Research On Bit-erasure Rate Adaptation With Rateless Codes

The adaptive technique based on rateless codes is one of rate adaptations which areimportant to enhance spectrum efficiency. It has fewer schemas and smaller capacity stepeven only with one schema and no step, but the buffer of the receiver is very large andneeds complex management, and some existing method has dense constellations that makesystem realization difficult.This thesis designs a new rate adaptive method based on biterasure which has common constellation.Firstly, the designation of Raptor code and soft information simplification ofmodulation symbol are discussed, and this thesis focus on demodulation based on biterasure and the new rate adaptive method, then two erasure means are raised: dynamicthreshold and demodulation ratio, the theory and simulation result show that both methodscan realize rate adaption very well and they are equal in statistics point. Secondly, for thenew adaptive method, this thesis makes use of Sora platform and designs two experimentscenes, indoor line-of-sight and indoor none line-of-sight, in which the receiver is staticand moves. The experiment is discussed on received symbols constellation anddistribution of SNR. The paper will deal with data off line for error frame ratio，transmission efficiency variation and spectrum efficiency.The results show that rate adaptive method based on bit erasure can adjust with smallstep and has a theoretic and practical significance.