QRM-MLD) suitable for soft-decision turbo decoding and investigates the throughput performance using QRM-MLD with the proposed likelihood function in multipath Rayleigh fading channels for orthogonal frequency and code division multiplexing (OFCDM) with multiple-input multiple-output (MIMO) multiplexing. Simulation results show that by using the proposed likelihood function generation scheme for soft-decision turbo decoding following QRM-MLD in 4-by-4 MIMO multiplexing, the required average received signal energy per bit-to-noise power spectrum density ratio (E/sub b//N/sub o/) at the average block error rate (BLER) of 10/sup -2/ at a 1-Gbps data rate is significantly reduced compared to that using hard-decision decoding in OFCDM access with 16 QAM modulation, the coding rate of 8/9, and 8-code multiplexing with a spreading factor of 8 assuming a 100-MHz bandwidth. Furthermore, we show that by employing QRM-MLD associated with soft-decision turbo decoding for 4-by-4 MIMO multiplexing, the throughput values of 500 Mbps and 1 Gbps are achieved at the average received E/sub b//N/sub o/ of approximately 4.5 and 9.3 dB by QPSK with the coding rate of R = 8/9 and 16 QAM with R = 8/9, respectively, for OFCDM access assuming a 100-MHz bandwidth in a twelve-path Rayleigh fading channel.

Performance comparison of MF and MMSE combined iterative soft interference canceller and V-BLAST technique in MIMO/OFDM systems

This paper proposes a complexity reduced iterative soft interference canceller (ISIC) to realize broadband mobile transmission in MIMO/OFDM systems and compares its performance with the V-BLAST technique. In the proposed scheme, we apply a minimum mean square error (MMSE) filter only in the first iteration and utilize a matched filter (MF) in the second and later iterations to reduce computational complexity by suppressing residual interference in the first iteration. Computer simulation results confirm that the proposed ISIC can achieve almost equal performance to the MMSE-based ISIC with multiplications reduced by 85 % and outperforms the V-BLAST receiver by about 2 dB in four transmit and receive antennas systems under exponentially distributed twelve path conditions.

Performance analysis of low complexity multi-user MIMO scheduling schemes for massive MIMO system

Massive MIMO is a promising technology for the 5G mobile communications system and contributes to the enhancement of multi-user MIMO transmission. However, the user scheduling of multi-user MIMO transmission requires a high computational complexity because the matrix operation is performed to estimate SINR, which is used as a user selection criterion. In this paper, we investigate low complexity multi-user MIMO scheduling schemes that estimate the SINR without the matrix operation. The schemes are the polynomial approximation scheme, which approximately estimates the SINR by channel correlation between users, and the single-user based scheme, which uses the SINR of single-user transmission instead of the SINR of multi-user MIMO transmission. Simulation results show that the complexity of the polynomial approximation scheme is reduced to a few tenths of that of the matrix operation based scheme without throughput degradation. It is also shown that the complexity of the single-user based scheme is reduced to a few thousandths of that of the matrix operation based scheme with little throughput degradation as the number of spatially multiplexed users increases.

Seamless networked mobile computing realized by wireless Internet access

This paper gives a solution for a seamless network platform which brings flexible network connectivity into the mobile computing world. Areas being studied include future communication architecture, IP mobility support, flexible accessible radio with low power RF devices, programmable modems and software oriented MAC technologies. We discuss how to harmonize network-layer mobility and the wireless network to realize the seamless network, and especially in the radio modem we point out the key elements required in the adaptable modem, in order for flexible access to different wireless infrastructures. The practical mobile host architecture and the developed mobile computing network system are also described.

Reduced complexity maximum likelihood estimator for high speed wireless access-TCS-MLSCE

This paper proposes a received signal estimator with excellent compensation capability against multipath distortion, referred to the estimator as tap coefficient shift maximum likelihood symbol candidate estimator (TCS-MLSCE). The estimator adopts symbol-by-symbol maximum likelihood criterion based on both symbol candidates and decision feedback data for pre- and post-cursor estimates, respectively. It is shown that the structure can dramatically reduce the hardware size and the amount of calculation, compared to those of maximum likelihood sequence type estimators. By introducing a tap coefficient shift algorithm, the estimator improves the performance, especially in a case of a non-minimum phase. In the simulation, the degradation against DDFSE ranges less than 2.5 dB of E/sub b//E/sub 0/.