SO that only a subset of the allowed TFCs can apply in compressed mode. 4.3.14.4 Transmission Gap Position We can place transmission gaps at different positions (Figure 4.39) for inter-frequency power measurement, acquisition of the control channel of another system/carrier, and actual handover operation. Thus, when using the single frame method, we locate the transmission gap within the compressed frame depending on the transmission gap length (TGL) as illustrated in Figure 4.39a. When applying the double frame method, we locate the transmission gap at the centre of two connected frames as illustrated in Figure 4.39b. Transmission gap Radio frame #Nfirst-1 #Niast+1 (a) Single-frame method Transmission gap First radio frame Second radio frame #Nfirst-1 #Nast+1 (b) Double-frame method Figure 4.39 Transmission gap position [10]. We calculate the parameters of the transmission gap positions as follows: TGL is the number of consecutive idle slots during the compressed mode transmission gap, i.e. TGL = 3, 4, 5, 7, 10, 14 . Nfirst specifies the starting slot of the consecutive idle slots, The UTRA Physical Layer Design N1ast shows the number of the final idle slot and is calculated as follows: If Nfirst + TGL 15, then N1ast = Nfirst + TGL -1 (in the same frame), If Nfirst + TGL > 15, then = + TGL - 1) mod 15 (in the next frame). When the transmission gap spans by two consecutive radio frames, we choose Nfirst and TGL SO that at least 8 slots in each radio frame get transmitted. Table 4.31 illustrates the detailed parameters for each transmission gap length for the different transmission time reduction methods. Table 4.31 Parameters for Compressed Mode6 [10] Frame Spreading Idle length Transmission time Idle frame combining factor reduction method 512-4 1.73-1.99 Puncturing (S) = Single frame method 256-4 1.60-1.86 Spreading factor (D) = (1,2) or (2,1) 512-4 2.40-2.66 division by 2 or 256-4 2.27-2.53 Higher layer (D) = (1,3), (2,2) or (3,1) scheduling 512-4 3.07-3.33 256-4 2.94-3.20 (D) = (1,4), (2,3), (3, 2) or (4,1) 5