What is SNR

Since the inception of the plain old telephone system (POTS) in the 1880s, it has formed the backbone of the communications world. Reliant on twisted pairs of copper wires bundled together for its operation, there has not really been any quantum jump in its transmission mode, except for its transition from analogue to digital at the end of the 1970s. Of the total bandwidth available on the copper wires, the voice portion, including the dial tone and ringing sound, occupies about 0.3 %—that is, the remaining 97.7 % is unutilized This seems to be poor resource management as prior to the advent of the Internet, telecommunication companies (telcos) have not really sought to explore better utilization of the bandwidth through technological enhancements—for example, promoting better voice quality and reducing wiring by routing two neighboring houses on the same line before splitting the last few meters. Two possible reasons could be cited for this. Advances in microelectronics and signal processing necessary for the efficient and cost-effective interlinking of computers to the telecommunications network have been rather slow (Reusens, van Bruyssel, Sevenhans, van Den Bergh, van Nimmen, & Spruyt, 2001). Also, up to about the 1990s, telcos were basically state-run behemoths which had little incentive to come out with innovative services and applications. With deregulation and liberalization of the telecommunication sector introduced in the 1990s, the entire landscape underwent a radical change that saw telcos instituting a slew of services, enhancements, innovations, and applications; in parallel, there was a surge in technological developments facilitating these. Prior to the advent of the Internet, POTS was used mainly for the transmission of voice, text, and low resolution graphics—the latter two are in relation to facsimile machines which became popular in the late 1980s. The POTS network is, however, not able to support high bandwidth applications such as multimedia and video transmission. Because of the ubiquity of POTS, it makes sense to leverage on it for upgrading purposes in order to support high bandwidth applications rather than deploy totally new networks which would need heavy investments. In recent times, asymmetric digital subscriber line (ADSL) has emerged as a technology that is revolutionizing telecommunications and is fast emerging as the prime candidate for broadband access to the Internet (Tan & Subramaniam, 2005). It allows for the transmission of large amounts of digital information rapidly on the POTS.