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課程名稱︰ 無線多媒體系統研究
課程性質︰ 多媒體
課程教師︰ 吳曉光
開課學院： 電資學院
開課系所︰ 資工系
考試日期（年月日）︰ 2011.04.15
考試時限（分鐘）： 180
是否需發放獎勵金： YES
（如未明確表示，則不予發放）
試題 :
1. (Wireless Mobile COmmunication)
(A) By the end of the '80s, however, afvances in semiconductor technologies
probided a vital boost to the cellular mobile industry. Using application-specific
integrated circuits (ASICs), the size of the phone shrank to a small handset.Explain
how the industry consumer base was changed from the second genaration cellular
system to the third generation cellular system. (B) Describe the difference between
narrowband CDMA system and wideban CDMA system. (C) Explain the possible chanllenges
to move from traditional circuit switched system to packet switch programmable system
in mobile network area. (D) Fixed xellular wireless technology provides a means to offer
broadband access to multimedia services without requiring extensive coppoer or fiber
subscriber plant. Relatively wide unused spectrum at frequencies above 20 GHZ has led to
the development of fixed broadband wireless acces system operating in these bands, such
as LMDS (local multipoint distribution system. Can you explain why LMDS does not turn
out to be one of the major broadband solutions as ADSL? (E) In order to fully utilize
spectrum resources, describe how "cognitive radio technologies" and "ultra-wideband radio"
technologies share the spectrum with existing wireless systems.
2. (Mobile Radio Propagation)
THe mobile radio channel places fundamental limitations on the performance of
wireless conmmunication systems. THe transmisson path between the transmitter
and the receiver can vary from simple line-of-sight to one that is severely obstructed
by buildings, mountains, and foliage. Modeling the radio channel has historically been
one of the most difficult parts of mobile radio system design, and is typically done in
a stastistical fashion, basd on measurements made specifically for an intended
communication systems or spectrum allocation. (A) List the factors to determine the Link
Budget (SNR) (B) Describe the two main factors to cause the small-scale fading? (C)
Explain the following three interference sources, in the cellular mobile system:
co-channel interference, adjacent channel interference, inter-symbol interference.
(D) Explain the large aread interference problem for IEEE 802.11.
3. (CSMA, MACA, adaptive CSMA, CSMA/CA Protocols)
In recent years , a wide variety of mobile computing devies has emerged, including
portables, palmtops, and personal deigital assitants, Providing adequate network
connectivity for these devices will require a new generation of wireless LAN
technology (A) Describe how CSMA protocol may cause and experience "hidden terminal"
and "exposed terminal" problems (B) Karn proposed MACA as an alternative to traditional
CSMA scheme. Explain why MACA might solve problem. (C) Explain the problem for MACA
scheme. (D) Describe how "adaptive CSMA" scheme proposed by Intel Corporation address
"hidden terminal problem" and "exposed terminal" problem? (E) Can you revise CSMA/CA
protocols to address on "exposed terminal problem" ?
4. Wireless TCP porposals, Packet loss Distinction
I.(A) A number of wireless TCP proposals have been proposed to address the wireless random
packet loss effect. In order to distinguish congestion loss and wireless random packet
loss, ECN(Explicit Congestion Notification) was proposed. Explain how ECN could function
properly to avoid unnecessary TCP congestion window reduction. Describe the disadvantage
of ECN scheme. (B) Explain how TCP Westwood utilized (availallbe) bandwidth estimation
scheme to avoid wireless performance degradation. Describe the disadvantage of TCP
Westswood.
II. Future broadband satellite networks relying on GEO, MEO,and LEO constellations intend
to provide a wide variety of high and medium bit-rate data services to the end user.
Given that IP application in general and TCP/IP(WWW,email,file transer) more specifically
are by far the most popular in the current data networks, it becomes quite evident that
TCP will be the transport protocol of a significant part of the traffice of all networks
including satellite networks. (C) For typical Satellite Networks with long propagation
delays and hihg link error rates, explain the possible adverse effects of TCP Reno.
(D) Propose and end revison solution of TCP Reno to address the adverse effects.
5. Network Mobility
Consider vehicles such as ships, aircrafts and trains that contain mobile networks with a
potentially large number of devices requiring gloval connectivity. These devices may or
may not be sophisticated nodes. By employing a special entity namely a Mobile Router to
act as a gateway, all devies with the network can achieve global connectivity irrepective
of their capabilities. NEMO working group identifies 3 types of nodes that woild be
supported by a mobile router. Local Fixed nodes, i.e., nodes which belong to the mobile
network and cannot move with respect to the mobile router, would typically not be able to
achieve global connextivity without the support of the MR. There could also be nodes which
can move with respect to the MR namely Local Mobile Modes(home link belongs to Mobile
Network) and Visiting Mobile nodes (home link does not belongs to Mobile Network).
Describe your solution to extend "mobile IP" to support local fixed nodes, visiting mobile
nodes and visiting network.
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