A 2G+ upgrade to GSM designed to improve data transmission rates. HSCSD improves channel throughput from 9.6 kbps to a maximum of 14.4 kbps in GSM host networks operating at 1800 MHz by lowering overhead through the use of improved mechanisms for forward error correction (FEC). HSCSD also supports the concatenation of multiple time slots per frame in support of higher speeds. As examples, two concatenated time slots yields a transmission rate of up to 28.8 kbps, three yields 43.2 kbps, and four yields 57.6 kbps. See also 2G, channel, concatenation, FEC, frame, GSM, overhead, throughput, time slot, and transmission rate.