Multiplex communications – Wide area network – Packet switching
Patent
1994-05-20
1995-12-05
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370 24, 375222, 375229, 375260, 379406, 379410, 379411, H04J 300
Patent
active
054736005
ABSTRACT:
An efficient data storage scheme for an echo canceller for a high-speed modem provides for storing in bulk memory, instead of a trellis-encoded codewords, unencoded words of lesser length in bits. For a v.32terbo modem operating at 19,200 bps, for example, the unencoded word has only eight bits as compared to nine bits for the trellis-encoded codeword. Therefore, one memory word (16 bits) can be used to store two unencoded words, resulting in memory savings of 50%. More particularly, in accordance with one embodiment of the invention, full-duplex, high-speed data communications using echo cancellation is performed by storing in memory transmit data represented in a first form, at predetermined intervals substantially equal to a round-trip delay time, reading out transmit data from memory and trellis-encoding the transmit data to produce trellis-encoded transmit data, and performing echo cancellation using data derived from the trellis-encoded transmit data. In accordance with another embodiment of the invention, an apparatus for high-speed data communications includes first circuitry, having a first encoder, for producing first signal element data from multi-bit data symbols, an echo canceller, circuitry for storing the multi-bit data symbols and outputting delayed multi-bit data symbols each after a predetermined time, and second circuitry for producing from the delayed multi-bit data symbols second signal element data substantially identical to the first signal element data and for applying the second signal element data to the echo canceller.
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Joseph Braue "The State of the Modem," Data Communications International, Jun. (1991): 85-98.
Hom Shick
Olms Douglas W.
Sierra Semiconductor Corporation
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