System Introspection for System Analysis on Mobile Devices

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Test No. Pattern Delay (ms) # Messages1 Singleline 100 2002 Multiline 100 2003 Complex Data 100 2004 Singleline 500 2005 Multiline 500 2006 Complex Data 500 2007 Singleline 1000 2008 Multiline 1000 2009 Complex Data 1000 200Table 7.2: Parameters <strong>for</strong> the latency test sequences evaluated - Thepattern describes the type of the payload attached to amessage. The delay is used to simulate a frequency <strong>for</strong>sending messages and placed between two messages. Thenumber of messages determines how many messages aresend in one test. Each parameter can be configured viathe GUI of the evaluation component thread.7.2.4 ResultsTo analyze the collected data the average latency and the standard deviation(STDEV) of the different patterns is calculated (see table 7.3). Figure 7.1shows the results on the mobile device, plotting the latency of sending thedifferent pattern with a delay of 100ms. The results <strong>for</strong> the other frequenciesand the results <strong>for</strong> the laptop can be found in the appendix. A first impressionon these results is that <strong>for</strong> sending smaller payloads like the Singleline andMultiline pattern the latency is quiet low. For the ComplexData pattern thelatency is with around 250-300 ms quiet higher and may be not suitable <strong>for</strong>transferring data with a high frequency. In comparison to the laptop thelatency seems to be higher on a mobile device.The Singleline data is intended <strong>for</strong> short message exchange with a higher rate.On the mobile device an average latency of 13.01ms (STDEV 15.42ms) couldbe measured <strong>for</strong> a high update rate of 100 ms. On the laptop the averagelatency measured was 2.67ms (STDEV 5.44ms). Exchanging small payloadscan be exchanged with a low latency even with a higher frequency. The Multilinesimulates bigger payloads containing several in<strong>for</strong>mation (e.g. lists aboutcomponent states). With an average latency of 13.74ms (STDEV 11.53ms) onthe mobile device and 5.16ms (STDEV 10.17ms) on the laptop even a highfrequency of 100ms can be achieved. For both patter, Singleline and Multiline,data supports the requirement to achieve a minimum delay (see chapter3). The ComplexData pattern can be compared to exchange bigger payloads(e.g. images or byte arrays). With an average latency of 291.15ms (STDEV57
Figure 7.1: Latency of receiving data on the mobile device - Theresults of sending the different pattern with a delay of100ms is plotted. For each pattern 200 messages weresend to the client.101.34ms) on the mobile device and 284.99 (STDEV 144.74ms) on the laptopusing a frequency of 100ms such data may only be used <strong>for</strong> observation withoutexpecting actual data. Using lower frequencies like 500ms or 1000ms seems notto reduce the latency.However several peaks can be observed in the plots of the results. For eachtest the robot was running the same internal processes active even if the probeis not attached to the robot software. To communicate both controlling laptopsuse the network of the plat<strong>for</strong>m. Observing the network devices on bothlaptops showed a usage of over 50% network usage used <strong>for</strong> communicationbetween these laptops. One reason <strong>for</strong> peaks occurring in the plotted data canbe the load on the network bandwidth. Whenever the bandwidth is used upby the exchange of messages consumes more time. Also a comparison of thetime of sending between two messages showed that the probe <strong>for</strong>wards the messagewith the defined delay. Each message is <strong>for</strong>warded to the communicationserver. Running as own process a processes running in parallel (e.g. receivingdata over the network interface) can interrupt the process of dispatching messagesand result in a time delay. On the client side the process priority caninfluence the processing of incoming messages as well. On the mobile deviceeach process underlies the control of the operation system which also controlsthe network interface. But even with the peaks the overall latency is nearlyconstant. No message got lost between the probe and the client. Regardingthe questions announced in the goal the results indicate that the payload influencesthe latency. Bigger payloads produce a higher latency. For smallerpayloads the delay is nearly constant even <strong>for</strong> faster message exchange. Alsothe results of the different clients are similar which indicates that the latency58
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Bringing System <s
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AbstractSystem <st
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output, so each component is offeri
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of the system and the decisions mad
Page 11 and 12: created a telelaboratory where two
Page 13 and 14: Like the telelaboratory there is a
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Page 21 and 22: Figure 4.3: The architecture behind
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Page 27 and 28: Figure 5.2: Message exchange betwee
Page 29 and 30: Figure 5.4: Beacon running between
Page 31 and 32: Figure 5.5: Reading and processing
Page 33 and 34: data and only forw
Page 35 and 36: For example a developer can select
Page 37 and 38: Figure 5.13: Principle of tabbed na
Page 39 and 40: 6.1 The Communication InterfaceThe
Page 41 and 42: 6.2 The Probe - Implementation of t
Page 43 and 44: stop all active processes of the co
Page 45 and 46: is received containing the TAG of t
Page 47 and 48: The selected sensors give a good im
Page 49 and 50: 1 2 4 6 8 Listing 6.2: Example of t
Page 51 and 52: TabConfig - The Status ViewThe TabC
Page 53 and 54: Each view adds a listener to the co
Page 55 and 56: LoginController which also observes
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Page 69 and 70: 8 ConclusionsIn the context of this
Page 71 and 72: 9 OutlookGiven this new tool its no
Page 74: BibliographyBurrell, A. and A. Soda
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Page 79 and 80: AppendixUse CasesUse Case 1: Connec
Page 81 and 82: Use Case 4: Disconnect from compone
Page 83 and 84: Use Case 9: Sending beacon to keep
Page 85 and 86: Figure 9.4: Latency of receiving da
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