總體流程
一、初始化
找卡:
User Identity Module/High[ mmgsdi.c 9083] USIM app. present
讀取搜網nv:
1) NV 00010:Digital/Analog Mode Preference,接入技術,通常採用Auto/2G/3G/4G四 個選項;
2) NV 00849:Network Selection Mode Preference,搜網模式,存在Auto和Manual兩個 選項;
3) NV 00850:Service Domain Preference,服務域選取,可以是僅PS、僅CS或者PS+CS;
4) NV 00722:Acquisition Database,用來存放WCDMA的歷史頻點信息;
5) LTE的頻段信息存放在nv/item_files/modem/mmode/lte_bandpref文件中,
二、PLMN選擇
PLMN選擇分爲自動搜網和手動搜網兩種模式:
1) 自動搜網:UE按照協議23.122 4.4.3.1.1 Automatic Network Selection Mode Procedure 規定的PLMN優先級進行搜網,即RPLMN->HPLMN->UPLMN->OPLMN。
2) 手動搜網:搜索RPLMN,協議23.122 4.4.3.1.2 Manual Network Selection Mode Procedure;UE會把所有的PLMN,包括不可用的PLMN列出來,供用戶選擇去註冊;
3) 當沒有找到可用的PLMN,單板會發起MMR_REG_REQ PLMN(0-0) RAT(LTE)的 請求,這樣單板就可以獲得限制服務,如緊急呼叫。
4)找到plmn則發起MMR_REG_REQ PLMN(460-0)
選擇PLMN的時候會從SIM卡中讀取,及配置文件中讀取已有的PLMN信息,如RPLMN(上次駐留的PLMN),HPLMN(SIM卡中的HPLMN),EHPLMN(等價的HPLMN,可以在NV65602中配置)等,device_config配置。
Call Manager/High [ cmph.c 54148] =CM= cmph_read_ehplmn_list SUCCESS plmn_count=4
MCFG/Medium [ mcfg_sel.c 729] =MCFG= Comparing PLMN 460:7 against prefix 460:7
NAS REG/High [ reg_sim.c 2788] =REG= HPLMN(460- 07)
三、掃頻
LTE掃頻有兩種方式:systerm scan和band scan。
1) System Scan會掃歷史記錄頻點,LTE的歷史頻點存放在NV的acq_db文件中,其具體 保存路徑爲nv/reg_files/modem/lterrc/csp/acq_db (最多保存10個歷史頻點),可以通過 QPST查看
信息,左側爲低位字節,右側爲高位字節;綠色部分標記Band信息,標示1之後有 幾個0);關於System Scan的相關log信息可以參考圖1.7,其中關於LTE earfcn的定義可以參考協議3GPP TS 36.104 5.7.3 Carrier frequency and EARFCN;
LTE RRC/Low [ lte_rrc_csp.c 7680] CSP: Found 4 systems to scan
系統掃頻掃到4個歷史頻點,並且都能SIB1找到對應plmnm,對這4個頻點的信號進行排序,選取優先最高的
LTE RRC/Low [ lte_rrc_csp.c 7291] CSP: Candidate list not present
LTE RRC/Low [ lte_rrc_csp.c 2542] CSP: PLMN found
LTE RRC/Low [ lte_rrc_csp.c 7296] CSP: req PLMN in SIB1 list
LTE RRC/Low [ lte_rrc_csp.c 7291] CSP: Candidate list not present
LTE RRC/Low [ lte_rrc_csp.c 2542] CSP: PLMN found
LTE RRC/Low [ lte_rrc_csp.c 7296] CSP: req PLMN in SIB1 list
LTE RRC/Low [ lte_rrc_csp.c 7291] CSP: Candidate list not present
LTE RRC/Low [ lte_rrc_csp.c 2542] CSP: PLMN found
LTE RRC/Low [ lte_rrc_csp.c 7296] CSP: req PLMN in SIB1 list
LTE RRC/Low [ lte_rrc_csp.c 7291] CSP: Candidate list not present
LTE RRC/Low [ lte_rrc_csp.c 2542] CSP: PLMN found
LTE RRC/Low [ lte_rrc_csp.c 7296] CSP: req PLMN in SIB1 list
LTE RRC/Low [ lte_rrc_csp.c 12630] CSP: All frequencies prioritized for Req PLMN
LTE RRC/Low [ lte_rrc_csp.c 12685] CSP: Prioritization of system scan results complete
LTE RRC/High [ lte_rrc_csp.c 19327] CSP: Prioritize System scan results for priority bands
LTE RRC/Low [ lte_rrc_csp.c 12680] CSP: 0 frequencies prioritized after pass 1
LTE RRC/Low [ lte_rrc_csp.c 12680] CSP: 0 frequencies prioritized after pass 2
LTE RRC/Low [ lte_rrc_csp.c 12680] CSP: 0 frequencies prioritized after pass 3
LTE RRC/Low [ lte_rrc_csp.c 12680] CSP: 0 frequencies prioritized after pass 4
LTE RRC/Low [ lte_rrc_csp.c 12685] CSP: Prioritization of system scan results complete
LTE RRC/High [ lte_rrc_csp.c 19331] CSP: System scan results after prioritization
LTE RRC/High [ lte_rrc_csp.c 19338] CSP: band:40 earfcn:39148 energy: -72
LTE RRC/High [ lte_rrc_csp.c 19338] CSP: band:38 earfcn:38098 energy:-107
LTE RRC/High [ lte_rrc_csp.c 19338] CSP: band:39 earfcn:38496 energy:-109
LTE RRC/High [ lte_rrc_csp.c 19338] CSP: band:41 earfcn:40936 energy:-114
2) Band Scan:當System Scan中的歷史記錄頻點Acq都失敗時,會進行band scan;按照 單板支持的band,一般情況下會從Band1開始掃每個Band的頻點,而在每個Band中 會將所有頻點按照RSSI排序,將達到信號強度門限值的頻點按信號強度從高到低列 出來,最多列出50個頻點作爲候選頻點,然後在這50個頻點中找一個合適的頻點, 直到找到一個符合當前網絡的頻點。可以通過QXDM過濾LTE RRC/CSP的log來查 看掃頻的過程時,如圖1.8所示;Band Scan掃頻時對每個頻點Acq log信息參考圖1.9
Log Analysis – System Scan
//Automatic service Request
11458 76:00:16:20.595reg_state.c1171HCM_SERVICE_REQ –AUTOMATIC
11491 89:00:16:20.600emm_reg_handler.c475HEMM: Received MMR_REG_REQ
//NAS sends service request to AS
11494 81:00:16:20.600emm_rrc_if.c310HEMM: Sent LTE_RRC_SERVICE_REQ
//RRC sends LTE_CPHY_START_REQ to ML1
11537 81:00:16:20.603lte_ml1_mgr_stm.c6923MLTE_CPHY_START_REQ
//LTE AS is initialized
11675 97:00:16:20.620lte_ml1_mgr_cphy_cnf_handlers.c976MLTE_CPHY_START_CNF
Status: 0
11680 89:00:16:20.620lte_ml1_mgr_stm.c12645LL1M: INACTIVE STATE ENTER
//ML1 initiates System Scan request
11704 153:00:16:20.620lte_ml1_sm_main.c1118HSM: Sys Scan Req module 1 num_sys 1
min_sys 0 early_abort 0 sys[0] band 13 earfcn 5230 bw 50
//RF tune request
11705 113:00:16:20.620lte_ml1_sm_main.c641HSM: RX cfg req freq 5230 BW 50 cell_id
65535
Log Analysis – Band Scan
//Acquisition database search (System Scan) is exhausted. No system found
11497 89:00:47:21.166lte_rrc_csp.c3603HCSP: All entries tried in acq list
11498 81:00:47:21.166lte_rrc_csp.c9373HCSP: Exhausted acquisition list
//Initiate Band Scan
11506 89:00:47:21.166lte_rrc_csp.c2191XCSP: Sending 1 bands in band scan
11507 81:00:47:21.166lte_rrc_csp.c2210XCSP: Sent Band Scan Request
11520 105:00:47:21.175rtr8600_lte.c866HRF LTE RX is tuned to band 13 and frequency 5230
所有頻段都掃完,寫到acq_db文件中,重新在做一次系統掃頻
四、小區搜索
LTE小區搜索實際上就是PSS ( Primary Synchronization Signal ) / SSS ( Secondary Synchronization Signal)同步,實現UE對小區的識別和下行同步。這樣單板就能收到小區廣播的MIB消息和SIB消
五、解系統消息
系統消息解析主要是去讀取MIB (Master Information Block)消息和SIB (System
Information Block)消息。系統消息的詳細定義可以參考協議3GPP TS 36.331 5.2 System
information。系統消息的獲取流程如圖1.10。
MIB消息包含天線數、下行帶寬、小區ID、註冊的頻點等消息,其格式定義如圖1.11。
空口消息解析如圖1.12
SIB消息會包含PLMN、小區ID、S準則中的q-RxLevMin(sib3中)等消息,當該PLMN、 和第二步得到的PLMN一致時纔可以進行下一步;否則掃下一個頻點,同時解系統消息會得 到S準則中參考信號功率的值和隨機接入時PreamblesGroup以及功率攀升因子等消息。 查看MIB、SIB消息可以通過QCAT過濾空口(OTA)消息來獲取,請參考圖1.12。消息
解析可以參考圖1.1
LTE RRC/High [ lte_rrc_csp.c 4650] CSP: Sent Get SIBs Request
LTE RRC/High [ lte_rrc_csp.c 7048] CSP: SIB-8 not scheduled in SIB-1
LTE RRC/Low [ lte_rrc_csp.c 11027] CSP: Cell is suitable
六、小區選擇
小區選擇過程就是S準則的判斷,可以參考協議3GPP TS 36.304 5.2 Cell selection and
reselection和3GPP TS 36.304 5.2.4.6 Intra-frequency and equal priority inter-frequency Cell
Reselection criteria。LTE的S準則定義爲:
LTE RRC/Low [ lte_rrc_csp.c 21301] CSP: Proceeding to cell select request
LTE RRC/High [ lte_rrc_csp.c 4554] CSP: Sent Cell Selection Request
LTE ML1/Medium [ lte_ml1_mgr_stm.c 14209] L1M: LTE_CPHY_CELL_SELECT_REQ
小區選擇請求成功
LTE ML1/Medium [ lte_ml1_mgr_stm.c 14209] L1M: LTE_CPHY_CELL_SELECT_REQ
WCDMA L1/High [ l1mcmd.c 1419] Received CELL_SELECTION_REQ
WCDMA L1/High [ wsrch.c 24181] Cell Selection Succeed
七、小區駐留
掃到的一個頻點滿足S準則,小區選擇成功後進行小區駐留。小區駐留log參考圖1.14。
小區駐留成功
LTE RRC/Low [ lte_rrc_csp.c 18478] CSP: Camped on physical cell ID 223 on earfcn 3775
小區駐留成功後發起attach請求
BCCH_DL_SCH / SystemInformationRadio Bearer ID: 0, Freq: 39148, SFN: 128
八、attach流程
LTE NAS EMM Plain OTA Outgoing MessageAttach request Msg
LTE NAS EMM Plain OTA Incoming MessageAttach accept Msg
LTE NAS EMM Plain OTA Outgoing MessageAttach complete Msg