NR TAC Tracking Area Code

TAC 大家都不陌生，用于UE 区域跟踪。网络侧寻呼时，知道UE在哪。

NR的TAC还有另外一个很大的作用：

38.331 6.3.2 PLMN-IdentityInfoList

trackingAreaCode

Indicates Tracking Area Code to which the cell indicated by cellIdentity field belongs. The presence of the field indicates that the cell supports at least standalone operation; the absence of the field indicates that the cell only supports EN-DC functionality.

UE如果在sib1中检测到了TAC,就认为这个cell支持SA; 否则只支持NSA.

  message c1 : systemInformationBlockType1 : {
    cellSelectionInfo {
      q-RxLevMin -70
    },
    cellAccessRelatedInfo {
      plmn-IdentityInfoList {
        {
          plmn-IdentityList {
            {
              mcc {
                1,
                1,
                1
              },
              mnc {
                2,
                2
              }
            }
          },
          trackingAreaCode '000000000000000000001001'B,
          cellIdentity '000000000110110101111100000000000010'B,
          cellReservedForOperatorUse notReserved
        }
      }
    },

未完待续。。。