d (Base Codebook Subset Indication is the rank-1 base codebook subset indication for interference mitigation with PMI coordination) in the AAI_DL_IM MAC control message. The procedure for a PMI coordination multi-BS MIMO scheme can be described as follows: 1. If the Feedback Polling A-MAP IE is received by an MS, it should periodically send the AAI_MultiBS_MIMO_FBK MAC control message containing the requested information (e.g., PMI or a set of PMIs, diversity set member identifier, or additional measurements) by the serving BS. 10.7 Multi-BS MIMO 2. The BS should communicate with the neighboring base stations on receiving the feedback from multiple mobile stations, to coordinate their PMIs using higher layer signaling. The BS should then broadcast codebook subset information in BC_SI in an AAI_DL_IM MAC control message to all mobile stations within its coverage area. 3. The BS may send a Feedback Allocation A-MAP IE with the corresponding Codebook Mode field set to 0b11 to the selected mobile stations. Those mobile stations that received the message should feed back their desired PMI from the codebook subset that is signaled through the BC_SI field. Inter-cell interference nulling can be performed using PMI which may be based on either the strongest interference from the neighboring cells or by detecting the neighboring cell's sounding signal. The interference mitigation techniques described in this section are based on joint MIMO transmission across multiple base stations. The base station and the mobile station may support one or both adaptive-precoding-based multi-BS joint processing techniques, e.g., Closed-loop Macro Diversity (CL-MD) or Collaborative MIMO (Co-MIMO) vii transmission. The CL-MD scheme is used with downlink MIMO mode 2, whereas Co-MIMO is used in conjunction with downlink MIMO mode 4. The multi-BS joint MIMO processing may be enabled by the BS for one or multiple mobile stations when adaptive precoding is utilized in the serving and the neighboring cells, and the user data is shared among mult