 133 us 15/30/60/120 11.7 us 267 us 16.4 us 400 us 30.5 us 800 us 40.4 us 66.7 us 66.7 us 267 us Table 5.2 - Short-sequence PRACH formats 5G Air Interface and Physical Layer Procedures - - Part 2 The short PRACH structure is essentially the same as the long one, with a CP, followed by a repetition of PRACH sequences, and ending with a guard period, as shown in the following figure: SEQ#0 SEQ#1 SEQ#2 SEQ#(N) seq - 1) Figure 5.19 - The short-sequence PRACH structure The PRACH and subcarrier spacing combinations are presented in the following figure for convenience. Bandwidth of PRACH Subcarrier index NRA allocation Af for PUSCH for PRACH expressed in number of RBs for PUSCH Figure 5.20 - PRACH and SCS combinations In this detailed table, you can find the allocated bandwidth, which is expressed in the number of RBs for PUSCH and the subcarrier index. Summary Format Support for restricted sets 1.25 kHz 24576K 3168K Type A, Type B 1.25 kHz 2.24576K 21024K Type A, Type B 1.25 kHz 4.24576K 4688K Type A, Type B 5 kHz 4.6144K 3168K Type A, Type B Format Support for restricted sets 15.2 kHz 2. 2048k.27 288K.2-M 15.2u kHz 2048k.27 576K.2-11 15.2u kHz 2048K.21 864k.2- 15.2 kHz 2048K.2 216K.2-M 15.2 kHz 2048K.1 2-11 360K.2-H 15.2u kHz 2048K.21 504k.2-11 15.2u kHz 2048K.2 936k.2- 15.2u kHz 48K.2-M 1240K.2-11 15.2u kHz 2048K. 2-M 2048K. 2-ll Table 5.3 - PRACH and SCS combinations The preceding table above shows the length of the sequences, the number of repeated sequences, the used subcarriers, the subcarrier spacings, the length of the cyclic prefixes, and their formulas, where K is taken as 64 in the calculations. In this section, we analyzed physical channels and signals playing a role in the initial access procedure. We examined in detail the SS block, PSS/SSS, and PBCH. Then, we saw a random access preamble, which is basically the PRACH. We finished the section by analyzing and comparing short- and long- sequence PRACH formats. Summary In this chapter, we learned that beam sweeping is required when operating at an mm Wave 