ponds to a 1 114 Open Radio Access Network (O-RAN) Systems Architecture and Design millisecond slot time at 14 symbols/slot. 4G carrier bandwidths and the number of occupied IQ samples per 3GPP are copied below (Tables 3-4 and 3-5): Fronthaul latency Like the end-to-end system latency that we calculated previously, we can estimate the fronthaul latency by accounting for each component in the system. DU termination latency is the cost of terminating the eCPRI frames in the DU. This cost includes the hardware overhead through Ethernet PHY and MAC components (assumed less than 1 microsecond), the (optional) latency associated with an Intelligent Network Interface Card (NIC) implements the fronthaul functionality in an offloaded manner (assumed around 10 microseconds or less). When termination is implemented as a software function (say, in DPDK), Virtual Machine or application wakeup latency needs to be accounted for in the receiver-this is the latency between arrival of an interrupt that indicates packet arrival and the start of the (high priority) application that processes the packet. This latency can be anywhere between 10 microseconds (optimized PREEMPT_RT application with no virtualization supported) and approximately 50 microseconds with virtualization worst-case. In addition, the software function to process the packet takes compute clock cycles that translate to about 1-5 microseconds depending on software optimization level. Ethernet Serialization and Physical Transmission Latency. Physical Ethernet transmission latency is calculated based on Ethernet speed and packet size. For example, the serialization delay of an 800-byte packet (as used by the end-to-end latency benchmark) 1 Gbps link is (800 bytes X 8 bits)/1 X 109 bps = 6 microseconds. Note that this Table 3-4 Number of 4G/NR occupied subcarriers for different RF bandwidths. 4G b/w Carriers Table 3-5 Example of 4G O-RAN fronthaul eCPRI IQ bandwidths-low-end. RF bandwidth Uncompressed IQ 9b/16b 12b/16b #Antenna layer (OBW) bandwidth compressed compress