0.1 X Total One-Way Delay (ms) UE Processing Delay (ms) Uplink Frame Alignment (ms) TTI Duration (ms) eNB Processing Delay (ms) HARQ Re-transmission (ms) 0.1 X 0.1 X 0.1 X 0.1 X 0.1 X 0.1 X 0.1 X Total One-Way Delay (ms) 12.10 3GPP LTE-advanced link-level and system-level performance In order to calculate the control-plane latency, the model shown in Figure 12-22 is used. The transition from the RRC_IDLE to the RRC_CONNECTED state in the 3GPP LTE comprises several steps that are shown in procedural order in Table 12-24. While the results of the analysis suggest that the 3GPP LTE Rel-8 satisfies the ITU-R requirements, using the improved features and protocols introduced in later releases would allow reduction of the control-plane latency to 50 ms. Note that since the NAS set-up process can be executed in parallel with the RRC set-up, it does not appear in the total latency calculation. The analysis in Table 12-24 shows that any of the 3GPP LTE configurations can fulfill the ITU-R requirements related to control-plane latency. 1) RACH Waiting 2) Preamble 3) Processing 4) Grant 5) Processing 6) RRC + NAS Request 7) RRC Processing 11) NAS Processing 8) RRC Setup 12) NAS Request 9) Processing 13) Processing 10) Connection Complete 14) NAS Setup 15) Processing 16) NAS Setup 17) Processing 18) Setup Complete FIGURE 12-22 Breakdown of RRC_IDLE to RRC_CONNECTED state transition in 3GPP LTE [13] CHAPTER 12 Performance of IEEE 802. 16m and 3GPP LTE-Advanced TABLE 12-24 Break Down of C-Plane Latency Components [13] Processing Procedure Time (ms) Average delay due to RACH scheduling period (1ms RACH cycle) RACH Preamble Preamble detection and transmission of RA response (Time between the end RACH transmission and UE's reception of scheduling grant and timing adjustment) UE Processing Delay (decoding of scheduling grant, timing alignment and C-RNTI assignment + L1 encoding of RRC Connection Request) Transmission of RRC and NAS Request Processing delay in eNB (L2 and RRC) Transmission of RRC Connection Set-up and UL grant Proc