Correlation Module Implementation and Codec-Switching Module Evaluation in Multipath VoIP Routing

Fall 2009

Jia Guo
Hyong Kim
Project description

The project is related to Multipath Routing, where multiple real-time streams are simultaneously sent via different IP routes to a receiving node. We try to achieve two main goals:

  1. Correlation Module Implementation

The correlation module is designed for a multipath routing system to avoid using IP routes that share common physical devices. It chooses the most "physical-layer topologically disjoint" paths, rather than the default IP-layer ones that can be failure-correlated. To realize this path selection, we refer to the paths' delay and jitter history, in order to decide which paths are failure-independent. The module then uses these paths to route multiple voice streams, aiming at eliminating future failure-correlation as much as possible.

The task in this module is to implement a distributed version of correlation-detection scheme based on "Dynamic Time Warping" technique. After the implementation, we plan to evaluate further the technique of the scheme and improve it if necessary.

2 Codec-Switching module Evaluation

To get the better voice quality, VoIP application needs to vary codecs when it detects network-condition change. The goal in this task is to find the most effective combination of codecs for each network condition. Specifically, multiple voice streams are transmitted simultaneously to a receiving node via different relaying nodes. We emulate dynamic network conditions by controlling queuing delays and packet-drop rates at relaying nodes. For each network condition, performances of all combinations of codecs are evaluated by using PESQ technique and recorded for further investigation. After obtaining the performances, we plan to determine when VoIP applications need to switch codecs and which combinations of codecs should be selected.

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