It is well known that satellite communications systems are effective and essential communication infrastructure for disaster relief. NICT sent researchers to Tsunami stricken area in March right after the Great East Japan Earthquake and provided broadband satellite communications link to support rescue activities. Through this experience, we learned many kinds of requirements of communications ...

This paper presents securing satellite communications using link level security (such as ATM security) or network level security (such as IPSEC), where both can be applied to military satellite communications. The paper examines the topic of securing very large multicast groups over satellites, where the group size and group dynamics have great impact on networks performance and network security.

In this paper we present methods to generate terrain models for mountainous regions. For these regions analytical and statistical methods are unsuitable for predicting service coverage probability, call blocking and termination probabilities. Modeled terrains are used to simulate environmental conditions in integrated mobile terrestrial and satellite communications systems. A coverage analysis ...

Over the years TCP have been designed and developed in the terrestrial network environment where the network propagation delay is in terms of 100ms. Recent advance in communication satellite technologies have introduced networks with longer delay (in terms of 500ms round-trip). This study is to evaluate the performance of TCP over such long-delay networks.

This paper proposes a novel dynamic bandwidth assignment multiple access (DBAMA) protocol employing a dynamic packet reservation technique for direct user terminal access to a ATM-based low earth orbit (LEO) satellite communications system. Performance analyses by simulations are presented. Methods to efficiently integrate ATM-based BISDN traffic are considered.

This paper discusses a code acquisition technique, for use in spread-spectrum communication system with large frequency offsets, where the frequency offset is similar to the symbol rate. This is the situation typically in satellite communications systems. The technique uses a very efficient method of performing the correlation where the frequency and time space can be searched with very little ...