Space Communication Protocol Standards (SCPS) has been developed for the reliable transfer of information in the space Internet. There is a need to have an evaluation of the SCPS protocol in a realistic space environment with a large bandwidth- delay product (BDP). An experimental evaluation of SCPS-TP was done by transferring user files using the SCPS protocol over the NASA's Advanced Communications Technology Satellite (ACTS) links. However, the user files were so small that the steady performance of the protocol could not be accurately evaluated. This paper describes an experimental evaluation of SCPS-TP over high-speed, asymmetric space links by transferring a large user file over asymmetric ACTS link, leading to its steady performance.

Space communication protocol standards-transport protocol (SCPS-TP) is a set of extensions to transmission control protocol (TCP) aimed at improving TCP performance over space links. Some work has been done on performance evaluation of SCPS-TP based on its methodology, or by testing it as an isolated entity or over satellite that deploys performance enhancing proxies (PEPs). It is needed to have an experimental evaluation of SCPS-TP in coping with heavy noise using the complete SCPS protocol stack, especially by comparing it with state-of-the-art terrestrial TCP. This paper describes an experimental evaluation of SCPS-TP over congestion free, error-prone, high-latency, point-to-point space links, through file transfer experiment by running the actual SCPS protocol stacks via a testbed. The results reveal that SCPS-TP is more tolerant of heavy noise and has significant throughput advantages over TCP. The performance advantage of SCPS-TP in a lossy link is attributed to its novel SNACK scheme and the advantage in asymmetric channel is from the contributions of the channel rate control and acknowledgment reduction mechanisms.

Space communication protocol standards (SCPS) has been developed for the reliable transfer of information in the future space and interplanetary Internet. Some work has been done on performance evaluation of SCPS by testing it over the low-rate channels and/or via an emulation test-bed. However, this work has been done by testing SCPS over the low rate channels and/or via an emulation test-bed. It is expected to have an evaluation of the complete SCPS protocol suite in a realistic space environment with a large bandwidth-delay product (BDP). In this paper, we present an experimental performance evaluation of SCPS suite, by comparing with standard TCP/IP, over the NASA's Advanced Communications Technology Satellite (ACTS) high speed links with data rate up to 4 Mb/s.

There is an urgent need for finding an optimal transmission mechanism in the space-based Internet. This paper presents an experimental analysis of the throughput performance and transmission behavior for the rate-based and window-based congestion control mechanisms in a simulated small-satellite environment using a PC-based test-bed. The experimental analysis revealed that the traffic shaping mechanism of a rate-based transmission is more effective than the bursting flow of a window-based mechanism in error-prone space environment with a long link delay. The window-based transmission mechanisms show performance degradation due to traffic bursts and frequent packet retransmissions caused by their ACK-clocked congestion control. Pure rate-control is preferable to other mechanisms in space when bandwidth reservation is available.

Space communication protocol standards-transport protocol (SCPS-TP) is a set of extensions to transmission control protocol (TCP) aimed at improving TCP performance in space communications. It is expected to have an experimental evaluation of the throughput performance of SCPS-TP over lossy communication links in a small satellite environment, especially by comparing it with standard TCP. This paper describes a performance evaluation of TCP and SCPS-TP over lossy links in a simulated small satellite environment using a test-bed. The results show that SCPS-TP is more tolerant of heavy noise and asymmetric channel and shows a much better performance, which make it more favorable over standard TCP in similar communication environments.

This paper investigates receiver structures for enhanced FQPSK modulation. A new receiver structure called the per waveform matched filter (PWMF) receiver is introduced. The bit error rate performance of averaged matched filter receiver, optimal linear MMSE receiver, PWMF receiver and the optimal receiver based on the Viterbi algorithm is studied for uncoded and coded EFQPSK signals with and without a nonlinear power amplifier. Our study shows that the various structures provide complexity performance trade off and their performance is little degraded due to the presence of the nonlinear amplifier. A low complexity receiver structure for Rayleigh frequency-flat fading channels is also investigated and is found to perform well.

The Advanced Communications Technology Satellite (ACTS) propagation experiment has collected four years of propagation data at 20.185 and 27.505 GHz. The objective of the experiment is to develop long-term statistics and modeling techniques for predicting atmospheric propagation effects in the Ka band. The experiment includes seven identical earth stations at different locations in North America. Each location is meant to characterize a unique rain region. This paper presents the data collected in White Sands, NM. The data from this site provide an excellent resource for validating rain attenuation models due to its unique arid climate with occasional high rain-rate storms. The seasonal and cumulative four-year attenuation statistics for the 20.2 and 27.5 GHz beacons are presented. The attenuation with respect to clear air (ACA) is compared to five different rain attenuation models and seven different frequency scaling models. The results illustrate how well each model predicts rain attenuation in a desert climate region.

This paper analyzes fade slope for the Alaska, Florida, and New Mexico Advanced Communications Technology Satellite (ACTS) propagation data at 20 and 27.5 GHz for the first two years of the experiment (December 1, 1993-November 30, 1995). The propagation experiment will continue to collect data for at least another 21 months. Fade slope is examined on a statistical basis for the three sites. The Florida and New Mexico receiver sites have very different weather characteristics but almost identical elevation angles, while the Alaska receiver terminal has an extremely low elevation angle. The cumulative statistics illustrate the relationship between fade slope, fade level, transmission frequency, and elevation angle for all three sites.