tween adjacent component carriers are grouped to form an integer number of PRUs. The structure of a guard-PRU is identical to that of a downlink subchannel. The guard-PRUs are used as mini-band CRUs in partition FP0 for data transmission only. The number of useable guard sub-carriers is predefined and is known to both the MS and the BS based on the component carrier bandwidth. The number of guard-PRUs in the left and right edges of each component carrier is shown in Table 9-2 (OFDMA parameters). The number of guard-PRUs in the left and right edges of the component carrier is denoted by NLG-PRU and NRG-PRU, respectively. The total number of guard-PRUs is NG-PRU = NLG-PRU + NRG-PRU. It must be noted that when a component carrier occupies the left-most segment of the spectrum among a number of contiguous component RF Carrier N-1 RF Carrier N RF Carrier N+1 Integer Multiple of Sub-carrier Spacing Integer Multiple of Sub-carrier Spacing Logical Resource Units FIGURE 11-6 An example of data transmission using guard sub-carriers 11.2 Sub-carrier alignment and use of guard sub-carriers Table 11-2 Number of Guard Resource Units in the Downlink and Uplink [2] Component Carrier Number of Guard-PRUs in the Number of Guard-PRUs in the Bandwidth (MHz) Left Edge of Component Carrier Right Edge of Component Carrier carriers, the number of guard-PRUs in the left edge of the carrier is zero. Furthermore, when a component carrier occupies the right-most segment of the spectrum among a number of contiguous component carriers, the number of guard-PRUs in the right edge of carrier is set to zero [2]. Note that the procedures for the formation of the guard-PRUs are the same in the downlink and uplink. The left and right guard-PRUs are denoted as G-PRUL[0], G-PRUL[1], G-PRUL[NLG-PRU-1] and G-PRUR[0], G-PRUR[1], G-PRURINRG-PRU-1], respectively, from the lowest frequency index. The guard-PRUs are indexed by interleaving G-PRUL and G-PRUR, i.e., G-PRU[i] = G-PRUL[i/2] for even-valued i, and G-PRU[i] G-PRU[(i-1)/2] for odd-valued i, where i