In this paper, we present the experimental measurement and evaluation of Transmission Control Protocol (TCP) performance over Internet Protocol (IP) using a real, heterogeneous network environment, incorporating at least one leg of satellite and land mobile link that, together, make an Integrated Satellite-Terrestrial Network (ISTN) testbed for our investigation and performance analysis. Originally, the TCP algorithm was developed for short latency and low link error network environments and has become a de-facto standard protocol for the reliable delivery of IP traffic over the Internet, which, in reality, is a heterogeneous network environment nowadays. Using the real latency figures measured with our testbed systems, we numerically analyse the performance of a standard TCP scheme and compare it with the newly developed TCP Hybla algorithm that claims to address performance degradation due to long round-trip-time (RTT) and high wireless link error channels such as Geostationary Satellite Links. The overall performance was compared with the achievable throughput of each of the two TCP algorithms and available bandwidth of the real testbed system. TCP Hybla performed better even with changing real values of RTT obtained from a real hybrid ISTN environment with a Geostationary Satellite link as the testbed.

In this work, a precise method for measuring end-to-end (E2E) latency in satellite Internet Protocol (IP) networks is proposed. Latency (i.e., time delay) is considered a key parameter that affects the quality of service (QoS) and the performance of communication systems. This is more pronounced in the IP over Satellite. Metrics such as throughput and bandwidth performance of communication systems are dependent on latency, which also has a direct impact on other QoS metrics, such as Internet packet transfer delay and delay variation (or jitter). The upper limits of QoS objective performance metrics are defined by E2E latency for different QoS traffic classes in this environment. Therefore, there is a need to develop efficient methods for the accurate measurement of E2E latency in a satellite IP environment. Two case study scenarios were developed for satellite heterogeneous networks to measure the latency in a satellite IP network. Two geostationary satellite network services were used to compare the performance of the different scenarios and networks. The results demonstrate that at least 50% of the E2E latency is due to the processing and transmitting of IP packets over the satellite in both scenarios. Inconsistent latency behaviour was also observed from daily results at different times of the day, which may degrade performance of jitter sensitive applications.

In a long-haul sensor network, sensors are remotely deployed over a large geographical area to perform certain tasks, such as target tracking. In this paper, we study the scenario where sensors take measurements of one or more dynamic targets and send state estimates of the targets to a fusion center via satellite links. The severe loss and delay inherent over the satellite channels reduce the number of estimates successfully arriving at the fusion center, thereby limiting the potential fusion gain and resulting in suboptimal accuracy performance of the fused estimates. In addition, the errors in target-sensor data association can also degrade the estimation performance. To mitigate the effect of imperfect communications on state estimation and fusion, we consider retransmission and retrodiction. The system adopts certain retransmission-based transport protocols so that lost messages can be recovered over time. Moreover, retrodiction/smoothing techniques are applied so that the chances of incurring excess delay due to retransmission are greatly reduced. We analyze the extent to which retransmission and retrodiction can improve the performance of delay-sensitive target tracking tasks under variable communication loss and delay conditions. Simulation results of a ballistic target tracking application are shown in the end to demonstrate the validity of our analysis.

In a long-haul sensor network, sensors are remotely deployed over a large geographical area to perform certain tasks. We consider a class of such networks where sensors take measurements of one or more dynamic targets and send state estimates of the target(s) to a fusion center via satellite links. The severe loss and delay inherent over the satellite channels render insufficient the number of estimates successfully arriving at the fusion center, thereby limiting the potential fusion gain and resulting in suboptimal accuracy performance of the fused estimates. The system can adopt certain retransmission-based transport protocols so that lost messages can be recovered over time. However, excess delay may be incurred that can potentially violate the deadline for reporting the estimate. For many applications, though, retrodiction/smoothing techniques can be applied so that the chances of incurring such excess delay are greatly reduced. In this work, we analyze the extent to which retrodiction, along with message retransmission, can improve the performance of delay-sensitive state estimation tasks. Results of numerical and simulation studies of an illustrative example and a ballistic target tracking application are shown in the end to demonstrate the validity of our analysis.