{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Chapter 15 - 125 Problems and Solutions(Chapter 15 1 How is...

Info iconThis preview shows pages 1–22. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 8
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 10
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 12
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 14
Background image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 16
Background image of page 17

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 18
Background image of page 19

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 20
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 125 Problems and Solutions (Chapter 15) 1. How is UWB difl’erent from frequency hopping used in Bluetooth? Ex- plain. [Solution] The difl’erence between UWB and bluetooth networks is that UWB sys- tems operate across a. wide range of frequency spectrum by transmitting a series of extremely narrow and low power pulses. Therefore, essentially, the whole frequ-cy spectrum is used by the transmitter and the data is sent in bursts. Therefore, we have a burst of data across the channel and then for some time period there is no data transmission. 0n the other hand, bluetooth employs frequency hopping for data. trans- mission. That means that data is sent on a channel in a particular fre- quency range and then the transmitter hops on to the next frequency spectrum and again transmits data. Therefore, the data transmission in bluetooth networks is continuous whereas it occurs in bursts in UWB. Moreover, bluetootb uses a part of the frequency spectrum whereas UW'B uses the whole spectrum. The amount of data transmitted (at an instant) in UWB is also much more than it is in bluetooth networks. Multimedia services have two components of video and voice data. Can you diaracterize them as non real-time and real-time traffic? Explain clearly. [Solution] Multimedia services have two types of data. that is transmitted to the user - video data. and voice data. Basically, both of these data types are real- time in the sense that the receiver should get the data frame by frame in order as it was transmitted by the sender in real-time. Hence both voice and video data can be characterized as real-time. However, between the two, it is more desirable for voice data to be transmitted in real-time. In other words, a little latency can be tolerated while transmitting video data while this is not the case with voice data. Therefore, we can categorize in some cases video data as non real-time traffic and voice data as real-time traffic. Can you use PTT technology to process multimedia traffic? Explain clearly. - [Solution] Since PTT (Push-To-Talk) is one of the potential IP multimedia services, it can process multimedia. trafic. Push-to-talk technology is a prime area for expansion of the Session Initiation Protocol in 2004 and exhibits the wands-talkie mode of radio communication betWeen preset speakers. Since PTT technology uses the capabilities of the IP Multimedia Subsystem (IMS) (as specified by 3GPP which enables IP connections between mobile phones) it can definitely support multimedia traffic. 126 4. Assume that traffic is as-gned four difl'erent priority levels taking into account real-time and handofl' traffic. How can you handle such traffic while supporting mobility? [Solution] If we have a wireless system in which the traffic has four priority levels, then essentially we have to take mobility management into account in the design phase of such a system. The traffic could be real—time or non-real time. In general, real-time traffic has a higher priority than non-real time traffic. We basically have to do the handofl' management in an efficient fashion for such a system with four priorities. In other words, the handofl" promss will be service dependent. Channel reservation One design consideration in this system would be the reservation of chan- nels. We can give priority reservation to traffic with high priority so that a fixed number of channels are always reserved for such high priority traffic requests. We would have queues for all the priority level traflic and the particular priority traffic request would wait in its assigned queue. The number of channels reserved could depend on the actual traffic priorities assigned. Therefore, we could reserve channels for each of the four priorities. We could also use a preemptive scheme in which a higher priority request would have the right to preempt the execution of a lower priority request. The preempted low priority request would then resume execution at a later stage. The higher priority request would preempt only if it finds no channel available. The preempted request would also have to be stored in a queue so that it can be executed later. Additionally, we could also consider the transmission delay. Ideally, we would like to minimize the delay for the traffic request that has the high- est priority as compared to a request with a lower priority. Hence, high priority requests need to be executed as fast as possible in such a network. What are the pros and cons of employing satellite communication for multicasting? Explain. [Solution] The pros of employing satellite communication for multicasting are: (9.) Providing uniform accessibility is easy via satellite, because the sig- nals sent via the satellite may be received by any receiver within the coverage area of the satellite (known as the satellite “footprint”). Typically, this allows the same signal to be received across a whole continent, if transmitted by satellites covering the whole surface of the earth. 127 (b) A satellite solution also minimizes the number of multicast-capable routers required in the core network, which will simplify initial de- ployment and operations [maintenance (c) No bottlenecks from low speed connections and no waiting for busy servers. The cons are: (a) Diflicultiu in providing the multicast service across a wide geograph- ical area. (b) Difficulties in upgrading existing deployed network routers. (c) The frequency bands normally used for satellite data services have become very congested and there is not sufficient capacity for a. ma jor new service To achieve wide area. coverage will require a. new generation of satellites operating in the Extra High Frequency band. ((1) High power operation too costly. 6. Can you do multicasting in a MANET? If yes, how and if no, why not? Explain clearly. [Solution] A MANET consists of a. dynamic collection of nodes with sometimes changing topologies that are composed of low bandwidth wireless links. Since each node has limited transmission range, not all packets may reach their destinations. As the nOdes are battery powered, the multicast pro- tocols also need to limit the amount of control information that is passed through them. Multicast protocols used in static networks do not perform Well in wireless ad-hoc networks because multicast tree structures are fragile and must be reconfigured as topology changes. The frequent exchange of routing vec- tors or link state tables, triggered by continuous connectivity changes, yields excessive channel and processing overhead. Hence, the tree struc- tures used in static networks must be modified or a. different topology between group members need to be deployed for efficient multicasting in wireless mobile ad hoc networks. ' Multicast can improve the efficiency of the wireless link when sending mul- tiple copies of messages by exploiting the broadcast property of wireless transmission. Hence, We can do multicasting in a. wireless medium but a lot of challenges need to be addressed. 7. If preemption is allowed in Prom-15.4, how would you do the scheduling and what are the relative advantages and disadvantages? [Solution] In a preemptive scheme, a treflic request with a higher priority can pre- empt a. request with a lower priority. The execution of the lower priority 128 request is halted and the higher priority request is allowed to execute if it finds no channel available. Queues may be present for both types of requests. The lower priority request resumes execution at a later time. Advantages: (a) Probability of packet loss is minimized for real-time transmission as such a request can be transferred from the queue of the current BS to that of another. (1)) High priority requests that otherwise not be allowed to execute are entertained. (c) Forwd termination probability of real—time requests is decreased. Disadvantages: (a) Tough to determine the level of priority calls that are to be pre- empted. Need to define a fixed level of priority for preemption. (b) Need to reserve queues for the requests that are preempted so that they can resume execution later. If you are given a choice of using either reactive or proactive routing protocol, which one would you prefer for Problem 15.7 with ad hoc network and why? [Solution] For the above problem, a proactive protocol would be preferred because you know the path for the high priority call that causes preemption. Such knowledge helps in doing preemption of existing call. if a. new path for a higher priority call, is feasible to melee at a given time. Otherwise, you do preemption of an existing call without being successful in setting up a. new call. Using your favorite MANET simulator, create an arbitrary MANET and find disjoint paths between an arbitrary source-destination pair. Assume all needed parameters. [Solution] To be done by student. 10. Compare the time requirements in Problem 15.9, if (a) The number of M35 is doubled. (b) The radio coverage area is doubled. (c) The node connectivity is doubled. ((1) Both parts (a) and (b) are done. [Solution] 'Ib be done by student. 129 11. For what applications, are direct~ditfusion based flat architectures or cluster- based sensor networks useful? Explain in detail. [Solution] Applications for a cluster based sensor network: (a) Security system consisting of an ad hoc network of video and acoustic sensors. (b) Wireless parking lot sensor networks to determine which spots are occupied and which spots are free. (c) Monitoring room temperature and turning on the A/C only if the temperature crosses a. threshold value. Applications for flat topology sensor networks: (a) Military sensor networks to detect enemy movements, the presence of hazardous material (sud: as poison gases or radiation), explosions, etc. (b) Environmental sensor netw0rks (such as in plains or deserts or on mountains or ocean surfaces) to detect and monitor environmental changes. (c) Wireless traffic sensor networks to monitor vehicle traffic on a high- way or in a congested part of a city. (d) Wireless surveillance sensor networks for providing security in a shop- ping mall, parking garage, or other facility. - 12. What are the uses of different types of queries in sensor networks? Explain clearly. [Solution] The various types of queries in a sensor network are (a) Historical queries (ask about past information, e.g., readings of pres- sure for the past week.) (b) Snapshot queries (query'the sensor network at a given point of time, e.g., the pressure reading at a particular time instant). (c) thure queries (query a sensor network over a future time interval, e.g., in the next one hour, if the temperature reading exweds 70, takes appropriate action). (d) Long running queries, e.g., those that deal with status over a user defined time period. 13. Using your favorite MANET simulator, create a sensor network. Assuming appropriate parameters, simulate a sensor network with 100 nodes. Find the query propagation time from one -d of the network to another end if: 130 (a) A flat architecture is used? (13) A cluster architecture is used? [Solution] Student to do this. 14. Using your favorite website, find different type of sensors if the idea is to_ explore the following applications: (a) Nuclear plant. (b) Under water project. (c) Noise level in a campus. (d) Air pollution over an industrial area. (e) Maintenance of a large bridge. (1') Speeding on a freeway. (g) Industrial discharge to a lake or e. river-bed. (h) Contamination due to an industrial chimney. (i) Ozone level determination in an area. (j) Flood-level monitoring. (k) Rock-falling (snow—mountain falling) in a mountainous area. (1) Underground earth movement determination. (In) Movement of ore and manpower in an underground mine. [Solution] (a) Nuclear plant A nuclear plant has numerous built—in sensors to watch temperature, pressure, water level, and other indicators important to safety. The sensors are connected to control and protect systems that adjust or shut down the plant, immediately and automatically, when pre-set safety parameters are approached or breached. In addition to these, some sensors are also fitted for security purposes. Intrusion detection sensors are fitted at all the emergency exits. they annunciate and record in a continuously staffed central alarm station to provide for the monitoring and assessment of alarms and the facility management and response force. More information is available at the following web sites: 0 www.nei.org/index.asp?catnum=2&catid=55 o www.gepower.com/dhtml/reuterstokes/en_us/ sensors/nuclear“ sensors/index.jsp o www.kinemetrics.oom/oondor.html 131 o m.control.com/1026146121/index_htrnl (b) Under water project Some sensors used in under water projects are descdbed below: Hydrophones are underwater acoustic sensors, which most commonly utilize piezoelectric technology. They can be used singly or in arrays that can contain domens or hundreds of individual units. They are used in marine geological and biological research, undersea mapping and navigation, and various commercial and military applications. Acoustic sensing instruments used sound waves in a wide variety of applications, including distance, proximity, level, nondestructive evaluation, web break detection, counting, and security. Acoustic sensors can also be used in underwater procedures. Hydrophones and arrays, microphones, sound and noise level dosimeters, and ultra- sonic and underwater transducers are included in this family. Under water acoustic transducers contain both transmitters and receivers. They sense reflected sound and use distance and directional data for communication, mapping and navigation. They have an operational range, but are usually designed to operate at their resonance fre- quency to maximize output power. They are most typically single frequency transmitters, but they may contain multiple transmitters and receivers for difierent frequencies. More information is. available at the following web sites: a www.globalspec.com/ProductGlossary/Sensorsu1ransducers__ Detectors/Acoustic__5ensing o www.mtersensorscom/ o wwwgreatmonitoringcoml - www.dt.navy.miI/pac/excerpts%20pages/ 2000/rov12fi00.html (c) Acoustic sensors and other microphone sensors can be deployed around the campus to measure the noise level. Along with amplifiers they can act as sound collectors. Microphone sensors AWA14423 and four presmplifiers AWA14602 can be used. Sound level sensor P's-2109 can also be used to measure sound level. Characteristics of PS-2109 are: i. Three snitch-selectable ranges (from 30 dB to 110 dB) provides greater functionality and flexibility ii. Displays both dBA (matching the sensitivity of the ear) and dBC (responding equally to all frequencies) iii. Measures both sound level and sound intensity (d) Air pollution over an industrial area Some sensors for countering air pollution are as follows: The air quality sensor, located near the fresh air inlet, serves to reduce the amount of pollution entering the vehicle cabin through 132 the HVAC system by sending a signal to close the fresh air inlet door/ventilation flap when the vehicle enters a high pollution area. By performing this function, the air quality sensor provides a key health benefit to drivers and occupants of motor vehicles. * GASMAN II Manufactured by Nortech GSI Inc, the GASMANII is Crowcon’s newest personal single gas monitor. Available to monitor diiferent gases such as H28, CO, CH4, or 02 the rugged and lightweight GAS- MANII oli'ers highly visible and audible alarms, data logging capa- bility with Windows compatible PC interface and intrinsic safety for use in hazardous areas. * CEA Gas Monitors CEA Series U portable gas monitors use unique, patented sensors that are highly specific, fast responding, poison resistant and are unaffected by moisture or temperature changes. Sensors are avail- able for ammonia, hydrocarbons, freons, ethylene oxide, hydrogen combustiblu, sulfur dioxide, hydrogen sulfide, carbon monoxide and others. Ranges are available to detect‘these gases in the low ppm, high ppm or %LEL levels without sensor damage. Described as com- pact, durable, and easy to maintain and operate, standard accessories include a leather instrument case, remote sensor wand and padded transportation case. Other features include user adjustable alarms and a built-in battery charger with low battery light. * UniMax Single-Point Gas Monitor UniMax, a compact, pocket sized, single gas microprocessor con- trolled monitor continuously detects and displays gas concentration on a large, easy to read digital display. The UniMa-x can be configured to monitor oxygen or a wide range of toxic gases including carbon monoxide, hydrogen sulfide or sulfur dioxide, chlorine, and chlorine dioxide. The unit uses state of the art electrochemical, interchange- able, offering easy adaptability and versatility for monitoring a. wide variety of areas. * BC Carbon Dioxide Detector Designed for immediate response of excessive concentrations of CO2, this detector (manufactured by Bacharach Corp and supplied by Willer Engineering Ltd.) and warning device will provide detection capability for workers in many industries including: agricmlture; hor- ticulture, nuclear power plants; the food processing and the beverage industry. "' Air Samplers . MiniVol Portable Air Sampler manufactured by Airmetrics is a portable ambient air sampler for particulate (PMID, PM2.5 and TSP) and/or non-reactive gases (CO, NOx). This instrument was jointly devel— oped by EPA and the Lane Regional Air Pollution Authority LRAPA) to address the need for portable survey sampling. (e) 133 FAQS Personal Air Sampler, from Levitt Safety is ideal for industrial, hospital and personal hygiene appiications. The PAQS can offer long- term air quality measurements. The mean average results obtained over extended period provide more meaningful information. This approach ensures that an air contaminant event is not missed, as would be the case using a simple, single point measurement. “ YES IAQ Monitor An indoor air quality monitor, YES-206 Falcon from Young Environ— mental Systems is ideal for walk-through surveys in building and long term data. logging with trend analysis. It monitors carbon dioxide, temperature and relative humidity. Using interchangeable sensors, it can be used to monitor gas levels including oxygen, carbon monoxide, sulfur dioxide, hydrogen sulfide, chlorine, nitrogen dioxide, nitric ox- ide, hydrogen cyanide, ammonia or ethylene oxide. An extra channel can allow for monitoring sensors and analyzers with a linear output. Additional information is available at - www.utoledo.edu/"aprg/conrsos/iap/text/APHWSTRUhtml - www.0it.doe.gov/sens_cont/pdfs/ factsheets/nrc2_fact.pdf o www.msorsmagcom/resources/ businessdigest/sbd0201.shtml o www.buscom.oom/waste/E049U.html Maintenance of a large bridge The hazards of ice, wind and low visibility are compounded on bridges. For this reason, Vaisala delivers a package of products and services to help road authorities to manage the special hazards of bad weather on bridga. These include a specially designed bridge-deck sensor that measures bridge surface state, temperature and depression of freezing point. There are sensors that process standard parameters (average, gust, direction, speed) and trigger alarm when they are exceeded. Vaisala’s present weather sensor, the PWD11, provides both roadside visibility measurement and precipitation classification (e.g. frozen/non-frozen). The IceCast system can also be brought into play to monitor bridge data in real-time, archiving it for future reference. Options include our Thermal Mapping service, which is especially useful in finding locations for bridge sensors. Vaisala NowCasting offers a fully automated, 3-hour forecast of bridge surface conditions (temperature and state) so that operators can deal with icing hazards in good time, before they become serious. Sensors to monitor the following parameters may also be needed 0 Air temperature 0 Relative...
View Full Document

{[ snackBarMessage ]}