Tuesday, 4 March 2008

wsc 13 Solutions 9

From Dr Chalermpol.

Chapter 9 Solutions
Review Questions

1. The term fixed wireless is generally used to refer to Building .

2. What is the connection that begins at a fast service provider, goes through the local neighborhood, and ends at the home or office?
Answer: Last Mile.

3. All of the following are last mile connections for home users except baseband.

4. A leased special high-speed connection from the local telephone carrier for business users that transmits at 1.544 Mbps is T1.

5. The transmission that treats the entire transmission medium as if it were only one channel is baseband.

6. WiMAX can communicate at speeds of up to 120 Mbps in the 10 to 66 GHz bands, over short distances.

7. The convergence sublayers in the WiMAX MAC protocol allow it to support T1,ATM, voice and video.

8. In the uplink direction, 802.16 transmits using TDMA.

9. LMDS has an advantage over MMDS in that the signals can travel up to 35 miles from the transmitter.False

10. One of the limitations of LMDS and MMDS is that these systems operate at frequencies that require line of sight.True

11. Devices in a WiMAX network must transmit in half-duplex only.False

12. The WiMAX base station controls all transmissions in a WiMAX network. True

13. Non-line-of-sight transmissions in the 802.16 standard are only supported in the 2 to 11 GHz bands.True

14. Sometimes called fiberless optical, Free Space Optics or FSO uses no medium like a fiber optic cable to send and receive signals; instead, transmissions are sent by low-powered infrared beams through the open air.

15. The maximum coverage area for a Local Multipoint Distribution Service (LMDS) network is five miles.

16. A single WiMAX base station can communicate with hundreds of terminals simultaneously.

17. WirelessHUMAN stands for the wireless high-speed unlicensed metro area network. This transmission mechanism is specific to 5 GHz U-NII band(s).

18. What is the significance of the fact that the distances in a WiMAX network are measured in miles (or kilometers)?
Answer: When compared to 802.11 networks, WiMAX will free users from the limitation of having to be within 300 ft. of an AP and increase user mobility.

19. What is the purpose of adaptive modulation in WiMAX?
Answer: It enables WiMAX to dynamically adjust the signal to reduce or eliminate errors and maintain the connection and communications with a subscriber station (remote device), within the coverage area, albeit at a reduced data rate.

20. List three modulation techniques used in 802.16.
Answer: BPSK, QPSK, 16-QAM, 64-QAM are all correct. Students may also reply OFDM, OFDMA, TDM, TDMA although these are transmission and access techniques and not modulation techniques. However, most texts refer to OFDM and OFDMA as modulations.

~The End~

Reference : Wireless# Guide to Wireless Communications Second Edition By: Jorge Olenewa and Mark Ciampa

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