Asymmetrical digital subscriber line (ADSL) downstream high speed cell bus interface protocol

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.