rds to layers. There is semi-static switching between SU-MIMO and MU-MIMO per UE. In addition, the following techniques are supported: codebook-based precoding with a single precoding feedback per full system bandwidth when the system bandwidth (or subset of resource blocks) is smaller or equal to 12 resource blocks and per 5 adjacent resource blocks or the full system bandwidth (or subset of resource blocks) when the system bandwidth is larger than 12 resource blocks, as well as rank adaptation with single rank feedback referring to full system bandwidth. The eNB can override rank report. In 3GPP LTE spatial multiplexing, up to two codewords can be mapped onto different layers. One codeword represents an output from the channel coder. The number of layers available for transmission is equal to the rank of the channel matrix. Precoding in the transmitter side is used to support spatial multiplexing. This is achieved by multiplying the signal with a precoding matrix prior to transmission. The optimum precoding matrix is selected from a predefined codebook which is known to both the eNB and the UE. The optimum precoding matrix is the one which maximizes the capacity. The UE CHAPTER 10 The IEEE 802. 16m Physical Layer (Part II) estimates the channel and selects the optimum precoding matrix. This feedback is provided to the eNB. Depending on the available bandwidth, this information is made available per resource block or group of resource blocks, since the optimum precoding matrix may vary between resource blocks. The network may configure a subset of the codebook that the UE is able to select from. In case of UEs with high velocity, the quality of the feedback may deteriorate. Thus, an open loop spatial multiplexing mode is also supported which is based on predefined settings for spatial multiplexing and precoding. In the case of four antenna ports, different precoders are assigned cyclically to the resource elements. The eNB will select the optimum MIMO mode and precoding configuration. The information is conveyed