Cislunar Communications Research Articles

Toward the Age in Cislunar Communication: An AoI-Optimal Multi-Relay Constellation With Heterogeneous Orbits

Toward the Age in Cislunar Communication: An AoI-Optimal Multi-Relay Constellation With Heterogeneous Orbits

Optimal Energy Efficiency for Relay Selection via Power Allocation in L2 Halo-Orbital Cislunar Communication Network

Optimal Energy Efficiency for Relay Selection via Power Allocation in L2 Halo-Orbital Cislunar Communication Network

Optimizing Lunar Map Partitioning for Multipath Fade Loss Analyses

A methodology is presented pertaining to the run-time optimization of quasi-optical ray-tracing simulations. These shooting-and-bouncing ray methods are used for assessing multipath fade loss in cislunar communication links. Our approach employs partitioning lunar terrain maps in shapes that approximate two-dimensional projections of Fresnel zone cross-sections. This technique drastically reduces computational run-time without causing significant loss of simulation accuracy.

Analytical characterization of licklider transmission protocol (LTP) in cislunar communications

The performance of delay/disruption tolerant networking (DTN) protocols in cislunar and deep-space communication systems has previously been studied by simulation. However, little work has been seen in characterizing in an analytical manner the performance of DTN protocols for space with respect to asymmetric channel rates. We present a performance characterization of the recently developed DTN Licklider transmission protocol (LTP) convergence layer adapter (CLA) (or simply LTPCL) over cislunar space channels with data-rate asymmetry. Analytical models are built to characterize LTPCL with respect to the minimum number of bundle protocol (BP) bundles that should be aggregated to avoid delay in acknowledgment (ACK) transmission and the optimal number of bundles to be aggregated for the best transmission efficiency of BP/LTPCL, with the effect of full overhead at all layers taken into consideration. The models are validated by file transfer experiments running BP/LTPCL protocols using a PC-based testbed.

Performance of DTN protocols in space communications

Delay/disruption tolerant networking (DTN) was developed to enable automated network communications despite the long link delay and frequent link disruptions that generally characterize space communications. The performance of DTN convergence layer adapter (CLA) protocols over asymmetric space communication channels has not yet been comprehensively characterized. In this paper, we present an experimental performance evaluation of DTN CLA protocols for reliable data transport over a space communication infrastructure involving asymmetric channel rates, with particular attention to the recently developed Licklider transmission protocol (LTP) CLA (i.e., LTPCL). The performance of LTPCL is evaluated in comparison with other two reliable CLAs, TCP CLA and a hybrid of TCP CLA and LTPCL, for long-delay cislunar communications in the presence of highly asymmetric channel rates. LTPCL is also evaluated and analyzed in a deep-space communication scenario characterized by a very long link delay and lengthy link disruptions.

Which DTN CLP is best for long-delay cislunar communications with channel-rate asymmetry?

Delay-/disruption-tolerant networking is considered one of the most suitable technologies to handle the delays and disconnection inherent in space internetworking. To date, little work has been done in evaluating its effectiveness in cislunar communications involving long link delay and highly asymmetric channel rates. In this article, we present an experimental study of DTN convergence layer protocols over a typical cislunar communication infrastructure accompanied by a very long link delay, various asymmetric channel rates, and varying data loss rate. The intent of the work was to find answers to two questions: which CLP is the best for long-delay cislunar communications in the presence of highly asymmetric channel rates, and whether aggregation of bundle protocol bundles is helpful for improving goodput of DTN in the presence of IPN channel asymmetry.

Licklider Transmission Protocol (LTP)-Based DTN for Cislunar Communications

Delay/disruption-tolerant networking (DTN) technology offers a new solution to highly stressed communications in space environments, especially those with long link delay and frequent link disruptions in deep-space missions. To date, little work has been done in evaluating the performance of the available “convergence layer” protocols of DTN, especially the Licklider Transmission Protocol (LTP), when they are applied to an interplanetary Internet (IPN). In this paper, we present an experimental evaluation of the Bundle Protocol (BP) running over various “convergence layer” protocols in a simulated cislunar communications environment characterized by varying degrees of signal propagation delay and data loss. We focus on the LTP convergence layer (LTPCL) adapter running on top of UDP/IP (i.e., BP/LTPCL/UDP/IP). The performance of BP/LTPCL/UDP/IP in realistic file transfers over a PC-based network test bed is compared to that of two other DTN protocol stack options, BP/TCPCL/TCP/IP and BP/UDPCL/UDP/IP. A statistical method of t-test is also used for analysis of the experimental results. The experiment results show that LTPCL has a significant performance advantage over Transmission Control Protocol convergence layer (TCPCL) for link delays longer than 4000 ms regardless of the bit error rate (BER). For a very lossy channel with a BER of around 10-5, LTPCL has a significant goodput advantage over TCPCL at all the link delay levels studied, with an advantage of around 3000 B/s for delays longer than 1500 ms. LTPCL has a consistently significant goodput advantage over UDPCL, around 2500-3000 B/s, at all levels of link delays and BERs.

Experimental Evaluation of TCP-Based DTN for Cislunar Communications in Presence of Long Link Disruption

Delay/disruption tolerant networking (DTN) technology is considered a new solution to highly stressed communications in space environments. To date, little work has been done in evaluating the effectiveness and performance of the available DTN protocols when they are applied to an interplanetary Internet, especially in presence of a long link disruption. In this paper, we present an experimental investigation of the DTN architecture with a Bundle Protocol (BP) running over TCP-based convergence layer (TCPCL) protocol in a simulated cislunar communication environment characterized by a long link disruption. The intent of this work is to investigate the effectiveness of the TCPCL-based DTN protocol in coping with long link disruptions, through realistic file transfer experiments using a PC-based test-bed. The experiment results show that the DTN protocol is effective in handling a long link disruption experienced in data transmission accompanied by a cislunar link delay and a high BER. The performance of the DTN is most adversely affected by link disruption time in comparison to the effect of link delay and BER. For the transmissions with a very long link disruption of hours, the variations in goodput are nominal with respect to the change in cislunar link delay.

TCP Convergence Layer-Based Operation of DTN for Long-Delay Cislunar Communications

Delay/disruption tolerant networking (DTN) is a class of network techniques developed to accommodate long link delay and frequent link disruptions. Little work has been done in evaluating the effectiveness and performance of the DTN protocols when they are applied for an interplanetary Internet (IPN). In this paper, we present an experimental evaluation of Transmission Control Protocol Convergence Layer (TCPCL)-based operation of DTN-2 (i.e., TCPCL/TCP) for long-delay cislunar communications, partially in comparison with Licklider Transmission Protocol (LTP)-based LTP/User Datagram Protocol (UDP). The experiment is conducted by transmitting a text file using the DTN protocol stack over a PC-based simulation test-bed. According to the experimental results, the TCPCL-based DTN protocol works effectively over less error-prone cislunar links with short delay and has performance advantage over LTP-based DTN. Along with the increase in link delay and channel noise, the performance of TCPCL-based DTN is getting far behind the LTP-based DTN. The TCPCL-based DTN protocol can successfully handle an experimented short link disruption around 30 s-120 s, even with an existence of a very long link delay and a high channel Bit-Error-Rate (BER), but its performance is poor compared to that of the LTP-based DTN.

Unreliable CCSDS File Delivery Protocol (CFDP) over Cislunar Communication Links

The Consultative Committee for Space Data Systems (CCSDS) file delivery protocol, also known as CFDP, is a new standard protocol designed to meet a comprehensive set of file transfer requirements in space communications, especially deep space missions. There has been theoretical and experimental evaluation on the performance of CFDP operation in low Earth orbit (LEO) and geo-stationary Earth orbit (GEO) space environments. However, very few works have evaluated the performance of CFDP in cislunar space, even though the protocol has been particularly developed for deep space communications. In this work we discuss an experimental investigation of the core file-delivery operation of unreliable CFDP, operating with reliable transmission control protocol (TCP), over a simulated cislunar communication link under various channel conditions. Our intention is to evaluate the transmission effectiveness of the core file-delivery operation in unreliable CFDP running on top of a reliable TCP/IP stack over a long-delayed cislunar link, especially when accompanied by link disruptions and a high bit error rate (BER). The performance of unreliable-CFDP/TCP is also compared with other protocol options of CFDP, such as reliable-CFDP/TCP and reliable-CFDP/UDP. The experiment was carried out through realistic file transfers by running the CFDP protocol stack over a communication test-bed incorporating the qualities that define cislunar communication channel characteristics. The research results and discussions presented in this paper should work equally well in any space mission with a round-trip time (RTT) that is comparable to that of the cislunar space.