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Enhancement of the NMSU Channel Error Simulator to Provide User-Selectable Link DelaysThis is the third in a continuing series of reports describing the development of the Space-to-Ground Link Simulator (SGLS) to be used for testing data transfers under simulated space channel conditions. The SGLS is based upon Virtual Instrument (VI) software techniques for managing the error generation, link data rate configuration, and, now, selection of the link delay value. In this report we detail the changes that needed to be made to the SGLS VI configuration to permit link delays to be added to the basic error generation and link data rate control capabilities. This was accomplished by modifying the rate-splitting VIs to include a buffer the hold the incoming data for the duration selected by the user to emulate the channel link delay. In sample tests of this configuration, the TCP/IP(sub ftp) service and the SCPS(sub fp) service were used to transmit 10-KB data files using both symmetric (both forward and return links set to 115200 bps) and unsymmetric (forward link set at 2400 bps and a return link set at 115200 bps) link configurations. Transmission times were recorded at bit error rates of 0 through 10(exp -5) to give an indication of the link performance. In these tests. we noted separate timings for the protocol setup time to initiate the file transfer and the variation in the actual file transfer time caused by channel errors. Both protocols showed similar performance to that seen earlier for the symmetric and unsymmetric channels. This time, the delays in establishing the file protocol also showed that these delays could double the transmission time and need to be accounted for in mission planning. Both protocols also showed a difficulty in transmitting large data files over large link delays. In these tests, there was no clear favorite between the TCP/IP(sub ftp) and the SCPS(sub fp). Based upon these tests, further testing is recommended to extend the results to different file transfer configurations.
Document ID
20000072577
Acquisition Source
Goddard Space Flight Center
Document Type
Other
Authors
Horan, Stephen
(New Mexico State Univ. Las Cruces, NM United States)
Wang, Ru-Hai
(New Mexico State Univ. Las Cruces, NM United States)
Date Acquired
September 7, 2013
Publication Date
April 30, 2000
Subject Category
Computer Programming And Software
Report/Patent Number
NMSU-ECE-00-001
Funding Number(s)
CONTRACT_GRANT: NAG5-7520
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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