VoIP Voice and Fax Signal Processing

19.3 VoIP ON DEDICATED PROCESSORS

Historically, the following processor classifications have gained popularity for VoIP voice and fax applications:

a) DSPs for voice and network processor for networking software

b) Network processor performing both voice and networking

c) DSPs performing both voice and limited networking

An overview of these three families of processors and processing is given in this section. In Fig. 19.2(a), one or more DSPs will perform voice chain processing, and network processors take care of VoIP signaling, system software, and other data and networking functions. Several solutions are on the market using this type of approach. In many cases, separate DSP and network processors are used; however, modern implementations typically combine both processors into a single system on a chip (SoC) to minimize cost and simplify system implementation. Several families of devices, including the TI [URL (TI-54x)], Mind speed [URL (Mindspeed)], Verisilicon [URL (Verisilicon)], and Ikanos [URL (Ikanos-Fusiv)], use this approach. The network processors were referred to by different names such as host processor, microprocessor, control processor, reduced instruction set computer (RISC) processor, and power PC. Several processor families are used for networking functions. In early devices, the DSP operated in the range of 80 to 100 MHz and the network processor in the range of 50 to 100 MHz, supporting two to four channels of VoIP processing. Subsequently both networking ...