VoIP Voice and Fax Signal Processing

18

VOICE PACKETS JITTER WITH LARGE DATA PACKETS

VoIP voice calls make use of Internet service. End-to-end packet delivery on an Internet Protocol (IP) network can face impediments. Voice packets are smaller, and data packets can be bigger in byte size. As explained in Chapter 2, VoIP customer premise equipment (CPE) also has a wide area network (WAN) interface and several local area network (LAN) interfaces. The WAN interface is the main outlet on CPE for connectivity to the Internet. As shown in Fig. 18.1(a), the CPE WAN interface is terminated on another main LAN interface of an Internet service modem [e.g., digital subscriber line (DSL) or cable]. As shown in Fig. 18.1(a) and Fig. 18.1(b), the LAN interface and some applications in CPE can send large data packets along with voice. These large packets can introduce delay and delay variations (jitter) to voice packets. The effect of jitter is mainly dominant with limited bandwidth physical interfaces. For completeness of the representations, Fig. 18.1(c) is included that conveys the usage of VoIP CPE with built-in direct WAN connectivity. This direct WAN connectivity could be DSL or cable. In this chapter, a DSL physical interface is considered for creating example calculations with bandwidth limits; however, similar conditions are also applicable with other interfaces. Many residential applications use DSL service. Various options in DSL service exist, which range from 256 kbps to several 100 Mbps of bandwidth support. In the ...