orative MIMO is three. The downlink collaborative MIMO scheme must be differentiated from the uplink collaborative spatial multiplexing scheme that has been inherited from the legacy systems. CHAPTER 10 The IEEE 802. 16m Physical Layer (Part II) A collaborative MIMO zone is defined in order to facilitate inter-BS coordination when supporting Co-MIMO transmission. The Co-MIMO zone is a time-frequency region comprising a number of LRUs over a number of subframes. The Co-MIMO zone utilized by the neighboring base stations associated to the same radio resource region. The permutation scheme used in the Co-MIMO zone is identical across the participating base stations. On the other hand, for uplink sounding-based CL-MD and Co-MIMO schemes, the same sounding sequence can be used for DL/UL channel calibration. Therefore, the mobile stations will send the calibration sounding sequence on receiving the AAI_MULTI_BS_SOUNDING-CAL MAC management message. The phases of the received uplink calibration sounding sequences are used by the BS to calculate the mismatch between the uplink and downlink channels. Each participating BS compensates the downlink and uplink phase mismatch based the above-mentioned method. The Co-MIMO transmission is managed by the core network, including the selection of base stations participating in the Co-MIMO transmission. If sounding-based Co-MIMO transmission is utilized, each Co-MIMO zone is allocated to one or more mobile stations and each BS can allocate multiple Co-MIMO zones to different mobile stations. The corresponding resource units and the permutation schemes in each Co-MIMO zone are negotiated and coordinated by the participating base stations through the backhaul prior to allocation. The BS broadcasts normalized interference power thresholds for multi-BS MIMO schemes and one common CINR threshold. The normalized inter- ference power is defined as the ratio of average interference power (with or without transmitter pre- coder) from one dominant interfering BS to the total interference powe