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(COMP4622)[2011](f)midterm~=plv933^_59205.pdf
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HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY
COMP 4622: Computer Communication Networks II
MID-TERM EXAMINATION
Fall, 2011
Time Limit: 2 hours
Q1. [20 Points] True or false
Determine whether the following statements are true or false. Circle the answer. Please briefly describe the reasons for your choice.
i. The infrastructure mode prohibits a wireless network from using multi-hop routing.
True False
There are wireless networks that use both base stations and multihop routing, e.g., some mesh networks and sensor networks.
ii. Because wireless channels are broadcast media, it is impossible for 2 wireless end systems to construct a point-to-point communication link.
True False
It is possible to construct a point-to-point communication link by directional antennae. Logically, the MAC layer can also use addresses to emulate point-to-point communication.
iii. Theoretically, the received power decreases linearly to the distance to the transmitter in the free space.
True False
The received power decreases at a rate inversely proportional to the square of the distance.
iv. The 3G cellular phones use the same physical layer protocol, in order to ensure GSM/UMTS phones can call CDMA-2000 phones.
True False
GSM and CDMA-2000 use different physical layer protocols with different multiplexing
techniques, modulation schemes, and coding schemes.
v. The length field in a MAC-layer frame must include the preamble bytes in the count.
True False
Usually the length specification in a MAC-layer frame does not count preambles. In particular, there is no guarantee that all preamble bytes, which arrive before the receiver is synchronized, will be received by the receiver.
Q2. [18 Marks] Multiple choices
Choose the BEST answer and write the corresponding letter in the blank space at the beginning of the question.
i. __C_Which of the following protocol is likely to be used for communication between a smart phone and a digital camera?
A. B-MAC B. GPRS (GSM 2.5G solution)
C. Bluetooth D. WiMAX
E. Geographic forwarding
ii. _B__ Which of the following description about LTE (Long Term Evolution) is NOT true?
A. LTE aims at providing broadband data service in cellular systems
B. LTE requires at least a 20MHz continuous frequency band to function correctly.
C. LTE supports mobility
D. LTE can co-exist with 2.5G and 3G GSM systems
iii. _A__ Which of the following descriptions most accurately characterizes mobile IP?
A. The care-of address of the mobile can change in a TCP connection over mobile IP
B. Mobile IP follows the direct routing approach
C. The core routers in the Internet must adjust their routing tables to conduct routing for the permanent address
D. The foreign agent does not need to know or process the mobiles permanent address
iv. _A__ W