Transmission of time critical data over a packet satellite link
This thesis presents some new techniques in frame oriented transmission systems with particular emphasis on HDLC (High Level Data Link Control) links. The advent of multimedia and applications requiring high bandwidth has prompted the development of high performance networks. In addition to that, accessibility is also an important issue. Satellite links have become a major contributor in providing access to larger networks where terrestrial connections are not possible due to geographical constraints. The development of VSATs (Very Small Aperture Terminal) has further increased the interest in providing extra-terrestrial links as a means of accessing a network. Because VSAT links are less reliable than terrestrial connections, bandwidth management becomes an important issue. The major problems are identified in this thesis. Frame oriented transmission systems have provided a very efficient method for data transmission. Data from several sources may be multiplexed into a common link. Recently, data networks have been successfully used for the transmission of various types of traffic. This diverse traffic has different QOS requirements such as throughput and delay. Certain types of traffic have an inherent priority. This traffic is referred to as time-critical or temporal. Temporal data has a short lifetime after which the data become useless regardless of whether the data has been corrupted or not. Some data sources such as voice and video, are able to tolerate small amounts of errors provided they are received within their lifetime period. From here we see that there are two very contrasting features of the data types. Conventional packet protocols are designed to ensure data integrity in return for packet delays due to retransmission and congestion control.