Layer 2 and layer 3 of UTRA-TDD

Within the Third Generation Partnership Project (3GPP) which was founded to harmonise the third generation technologies by different standardisation authorities, the UMTS Terrestrial Radio Access (UTRA) was created to form a global standard. UTRA FDD is based on WCDMA, UTRA-TDD is based on TD-CDMA. Using the results of the physical layer harmonisation between both modes a set of specifications representing the layer 2 and layer 3 covering both TDD and FDD was created in 3GPP. The medium access control (MAC), the radio link control (RLC), the broadcast/multicast control (BMC) and the packet data convergence protocol (PDCP) belong to the layer 2 of the UTRA network, UTRAN. The radio resource control (RRC) represents the layer 3 protocol which belongs to access stratum. All these protocols are basically common for TDD and FDD. Based on an harmonised design FDD/TDD dual mode operation is facilitated, which provides a basis for the development of low cost terminals. Also, harmonisation of UTRA with GSM is ensured. The paper provides an overview of UTRA TDD operation in layer 2 and layer 3. It describes the protocol architecture, logical channels and the transport channel concept applicable for TDD.