On Unequal Error Protection Block Codes

Unequal error protection block codes are investigated in the dissertation.The first chapter is an introduction of the background and history of unequal error protection codes,also the summary of the dissertation is given.In the second chapter,some measurements of unequal error protection block codes are discussed,and a couple of fundamental definitions are given. The relationship between separation and the set of minimum distance message pairs is discovered,which leads to a theorem of sufficient and necessary condition of unequal protection. Based on the definition of separation of code symbols,the large weight error patterns correction criteria of a given code is derived.In the third chapter,two modified bounds for unequal error protection codes are derived. One is modified Plotkin bound,which has the same form of the original Plotkin bound while replacing the minimum distance by the newly defined "average separation". The other is the modified Hamming bound,also the geometry of the bound is introduced.The fourth chapter is about the linear block codes and their unequal error protection capability. Some properties of separation vector of linear block codes are shown,the relationship of a variety of codewords subspace and separation vector is derived,also a serie of theorems of parity check matrix and code symbol separation are proved. The Singlton bound of separation is then proved. Finally,the optimum encoding of an unequal error protection linear code is discussed.Turbo codes and their unequal error protection are studied in the fifth chapter. After performance analyzing of Turbo codes,the MAP decoding algorithm and its simulation results are given. Then,the properties of generator and parity-check matrix of Turbo codes are presented,the simulation results show that Turbo codes are unequally protected. Three kinds of constructions of unequal error protection Turbo codes are introduced finally.The last chapter is the conclusion and further research issues.