Satellite Delivery of Wideband Services by ACTS
Douglas Hoder and Michael Zernic
Abstract | Full Paper (PDF, 185 KB)
In order for a satellite system to deliver wideband services compatible with terrestrial fiber networks, several major technological obstacles needed to be overcome. The solutions used in the ACTS Gigabit Satellite Network provided varying levels of success. Three major concerns prevail.
The first set of problems concerns channel bandwidth and signal quality. Most terrestrial networks are capable of providing bandwidth in excess of 622 Mb/s (SONET OC-12) on a single fiber, and at error rates of less than 10-12. Although the ACTS satellite is capable of providing bandwidth for SONET service up to the OC-12 level, the construction of a ground station network required to utilize the ACTS bandwidth and get adequate error performance presented a major challenge.
Another issues associated with SONET service over satellite is the physical layer compatibility with terrestrial SONET equipment and networks. These were dealt with throughout the design and integration of the GSN. The Satellite TDMA system and terrestrial interfces were designed specifically to accommodate SONET service. The integration of the network was done in a manner of increasing network complexity, beginning with simple point-to-point connections, and finishing with interconnection of existing terrestrial fiber SONET and ATM testbeds.
The final concerns arise from the incompatibility of the satellite path latency with communications protocols existing in the machines and applications connected to the network.
NASA's Advanced Communications Technology Satellite (ACTS)