Transmission and Multiplexing (TM); Generic Frame Structures for the Transport of Various Signals (Including Asynchronous Transfer Mode (ATM) Cells) and Synchronous Digital Hierarchy (SDH) Elements) at the CCITT Recommendation G.702 Hierarchical Rates of 2 048 Kbit/s, 34 368 Kbit/s and 139 264 Kbit/s