This block is responsible to initiate and calculate the eCPRI one-way delay measurement on the transport link. The eCPRI one-way delay measurement can be performed without (one-step) or with a follow-up message (two-step). The process is initiated when a CSR is written to eCPRI Message 5 Control Register. The IP transmits eCPRI message 5 with one-step first before sending eCPRI message 5 with timestamp t1 and cv1 for two-step delay measurement. The packet parser assembles an eCPRI message 5 with timestamp t1 taken from Time-of-Day (TOD) module. Then, this eCPRI message 5 is sent through the Ethernet MAC with compensation value cv1 filled using 1588 PTP hardware.
On the receiving end, the eCPRI IP responses the message 5 with t2 and cv2. Upon receiving the response packet, this calculates the transport delay using the formula:tD12= (t2-+tCV2) - (t1 + tCV1)
The waveform below shows an example of the Avalon® streaming interface
source and sink data through L2/L3 parser. The example in this section uses E-tile Ethernet Hard IP with 1588 PTP feature enabled.
The timing diagram below illustrates the eCPRI message 5 in one-step one way delay measurement.
The timing diagram below illustrates the eCPRI message 5 in two-step one way delay measurement.
The one and two- steps one way delay measurement sequences uses same remote request type. The only difference is destination eCPRI IP measures t1 and tcv1 while the source eCPRI IP measures t2 and tcv2.