In this paper, a novel model is proposed to analyze the throughput of multi-hop CSMA/CA network. Under certain assumptions, a product-form expression is derived for the stationary distribution of the underlying discrete-time Markov chain, and the throughput formula is given for each link. Interestingly, it is shown that the model includes slotted ALOHA, wireless LAN [Bianchi] and idealized CSMA [csma-87] as special cases. Therefore, it not only provides a unified view of the different models but also covers many new cases. Based on the model, we design fully distributed algorithms to improve the throughput and fairness of CSMA/CA networks. In particular, a transmission-length control algorithm is shown to be throughput-optimal (even with collisions), although it has higher overhead than a transmission-probability control algorithm. And a cross-layer algorithm is given to achieve fair bandwidth sharing among different flows. Our analytical results are corroborated by comprehensive simulations.