Error correction strategies for data broadcasting

The choice of error correction technique is dependent both on the characteristics of the transmission channel, and on the nature of the data. The broadcaster therefore needs a range of coding and transmission options so that a selection can be made based on the error tolerance of the data, the reliability of service required, and the frequency of any information repetition within the service. The MAC/packet channels offered by DBS will allow a major expansion of broadcast data services, which initially at least, will be based on established teletext data formats. The proposed specification for conveying teletext data in MAC packets provides the required flexibility for data services by offering two packet structures with different levels of error protection, either of which can be combined with packet repetition