最可口的聯網嵌入式系統報告

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最可口的聯網嵌入式系統報告

  1. 1. Kwiizya: Local Cellular Network Services in Remote Areas Mariya Zheleva, Arghyadip Paul, David L. Johnson and Elizabeth Belding Department of Computer Science University of California, Santa Barbara {mariya, arghyadip, davidj, ebelding}@cs.ucsb.edu http://cs.ucsb.edu/~mariya/docs/mobisys254-zheleva.pdf
  2. 2. INTRODUCTION  mobile phone usage has become one of the most prevalent means of communication worldwide  low population coverage may be spotty or non-existent
  3. 3. INTRODUCTION  many residents own phones and buy either subscriptions or pre-paid plans  in developing regions coverage is often limited to 2G, or 2G + EDGE at best http://ccumba.blogspot.tw/2013/01/100-gigishop.html
  4. 4. INTRODUCTION  there will be recurring need for lower cost solutions to serve those areas.  EX:crop prices,health care availability  Our work is in partnership with the LinkNet organization in Macha
  5. 5.  owns a cell phone(multiple phones ), few have coverage at their homes  utilizes different open-source software components , offers SMS and IM-to-SMS functionality http://goo.gl/mHfhGU
  6. 6. several contributions  design and integration of a low-cost cellular network  evaluation of a fully operational instance of our system deployed in the field  modification of OpenBTS to support Instant Message to SMS functionality for SMS-based applications
  7. 7. VOICE COMMUNICATION IN RURAL ZAMBIA http://goo.gl/tBj18J
  8. 8.  briefcase buyers problem  Zambian Food Reserve Agency (FRA)  get information about crops prices http://goo.gl/sZxA9r
  9. 9.  Village : Macha (Zambi)  135,000 people in the area spread over a large radius of 35km.  households rarely have access to electricity.  travel to powered public spaces to charge cellphones  charge their phones while at work
  10. 10.  Macha is connected to the Internet through one of Zambia’s Internet service providers.  A monthly subscription limited at 1GB traffic costs 30 USD  access the Internet from work or from an Internet caf´e in order to use VoIP services.
  11. 11. SOCIAL SURVEYS http://blog.pepe.tw/7332
  12. 12. Social survey  We interviewed 26 people , between 20 to 48  14 female 12 male  1-2km for residents of Hamoonde and Chikanta to reach to an area with coverage and conduct a call.  They use the phone to obtain information, such as crop pricing for farmers.  Result: Browsing is slow and frustrating.
  13. 13. KWIIZYA http://goo.gl/UamVI3
  14. 14.  low-cost cellular system that leverages existing  unmodified mobile phones and SIM cards to provide voice and text messaging for free  the voice and text messaging operation
  15. 15. Architecture  free open-source software to provide voice and text message services  standard Um radio interface for commodity 2G and 2.5G cellphones. http://goo.gl/x3scNa
  16. 16.  FreeSwitch connects to OpenBTS via SIP and RTP and routes calls  Sipauthserve and SMQueue to handle user authentication and text messaging http://goo.gl/iBg18J
  17. 17.  exposes an API that can leverage text broadcasting functionality to automate message generation send IM messages  EX : automatic weather alerts, dissemination of crops prices , and health care availability updates
  18. 18. rural setting:  A small memory footprint of the IM client on the host device  Usability across various operating systems to target a heterogeneous set of devices.  Ability to leverage the existing SIP switching/routing capability available in FreeSwitch
  19. 19.  stores the IP address of the host where the IM client is installed  standard SIP MESSAGE http://goo.gl/CZaVeK
  20. 20. http://goo.gl/vkyz6s
  21. 21.  If the user is not associated, SMQueue stores the message and regularly attempts delivery http://goo.gl/wRfvhx
  22. 22. MACHA DEPLOYMENT http://goo.gl/FjEJ4h
  23. 23.  We chose Macha for our first field deployment  because Macha is fairly well connected in terms of Internet access.
  24. 24. Design challenges  Power.  the voltage varies from 150V to 240V with frequent power failures.  harmful for computer equipment.
  25. 25. http://goo.gl/kcUiRD
  26. 26.  Internet access.  due to an outage in the upstream link, the village gateway cannot connect to the Internet.
  27. 27. http://goo.gl/8LE6PX
  28. 28. Technical details  we use one of the base station PCs as a network central server, running FreeSwitch, Sipauthserve and SMQueue  the second base station runs only OpenBTS and connects to the first one
  29. 29.  LinkNet IT Academy
  30. 30. LinkNet IT Academy
  31. 31.  Each call in Kwiizya has two associated VoIP sessions  one for the mobile call originator (MCO)  one for the mobile call terminator (MCT). http://goo.gl/CJcBzd
  32. 32. EVALUATION OF KWIIZYA http://goo.gl/1HcRfq
  33. 33.  (i) controlled experiments  (ii) evaluation of system usage in the wild following our Macha deployment. http://goo.gl/f035iW
  34. 34. controlled experiments  SMS and Voice Calls  we sent 100 consecutive messages, with 6 seconds inter-message delay. 99 of these messages were received by Kwiizya.
  35. 35. As the graph shows, 99% of the messages were delivered to their destination in 6-9 seconds; the maximum observed delay is 11 seconds. The average delay over all 99 messages is 7.06 seconds
  36. 36. The major contributors to the end- to-end delay are the radio interfaces from the MMO to OpenBTS and from OpenBTS to the MMT
  37. 37. non-Um delay is only 2.9 ms. http://goo.gl/si6RkA
  38. 38. we measure the callestablishment time.
  39. 39.  The figure indicates that with one exception, it typically takes between 2 and 4 seconds for a call to initiate. (ID14 = glitch)
  40. 40. controlled experiments  Instant Messaging to SMS  evaluates the time for message delivery when the IM client sends bursts of messages to associated users. http://052765985.tranews.com/
  41. 41.  each phone can only receive one message at a time. Thus, if five messages are sent simultaneously to the same phone, the first message should arrive in X seconds, the second in 2X seconds and so on.  we used three phones to receive bursts ranging in size from 15 to 75 messages.
  42. 42. Each point on the plot corresponds to delay for a single message and each vertical line indicates the burst size. demonstrates that Kwiizya is capable of handling bursts of variable size without incurring delay in message delivery.
  43. 43. Voice call quality  Delay, Jitter and Packet Loss.  Delay, jitter and packet loss are three characteristics of a VoIP session that are critical to voice quality. http://goo.gl/U4alWE
  44. 44.  ITU recommendation G.114 mandates that tolerable one way delay is up to 150 ms .  Kwiizya uses GSM 6.10, for which the minimum delay is 20 ms.
  45. 45. shows the average jitter within that VoIP session.
  46. 46.  Only three of all sessions suffered non-zero packet loss.  however, these three were all less than 0.5%, which is within the limit for satisfactory call quality.
  47. 47. Mean Opinion Score (MOS) a metric that describes the call quality as perceived by the communicating parties. http://goo.gl/ZHxE6h
  48. 48. RELATED WORK  There is increasing effort to develop applications that use plain text messaging and voice  For instance:  a social network based on voice forumsfor farmers to exchange knowledge about crops and crop prices
  49. 49.  Numerous applications use text messaging as a platform.  Use cases include update of remote databases through SMS , attendance tracking , web search and health care  The drawback of these solutions is that they all assume existence of an underlying cellphone network http://goo.gl/pfJWdR
  50. 50.  A few projects discuss alternative cellular network solutions for remote areas  what they lack is holistic system design and large-scale evaluation of feasibility from a system point of view
  51. 51. 8  Software that converts GSM signals to voice over IP allows design of low-cost local cellular networks.  Kwiizya leverages unmodified cellphones to provide voice and SMS services.  Kwiizya can also interface with global services such as GoogleVoice, Skype or commercial operators
  52. 52.  Kwiizya relies entirely on free, open-source software.  A reliable power supply is a major fraction of both capital and operating expenses in remote cellular deployments.  Kwiizya reduces the capital expense by using free open-source software, SDR-based hardware and universal IP backbone.
  53. 53. thanks
  54. 54. http://goo.gl/gbWLiv

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