F ACULTY OF C OMPUTER S CIENCE & E NGINEERING Chapter 03. Spread Spectrum Technologies

Q UESTION 1 1. Increasing the dwell time for an FHSS system will increase the throughput. A. This statement is always true B. This statement is always false C. It depends on the manufacturer of the equipment

Q UESTION 2 2. Which one of the following dwell times will result in the greatest throughput in a FHSS system and will still be within FCC regulations? A. 100 ms B. 200 ms C. 300 ms D. 400 ms

Q UESTION 3 3. An b compliant wireless LAN configuration using DSSS can have a maximum of ___ non-overlapping, co-located access points. A. 3 B. 15 C. 26 D. 79

Q UESTION 4 4. Consider the following two wireless LAN configurations: System 1. IEEE compliant FHSS system, 6 co- located access points running at maximum data rate. System 2. IEEE b compliant DSSS system, 3 co- located access points running at 50% of maximum data rate. Which one of the following statements is true? A. System 1 will have more throughput B. System 2 will have more throughput C. System 1 and System 2 will have the same throughput

Q UESTION 5 5. Channels on direct sequence systems for b equipment are ___ MHz wide. A. 5 B. 20 C. 22 D. 83

Q UESTION 6 6. Which of the following are advantages of b DSSS over FHSS? Choose all that apply. A. Cost B. Throughput C. Security D. Resistance to narrowband interference

Q UESTION 7 7. If having compatible equipment from different manufactures were an important factor when purchasing wireless LAN equipment, which of the following spread spectrum technologies would be the best choice? A. FHSS B. DSSS

Q UESTION 8 8. The FCC has two sets of rules regarding FHSS that are known as before and after which of the following dates? A. 06/30/2000 B. 08/31/1999 C. 08/31/2000 D. 08/31/2001

Q UESTION 9 9. The latest published FCC rules regarding power output for FHSS states a maximum output of which one of the following? A. 100 mW B. 125 mW C. 200 mW D. 1 W

Q UESTION The FCC specifies how many channels in the 2.4 GHz ISM band that can be used for DSSS in the United States? A. 3 B. 6 C. 9 D. 11

Q UESTION You have been hired on as a consultant to increase the capacity of an existing wireless LAN based on FHSS technology. After your research is completed you recommend that a replacement system based on DSSS would be better. Which of the following could be your arguments to defend your position? Choose all that apply. A. The DSSS devices will cost less and have more throughput B. The DSSS devices will cost more but have more throughput C. Additional new FHSS devices may not be compatible with the older devices D. DSSS is more secure than FHSS

Q UESTION The statement, “802.11b wireless LAN devices are backward compatible with wireless LAN devices” is: A. Always true B. Always false C. Sometimes true

Q UESTION What is considered to be the maximum number of co-located FHSS access points in a wireless LAN, if non-synchronized radios are to be used? A. 3 B. 16 C. 20 D. 26

Q UESTION In Frequency Hopping wireless LAN systems, the term hopping refers to which one of the following? A. Switching between throughput speeds from 11 Mbps to 5.5 Mbps B. What happens when the carrier frequency is changed C. The change that occurs as a result of the RF signal getting weaker D. Changing technologies from FHSS to DSSS

Q UESTION A DSSS channel is more susceptible to narrowband interference than a FHSS channel because of which of the following? Choose all that apply. A. The DSSS channel is much smaller (22 MHz wide instead of the 79 MHz wide band used by FHSS) B. The information is transmitted along the entire band simultaneously instead of one frequency at a time C. FHSS systems simply avoid the frequency on which the narrowband interference is located D. FHSS systems only use one frequency at a time, so the narrowband interference must be on the same exact frequency at the same time

Q UESTION The noise floor is defined by which one of the following? A. The general level of RF noise in the environment around the wireless LAN B. The noise that is generated as a result of foot traffic C. A fixed level of -100 dBm D. The level of noise at which a wireless LAN starts working

Q UESTION Which one of the following is not described by the IEEE and OpenAir standards regarding FHSS systems? A. What frequency bands may be used B. Hop sequences C. Allowable levels of interference D. Dwell times E. Data rates

Q UESTION An RF signal is considered spread spectrum when which of the following are true? Choose all that apply. A. The system sending the signal is using infrared technology B. The power required to send the information is significantly greater than is necessary C. The bandwidth used is much wider than what is required to send the information D. The bandwidth used is much less than what is used to send the information

Q UESTION Some 2.4 GHz FHSS systems operate at 3 Mbps or more. Which of the following is true regarding these systems? A. They are always IEEE compliant B. They may not interoperate with other FHSS systems C. They are always OpenAir compliant D. They are backwards compatible with 900 MHz systems

Q UESTION How many different types of implementations of spread spectrum technology does the FCC specify for the 2.4 GHz ISM band? A. 1 B. 2 C. 3 D. 4

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