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Koo, Cheol Hea,Burleigh, Scott C. 한국통신학회 2023 Journal of communications and networks Vol.25 No.4
Several elements characterize deep space communi-cations, including weak signal-to-noise-ratio (SNR), high bit errorrate (BER), asymmetric channel bandwidth, and long propaga-tion delay. In deep space missions, one-way light time (OWLT)is relatively much longer than in near-Earth missions. OWLTdominates data delivery completion time during a Licklidertransmission protocol (LTP) transaction, making other commu-nication elements relatively insignificant. As delay-/disruption-tolerant networking (DTN) technology plays a major role incommunication for space exploration missions, especially Artemismissions in a cislunar environment, the performance of the LTP“convergence layer” protocol grows more important; reducingthe time required to close an LTP transmission session willbe increasingly critical. LTP session completion is crucial formission operation because it must be bounded to support real-time operation. This study found that the LTP session closingtime can be unacceptably long when link performance is in theBER range of 10− 5 to 10− 6, which is commonly experiencedin space exploration communications. This paper presents anaggressive and proactive LTP control signal handling mechanism,conforming to the published LTP standard, that can reduce thelatency of LTP session closing time at the cost of somewhatdiminished goodput ratio. By applying this scheme in testsconfigured for segment size 2000 and BER 10− 6, 99.67% of LTPsessions closed within 5 OWLTs, while similar tests in which thisscheme was omitted which has 8.39% of shorter session closingtime and only 4% chances of exceeding 5 OWLTs against acase non-applying it. Through numerical models and simulations,we show that the overhead is marginally acceptable and cancontribute to better QoS over DTN operation in cislunar or deepspace missions by bounding the LTP session closing time.
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구철회,Scott C. Burleigh 한국통신학회 2022 韓國通信學會論文誌 Vol.47 No.12
Delay- and disruption-tolerant networking (DTN) technology is increasingly being considered for deep space exploration missions. In particular, DTN is being considered for trunk-line communications between ground and lunar elements of the Artemis program. Licklider transmission protocol (LTP) is a DTN protocol that supports reliable data transmission within a network and, as such, functions as a necessary “convergence-layer” protocol in the architecture. Korea Aerospace Research Institute (KARI) has recently developed an LTP reference implementation and performed an interoperability test with the National Aeronautics and Space Administration (NASA)’s Interplanetary Overlay Network (ION) DTN software. The test revealed that there can be significant variation in issuing report segments and data segment retransmission, which can lead to errors or malfunction during LTP transaction. This paper presents the results of the interoperability test between different implementations of LTP together with some implementation considerations suggested by the results to overcome the issues of the interoperability among different LTP implementations.
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