The telecommunication industry has advanced rapidly over the past century. The
invention of telephone has sparked the beginning of the telecommunications era.
Today, an immense Public Switching Telephone Network (PSTN) exists to provide
services to millions of users worldwide. Though for many years our communication
needs have been satisfied by the telephone networks, in the past few decades
computer and integrated circuits (IC) technology have reshaped our communication
needs to include not only voice but data and video as well. Conveying data
information worldwide, computer networks, such as the Internet, have become
prevalent. This growth has been fueled by advances in IC technology that have
enabled affordable consumer products, such as high speed modems which have made
computer accesses as easy as making a phone call. Sophisticated image and speech
processing are also becoming available in integrated circuits to enable embedded
multimedia capabilities in portable laptops.
Currently, high quality affordable multimedia content is becoming available through emerging technologies, such as digital cable and digital subscriber lines (DSL).
Communication speed on twisted pair using sophisticated echo cancellation and
equalization is enabling data rates up to several megabits per second on twisted pairs and hundreds of megabits per sec on coaxial cable. In this new millennium, abundant bandwidth will be supplied through optical fiber backbones, enabling the delivery of high quality multimedia services to homes via cable, twisted pair, or even directly through fibers.
Concurrent with rapid advances in wireline-based technology, there is a surging
demand for wireless communications. Although most of our communication needs are
being met by the current wireline systems, our communications are limited to areas
with pre-installed wireline access to information services. We are, in a sense, tethered
to the wire or fiber that carries our communications. When we are on the move, it is desirable to have untethered communications such that we may have ubiquitous
access to the available information services. The key to this ubiquitous
communication lies in the ability to communicate via wireless links.