搜网过程
modem 的搜网分为主动搜网和手动搜网，下图是手动搜网的流程框图，涉及到的modem侧的模块有Call manager、NAS REG、NAS MM, 以及跟模式相关的LTE RRC，TDS RRC和GSM/GPRS GRR，最后由Layer 1层做具体的Power Scan扫频工作。
Layer 1层（物理层）完成扫频工作之后会将结果上报给RRC(GRR)层，RRC再报给NAS层，NAS层返回给CM层，CM通过QMI indication主动通知给AP侧的QCRIL模块，Qcril收到主动上报后，事件循环机制触发qcril_qmi_nas_perform_incremental_network_scan_ind_handler 回调函数对搜网结果结果进行处理，之后是Telephony 层和UI层处理。
对应CDMA 搜网，属于3GPP2的范畴，不存在NAS层的概念，另有描述，以下只针对3GPP的规范流程。
Manual PLMN search flow
qcril send network scan request to CM through QMI interface
CM Layer
Call manager handles NETWORK_LIST_REQ from QCRIL, and wait for CM_NETWORK_LIST_CNF be confirmed from MM layer which means plmn search results confirmed!
NAS Layer
REG module handle CM_NETWORK_LIST_REQ from CM Layer , then sent MM_PLMN_SEARCHto
NAS MM module, NAS MM then send LTE_RRC_PLMN_SEARCH_REQ to LTE RRC layer ,LTE RRC then inform TDS RRC and GSM RR layer to perform plmn search operation, and NAS REG module wait until CM_NETWORK_LIST_CNF be confirmed from RRC layer
LTE RRC Layer inform TDSCDMA RRC Layer to perform TDS plmn search
TDS RRC layer inform TD-SCDMA L1 to perform Frequency Scan(Power Scan)
LTE RRC also inform GSM/GPRS GRR layer to do GERAN plmn search
GRR then inform GSM L1 to perform Power Scan
Modem Report network search result to QCRIL through QMI message
