 applied. 7 bits indicating the operation mode with the mode-specific values. 11 reserved bits for future extensions. Fig. 6.12 shows the mapping of NPBCH to physical resources. After physical layer base- band processing, the resulting MIB-NB is split into eight blocks. The first block is transmit- ted on the first subframe (SF0) and repeated in SFO of the next seven consecutive radio frames. In SFO of the following radio frame, the same procedure is performed for the sec- ond block. This process is continued until the entire MIB-NB is transmitted. The use of SFO for all transmissions ensures collision avoidance of NPBCH with MBSFN transmissions in LTE, if NB-IoT is deployed in in-band operation mode. The MIB-NB and SystemInformationBlockType1-NB use fixed scheduling. The periodic- ity of MIB-NB is 640 ms in comparison to the periodicity of MIB in LTE, which is 40 ms. The periodicity of SIB1-NB is 2560 ms relative to the periodicity of LTE SIB1 that is 80 ms. The MIB-NB contains the information required to acquire SIB1. SIB1-NB contains the information to acquire other SIBs (see Table 6.2 for a list of NB-IoT SIBs). The broadcast control channel and other logical channels cannot be transmitted in the same subframe. The NB-IoT UE is not required to detect SIB changes in RRC_CONNECTED state. The NPBCH consists of eight independent 80 ms blocks. A block is always transmitted in SFO of a radio frame and then repeated eight times once per radio frame. The NPBCH is not transmitted in the first three symbols to avoid colli- sion with the LTE control channels. The NPBCH symbols are mapped around the NRS and the LTE CRS resources, where it is always assumed that two antenna ports are defined for NRS and four antenna ports for CRS. This assumption is necessary, because the UE obtains the actual antenna port information only after detecting the MIB-NB. The reference signal location in the frequency domain is given by NNcell provided by the NSSS. Although the NNcell may be different than PCI in the in-band operation, its ran