A hierarchical power distribution methodology that enables more than dozen power domains in a chip and a power management scheme using 20 power domains are described. This method can achieve very low leakage current in the partial active mode of a single chip mobile processor. The single chip mobile processor embedded three CPU's that is baseband processor, application processor, and multi-media processor. In the "waiting for calling" mode of the mobile handsets, application processor and multi-media processor part can be power-off. This chip can power off these power domains although the some of baseband parts are actively operating.. Many new techniques for multiple power domains in the chip are described.This paper describes the output of two projects. (1) Fundamental circuits research on hierarchical power domain = joint research by Hitachi, Ltd. and Renesas Technology Corp.[4] (2) LSI design for one chip mobile processor = joint development by NTT DoCoMo Inc. and Renesas Technology Corp.[5].

High-speed downlink packet access (HSDPA) is specified in the 3rd generation partnership project (3GPP) to cope with the increasing demand for high-speed Internet-based multimedia services. This paper presents field experimental results of the user throughput performance in HSDPA to clarify the effects of the maximum number of multi-codes, transmit diversity, and advanced user equipment (UE) such as receive diversity and a chip equalizer. The field experimental results show that 15-multi-code UE, transmit diversity, and receive diversity achieve the peak throughput of 6.5, 8.5, and 10.2 Mbps, respectively, at the average moving speed of 30 km/h in an actual multi-path fading propagation channel, and the average received signal-to-interference power ratio (SIR) is 24 dB. Furthermore, the results show that transmit diversity, receive diversity, and the chip equalizer can improve the average throughput to 27.0%, 54.6%, and 12.8%, respectively, compared to the conventional single antenna Rake receiver when the average received SIR is 16.3 dB.

This paper estimates the cell capacity of a cellular DS-CDMA mobile radio system that uses coherent detection, RAKE, diversity and forward error correction (FEC). Coherent detection reduces the required E/sub b//N/sub 0/ (bit energy to noise density power ratio). The performance of two coherent detection schemes and differential detection is compared. One of the coherent detection method uses the pilot symbols transmitted through another channel via a different spreading code, and the other uses the pilot symbols embedded periodically in the same channel as the data symbols. This paper shows that coherent detection offers a 50% higher capacity than differential detection, furthermore, by employing diversity, the cell capacity is doubled from that of 1 branch, and by RAKE combining, a 10% higher cell capacity can be achieved.

A time diversity automatic repeat-request (ARQ) scheme with a finite number of transmissions is investigated for a digital FM mobile radio with frequency demodulation (FD). It processes all the retransmissions of a single data block using postdetection diversity combining. The analysis of the signal energy per bit required for a given bit error rate (BER) and the spectral efficiency in a cellular mobile radio system are presented. The results obtained from the numerical calculations show that this ARQ scheme offers a performance superior to both the basic ARQ scheme and the time-diversity scheme.>