SIB1 in 5G:

SIB1 (System Information Block Type 1) from 3GPP

SIB1 (System Information Block Type 1), as defined by the 3GPP TS 38.331, contains essential parameters for the initial access, cell selection, and network configuration in 5G NR (New Radio). These parameters are presented in the form of Information Elements (IEs), which provide the necessary information to the user equipment (UE) to connect and operate within a 5G network.

Below is a detailed breakdown of the key Information Elements (IEs) present in SIB1, along with their functions, as specified by 3GPP standards.

1. PLMN-IdentityList

  • Description: This IE provides a list of one or more Public Land Mobile Networks (PLMNs) that the cell broadcasts.
  • Purpose: Helps the UE identify which PLMNs it can connect to, enabling network access when the UE’s PLMN matches an allowed PLMN.
  • Key Parameters:
    • PLMN-Identity: Contains the MCC (Mobile Country Code) and MNC (Mobile Network Code) identifying the network operator.
    • TrackingAreaCode (TAC): Identifies the tracking area where the gNB (gNodeB or base station) is located.

2. CellAccessRelatedInfo

  • Description: Provides information about cell access restrictions and reselection policies.
  • Purpose: Guides the UE on whether it can access the cell and under what conditions it can reselect to other cells.
  • Key Parameters:
    • CellBarred: Indicates if the cell is barred (i.e., the UE should not attempt to connect to this cell). If set to "barred," the UE must avoid this cell.
    • IntraFreqReselection: Determines whether the UE is allowed to reselect other cells on the same frequency.

3. ServingCellConfigCommon

  • Description: This IE contains the common configuration information related to the serving cell.
  • Purpose: Provides the UE with essential configuration parameters for operation in the serving cell, including subcarrier spacing and beam management.
  • Key Parameters:
    • SubcarrierSpacingCommon: Defines the subcarrier spacing to be used for downlink and uplink communication. The values can be 15 kHz, 30 kHz, 60 kHz, 120 kHz, or 240 kHz.
    • SSB-PositionsInBurst: Specifies the position of Synchronization Signal Blocks (SSB) in the burst. This helps the UE find and align with the SSB transmission for synchronization and initial access.

4. Frequency Band Indicator

  • Description: Indicates the frequency band that the gNB is operating on.
  • Purpose: Enables the UE to know which frequency band it should use for communication and whether it matches its capabilities.
  • Key Parameters:
    • NR-ARFCN: The absolute radio frequency channel number that defines the specific carrier frequency in use.

5. System Frame Number (SFN)

  • Description: The system frame number that indicates the current frame within the radio frame structure.
  • Purpose: Ensures that the UE is synchronized with the gNB in terms of timing, which is necessary for effective communication.
  • Key Parameters:
    • SFN: A number between 0 and 1023, identifying the frame in which the UE and network are currently operating.

6. SIB1 Periodicity

  • Description: Indicates how often SIB1 is broadcast by the gNB.
  • Purpose: Allows the UE to schedule when to receive SIB1 and ensures that the UE can retrieve the necessary system information if it misses the current broadcast.
  • Typical values: SIB1 is usually broadcast every 160 ms, 320 ms, or other standard intervals as defined by network configuration.

7. RACH-ConfigCommon

  • Description: Contains configuration parameters for the Random Access Channel (RACH) procedure, which is used by the UE to initiate connection with the network.
  • Purpose: Provides the UE with the configuration needed to perform random access when it first connects to the network or when recovering from radio link failure.
  • Key Parameters:
    • prach-ConfigIndex: Specifies the configuration index for PRACH (Physical Random Access Channel) parameters.
    • Msg1-FDM: Specifies how many frequency division multiplexing (FDM) opportunities are available for Msg1 in random access.
    • RACH-Configuration: Defines the number of preambles and the time/frequency resources used for the random access procedure.

8. PDCCH-ConfigSIB1

  • Description: Configures the Physical Downlink Control Channel (PDCCH) for SIB1.
  • Purpose: Specifies the parameters for the PDCCH that carries the scheduling information for SIB1, enabling the UE to decode the control information properly.
  • Key Parameters:
    • ControlResourceSetZero: Defines the set of resources in the control channel for SIB1 transmission.
    • SearchSpaceZero: Specifies the search space that the UE must monitor for the PDCCH carrying SIB1.

9. Paging Information

  • Description: Provides information on how the network pages the UE when it is in idle mode.
  • Purpose: Helps the UE know when and how to monitor for paging messages, ensuring it can receive calls, messages, or notifications while conserving battery power.
  • Key Parameters:
    • PagingCycle: Determines how frequently the UE checks for paging messages. A longer cycle reduces power consumption, while a shorter cycle improves responsiveness.
    • PagingOffset: Specifies the offset within the paging cycle at which the UE should listen for paging messages.

10. Q-RxLevMin

  • Description: Specifies the minimum required reference signal received power (RSRP) level for the UE to access the cell.
  • Purpose: Ensures that the UE only tries to access the cell if the signal strength meets a certain threshold, improving the chances of a successful connection.
  • Key Parameters:
    • Q-RxLevMin: A value representing the minimum signal strength (in dBm) that the UE needs to consider the cell as suitable for connection.

11. P-Max

  • Description: Defines the maximum allowed transmit power for the UE in the current cell.
  • Purpose: Controls the UE’s transmit power, ensuring that it stays within the network's power limits and avoids causing interference with other devices.
  • Key Parameters:
    • P-Max: Specifies the maximum transmit power level, typically measured in dBm, for uplink transmission.

12. TimeAlignmentTimerCommon

  • Description: Defines the duration of the timing alignment timer used to synchronize uplink transmissions between the UE and the gNB.
  • Purpose: Ensures that the UE maintains proper time alignment with the gNB during uplink transmissions. If the timer expires, the UE must initiate a new random access procedure to regain synchronization.
  • Key Parameters:
    • TimeAlignmentTimer: Specifies the timer duration, after which the UE assumes its timing alignment with the network is lost.

13. Beam Management Information

  • Description: Provides configuration information related to beamforming, a key technology in 5G that enhances signal quality by focusing the transmission in a specific direction.
  • Purpose: Helps the UE optimize communication with the gNB, especially in environments where beamforming is used for high-frequency bands.
  • Key Parameters:
    • BeamManagementConfig: Specifies parameters for managing multiple beams used by the UE and gNB for signal transmission and reception.

Conclusion

The Information Elements (IEs) in SIB1 provide vital data that helps the UE perform initial network access, cell selection, random access, and synchronization in a 5G network. These IEs are carefully structured according to 3GPP standards to ensure that the UE has all the necessary parameters to establish and maintain communication with the 5G New Radio (NR) network efficiently.

by at

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)