Medium access control protocols for satellite networks.

摘要

The means of achieving full duplex broadband access to either the home or office has been the focus of much research and entrepreneurial development in the past five years. This is the so-called “last mile” problem. One approach is duplex access to a geostationary earth orbit satellite through a relatively small satellite dish located at each home or office. This scenario gives rise to a multiple access problem in the uplink (i.e. terrestrial earth terminal to satellite) channel, since this channel is considered many-to-one.; We first focused on real-time medium quality video transmission. To efficiently transport this medium, we developed a new medium access control protocol, Random Access/Demand Assigned Multiple Access (RA/DAMA). The RA/DAMA medium access technique uses a time division multiple access Physical Layer and seeks to adaptively minimize the delay of each Network Layer packet that arrives to the output queue by transmitting packets on either a collision free demand assigned channel or on a collision possible random access channel. Combined with this dual channel transmission method is a new technique for acquiring demand assigned bandwidth, called a packet flow rate metric. This metric seeks to track the slow time behavior of video traffic, leading to a significant reduction in the amount of demand assigned multiple access signaling. We conducted extensive simulations of this protocol, using the network simulator ns. Our results show that if light packet loss is tolerable (less than three percent), then significantly lower delays and higher link utilization can be achieved.; We next turned our attention to Hyper Text Transfer Protocol based World Wide Web browsing, bulk file transfers, and interactive computing. To accommodate these traffic types, we developed another medium access technique dubbed Response Initiated Multiple Access (RIMA). RIMA also uses a time division multiple access Physical Layer, but relies on replies from a remote server to instantiate collision free uplink bandwidth for clients attached to terrestrial earth terminals. We again conducted extensive simulations using ns and showed that for all three types of traffic under consideration, RIMA significantly out performs previously proposed medium access control protocols designed for computer data applications.