Tsuguo Maru

A turbo decoder for high speed downlink packet access

The paper presents a new turbo decoder architecture, which uses an algebraic object known as a semi-ring, for high speed downlink packet access (HSDPA) in W-CDMA systems. By speeding up the state metric recursive operations in the BCJR algorithm with the help of semi-ring matrix algebra, this turbo decoder architecture can improve latency and throughput of about 10 Mbps, which cannot be achieved even with high-speed pipelined architectures. An implementation of the proposed architecture using ordinary commercially available FPGA demonstrates the reduced latency of the turbo decoder equivalent to the target throughput of 10 Mbps on 48 MHz clock frequency with 8 iterations without performance degradation, enabling efficient HSDPA data services.

Line-of-Sight MIMO Transmission for Achieving High Capacity Fixed Point Microwave Radio Systems

Despite the lack of rich scattering which is necessary for MIMO systems in mobile environments, this paper proposes line-of-sight MIMO systems with the highest MIMO capacity in some tens of GHz microwave radios. The proposed scheme constructs spatially orthogonal MIMO channels by using geometric arrangement of antennas and can use individual local oscillator signals without feedback signals for a transmit matrix. It can also compensate for the fluctuation of the carrier phase caused by the geometric small shift of the antenna position.

Single Carrier Radio Access with an Equivalent Transmission Speed of 256-QAM

In this paper, we propose an evolved partial response scheme capable of 256-QAM single carrier radio access. Rather than using such high order modulations as 64-QAM or 256-QAM, we employ aggregations of low order modulation signals whose transmission speeds are beyond the Nyquist rate. To detect these modulation signals, we use a semi-ring structure and reduced state methods in order to exploit the turbo principle, and this makes it possible to achieve high speed processing and low complexity. Simulation results show that, at the same coding and bit rates, the proposed method performs better than do high order modulations over AWGN and multi-path radio channels. Further, by employing opportunistic scheduling transmission, the proposed method is able to achieve improved FER performance. It does this by exploiting a property which turns a severe multipath fading condition into a performance benefit for a channel, making possible a better single carrier radio access scheme.