A high-speed analog subscriber modem operates at speeds as high as 64 kbps in both the downlink and uplink directions using a standard POTS line augmented with an enhanced codec. This enables increased upload speeds and supports 56 kbps peer-to-peer analog subscriber connections. An enhanced network codec according to the present invention supports on a POTS line both high-speed modem communications and standard PCM speech communication. The enhanced codec of the present invention may be designed to be plug-compatible with existing codecs and may be used to upgrade POTS service to support data rates approaching 64 kbps. Similarly, the present invention may be used to increase the use of the POTS channel in a DSL system.