itted using two-stream SFBC with precoding, which is decoded by the MS without any information on the precoding and antenna configuration. The S-SFH sub-packet IEs (i.e., S-SFH SP1 IE, SP 2 IE, and SP3 IE) are transmitted by the BS with certain period for each sub-packet where TSPI < TSP2 < TSP3. The periodicity of S-SFH sub- packet scheduling is transmitted in the S-SFH SP3 IE, as shown in Table 9-14. The BS transmits P-SFH IE containing the S-SFH scheduling information bitmap, S-SFH change count, S-SFH SP 9.14 Superframe headers (broadcast channel) 6 OFDMA Symbols P-SFH NP-SFH Distributed Logical Resource S-SFH NS-SFH Units Data and Control Blocks 20 ms 40 ms 80 ms 160 ms P-SFH S-SFH SP2 S-SFH SP3 S=SFH SP1 FIGURE 9-63 Structure and timing of superframe header components [2] change bitmap, and start superframe offset where new S-SFH information is used in every super- frame. The S-SFH change count remains unchanged as long as all of the values (except MSB of superframe number in S-SFH SP1 IE) of the S-SFH SP IEs remain unchanged. The S-SFH change count is incremented by one (modulo 16) whenever any of the values (except MSB of superframe number in S-SFH SP1 IE) of the S-SFH IEs change. The changed S-SFH SP IEs are transmitted at the scheduled superframes intervals corresponding to each S-SFH SP IE. If the MS determines that the S-SFH Change Count field in P-SFH has not changed, then it concludes that its copy of the system information is up-to-date. Each bit of the S-SFH sub-packet change bitmap is an indication of the change of the corre- sponding S-SFH sub-packet IE where the least and most significant bits are mapped to the S-SFH SP1 IE and S-SFH SP3 IE, respectively. The Start Superframe Offset parameter indicates the time relevance of the S-SFH change where the new system parameters are applied. Using the S-SFH Change Count, S-SFH SP Change Bitmap, and Start Superframe Offset parameters, an MS can determine whether it needs to decode S-SFH IE in the current superframe and to update its system parameters. T