Stabilized precoder for data transmission
AssigneeAdaptive Broadband Ltd.
InventorMalcolm Paul Sellars
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Abstract
A precoding scheme for digital data transmission across multipath channels is described, which improves on existing methods of precoder stability. This precoding scheme uses radial reduction of unstable roots to stabilize the precoder. Furthermore, in a broadband access system in which the preceding scheme is used, all of the precoding and equalization is performed in the subscriber units. This eliminates the problems of equalization and training delays occuring at the base station, thus allowing rapid demodulation of data arriving at the base station for several disparate subscriber terminals units.
Claims27
A precoder for pre-equalizing data to be transmitted over a channel, comprising:
- a feedback filter loop including a feedback filter having a feedback transfer function, said loop arranged to receive from an input the data to be transmitted and to partially pre-equalize said data;
- and
- a feedforward filter having a feedforward transfer function, said feedforward filter arranged to receive said partially pre-equalized data from the feedback filter loop and to output substantially pre-equalized data onto the channel;
- wherein said feedback filter loop further includes means for modifying the feedback transfer function to maintain the stability of the feedback filter thereby stabilizing the feedback filter loop.
A precoder according to any of the preceding claims wherein the feedback filter loop further includes summation means arranged to sum the output of the feedback filter with the input data to produce the partially pre-equalized data.
A method of precoding for pre-equalizing input data to be transmitted on a channel, comprising the steps of:
- i) partially pre-equalizing the input data in a feedback filter loop having a feedback transfer function;
- and
- ii) substantially pre-equalizing the partially pre-equalized data in a feedforward filter,
- wherein the partially pre-equalizing step further includes the step of modifying the feedback transfer function to maintain the stability of the feedback filter loop.
A wireless data communications system providing for time division duplex operation over a channel between a base station and at least one subscriber terminal characterized in that the subscriber terminal includes:
- an equalizer arranged to substantially remove any interference introduced by the channel into any received data;
- and
- preceding means for pre-equalizing data to be transmitted over the channel to the base station, the preceding means comprising:
- a feedback filter loop including a feedback filter having a feedback transfer function, said loop arranged to receive from an input the data to be transmitted and to partially pre-equalize said data, and means for modifying the feedback transfer function to maintain the stability of the feedback filter thereby stabilizing the feedback filter loop;
- and
- a feedforward filter having a feedforward transfer function, said feedforward filter arranged to receive said partially pre-equalized data from the feedback filter loop and output substantially pre-equalized data onto the channel;
- whereby said data communications system is further characterized in that all data equalization and precoding is performed in the subscriber terminal.
A wireless data communications method providing for time division duplex operation over a channel between a base station and at least one subscriber terminal comprising the steps of:
- equalizing received data at the subscriber terminal to substantially remove any interference introduced therein by the channel;
- and
- pre-equalizing data to be transmitted over the channel to the base station, the step of pre-equalizing further comprises:
- partially pre-equalizing the input data in a feedback filter loop having a feedback transfer function, the step of partially pre-equalizing including modifying the feedback transfer function to maintain the stability of the feedback filter loop, and
- substantially pre-equalizing the partially pre-equalized data in a feedforward filter,
- wherein said equalizing and pre-equalizing steps are each performed by said at least one subscriber terminal.
Dependencies are inferred from the claim text.