Showing papers by "Ruhai Wang published in 2014"

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

Abstract: 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.

Memory dynamics for DTN protocol in deep-space communications

Abstract: Considering the signifcant success of the terrestrial Internet, the National Aeronautics and Space Administration (NASA) and other space agencies have been working for a few decades to enable space communications using the Internet-type protocols such as transmission control protocol/ Internet protocol (TCP/IP), namely, space internetworking or simply space Internet. It is well known that long propagation delays, intermittent connectivity, heavy channel noise, and asymmetric link rates in space environments all conspire to limit the effectiveness and performance of TCP over space communication channels, especially in deep-space communications [1]. The space Internet in deep-space interplanetary environments is generally named interplanetary Internet (IPN) [2]. Numerous literature surveys [2]?[7] have been done on IPN architectures and protocols.

On storage dynamics of space delay/disruption tolerant network node

Abstract: Delay/disruption tolerant network (DTN) plays a promising role in prospected information infrastructures for future space activities, such as Interplanetary Internet (IPN) or Solar System Internet (SSI). Over such long-haul and intermittent links, DTN technique makes scientific data return end-to-end reliable by the typical custody transfer and store-and-forward mechanism. Due to lack of enough space spacecrafts deployed for DTN, now and in the near decades, there will be some intermediary nodes which would carry a large proportion of network traffic as DTN routers. Consequently, the behaviors and capabilities of managing bundles in the intermediary nodes would have impacts on the data transport over space DTN. Focusing on the storage dynamics of bundles, in this paper, we propose an analytical framework based on two-dimension Markov chain to evaluate the behaviors of bundles delivery in DTN intermediate nodes. Accordingly, a delay model and a transmission success probability model for bundles delivery over space DTN are developed separately, both dependent closely on the sojourn time in node storages. The evaluation results indicate that: (1) Dividing the source files into bigger bundles for transmission causes a longer storage-occupancy time on intermediary nodes; (2) bundle sizes have more explicit impacts on the storage-occupancy time at a node than segment sizes do; and (3) the transmission success probability of a bundle is more dependent on a DTN bundle size than on a LTP segment size.