How Synchronization Channel Works in LTE?

After the power on, the UE knows: 
  • the UE category and capability.
  • the preferred PLMN.
    the carriers.
The UE needs to know:
  • The frame synchronization to be able to decode the DL radio frame.
  • The cell parameters to be able request a connection.
The UE can use:
  • The PSS: Primary Synchronization Signal.
  • The SSS: Secondary Synchronization Signal.
  • The BCH, the broadcast channel.

The synchronization signals provide the cell id to the UE.
LTE supports 510 different cell identities.

  • They are divided into 170 cell id groups and there are 3 cell ids per group.
  • Cell id = 3* Cell_Group_id(0 to 169 Provided by the SSS) + Cell_id_in_group(0 to 2 Provided by the PSS )
The Primary Synchronization Signal (PSS):

  • is used for the slot synchronization.
  • is on the last OFDM symbol of slots 0 & 10 in the 1st & 6th sub-frames of each frame.
  • carries one of the 3 cell id in group sequence.
The Secondary Synchronization Signal (SSS):

  • is used for the frame synchronization.
  • is on the same slot as PSS.
  • is on the next to last OFDM symbol of slots 0 & 10 in the 1st & 6th sub-frames of each frame.
  • carries one of the 170 unique cell group identifiers.
The PSS, the SSS and the BCH are carried over 6 Resource Blocks (RB) whatever the bandwidth
6 RBs = 6 * 12 Sub-ca = 72 Sub-carriers
By this way, these signals are independent from the bandwidth and can decode this signal without knowing it.

Google serves cookies to analyze traffic to this site and for serving personalized ads. Learn more