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Implementation of IP Mesh Network using ULE Protocol over DVB-S Links. Wan Tat Chee Network Research Group School Of Computer Sciences Universiti Sains Malaysia 11800 USM, Penang, Malaysia. tcwan@cs.usm.my. Introduction. Satellite-based Internet connectivity
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Implementation of IP Mesh Network using ULE Protocol over DVB-S Links Wan Tat Chee Network Research Group School Of Computer Sciences Universiti Sains Malaysia 11800 USM, Penang, Malaysia. tcwan@cs.usm.my
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.) (c) 2006 TC Wan
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 (c) 2006 TC Wan
Existing Point-to-Point Satellite Links (c) 2006 TC Wan
UniDirectional Link Mesh Networking Approach (c) 2006 TC Wan
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.org/wiki/index.php/DVB-S_cards. • A DVB-S modulator (Newtec NTC2177). (c) 2006 TC Wan
Node Configuration (for 3-Node WAN network) (c) 2006 TC Wan
Configuration for 3 Nodes Test Bed (c) 2006 TC Wan
Bidirectional DVB-S ULE Architecture (c) 2006 TC Wan
Experiment and Result (c) 2006 TC Wan
Experiment and Result (cont) (c) 2006 TC Wan
Experiment and Result (cont) (c) 2006 TC Wan
Experiment and Result (cont) (c) 2006 TC Wan
Experiment and Result (cont) (c) 2006 TC Wan
Experiment and Result (cont) (c) 2006 TC Wan
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. (c) 2006 TC Wan
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. (c) 2006 TC Wan
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. (c) 2006 TC Wan
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@cs.usm.my • Developers: cwtan@nrg.cs.usm.my, chteh@nrg.cs.usm.my, wcang@nrg.cs.usm.my. (c) 2006 TC Wan