Koji Horisaki

High-Throughput, Low-Power Software-Defined Radio Using Reconfigurable Processors

A new, low-power software-defined radio baseband supports up to 600 Mbps. Wireless LAN and WiMax are implemented on a dynamically reconfigurable processor thats fully utilized in the baseband operation. Power is estimated at 500 mW in a 40-nm CMOS design. The platform also permits fast runtime switching between multiple wireless standards.

An area-efficient, standard-cell based on-chip NMOS and PMOS performance monitor for process variability compensation

A completely-digital, on-chip performance monitor circuit is newly proposed. In addition to a traditional ring-oscillator, the circuit has a special buffer-line whose output duty ratio is emphasized by the difference in performance between NMOS and PMOS transistor. Thus the performance of NMOS and PMOS transistor can be estimated independently. As the monitor is designed with area-efficient by standard-cells only, it can be used widely. To demonstrate the accuracy of performance estimation and the usability of the monitor, we have fabricated the monitor in 90nm CMOS process. The estimation errors of the drain saturation current of NMOS and PMOS transistors are 2.0% and 3.4%, respectively. We also successfully reduced the output amplitude variation of D/A converter to 50% by the calibration with the estimated results by using the monitor.

A multimodal wireless baseband core using a coarse-grained dynamic reconfigurable processor

Software Defined Ratio (SDR) is indispensable technology when wireless baseband processing has to support a wide variety of wireless communication standards. This paper describes the implementation and software optimization for IEEE 802.16e (Mobile WiMAX) on ADRES, a coarse-grained dynamic reconfigurable processor. The paper also explains switching between 802.11a (WLAN) and 802.16e at runtime. The switching time is 2.6 milliseconds which is shorter than 5.0 milliseconds, 1 frame time period of 802.16e specification.

Feasible criteria of link adaptation for wireless LANs using soft output Viterbi decoder

This work presents a simple data rate choosing method for multi data rate communication systems. This method is based on Viterbi decoding and aims to utilize relative likelihood between selected and unselected paths in the decoding. We confirmed the validity of our proposed method with computer simulations. The physical layer specifications follow the IEEE standard 802.11a, and then an AWGN channel and an ETSI-profile multipath channel are assumed in the simulations. The simulation results show that the proposed method can provide an effective link adaptation for communication systems that equip a Viterbi decoder and support plural data rate.