Data Transmission with Reliability Indication

In most digital communication systems, the information bits to be transmitted are protected against transmission errors. Typically, in the transmitter redundancy is added in a clever way by means of an encoder. In the receiver, a corresponding decoder is able to detect or to correct transmission errors by exploiting the redundancy. This technique is called channel coding. Applications of channel coding include digital cellular radio, data modems, wireless local loops, satellite systems, digital broadcasting systems, and even the compact disk. Conventionally, the decoder does not output any reliability information about the decoded bits. Hence, it is not clear which of the decoded bits are reliable, if any. That knowledge would be important for subsequent processing stages, however. Therefore, decoding with reliability information has become a popular area of research particularly in the last decade: the transmission power can be signiicantly reduced given the same transmission medium and a similar bit error rate performance. In this tutorial, we rstly introduce the basic concept of encoding and decoding. Then, we illustrate a technique to obtain reliability information, before we nally feature some examples. We point out similarities with other research areas, for example classical analog transmission, equalization, digital lters, neuronal networks, etc.