Showing papers by "Ruhai Wang published in 2011"

Licklider transmission protocol (LTP)-based DTN for cislunar communications

Abstract: 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.

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

Abstract: 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.

Experimental evaluation of TCP-based DTN for cislunar communications in presence of long link disruption

Abstract: 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.

Interplanetary Overlay Network (ION) for Long-Delay Communications with Asymmetric Channel Rates

Abstract: Interplanetary Overlay Network (ION) is an implementation of delay/disruption tolerant networking (DTN) developed as infrastructure for space communications in interplanetary flight mission systems. To date, no work has been done in evaluating the effectiveness of ION when it is applied to an interplanetary Internet involving very long link delay and highly asymmetric channel rates. In this paper, we present an experimental evaluation of ION over a typical three-node interplanetary infrastructure in the presence of a long link delay, highly asymmetric channel rates and varying data loss rate. One major conclusion is that the hybrid of TCP and Licklider transmission protocol (LTP) convergence layer protocols has significant goodput advantage over other protocol options as the ratio of data channel rate to ACK channel rate increases.

A Novel Frequency Sense Solution for Cognitive Radio Based on Tracing Localization

Abstract: Cognitive radio has potential to improve spectrum efficiency in future wireless multimedia communications. There exist various performance problems in the dynamic spectrum resource management, frequency sense and utilization for cognitive radio. In this paper, a novel frequency sense solution based on the double-station cooperation and multi-hop tracing localization is proposed to resolve the hidden and exposed problems in spectrum resource management. In specific, the solution is proposed to improve reliability and efficiency of frequency sense and increase the utilization of spectrum. With this solution, a secondary user can obtain more accurate primary user's location by an improved centroid localization algorithm cooperated with a known position user. The tracing localization accuracy is also analyzed. Simulation results show that the proposed solution significantly improves the performance while location accuracy is still within controllable range after multiple tracing hops.