 a total of NRU distributed LRUs. There is no sub-carrier permutation defined for the downlink localized resource allocations. The CRUs are directly mapped to the sub-band and mini-band LRUs within each frequency partition. Example procedures for formation of downlink CRUs and DRUs for 10 MHz bandwidth are illustrated in Figures 9-23 to Figure 9-25. The guard sub-carriers between contiguous frequency channels can be utilized for data trans- mission, if the sub-carriers from adjacent frequency channels are precisely aligned. In mixed mode operation, the legacy channel raster of 250 kHz is maintained [6]. The channel raster is the frequency steps/increments that a mobile device will use when scanning for the desired downlink RF carrier. The frequency separation of contiguous RF carriers used for carrier aggregation must be an integer multiple of the OFDM sub-carrier spacing. In order to align the sub-carriers associated with adjacent frequency channels, a frequency offset can be applied to the center frequency. The guard sub-carriers can be utilized for data transmission, if the information of the available guard sub-carriers suitable for data transmission is communicated to the mobile station. This information includes the number of available sub-carriers in the upper and lower band edges. As shown in Figure 9-26, the guard sub-carriers between adjacent RF carriers are grouped to form an integer multiple of PRUs. The structure of a guard PRU is identical to downlink subchannel structures. The guard PRU is used as a mini-band CRU at partition FP0 for data transmission only. The number of useable guard sub-carriers is predefined, and is known to both MS and BS based on the RF carrier bandwidth. The number of guard PRUs in the left and right edges of each RF carrier are shown in Table 9-2. The number of guard PRUs in the left and right edges of the RF carrier are denoted by NLG-PRU and NRG-PRU, respectively. The total number of guard PRUs are NG-PRU = NLG- PRU + NRG-PRU. It must be noted that when an RF carrier occup