Sumaru Niida

Fundamental Analysis of Two-layered Scheduling Algorithm for a Wireless Packet System

Third generation mobile communication systems are currently spreading worldwide and the associated high speed data services are being widely utilized by the public at large. As more rapid services are established, the provision of wider band wireless systems is expected in next generation mobile communication systems. Wireless packet technology has recently been attracting considerable attention for its high throughput performance and is required for QoS (quality of service) control, given its applicability for all type of services, non-real time as well as real-time. In this paper, we propose a new packet scheduling algorithm for wireless communication systems. It has a two-layered structure, to guarantee QoS and also high frequency efficiency. We estimated the performance of our proposed algorithm using a computer simulation. The results show that the proposed algorithm can achieve a higher throughput and improved delay performance compared to conventional algorithms, such as maximum CIR, proportional fairness and round robin

A Web Script-Based Method to Evaluate User Satisfaction of Mobile Services in the Field

Providing mobile services that ensure user satisfaction is one of the most crucial issues for telecommunication carriers and service providers. Traditionally, user satisfaction with the service, i.e., the Quality of Experience (QoE), has been assessed in a laboratory. However, a reliable QoE for a target mobile service in the context of actual use cannot be obtained by laboratory experiment. This paper proposes a novel Web script-based method that evaluates user satisfaction for waiting time of mobile services in the field. The proposed method has the following practical advantages. Since experimental conditions, especially communication conditions, can be simulated with a Web script, such as FlashLite, a subjective assessment can be conducted anywhere using the mobile terminal of the participant. Thus, QoE for a target mobile service in the field can easily be obtained. The main contribution of this paper is that we clarified that a subjective assessment system that implements the proposed Web script-based method is suitable for evaluating user satisfaction regarding waiting time where this time ranges from a few hundred milliseconds to a few seconds.

A study on receiver performance of a wideband CDMA testbed system for IMT-2000

We have developed a testbed system for wideband code division multiple access (CDMA). This testbed system is equipped with a 2D-RAKE receiver and transmission power control system based on a signal power to noise power ratio (SIR). We report the receiver performance of the testbed system estimated from results of laboratory experiments. This paper describes the influence of the number of fingers under multipath fading environments. As compared with a single-path receiver, a 4-finger RAKE receiver saves an average transmitted power of around 7 to 8 dB, although deterioration of the preciseness of detection due to the increase of the number of paths debases the performance of the receiver. We also discuss the influence of the parameter of transmission power control on receiver performance. When the TPC step=0.5 dB and the TPC period=0.625 ms, the transmission power of around 0.7 to 1.0 dB can be reduced as compared with the result for the TPC step=1.0 dB and TPC period=1.25 ms.

Wideband CDMA base station with co-channel interference canceller

The authors made a prototype of a wideband CDMA base station equipped with an interference canceller. It also enables real-time connection of voice and high-speed data mobile stations under a call control application. It further implements the high-speed power control and experimental data collection functions.

Implementation and field test result of a base station cancelling CDMA interference for the IMT-2000 air interface

We have developed a cochannel interference canceller-base station (CIC-BS), in compliance with a tentative air interface designed for IMT-2000, and evaluated its performance both in the laboratory and in the field. In laboratory experiments using 5 MSs, where the loading factor is set to around 10 dB, a transmission gain of 8 to 9.5 dB and a receiving gain of 7 dB have been confirmed. In field experiments using 2 MSs, a transmission gain of around 2.5 dB has been confirmed when the loading factor is an estimated 3 dB.

User study of the subjective quality of mobile streaming service

The number of smartphone users has increased markedly in recent years. They enjoy multimedia services, such as video streaming, unconstrained by time and place. However, mobile streaming services require a high throughput, and may have an impact on network capacity. The control of service quality is important from both the perspective of user experience and network quality. However, the quality of a video service has mainly been evaluated by examining the picture quality. It is less common to use a network design viewpoint to evaluate video streaming services. In this paper, we discuss the subjective quality of streaming video on mobile terminals. The main contribution of this paper is to quantitatively show the relation between the overall satisfaction, network quality and picture quality, based on the results of the user study.

Performance of adaptive coding by selection of space-time block code matrix [3G mobile communication]

The 3G mobile communication systems are currently spreading throughout the world and high speed data services on mobile systems such as streaming video, streaming audio and video phone are being widely utilized by the public at large. As higher speed rate services are infiltrated, the provision of wider band wireless systems is expected. MIMO systems, which equip several antennas with both a transmitter and receiver, have recently been attracting much attention. Space-time coding is a technique that exploits transmission diversity and achieves high performance under a fading environment. The space-time block code (STBC) is attracting particular attention for its high performance and decoding simplicity. We propose an adaptive coding scheme using the STBC. It changes the STBC pattern and the modulation symbol according to the receiving condition. In this paper, we discuss this scheme and evaluate its throughput and transmission power performances based on simulation results using ideal propagation environments and measured data in the experiment.