Filtered multitone transmission application to DSL technologies
AssigneeInternational Business Machines Corporation
InventorsGiovanni Cherubini, Evangelos S Eleftheriou, Sedat Oelcer
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Abstract
Transmission techniques suitable for use in digital subscriber line (DSL) systems such as very high rate digital subscriber line (VDSL) systems are described. One embodiment of the present invention describes a transmission technique related to OFDM from high-speed transmission over twisted-pair cables. The scheme, also known as filtered multitone modulation (FMT), exhibits significantly lower spectral overlapping between adjacent subchannels and provides higher transmission efficiency than discrete multitone modulation (DMT).
Claims44
A digital transmission scheme for use in digital subscriber line (DSL) communication systems comprising a channel with bandwidth of 1/Tc Hz, employing M subcarriers for transmission of blocks of M symbols, each taken from a symbol constellation over M subchannels, where
- the transmission over the i-th subchannel, with i=0, . . . , M−1, takes place at a modulation rate of 1/(miTc) symbols/s,
- the i-th subchannel has a bandwidth of 1/(miTc) Hz, where the numbers mi satisfy the condition ∑ i = 0 M - 1 1 m i = 1
- at least one subchannel has spectral nulls at the bandedges, and
- at least one subchannel has zero guard bands.
The scheme according to any of the preceding claims, where time-domain filtering is carried out for adjustment of the system's channel phase characteristic.
The scheme according to any of the preceding claims, where oversampling of subchannel output signals is performed to allow interpolation/equalization of said subchannel output signals prior to symbol detection.
A digital communications system for bidirectional transmission of information over a channel (42) between a first transceiver (45) and a remote transceiver (43), said channel (42) having a bandwidth of 1/Tc Hz and being divided into M subchannels, said system employing M subcarriers for transmission of blocks of M symbols, each taken from a symbol constellation over said M subchannels, whereby
- the transmission over the i-th subchannel, with i=0, . . . , M−1, takes place at a modulation rate of 1/(miTc) symbols/s,
- the i-th subchannel has a bandwidth of 1/(miTc) Hz, where the numbers mi satisfy the condition ∑ i = 0 M - 1 1 m i = 1
- at least one subchannel of said M subchannels has spectral nulls at the bandedges, and
- at least one subchannel of said M subchannels has zero guard bands.
Dependencies are inferred from the claim text.