ETEK1500-MOD-04 Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. ____ 1. What is the top layer of the OSI reference model? a. application c. physical b. presentation d. transport ____ 2. Which layer of the OSI reference model permits the devices on the network to hold ongoing communications across the network? a. presentation c. transport b. session d. network ____ 3. ____ signals by nature transmit on only one frequency or a very narrow portion of the frequencies. a. Broadband c. Radio b. Computer d. Heat ____ 4. What is a disadvantage of narrowband transmissions? a. requires a complicated algorithm c. expensive to implement b. not well regulated d. interference from another radio signal ____ 5. When was the concept used by FHSS technology developed? a. during World War I c. in the 1960s b. during World War II d. in the 1980s ____ 6. In FHSS, the amount of time needed to move from one frequency to another is the ____ time. a. dwell c. lift b. switch d. hop ____ 7. According to FCC regulations, all FHSS systems in the 900 MHz band must change frequencies through 50 channels and cannot spend more than ____ on one frequency each 20 seconds. a. 20 milliseconds c. 400 milliseconds b. 30 milliseconds d. 1 second ____ 8. Bluetooth divides the 2.4 GHz frequency into ____ different frequencies spaced 1 GHz apart. a. 52 c. 79 b. 68 d. 93 ____ 9. DSSS uses a bit pattern called a ____ code. a. hopping c. dwelling b. setting d. chipping ____ 10. ____ is not part of a frame. a. Length c. Channel b. Parity d. Data ____ 11. Because a device must wait to transmit until it receives the last reflected signal, this in effect puts a ceiling limit on the overall speed of the WLAN. What is the current ceiling for WLAN speed? a. under 10 Mbps c. between 20 and 30 Mbps b. between 10 and 20 Mbps d. over 50 Mbps ____ 12. How does OFDM work? a. signals are broken up and the parts are sent in parallel b. the same signal is sent on multiple channels c. one signal is sent twice on the same channel d. a signal is sent over a wired network at the same time as the wireless network ____ 13. Which system is preferred for 802.11b WLANs? a. DSSS c. OFDM b. FHSS d. All are equally preferred ____ 14. IEEE has divided the ____ layer into two sublayers: Logical Link Control (LLC) and Media Access Control (MAC). a. Physical c. Transport b. Data Link d. Session ____ 15. Into which layers are WLAN features isolated by IEEE standards? a. PHY and PMD c. PHY and MAC b. MAX and PLCP d. PMD and PLCP ____ 16. When using the Shared Wireless Access Protocol, devices can be as far as 45 meters (150 feet) apart and can send and receive data at rates up to ____ Mbps. a. 2 c. 10 b. 5 d. 14 ____ 17. The Physical Layer Convergence Procedure (PLCP) standards for 802.11b are based on ____. a. DSSS c. OFDM b. FHSS d. PYS ____ 18. The 802.11b standard specifies ____ frequencies that can be used, beginning at 2.412 GHz. a. 4 c. 14 b. 10 d. 30 ____ 19. The ____ coding technique consists of a set of 64 8-bit code words. a. chipping c. Barker b. fixed scramble d. complementary code keying ____ 20. What techniques are used by vendors to achieve 2x mode for transmissions? a. combine two frequency channels c. reallocating the individual carriers b. use different coding rate schemes d. All of the above ____ 21. The ____ field of an 802.11a frame consists of 10 repetitions of a short training sequence signal and two repetitions of a long training sequence signal. a. Rate c. Synchronization b. Service d. Parity Completion Complete each sentence or statement. 22. Narrowband transmissions require significant power for the signal to be transmitted because the signal must exceed the ____________________, or the total amount of outside interference, by a substantial margin. 23. The amount of time that a transmission occurs on a specific frequency is called the ____________________ time. 24. The _________________________ Protocol defines a set of specifications for wireless data and voice communications around the home. 25. Although 54 Mbps is the “official” top speed of 802.11a, the IEEE specification also allows for higher speeds. These higher speeds are known as ____________________ mode or 2X mode. 26. Users can upgrade from an 802.11b network to a faster 802.11g network simply by replacing the ____________________. Matching Match each term with the correct statement below. a.physical layer f.direct sequence spread spectrum b.channel bonding g.quadrature phase shift keying c.frequency hopping spread spectrum h.transport layer d.Forward Error Correction i.orthogonal frequency division multiplexing e.network layer ____ 27. uses an expanded redundant code to transmit each data bit ____ 28. uses a range of frequencies that change during the transmission ____ 29. transmits a secondary copy along with the primary information ____ 30. sends signals to the network or receives signals from the network ____ 31. can double the amount of data encoded over PSK to 250 Kbps per channel, which produces a 12 Mbps (250 Kbps x 48) data rate ____ 32. ensures that error-free data is given to the user ____ 33. two channels are combined (one for sending data and the other for receiving) to provide the necessary frequency for the higher speeds ____ 34. sending multiple signals at the same time ____ 35. picks the route packets take and handles addressing of packets for delivery Short Answer 36. What is the Open Systems Interconnection (OSI) reference model? 37. What is a disadvantage of narrowband transmissions? 38. Describe the FCC restrictions on FHSS. 39. What are the advantages to using DSSS with a chipping code? 40. How does OFDM avoid problems caused by multipath distortion? 41. What are the fields that make up a PLCP frame? 42. There are two disadvantages to using U-NII. What are they? 43. The modulation techniques used to encode the 802.11a data vary depending upon the speed. Describe the techniques used to transmit at 24 Mbps. 44. The 802.11g standard outlines two mandatory modes along with one optional mode. Describe each mode. 45. What are disadvantages of the 802.11g standard?