Survey of VOIP-based Technology and Suggestions for Improvements

Abstract

VoIP over WLAN is poised to become an important Internet application. However, there are two major technical problems that stand in the way. These are low VoIP capacity in WLAN and unacceptable VoIP performance in the presence of coexisting traffic from other applications. In this paper we review literature [11] (Ganguly, 2006), containing ways of improving VoIP performance. One method of improving VoIP performance is giving higher priority to VoIP packets at the Access Point when there is a mixture of TCP and VoIP packets. Another method is multiplexing packets from several VoIP streams. This helps increase the amount of data sent by reducing the number of packets as there is an overhead associated with each packet. Reducing the number of packets would allow more data to be transmitted. The jitter buffer repeats old packets to prevent reduced quality due to delayed packets. Algorithms can be applied to reject packets which have been delayed too long to prevent the jitter buffer from growing too long at the access point. The sampling rate of the voice analog message can be adjusted to prevent too many packets from being transmitted and still keep the VoIP signal quality high. The number of hops (Comeras, 2007) is studied [6] to find the optimal number of hops without saturation of bandwidth. End-to-end model is simulated [7] with different parameters, like packet size, to find an optimal set of parameters. Interference to VoIP devices from blue-tooth devices is investigated [8]. When multiple devices send packets through a media, collisions occur. When a collision occurs, the devices have a back-off period. ii Random back-off period is investigated [11] to increase capacity. When VoIP devices leave one