Credit-based variable-to-variable length coding: Key concepts and preliminary redundancy analysis

A new coding concept called credit-based variable-to-variable length (cbv2v) coding is proposed in this paper. A binary cbv2v code is constructed, and analysis of its performance shows that cbv2v coding can achieve much better trade-off among the coding delay, redundancy, and space complexity than does variable-to-variable length (v2v) coding. Specifically, let L be the total number of source words. With finite coding delay, the redundancy of our proposed cbv2v code decreases in the order of O(L^−0.5) while the redundancy of binary v2v coding is lower bounded by Ω ((log L)^−5−ε) where ε is an arbitrary positive real number. Furthermore, we also show that under mild conditions, the redundancy of any cbv2v code can be lower bounded by Ω(L^{−2∣χ∣−1−ε}), where ∣χ∣ is the size of source alphabet.