Shinsuke Ogawa

Mobile Terminals toward LTE and Requirements on Device Technologies

This paper overviews the universal mobile telecommunications system long term evolution (LTE) and discusses the requirements for device technologies pertaining to mobile terminals. The LTE represents the next generation cellular phone technology that is intended to achieve a high peak data rate, low latency, and high radio efficiency in addition to low cost and sufficiently high mobility characteristics. Vigorous discussion regarding the specifications for LTE is currently ongoing in the 3rd generation partnership project. This paper also introduces various device technologies that support current mobile terminals.

Experiments on HSDPA Throughput Performance in W-CDMA Systems

In this paper, we present laboratory and field experimental results using High Speed Downlink Packet Access (HSDPA) test-beds in order to reveal the actual HSDPA performance based on key technologies such as base station (BS) scheduling, adaptive modulation and coding, hybrid automatic repeat request, and advanced receiver design. First, this paper evaluates the effects of advanced user equipment capabilities such as the maximum number of multi-codes, transmit diversity, receive diversity, and a chip equalizer. Increases in throughput of 60% and 85% due to using 10 and 15 codes were observed compared to 5 codes, respectively. The gain of 22% was obtained by applying closed-loop transmit diversity to the HSDPA network. Receive diversity improves the throughput in the region from low to high signal-to-interference ratio, and the gain of 45% was obtained by applying receive diversity to the conventional RAKE receiver. A throughput gain of approximately 17% due to the use of the chip equalizer was obtained and it was observed mainly in the high Ior/Ioc region and under multi-path conditions. Second, field experiments are conducted to elucidate the effects of multi-user diversity using a BS scheduling algorithm, and reveal that proportional fairness scheduling provides both the increase in sector throughput of 18% and a sufficient degree of fairness among users. The transmit control protocol (TCP)-level throughput performance is also investigated in order to reveal the actual end-user throughput. The results show that the throughput rate of approximately 90% of the throughput of the MAC-hs layer is achieved in the TCP layer in the laboratory experiments and in the field experiments.

W-CDMA experimental system testbed

NTT DoCoMo undertook the research and development of wideband-code division multiple access (W-CDMA) as the radio access method for IMT-2000 (International Mobile Telecommunications-2000), the next generation mobile communications system that aims to establish global, high quality, multimedia and personal communications. NTT DoCoMo has been very active in conducting system experiments on not only radio transmission functions, but also on various control functions and hard-wired transmission between nodes. This article describes the essential results of the system experiments.

W-CDMA system experiments

This paper describes wide-band code division multiple access (W-CDMA) mobile communication system experiments. The W-CDMA supports voice and multimedia communication, multiple access control, and diversity hand-over (DHO) control. This paper outlines the W-CDMA experimental system, and presents the measurement result of delay profile, fast cell search time, frame error rate performance, transmission power characteristics, DHO characteristics, and system capacity.

Field Experiment Results of User Throughput Performance in WCDMA HSDPA

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