LTE 终端开机过程
引子
General Procedure
\\ From Power-On to PRACH(从开机到发起随机接入)
i. UE is Off
ii. Power On UE
iii. Frequency Search
iv. Time and Frame Synchronization : In this process, PSS and SSS will be decoded as well.
v. PCI (Physical Cell ID) detection
vi. MIB decoding : UE can figure out System Bandwidth and Transmission Mode in this process. (As you see in Downlink Framestructure, MIB/PBCH is located at the 6 RBs around the center frequency. So the success of MIB decoding does not guarantee that signal quality across the whole band is good)
vii. Detect CSR (Cell Specific Reference Signal) and perform Channel Estimation and Equalization. In this process, UE will detect/measure reference signal across the whole system bandwidth. So RSRP/RSRQ measured at this step can be a good indicator for overall signal quality.
viii. Decode PDCCH and extract DCI information for SIB. PDCCH is spread across the whole bandwidth, so the signal quality across the whole bandwidth should be good enough for this step.
ix. SIB deconding (SIB1 should be decoded first and then SIB2 and then remaining SIBs)
x. Cell Selection : UE may find multiple suitable cells, but it try camp on to HPLM cell with the highest priority
xi. Initial RACH Process
以上各步骤在代码中的反映
\\iv) viii) viii)步骤
\\ix) Cell Selection
\\x) Initial RACH Process
\\Cell camped and send Camped Indication to NAS(EMM ,etc)
\\EMM send camped indication to other module(ESM-sent PDN connectivity Request to trigger \\Attach procedure ,Regproxy-CM_CAMPED_IND,SD-on which RAT ,which domain support \\&service status)
\\PDN conn request to trigger Attach initiation
\\Start RRC connection establishment, to trigger RACH procedure (MAC layer)
\\Received MAC_ACCESS_CNF. RACH Successful
\\Attach accept and network sent to UE to Activate default EPS bearer context request
\\Data call connected means ATTACH_COMPLETE
