chapter 1 que cards

Flashcard 1: Q: How do diffused infrared transmissions transmit data?
A: Diffused infrared emitters send a signal as a wide-focused beam of infrared light. The signal is expected to bounce off of a surface and fill an enclosed area.

Flashcard 2: Q: How does QAM modulate digital data onto the carrier?
A: QAM combines AM and PM to provide 16 different combinations of amplitude and phase changes, transmitting up to 4 bits at a time.

Flashcard 3: Q: This radio technology transmits the most bits per wave cycle:
A: QAM

Flashcard 4: Q: Which binary modulation technique varies the starting point of the wave?
A: PSK

Flashcard 5: Q: This transmission technique reduces the risk of radio interference and eavesdropping by rapidly switching frequencies:
A: FHSS

Flashcard 6: Q: What property of a wave is measured in Hertz?
A: Frequency

Flashcard 7: Q: How does FHSS transmit data?
A: FHSS uses a range of frequencies and changes the frequency of the carrier several times during the transmission. A short burst of data is transmitted in one frequency, then the transmitter and receiver switch to another frequency.

Flashcard 8: Q: How are radio waves different from infrared transmission?
A: Radio waves can travel over greater distances than infrared.

Flashcard 9: Q: How many possible signal changes are required to transmit up to four bits at a time?
A: 16

Flashcard 10: Q: How are FM and FSK similar?
A: Both modify the frequency.

Flashcard 11: Q: How does the RZ technique represent digital data?
A: 0 bits are represented by zero voltage for the entire bit-time period. 1 bits are represented by positive voltage for most of the bit-time period, then returning to zero voltage before the end of the period.

Flashcard 12: Q: You're designing a wireless system. You want the system to have high throughput. What difficulties are possible if you used radio signals?
A: This method is vulnerable to radio interference.

Flashcard 13: Q: You want to connect a home WLAN. What type of wireless signal is your WLAN most likely to use?
A: Radio

Flashcard 14: Q: You're designing a wireless system and want high throughput. What difficulties are possible if you used diffused infrared signals?
A: This method is too slow for this scenario.

Flashcard 15: Q: Which transmission technique splits the frequency band into orthogonal frequencies?
A: OFDM

Flashcard 16: Q: Which device encodes digital signals onto analog signals for transmission and decodes incoming analog signals back into digital signals?
A: Modem

Flashcard 17: Q: You're tuning into a radio station. 650 KHz is the ______.
A: Frequency of the carrier wave

Flashcard 18: Q: This contains information modulated onto a continuous wave:
A: Carrier wave

Flashcard 19: Q: What is the wavelength of a wave?
A: The distance between any point in one wave cycle and the same point in the next wave cycle.

Flashcard 20: Q: How does ASK modulate digital data onto the carrier?
A: It uses NRZ encoding to change the height of the carrier signal.

Flashcard 21: Q: How does a Barker code improve the reliability of radio transmissions?
A: It's mathematically optimized for modulating radio waves as well as for being detected correctly by the receiver.

Flashcard 22: Q: What happens when a transmitter increases its voltage?
A: The radio signal's amplitude increases.

Flashcard 23: Q: How does OFDM transmit data?
A: It splits a frequency range into orthogonal frequencies that won't interfere or will cause only minimal interference with each other. Data is then encoded onto each frequency.

Flashcard 24: Q: How does modulation make wireless communication possible?
A: It transmits data—analog audio or video signals or digital signals—over long distances by encoding the data onto an analog radio wave.

Flashcard 25: Q: Which feature does NOT improve the reliability of wireless transmission?
A: DSSS transmissions use lower power levels (amplitude) at any given frequency