Voice over IP in networked virtual elements
- J. Liesenborgs
- Ph.D dissertation, University of Maastricht,
Voice over IP (VoIP) is transporting speech signals over IP network. What makes VoIP challenging is IP network is not designed to serve for real time applications. Real-time aspects of the conversation must be respected; the overall delay between both ends of the conversation should be low to avoid irritably long gaps of silence. This of course should be addressed differently than the broadcast programs where it is not interactive and desire less stringent requirement. VoIP is an alternative to telephony network and could be seen as a replacement technology. A computer network may replace telephony network by installing VoIP system and the only connection to the telephony network might be a gateway that does address translation from IP to phone number or vice versa. The real benefit arises when considered capacity since the capacity of a computer network could be utilized better and bandwidth is cheap compared to telephony network. Long distance calls could be possible along with certain applications like whiteboarding, application sharing, file transfer, video image . Conversation within the LAN is possible without effort but across the LAN when the WAN is involved delay matters. End to end delay is important and when it gets too large, the conversation experience distortion. This could happen due to the heavily loaded roads and lost packets during the routing inside the WAN. Also, a high percentage of packet loss will decrease the quality of the conservation. Moreover, there is a difference in the delay of the packet arrivals to the receivers due to the variations in the congestion level of the network over time. The rest of the report is as follows: Section II explains the components of the VoIP communication. Section II-A gives compression techniques that are currently available for VoIP applications. Section III shows the range of delay in each part of the voice communication. Section IV gives the basics of IEEE 802.11a and 802.11e. Section V explains a new protocol called HEARW¡P that can increase the delay characteristics of VoIP applications in WLANs. Section VI gives the implementation results of HEARW¡P . Section VII concludes the report.