f the first symbol of the channel and NRA is equal to 0 or 1, depending on the spacing between the subcarriers. In the frequency domain, the physical channel is transmitted over a set of resource blocks (RB). The start of the band and the number of PRACH opportunities allocated in the frequency domain are transmitted via the SIB2 information message by the msgl-FrequencyStart and msgl-FDM values, respectively. Random access is the first step used by the mobile to set up a connection to the gNB entity. The mobile UE sends its connection request via the physical PRACH. If the radio node does not respond, the mobile makes a new request by increasing the transmission power according to a ramping factor (powerRampingStep). The number of PRACH requests is limited by the preambleTransMe value transmitted via the SIB2 information message. During random access, the mobile is synchronized in transmission with the received synchronization signal. The random access procedure will estimate the radio propagation time, which is formulated by the TA (Timing Advanced) value. The preamble consists of a Cyclic Prefix (CP) of duration TCP and a sequence of duration TSEQ- The time guard TG is equal to TPRACH+(Tcp+TsEQ). 5G-NR Radio Interface - The Physical Layer The guard time corresponds to the maximum round trip time (RTT) and determines the maximum value of the radius R of the cell R(km)=To(us)/6,6. RACH sequences are Zadoff-Chu sequences over 139 bits (short sequences) or 839 bits (long sequences). The PRACH sequences are generated by the following equation (with M=139 for a short sequence or M=839 for a long sequence): C, is an offset of the base sequence. The PRACH is time and frequency multiplexed with the PUSCH channel of the other UEs. In the frequency domain, the long sequences are transmitted in the FR1 band. PRACH sequences span 6 RB for a 1.25 kHz subcarrier spacing, or 24 RB for a 5 kHz subcarrier spacing. In the time domain, the long sequence consists of 839 symbols. The reference duration of a slot is 1 ms. Table 4.13