RTI2

Real-time Interaction over the Internet

Christophe Salzmann, Denis Gillet


Overview

Remote experimentation is an effective e-learning paradigm for supporting hands-on education using laboratory equipment at distance. The current trend is to enable remote experimentation in mobile and ubiquitous learning. While the current Internet bandwidth allows remote experimentation to work flawlessly on fixed connections such as LANs, mobile users suffer from both the versatile nature of wireless communications and the limitation of the mobile access devices. These conditions impose that the remote experimentation software should integrate adaptation features.
For effective remote experimentation, it should ideally be guarantee that the information representing the state of the remote equipment is rendered (to the end user) at the same pace at which it has been acquired, yet possibly at the cost of a minimal time delay between the acquisition and rendering phases. In this respect, an end-to-end adaptation scheme is proposed that explicitly handles the inherent variability of the connection and the versatility of the mobile devices considered in remote experimentation. Instead of relying on a stochastic approach, the proposed adaptation scheme relies on a deterministic mass-balance like model.

Keywords : Interaction ; end-to-end adaptation ; network ; remote experimentation

 

Real-Time Interaction over the Internet

/webdav/site/la/shared/import/migration/RTI2/RTI2_300.jpgObjectives

• Provide the user with the best possible experience
– defined by the RTI2 QoS

• Context: remote experimentation of mechatronic systems
– challenging systems: fast dynamics, rich visual content, intrinsic dynamics in the order of magnitude of the information transmission time

• Contrains: ubiquitous, adaptable
/webdav/site/la/shared/import/migration/Servo_300.jpg RTI2 is a new Internet Service

• We consider the E2E system at the application level
– this is different than E2E network level
– client and server applications are also considered
– required since the client component can be the bottlenck

• We propose a solution that is fair, ubiquitous and adaptable
– compatible with the Internet best practices (TCP friendly)
– transmission protcols independance (TCP, UDP, etc)
– infrastructures independence
– adapt in real-time to the E2E characteristics variations
– no reservation mechanism involved
– the sementic information can be represented with a few bytes to hundreds of kBytes

• We control the round trip time of the information (block)
– we can guaranty the level of interaction
– we can ensure that the equivalent E2E buffer stays empty
– we can compensate/reconstruct missing information

• Current technologies
– Video streaming: use buffers to smooth playback
– Video conferencing: symetrical transmission, sound emphasis
– Channel with guaranties QoS: require specific infrastructure/software /webdav/site/la/shared/import/migration/block_300.jpg
QoS

• The level of interaction: how quickly feedback is provided to the user
• The dynamics perception: how accurately in time the behavior of the remote system is perceived
• The semantic content: how well the distant system state and conditions of operation can be perceived by the client

Abstractions

• E2E infrastructure at the application level
• Streams of information aggregated in Blocks

Metrics

• d: E2E round trip time at the application level
• τ (timeliness) and ε (integrity): characterize the capacity of E2E structure to handle the current block /webdav/site/la/shared/import/migration/adapt_300.jpg

Adaptation

• Track the block round trip time d at the application level
• Modify the block size and/or pace to follow a d ref
• Real-time model estimation (bandwidth and propagation delay)

/webdav/site/la/shared/import/migration/Meas_300.jpgExemple

• Desktop computer <-> Palm T3
• Bluetooth transmission using TCP
• Track round trip time d at the application level
• reference round trip time 200 ms

At some point the user move away from the BT access point
– the block round trip time increase
– the controller reduce the block size S

See a 30 sec QuickTime movie(1.7 MB)