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Blog 2018-10-16T19:22:55+00:00

Stage 4: Redirection to UMTS

Stage 4: Redirection to UMTS Stage 4: Redirection to UMTS When the LTE eNodeB processes an Event A2-based Measurement Report message, if it decides to direct the UE to move to a UMTS cell, it has to first transition the UE from the RRC-Connected state to the RRC-Idle state. Moreover, the eNodeB may direct the UE to a specific UMTS carrier. This is accomplished in LTE by the eNodeB sending an RRC Connection Release message to the UE. The message may contain the parameter RedirectedCarrierInfo, which contains UMTS carrier frequency information such as the band (e.g., 900 or 1900MHz) and the center frequency of the UMTS carrier. After the eNodeB sends the RRC Connection Release message to the [...]

By | April 4th, 2019|4G-LTE Optimization Part-1|0 Comments

Stage 3: Measurement Reporting

Stage 3: Measurement Reporting Stage 3: Measurement Reporting Let us look at the information sent by the UE in the Measurement Report message to the eNodeB. Key information sent in the report includes: Measurement ID: UE conveys the measurement information that is being sent in this message. Please note that the eNodeB sends this value to UE as part of measurement configuration. Measurement Results for Serving cell: UE report sends the filtered RSRP and/or RSRQ values to eNodeB in this message. The information element values may be converted to actual values using the following conversion: ― -140 + Information element value - 1<= RSRP < -140 + Information element value ― -19.5 + (Information element value – 1) [...]

By | April 3rd, 2019|4G-LTE Optimization Part-1|0 Comments

Event A3 Periodical Reporting

Event A3 Periodical Reporting Event A3 Periodical Reporting Let us look closer at the measurement reporting done by the UE once the A3 entry is triggered. As soon as the UE detects an entry condition, it will start the time-to-trigger timer. If the conditions change and the entry condition is no longer valid before the timer expires, it will not report anything to the eNB. If the condition continues to be valid and the time-to-trigger timer expires, the UE will send a Measurement Report message to the eNB and start a reportIntervalA3 timer. If conditions remain valid and the reportIntervalA3 timer expires before the eNB responds to the UE, the UE will send a new Measurement Report message. [...]

By | April 2nd, 2019|4G-LTE Optimization Part-1|0 Comments

Event A3

Event A3 Event A3 Event A3 is defined as a triggering event when a neighbor cell becomes an offset better than the serving cell. The UE creates a measurement report, populates the triggering details and sends the message to the serving cell. The parameters that define the trigger are discussed below. The role of the Offset in Event A3 is to create inertia for the UE by making the serving cell look better than its current measurement in comparison to the neighbor. The role of the Hysteresis in Event A3 is to make the measured neighbor look worse than measured to ensure it is really stronger before the UE decides to send a measurement report to initiate a [...]

By | April 2nd, 2019|4G-LTE Optimization Part-1|0 Comments

Stage 1: Measurement Config

Stage 1: Measurement Config Stage 1: Measurement Config Let us discuss some of the measurement configuration information sent by the eNB to the UE as part of the RRC Connection Reconfiguration message Measurement ID: Whenever the eNB directs a UE to do a particular measurement, it defines it by giving it a unique ID. Typically, vendor implementations use a specific value for each type of measurement. For example, an RSRP measurement may always be identified by a measurement ID of one in a vendor’s implementation if it is being configured. Measurement Object: The eNB clearly specifies what the UE should do the measurement on. Information includes carrier frequency and measurement bandwidth for each measurement ID. Report Configuration: The [...]

By | April 1st, 2019|4G-LTE Optimization Part-1|0 Comments

Handover Call Flow

Handover Call Flow Handover Call Flow This diagram shows X2 interface-based handover call flow at a high level. 1. The handover procedure is used only when a UE moves from one cell to another in the RRC Connected state. 2. Once a UE is in RRC Connected, the eNB will send the RRC Connection Reconfiguration message, which will define the measurement configuration, to the UE. 3. One of the key measurement configuration parameters is s-Measure. S-Measure is the level of RSRP for the current cell below which the UE is required to start handover-related measurements. As long as the current cell RSRP is below s-Measure, the UE will continue its measurements. 4. When UE measurements meet event triggers [...]

By | April 1st, 2019|4G-LTE Optimization Part-1|0 Comments

Intra-Freq Handover Stages

Intra-Freq Handover Stages Intra-Freq Handover Stages In LTE, intra-frequency handover is defined as a series of stages as follows: The first stage is where the eNB will configure the UE for measurements that the UE needs to do. In 3GPP technologies, the network typically controls the device by sending specific configuration requirements for measurements. In LTE, this information would include what quantity to measure (RSRP or RSRQ), when to measure, what events would trigger measurement reporting, and what to include in the reports sent to the eNB. The second stage is where the UE starts doing the measurements. For example, the UE may be required to start a measurement only when the current cell signal falls below a [...]

By | March 30th, 2019|4G-LTE Optimization Part-1|0 Comments

Stage 5E: Establish Default Bearer

Stage 5E: Establish Default Bearer Stage 5E: Establish Default Bearer After the security mode and the UE capabilities negotiation phases are completed, the eNB sends the default EPS radio bearer-related dedicated radio resource information to the UE in the RRC Connection Reconfiguration message. It also includes measurement related control parameters to allow the UE to start sending Measurement Report messages. Then, the UE acknowledges the RRC connection reconfiguration with the RRC Connection Reconfiguration Complete message. The eNB, upon receiving the RRC Connection Reconfiguration Complete, responds back to the MME with the Initial Context Setup Response. This message contains the confirmation for the MME that the requested UE context was set up successfully. The UE now sends the Attach [...]

By | March 30th, 2019|4G-LTE Optimization Part-1|0 Comments

Stage 5: Establish Default Bearer

Stage 5: Establish Default Bearer Stage 5: Establish Default Bearer After selection of the S-GW, the next important step is to create the default EPS bearer for the UE. The MME keeps track of all bearers created for a UE by the bearer identity and the default bearer identity. This information is stored in the context for that UE on the MME. The MME sends a Create Session Request message to the S-GW pegging a counter, typically indicating the request to create a session. The S-GW allocates UE context, control plane and user plane resources (for example, data buffers) for the UE’s PDN connectivity and creates endpoints for the default bearer and all the associated details of the [...]

By | March 29th, 2019|4G-LTE Optimization Part-1|0 Comments

AS Security Mode Procedure

AS Security Mode Procedure AS Security Mode Procedure After the UE context has been created, the MME sends the Initial Context Setup Request message (S1- AP) which contains the S1AP identifiers, the AMBR for the UE, and details of the Radio Access Bearers that the MME has approved for set-up, including the TEIDs associated with the RABs that are being set up. The eNB then sends a security mode command. The Enb selects the integrity and encryption algorithms to be used. Selection is done based on the prioritized list sent by the MME and the security capabilities of the UE. The UE makes a note of the selected encryption and integrity algorithms, and generates the keys required for [...]

By | March 29th, 2019|4G-LTE Optimization Part-1|0 Comments
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