ransmitting TM RLC entity via the lower layers. A UM RLC entity is configured either as a transmitting UM RLC entity or a receiving UM RLC entity. The transmitting UM RLC entity receives RLC SDUs from an upper layer and sends RLC PDUs to its peer receiving UM RLC entity via the lower layers. The receiving UM RLC entity delivers RLC SDUs to an upper layer and receives RLC PDUs from its peer transmitting UM RLC entity via the lower layers. An AM RLC entity consists of a transmitting side and a receiving side. The transmitting side of an AM RLC entity receives RLC SDUs from an upper layer and sends RLC PDUs to its peer AM RLC entity via the lower layers. The receiving side of an AM RLC entity delivers RLC SDUs to an upper layer and receives RLC PDUs from its peer AM RLC entity via the lower layers. Figure 7-22 illustrates the structure of the RLC sub-layer. The octet-aligned RLC SDUs of variable sizes are supported for all RLC entity types (i.e., TM, UM, and AM RLC entities). The RLC PDUs are formed on notification of a transmission opportunity and are delivered to the MAC sub-layer. As shown in Figure 7-23, a TM RLC entity can be configured to deliver RLC PDUs through BCCH, DL/UL CCCH, and PCCH logical channels. When a transmitting TM RLC entity forms Transparent Mode Data (TMD) PDUs from RLC SDUs, it does not segment or concatenate the RLC SDUs, and does not include any RLC headers in the TMD PDUs. A UM RLC entity can be configured to deliver RLC PDUs through DL/UL DTCH logical channels. When a transmitting UM RLC entity constructs Unacknowledged Mode Data (UMD) PDUs from RLC SDUs, it segments and/ or concatenates the RLC SDUs SO that the UMD PDUs fit within the total size of RLC PDU indicated by the lower layer at the particular transmission opportunity, and includes relevant RLC headers in the UMD PDU. When a receiving UM RLC entity receives UMD PDUs, it detects whether duplicate UMD PDUs have been received and discards duplicated UMD PDUs, it reorders the UMD PDUs, if they are received out of sequence, it detec