e the bits input to the turbo coder, i.e. both first 8-state constituent encoder and turbo code internal interleaver, and K is the number of bits, and Z1,Z2,... and Z'1,Z'2,...,Z'K are the bits output from first and second 8-state constituent encoders, respectively. The bits output from turbo code internal interleaver are denoted by X'1,X'2,...,XXK and these bits are to be input to the second 8-state constituent encoder [10]. 1st constituent encoder Input Input Output Turbo code internal Interleaver 2nd constituent encoder Output Figure 4.51 Turbo coder structure of rate 1/3 (dotted lines indicate termination only). The UMTS Network and Radio Access Technology Other details such as trellis termination, internal interleaver, of the turbo coder can be found in [10]. 4.6.4 Radio Frame Size Equalization Radio frame size equalization implies padding the input bit sequence in order to ensure that the output can be segmented in Fi data segments of same size, e.g. rate matching. Radio frame size equalization occurs only in the UL (DL rate matching output block length is always an integer multiple of Fi). We denoted by the input bit sequence to the radio frame size equalization, where i is TrCH number and E the number of bits. We denote the output bit sequence by where Ti is the number of bits. Then the output bit sequence follows as: and tik={{0,1} for k=E +1,...,T, if < T, (4.76) where Ti = F X N; and i=[E;F|] is the number of bits per segment after size equalization. 4.6.5 First Interleaving In a compressed mode through puncturing, bits marked with a 4th value on top of {0,1,8} and noted p, get introduced in radio frames to be compressed at positions corre- sponding to the first bits of the radio frames. They will be removed in a later stage of the multiplexing chain to create the actual gap. We perform additional puncturing in the rate matching step, over the Transmission Time Interval (TTI) containing the com- pressed radio frame, to create room for these p bits. Specifications in [10] provide this and other first in