Comparative Performance Evaluation of Voice Coding Schemes in Bandwidth-Constrained VoIP Networks

In Voice over Internet Protocol (VoIP) networks,bandwidth consumption depends on the coding scheme orencoding algorithm used. The lower the coder/decoder(CODEC) bit rate, the less bandwidth is required fortransmission, leading to a more efficient system. On the otherhand, the higher the bit rate of the encoded bit stream, thehigher the voice quality but at a higher cost. That is, morebandwidth or transmission capacity is required. However, thegreater the savings in transmission data rate (that is, lower bitrate), the worse the perceived quality as a result of the longertime it takes to encode the voice samples. Hence, a trade-off isnecessary to satisfy the demands of a particular application.This paper presents the performance evaluation comparison ofthe G.۷۱۱, G.۷۲۶ and G.۷۲۹ coding schemes in an optimizedquality of service (QoS)-based packet scheduling algorithm forbandwidth-constrained VoIP networks. The design of anoptimized packet scheduling model as well as an analyticalappraisal of the developed model were carried out. Riverbed(formally OPNET) Modeler version ۱۷.۵ was used to simulatethe developed model. Simulation results for CODEC end-to-enddelay performance gave ۳۴.۱۹%, ۳۳.۸۶% and ۳۱.۹۴%respectively for G.۷۱۱, G.۷۲۶ and G.۷۲۹. Packet loss probabilityperformance gave ۶۰%, ۳۳.۳۳% and ۶.۶۷% respectively.Resource utilization performance gave ۴۴.۴۴%, ۳۷.۰۴% and۱۸.۵۲% respectively. The results obtained show that the G.۷۲۹coding scheme, which has the lowest bit rate offers the bestperformance and therefore guarantees better network QoSperformance. This fact validates the optimal performance of theproposed QoS-based model in bandwidth-constrained VoIPnetworks.

Keywords:

coder , decoder , performance , evaluation , delay , packet-loss , resource , utilization