Abstract: An asymmetrical digital subscriber line (ADSL) downstream high speed cell bus interface protocol allows ADSL cell packets to be transmitted downstream from an ADSL bank control unit (ABCU) to a plurality of ADSL line units at a high rate of downstream throughput with flexible and efficient allocation of bandwidths and reduced error probability. The frame boundaries of an ADSL frame are derived from a conventional subscriber bus interface (SBI) frame for carrying conventional narrowband plain old telephone service (POTS) traffic, thereby allowing the ABCU and the ADSL line units to be implemented in existing channel banks with standard channel bank backplane traces.

Abstract: Asymmetrical digital subscriber line (ADSL) upstream subscriber bus interface (SBI) protocol provides a SBI frame format which allows compatibility between an ADSL line card and either an ADSL bank control unit (ABCU) or a conventional narrowband bank control unit (BCU), and compatibility between a conventional plain old telephone service (POTS) line card and either the ABCU or the conventional narrowband BCU.

Abstract: A subscriber bus interface (SBI) frame format provides discrimination between asymmetrical digital subscriber line (ADSL) signal traffic and non-ADSL traffic. In the frame format, ASDL identification tag (AIT) bits are assigned to a higher order byte of an SBI time slot of an SBI frame for identifying whether or not a line card transmitting the SBI frame is an ADSL line card. Further, an overhead byte is assigned to a lower order byte of the SBI time slot. The overhead byte includes cell type indicator bits for indicating if the SBI frame contains asynchronous transfer mode (ATM) payload bytes found in ADSL signal traffic. The AIT bits of the higher order byte include an alternating pattern of binary “0”s and “1”s to prevent accidental generation of the AIT bits by a non-ADSL line card.