Wireless Signals It 242 Week 8

Wireless Signals

Phillip Petrusky

IT 242

April 5, 2015

Dr. Barbara A. Lewis

Wireless Signals

There are four types of signals that make up the invisible world around us; FDMA (ex. coaxial transmission), TDMA (ex. cellular voice and data), CDMA (ex. 3G data) and SDMA (ex. fiber optic connections). Each signal has its own benefits, and technologies associated with them. WANs around the world use these signals every day in one way or the other, and the average person uses most of them in daily life.

The first, and generally older, signal type is FDMA. This signal type is used today in television networks to transmit video signal over coaxial, and in fiber optic applications. FDMA divides a channel, or bandwidth, into individual bands. Each band is dedicated to one user. The data is modulated on to the subcarriers and linearly mixed. The best example of this signal is the old analog telephone network and the early satellite signals. The telephone network multiplexes multiple calls onto a single line while the earlier satellite networks shared the 4-GHz to 6-GHz range for voice, video or data signals. Today TDMA is used for these technologies. A WAN today would use this type of signal for a television network mainly. Other applications are around (such as fiber optic data), but other signals are more frequently used.

TDMA is a signal that has mostly replaced FDMA. This signal is digital and divides a channel into time slots. One byte, or segment, is transmitted at a time in a sequential serial data format. This type is best used for slow voice signals, compressed video, and high-speed data. A T1 network is one way this technique is used in today’s world. T1 has been used in the telecom industry for many years. GSM cellular phones are TDMA based, and is one of the most common uses. Voice signals, texts and emails are transmitted with this technique.

CDMA is the second purely digital signal, but is also called DSSS (Direct Sequence Spread Spectrum). This...