Fixed/Mobile Convergence and Beyond

Chapter 6. UMC - Layer 1 and 2 Media Requirements

The key component of any telephony architecture is the media—that is, the methodology used to digitize a human voice and transport it over a network, to be converted back into an analog signal to be listened to.

6.1. A Bit of History

Original telephony products were based on an analog design in which a human voice was changed into a varying voltage or current that was translated at the other end in an inverse manner. Typically requiring relatively high voltages (48 volts DC), these devices “worked” for over a century but at a price of heavy (literally) wiring infrastructure and high power consumption. In a circuit-switched environment, however, this was pretty straightforward, since the end-to-end ...