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Author:Kilappa, Tatu
Title:Determining audio buffer size from LAN-WLAN vertical handover delay
Publication type:Master's thesis
Publication year:2010
Pages:v + 77 s. + liitt. 11      Language:   eng
Department/School:Informaatio- ja luonnontieteiden tiedekunta
Main subject:Ohjelmistotekniikka   (T-106)
Supervisor:Soisalon-Soininen, Eljas
Instructor:Ranta, Mervi
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto     | Archive
Keywords:vertical handover
real-time audio
HIP
TCP
network delay
Abstract (eng): When playing audio over the network in a mobile environment, any interruptions in the network connectivity may cause undesired breaks in audio playback.
To circumvent this, networked audio players have buffers that are filled when possible, and wherefrom the audio is played.

This thesis examines the real delay in the network caused by uninformed LAN to WLAN handovers.
In particular, the focus is on the effect of the duration of these handovers to the required audio buffer size for real-time network audio playback.
The handover is initiated by disconnecting the LAN cable, through which the connection is being routed, forcing a switch to wireless LAN.

The test application for making the measurements is the PM&RG Ämppäri mobile music player, that which is capable of playing music directly over the network.
The mobility management platform that allows transferring the existing TCP connections to a new interface is hip4bsd implemented by Ericsson.
Both of these solutions were designed and implemented during the MERCoNe project, although their earlier versions date to previous VHO and GO projects.
The measurements and analysis were made during on the WISEciti project.

The measurements reveal that in this setting, the delay effect caused by the vertical handover requires the playing application to have playback buffer size of up to 3.4 seconds of uncompressed audio.
The reaction time from the 1mk down event of cable disconnection to a successful handover in the mobility management system extended up to 1.5 seconds, and is the largest single factor in the delay.

The experiment was done using a laptop streaming media to a desktop computer in a network with no other traffic or error factors.
The experimentation setting was carefully planned to be reliable and reproducible.
Thus, the experimentation plan can be applied to examine vertical handover delays among other types of access networks.
ED:2010-04-15
INSSI record number: 39478
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