Low-density parity-check codes for digital subscriber lines

The paper investigates the application of low-density parity-check (LDPC) codes to digital subscriber-line (DSL) transmission systems that employ discrete multitone modulation. A family of linear-time encodable binary LDPC codes that are well-suited for DSL transmission is introduced. Encoding and symbol mapping for multilevel modulation are described. Simulation results show that even under tight latency constraints good net coding gains can be achieved. Implementation complexity is analyzed and compared with that of trellis-coded modulation as employed in current asymmetric DSL transceivers. The incorporation of powerful LDPC coding techniques into next-generation DSL modems appears to be possible with reasonable increase in transceiver complexity.