课程名称︰无线多媒体系统研究 课程性质︰多媒体 课程教师︰吴晓光 开课学院：电资 开课系所︰资工 考试日期（年月日）︰2011.01.16 考试时限（分钟）：180 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 1. Mobile Ad hoc Networks (a) Describe two main motivations for the Terminal Project: Toward Self- Organized MObile Ad Hoc Networks. (b) Describe Ad hoc network evolutions from early stage to the future. (c) Describe the characteristics of ad hoc networks (d) In the early stage, two representative kinds of routing schemes are:(1) table driven routing scheme (such as DSDV) (2) on demand routing scheme (such as AODV). Explain the differences between them. (3) Different from traditional routing schemes, recently, geographical methods have been utilized for routing. .Describe how geographic information can be helpful for the routing function. (4) For large scale ad hoc networks, describe the problems and possible solutions for the routing schemes. (e) Describe the similarities and differences between ad hoc networks and vehicular Ad Hoc networks (VANET). 2. MANET Routing Protocols MANETs are basically peer-to-peer, multihop wireless networks in which information packets are transmitted in a store-and-forward manner from a source to an arbitrary destination, via intermidiate nodes. (A) Describe the looping problem by Figure 1 example. (B) In ad hoc networks, it is sometimes desirable to transmit packets of a single message using multiple paths. Can you think of any specific reasons for this? If you need to employ two alternative paths,how would you revise AODV or DSR protocols to obtain two alternative paths? (C) What are the similarities and differences between ad hoc networks and sensor networks? 3. QoS routing for MANETS Providing real time services such as voice or video over ad hoc network is a challenge. Usually QoS routing will be required for real time connections.(a) Describe the difference between QoS routing and shortest path routing. (b) Usually bandwidth constraint must be satisfied for the required voice and video. How do you calculate the available bandwidth for an ad hoc node if you have 2M bits per second(e.g. 802.11b) bandwidth and each requested video stream require 50K bit per second bandwidth. As Figure 2, the video connection is constructed from sender to receiver, how many bandwidth resources could be consumed for each node (sender, R1,R2,and receiver).(c) If you need to employ two alternative paths, how woulf you extend DSR algorithm? (d) Multipath routing has been proposed to satisfy QoS requirements. Can you describe the advantages and disadvantages for multipath routing? (e) QoS routing protocols assumed that all nodes had the same capacity. In practice, since the wireless medium is shared and collision-based, different nodes may have different capacities, depending on their densities of contending nodes. Descibe hidden routing problem and the corresponding possible solution for QoS routing. 4. VANET Routing (A) Explain why current routing solutions (such as AODV) developed for Mobile Ad hoc Networks happen to be highly inappropiate for VANETs. (B) However, location based stateless routing schemes such as Greedy Perimeter Stateless Routing (GPSR) are particularly efficient on highly dynamic networks. Using geo-localization information, packets are greedily forwarded to the vehicle bringing the maximum progress towards the destination. In some cases, there might not be such a vehicle and a recovery strategy, called perimeter routing in GPSR, is used to find an appropriate next relay. Explain specifically how they work. (C) Design a location based QoS routing solution for Vehicular Ad hoc Network given than location-based stateless routing protocols (such as GPSR) are efficient on highly dynamic networks. 5. Mobile Multicast The mobile multicast protocl must deal not only with dynamic group monagement but also with dynamic member location. The current version of mobile IP proposed two approaches to support mobile multicast, i.e. bidirectional tunneling and remote subscription. (A) Can these two approaches (bidirectional tunneling and remote subscription) handle source mobility and recipient mobility? (B) A direct mechanism for achieving multicast reception on MHs is to let HA handle mutlicast routing by executing IGMP and delivering multicasts to the MHs as if it was at home. In Current IETF mobile multicast, is it qualified as remote subscription or bi-direction tunnel multicast? Advantage? Disadvantage? (C) What is the duplication problem? (D) What is the tunnel convergent problem? (E) Can you describe what is "combined routing"? Advantage? Disadvantage? -- Nothing is Impossible --

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