Exam 2: Wireless Data Transmission

What is quadrature amplitude modulation (QAM) and how does it work? QAM is a modulation method that changes both the phase and height of a wave, in order to encode more than one bit per signal change (baud).

Which range of the electromagnetic spectrum is less susceptible to interference from sources of visible light?

Radiotelephony or radio travels in waves known as _________ waves.

PSK is an example of _______.

Why do computers and data transmission equipment use binary?

Which type of transmission is used when human voice is modulated directly onto a carrier wave?

Infrared wireless systems require that each device have only one component: either an emitter that transmits a signal or a detector that receives the signal.

The American Standard Code for Information Interchange (ASCII) can represent up to 1024 characters.

Explain the difference between bps and baud rate. Baud rate refers to the number of signal changes per second. Because each signal change can represent more than one bit, the number of bits-per-second, or bps, can be higher than the baud rate.

Explain how a radio antenna works when transmitting a signal. When the electricity moves back and forth in the antenna at the same frequency as the radio waves, it creates both a magnetic field and an electrical field around the antenna. This continuous (analog) combination of magnetism and electrical pressure moves away (propagates) from the antenna the same way that water waves move away from the point of impact when you throw a rock in a pond.

The distance between one positive peak and the next positive peak of a wave is called: _________.

Eight binary digits grouped together form which of the following?

Explain the difference between amplitude modulation, frequency modulation, and phase modulation. Amplitude modulation changes the height of a wave. Frequency modulation changes the frequency of a wave, and phase modulation changes the starting point of a wave with reference to the previous cycle of the same wave.

Unlike a digital signal, a(n) ________ signal is a continuous signal with no "breaks" in it.

Changing a signal to encode data onto it is known as __________.

Letters of the alphabet and symbols are stored using the ASCII code, but not numbers used in calculations.

Infrared wireless transmission can be either directed or _________.

Infrared wireless systems send data by the intensity of the light wave instead of whether the light signal is on or off.

List and describe the three different types of binary signaling techniques. In return-to-zero, the absence of a voltage, or zero volts, represents a 0 bit and an increase in voltage represents a 1 bit. The signal rises and falls within a bit time period. In non-return-to-zero, the voltage does not change when the next bit is the same as the previous bit. Non-return to zero level, works the same way as non-return- to-zero, but the voltage changes between a positive and negative level, rather than between a positive voltage and zero volts, as in the previous two techniques.

Infrared light, though invisible, has many of the characteristics of visible light.