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LTE Call Flow

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 User Equipment send the Random access preamble(Through RACH Channel) to eNodeB for Network access. eNodeB received the message and send the RA-Response with allotting a temporary identity named C-RNTI (Cell Radio Network Temporary Identity).   After receiving the RA-response from eNodeB, User Equipment send the request for RRC Connection(With Received C-RNTI) to eNodeB. eNodeB send the RRC Connection Setup to User Equipment.  After established the RRC Connection between eNodeB & User Equipment. User send the first NAS message for Attach to core Network(with IMSI) and PDN Connection Request. 5(ii) eNodeB forward this message to connected MME. MME look this message and send the IMSI to HSS for authentication. IMSI is already stored in HSS.HSS verify it and send the K,RAND and XRES to MME.6(ii) MME send the response given by HSS to User Equipment via eNodeB for authentication. After receiving the RAND value User Equipment compute value and find the result RES.RES value send to the MM
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LTE Network Architecture

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  MME(Mobility Management Entity)  : Manages UE access network and mobility, as well as establishing the bearer path for UE's. It is responsible for selecting the S-GW for a UE at the initial join and at a time of intra- LTE Handover. S-GW(Serving Gateway)  : S-GW will act as Router, which will forward user data to P-GW. S-GW creates Bearer table. P-GW(Packet Data Network Gateway)  : Allocates QOS(Quality of service) to those Bearer table. Allocates the IP address to the UE. HSS(Home Subscriber Server)  : User's Subscription Profile will be stored in the HSS.MME will download the subscription profile from the HSS when any mobile will be Registered to the MME. PDN(Packet Data Network)  : PDN is the point with which user can communicate with outside world. 3 Types of PDN  : Internet Corporate VPN IMS DRB= Data Radio Bearer GTPU= GPRS Tunneling Protocol User Plane GTPC= GPRS Tunneling Protocol Control Plane
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2G KPI

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SD Block SD Blocking means that you are not getting SD resource for the call origination. When MS connects with Network then RACH and AGCH are provided. After AGCH, SDCCH is provided but if SDCCH is not provided at this time due to some problem or due to unavailable of SD by BSC. Reason for SD Blocking: •         LAC Boundary •         High Volume of SMS •         SD utilization is high •         Time Slot faulty •         Wrong SD Dimension •         Hardware Issue SD Drop When SD is assigned for a mobile during call connection process and during this time due to any problem or any mismatch occurs by which SD loss occurs, It is between allocation of SD and before TCH allocation. Reason for SD Drop: •         Overshooting •         Shift the SD time slot •         Interference (bcch clash) •         HW Issue •         Wrong parameter planning •         Bad coverage •         MAIO mismatch •         High LAPD utilization •         Wrong Power control settings •         Check the Timer
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POWER ON PROCEDURE

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When UE is getting power on, No idea of frequency to be latched. FBS=Full Band Scan(For New Phone/New SIM) DBS=Derived Band Scan(For Old Phone/Old SIM) UE POWER ON STEP1: RSSI Scan(it is just to measuring power/power level) Lets take an example, Our UE support bands like 2,3,20. FREQUENCY_SCAN_REQ  Earfcn 760(B2),1348(B3),6289(B20) report RSSI. STEP2: Filter by RSSI Threshold CELL_SCAN_REQ Earfcn 1348(B3) STEP3: PSS,SSS Decoding STEP4: MIB Decoding STEP5: SIB Decoding POWER ON PROCEDURE IN DETAIL
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Retainability KPI

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 Retainability is defined as the ability of a user to retain the E-RAB once connected for the desired duration. Retainability Investigation  : Major Reasons  for Poor Retainability  : Poor Coverage. Alarms High Load(High traffic) Hardware issue(Reset first),if required replace RRU. VSWR over threshold. HO failure: If a sector is having high HO Execution fail, it results in poor retainability.   Probable Solution  :The counter pmErabRelAbnormal/EnbActHo is checked. If this counter is pegging high, it implies poor retainability and resolution of sector HOSR is required.
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LTE EVENTS

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  A1=Serving cell better than threshold A2=Serving cell worst than threshold A3=Neighbor becomes better than threshold with offset.           (Intra frequency HO) A4=Neighbor becomes better than threshold.(Inter frequency HO) A5=Serving is worst than threshold & Neighbor is better than threshold. B1=IRAT becomes better than threshold. B2=Serving worst than threshold & IRAT NBR better than threshold.
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Mobility KPI

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 Mobility is the key procedure for ensuring that users can move freely within a network, without dropping the call or session  Intra-Frequency Handover  :Within same LTE Frequency(Event A3 is triggered when a neighbor cell becomes better than the serving cell by an offset). Inter-Frequency Handover  :Different LTE Frequency(Event A4 is triggered when a neighbor cell becomes better than a threshold). TRAT Handover  :Between different Radio System Technology like LTE to 3G or 2G.(Event B1 & B2) LTE Handover have two version: X2-Based and S1-Based X2-Based  :When Source and Target eNB are served within the same MME Pool. S1-Based  :When Source and Target eNB are served in different MME Pool. Intra eNB Handover  :Handover between two cells of same eNB.(S1 or X2 handover not required) Preparation Phase  :Admission Control and Resource Allocation. Execution Phase  :Detach from old cell and synchronize to new cell. Admission Control Failure  :Target site are congested, so it is not ready
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