Showing papers by "Ruhai Wang published in 2015"

Modeling memory-variation dynamics for the Licklider transmission protocol in deep-space communications

Abstract: Delay/disruption-tolerant networking was developed to enable automated network communications despite the long link delay and frequent link disruptions that generally characterize deep-space communications. It uses the well-known approach of store-and-forward with optional custody transfer, in which a node agrees to hold a file in memory (or storage) until its successful reception is acknowledged by the next node. The performance and memory consumption of delay/disruption-tolerant networking's Licklider transmission protocol (LTP) and bundle protocol in deep space will bear on decisions to adopt this technology. There is currently an urgent need to evaluate the performance and memory dynamics for file transmission by LTP and bundle protocol. In this paper, we present a study of memory dynamics for LTP-based transmission in a typical relay-based deep-space communication system characterized by an extremely long signal-propagation delay, lossy data links, and asymmetric data rates. Analytical models are built to quantify the dynamics of memory occupancy/release and memory release latency imposed by the use of LTP for reliable and complete file delivery in deep-space missions. File-transfer experiments are conducted using a test bed to validate the models.

Performance modeling of licklider transmission protocol (LTP) in deep-space communication

Abstract: Delay/disruption tolerant networking (DTN) offers a solution to communications in “challenged” networks Some work has been seen in evaluating the performance of DTN protocols based on simulated or emulated file transfer experiments However, there is a need for a model of the performance of the DTN Licklider transmission protocol (LTP), which particularly targets reliable data transmission in deep space In this paper, we present a performance model of LTP-based DTN data transmission in challenging communications characterized by extremely long signal propagation delay, lengthy link disruptions, and highly lossy channels that are typical of deep-space links The model is verified by file-transfer experiments using a PC-based testbed

Memory Dynamics and Transmission Performance of Bundle Protocol (BP) in Deep-Space Communications

Abstract: Delay/disruption tolerant networking (DTN) was proposed as an end-to-end networking architecture providing file delivery service in and/or through stressed communication environments. Bundle protocol (BP) of DTN utilizes the well-known store-and-forward mechanism together with custody transfer option for which a node agrees to hold a file in memory (disk storage in this paper) until its successful reception is acknowledged by the next node. The variation in memory occupancy constrains the volume of memory that is available for other DTN functions. Characterizing the memory dynamics of BP during file transfer is crucial. In this paper, we present a study of memory variation dynamics and transmission performance in the operation of BP for file transmissions over a typical relay-based deep-space communication system characterized by multiple data source nodes, an extremely long signal propagation delay, and lossy data links with both symmetric and asymmetric channel rates. Analytical models are built to estimate the memory variation dynamics and the total file delivery time (and goodput) characterizing BP transmission in deep space. The models are validated by running file transfer experiments using a testbed.

CFDP-based two-hop relaying protocol over weather-dependent Ka-band space channel

Abstract: In this paper, we propose a novel relaying protocol based on the Consultative Committee for Space Data Systems File Delivery Protocol (CFDP) over a weather-dependent Ka-band channel, which exploits a dual-hop link instead of the traditional single-hop link for a 100% file delivery service on scientific data return.We designed the specific model of the proposed protocol and provide the analytical results on the expected latency and link efficiency of the file delivery. Based on the proposed model, we discuss the exact location of the relay node that could minimize the expected file delivery delay by examining several practical relay locations for the proposed protocol. The simulation results show that, compared with the traditional CFDP, the proposed file delivery protocol could effectively reduce the total file delivery time by several orders of astronomical units and enhance link efficiency with noticeable increments, especially under conditions of high bit error rates (above 10−5).