This paper presents an analytical model which extends Markov Chain models previously proposed for IEEE 802.11 data link protocol. Unlike already published models, the proposed Markov Chain accounts jointly for the following three factors. First, in addition to collision, it accounts for frames that may be lost due to a low signal-to-noise ratio value at the link receiver (frame corruption). Second, it accounts for the various link transmission rate options which affect both the frame transmission time and probability of frame corruption. Third, it accounts for co-operative protocol variants of the IEEE 802.11 protocol. According to these protocols, a third node (relay) - besides the sender and receiver - may help improve the link capacity. In such a case, the active participation of the relay node must be properly captured by the analytical model. All the above factors are combined into one single Markov Chain model by leveraging a multi-dimensional approach.