Diversity analysis of irregular fractional cooperation

In fractional cooperation, each available relay node selects a small fraction of the source´s transmission to be relayed. In previous work, it was assumed that every node relayed the same number of source symbols, and large diversity order gains were observed. In this paper, a theoretical basis is developed for irregular fractional cooperation, in which each node relays a different number of symbols. A general expression of the system diversity order is derived. A bound is introduced on the system performance of fractional cooperation, known as the erasure channel bound. Distributions of diversity order using this bound are given when the fraction relayed by each user is random.