Hybrid TDMA/CDMA system based on filtered multitone modulation
AssigneeInternational Business Machines Corporation
InventorGiovanni Cherubini
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Abstract
A multiple access communications network system in which a head-end controller (HC) broadcasts data and medium-access control (MAC) information over a set of downstream channels to several stations, and these stations send information to the HC over a shared upstream channel.
Claims48
A digital transmission scheme for use in a multiple access communications network system with a system comprising an upstream channel with a bandwidth of 1/Tc Hz for transmission of information from remote stations to a head-end node, where a baseband signal is transmitted as passband signal employing a modulator, said baseband signal being generated by employing M subcarriers for transmission over M subchannels of blocks of M symbols, each taken from a symbol constellation, where
- the transmission over the i-th subchannel, with i=0, . . . , M−1, takes place at a modulation rate of 1/(mi Tc) symbols/s,
- the i-th subchannel has a bandwidth of 1/(mi Tc) 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 claim 6, where there are M QAM (quadrature-amplitude modulation) constellations which are not identical.
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.
A multiple access communications network system having a head-end node and at least one station node, said head-end node comprising a head-end controller (HC) capable of transmitting data and medium-access control (MAC) information to said station node over at least one downstream channel within a first frequency range, and capable of receiving information from said station node transmitted as passband signals over L subchannels, with L=1, 2, . . . , M, on a shared upstream channel, where said station node generates baseband signals and transmits them as passband signals employing a modulator, where said baseband signal is generated by employing
- L subcarriers for transmission of blocks of L symbols, each taken from a symbol constellation, such that
- the transmission over the i-th subchannel, with i=0, . . . , M−1, takes place at a modulation rate of 1/(mi Tc) symbols/s,
- the i-th subchannel has a bandwidth of 1/(mi Tc) 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.
Dependencies are inferred from the claim text.