Implementation of IP Mesh Network using ULE Protocol over DVB-S Links

1
Implementation of IP Mesh Network using ULE
Protocol over DVB-S Links

• Ang Way Chuang (wcang_at_nrg.cs.usm.my)
• Wan Tat Chee (tcwan_at_cs.usm.my)
• Network Research Group
• School Of Computer Sciences
• Universiti Sains Malaysia
• 11800 USM, Penang, Malaysia.

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Introduction

• Satellite-based Internet connectivity
• Provides access to rural / underserved
  communities
• Able to operate in areas without existing
  telecommunications infrastructure
• Quick setup for disaster relief and recovery
  efforts (e.g., earthquakes, tsunami, etc.)

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Issues

• Existing satellite-link based Internet access
  equipment is expensive
• Existing technology has inefficient spectrum
  usage
• Existing hub-based network averages two hops
  among nodes (high latency)
• DVB-S is a cost-effective method used in
  satellite TV broadcast (e.g., Astro)
• However, It is unidirectional in nature
• Unidirectional Link Mesh Network implements
  bidirectional network access using DVB-S
  technology

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Existing Point-to-Point Satellite Links
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UniDirectional Link Mesh Networking Approach
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Hardware Requirements

• An ASI (Asynchronous Serial Interface) card to
  transmit MPEG2-TS packet (Linear Systems DVB
  Master FD).
• (N 1) DVB receiver cards where N is the number
  of nodes in the UDL mesh network. List of
  supported DVB receiver cards http//www.linuxtv.o
  rg/wiki/index.php/DVB-S_cards.
• A DVB-S modulator (Newtec NTC2177).

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Node Configuration (for 3-Node WAN network)
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Configuration for 3 Nodes Test Bed
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Bidirectional DVB-S ULE Architecture
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Experiment and Result
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Experiment and Result (cont)
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Experiment and Result (cont)
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Experiment and Result (cont)
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Experiment and Result (cont)
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Experiment and Result (cont)
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Analysis of Result

• All UDL nodes are allocated 8Mbps of bandwidth
  for the tests.
• The throughputs of TCP and UDP traffic are about
  1/2 and 1/8 of allocated bandwidth respectively.
• ASI card buffer queue affects the latency of
  packet sending. Less buffer queue decreases
  latency, but increases CPU usage due to more
  interrupts and context switches.

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Analysis of Result (cont)

• Faulty ASI card firmware disables automatic null
  packets insertion. Thus bidirectional module need
  to insert null packets manually.
• Consequently, real data packets have to compete
  with null packets for resources. Thus the
  performance is less than ideal.
• Due to high latency, bigger TCP window size
  results in better throughput.

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Future Work

• Reimplemention of bidirectional module as a
  kernel space module to cut the cost of context
  switches and improve performance.
• Try to obtain an ASI card that properly insert
  null packets automatically.

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Links Contacts

• IP over DVB-S via ULE research page
  http//nrg.cs.usm.my/satellite_ule.htm
• Bidirectional module research page
  http//nrg.cs.usm.my/ule.htm
• Coordinator tcwan_at_cs.usm.my
• Developers cwtan_at_nrg.cs.usm.my,
  chteh_at_nrg.cs.usm.my, wcang_at_nrg.cs.usm.my.