In a FDD system one ARFCN number is required for downlink and another for uplink as downlink and uplink frequencies are different while for TDD system only one ARFCN number is enough as downlink and uplink frequency remains same.
In a FDD system one ARFCN number is required for downlink and another for uplink as downlink and uplink frequencies are different while for TDD system only one ARFCN number is enough as downlink and uplink frequency remains same.