Masami Kato

The effect of segmentation mismatch on quality of continuous media transmission by Bluetooth

This paper examines the effect of segmentation mismatch on audio-video transmission by Bluetooth. We focus on the segmentation mismatch caused by the difference between the RFCOMM maximum frame size and the baseband packet payload size. By experiment, we assessed the maximum throughput and media synchronization quality for various types of ACL packets. In the experiment, a media server transferred stored video and audio streams to a single terminal with point-to-point communication; we supposed no fading environment and added white noise by which interference from DSSS systems is modeled. The experiment showed that the effect of segmentation mismatch is large especially when the total bit rate of the two streams is near the channel transmission rate. We also observed that the media synchronization control is effective in compensating for the disturbance by the segmentation mismatch in noisy environments.

Application-level and user-level QoS assessment of audio-video transmission with EDCA of IEEE 802.11e

This paper studies audio-video transmission in a wireless LAN with the EDCA of the IEEE 802.11e MAC protocol in terms of application-level QoS and user-level QoS (i.e., perceptual QoS). By simulation, we first compare the performance of the EDCA and the legacy IEEE 802.11 DCF in the case where audio, video, and data are transmitted in a common wireless channel. The EDCA supports priority control for multimedia transmission. Numerical results show that the EDCA can improve the audio and video quality of the DCF when data traffic load is heavy. We then study the effects of dynamic video-resolution and media synchronization control on the application-level QoS. Simulation results show that the two kinds of control at the application layer in addition to priority control with the EDCA at the MAC layer is effective in achieving excellent application-level QoS of audio-video transmission. Furthermore, we assess user-level QoS by the method of successive categories, which is one of the psychometric methods

A media synchronization experiment on continuous media transmission in Bluetooth LAN access

This paper assesses the media synchronization quality in a Bluetooth LAN access system by experiment. We consider a situation where a server transfers stored video and audio streams to a terminal with point-to-point communication. Both FEC and ARQ are adopted as error control schemes. The slide control scheme is used for media synchronization control. We examine how the interference from DSSS systems affects the quality. For simplicity of experiment, we suppose that the Bluetooth terminal does not move while the media streams are transferred, i.e., fading does not occur. In the experiment, we evaluated several performance measures such as mean square error of intra-stream synchronization. We then found that delay jitters caused by retransmission of DM1 packets disturbed temporal relations of the streams. We also observed that the media synchronization control is effective in compensating for the disturbance.

Stored media synchronization based on buffer occupancy in PHS

This paper proposes a scheme for synchronization of stored video and audio streams in the Personal Handy phone System (PHS). A video stream of H.263 is transmitted over a PHS channel with ARQ control, while an audio stream of 32 kbit/s ADPCM is sent on another channel without any control. In order to preserve the temporal constraints within the video stream as well as the relationship between the video and audio streams, we adopt a new control scheme which modifies the target output time according to the amount of video data in the receive buffer. Through simulation we assess the characteristics of this scheme in both random and burst error environments and confirm the effectiveness of the scheme.

Experimental assessment of media synchronization quality in IEEE 802.11 b under Bluetooth interference

This paper assesses the media synchronization quality of audio-video transmission over the IEEE 802.11b wireless LAN under Bluetooth interference by experiment. In this situation, the temporal constraints of audio and video may be disturbed, since the Bluetooth interference cause delay jitter due to retransmission and carrier sensing in the MAC layer of IEEE 802.11b. In the experiment, a media server transfers stored video and audio streams to a mobile terminal over an IEEE 802.11b wireless LAN; as radio interference from Bluetooth, two other terminals transmit data over Bluetooth at the same time. We examine the influence of Bluetooth on the audio-video transmission over IEEE 802.11b in terms of the Bluetooth signal level and its data load. We also apply a media synchronization control scheme and confirm its effectiveness.