Method for polar diagram shaping in a radio communications system
View Patent ↗A method forms polar diagrams in a connection between a subscriber and a base station with an antenna arrangement in a radio communications system using multiple access methods. Antenna signals are associated with polar diagrams of the antenna arrangement by a common beam forming network. The common beam forming network is used to form weighted sum signals, which are passed as input signals to a user-specific beam forming unit. A selector which is arranged there takes from the input signals a user-specific subset Kc of signals, to which an eigen polar diagram forming algorithm is applied.
1. A method for forming polar diagram in a radio communications system using multiple access methods and with Ku subscribers, comprising:
transmitting a subscriber signal from an individual subscriber to an antenna arrangement, which has Kb polar diagrams and Ka individual antennas, which produce Ka antenna signals from the subscriber signal,
passing the Ka antenna signals as input signals to a common beam forming network with Ka inputs and Kb outputs,
forming Kb weighted sum signals in the common beam forming network from the Ka antenna signals, the Kb weighted sum signals being formed for each of the Ku subscribers, the Kb weighted sum signals being sent respectively to the Kb outputs of the common beam forming network,
assigning each of the Kb outputs of the beam forming network one, and only one, of the Kb polar diagrams of the antenna arrangement,
for each of the Ku subscribers, passing the Kb weighted sum signals from the common beam forming network respectively to Kb inputs of an adaptive user-specific beam forming unit with Kb inputs, and
selecting a user-specific polar diagram for each of the Ku subscribers, the user-specific polar diagrams being selected in the beam forming unit from the Kb weighted sum signals passed to the Kb inputs of the beam forming unit, wherein
a selector is provided in the user-specific beam forming unit to select, on a user-specific basis, a subset of Kc signals from the Kb weighted sum signals,
the user-specific polar diagram is selected based on the Kc signals, and
to form the subset of Kc signals, the selector selects the Kb weighted sum signals whose user-specific weighted combination forms an optimum ratio between a respective subscriber useful signal and disturbing interference signals and noise.
2. The method as claimed in claim 1 , wherein the common beam forming network converts the Ka antenna signals for each of the Ku subscribers into baseband signals and then performs analog to digital conversion on the baseband signals to form digital baseband signals which are combined to form the Kb weighted sum signals such that the respectively assigned polar diagram covers a defined three-dimensional area.
3. The method as claimed in claim 1 , wherein
the common beam forming network combines the Ka antenna signals for each of the Ku subscribers on a carrier-frequency basis to form the Kb weighted sum signals, such that the respectively assigned polar diagram covers a defined three-dimensional area, and
the Kb weighted sum signals are converted to baseband signals, and analog to digital conversion is performed on the baseband signals.
4. The method as claimed in claim 3 , wherein the Ka antenna signals are combined to form the Kb weighted sum signals by a Butler matrix.
5. The method as claimed in claim 1 , wherein the subset of Kc signals are passed to an eigen beam former.
6. The method as claimed in claim 5 , wherein the subset of KC signals passed to the eigen beam former:
are used to form an interference covariance matrix with an interference covariance estimation device,
are used to form a signal covariance matrix with a signal covariance estimation device, and
are passed to a despreading device to form despread output signals.
7. The method as claimed in claim 6 , wherein weights are calculated from the individual polar diagrams with a weighting device and with the interference covariance matrix and the signal covariance matrix, using eigen value decompositions, and the weights are passed together with despread output signals to a combiner.
8. The method as claimed in claim 7 , wherein an eigen beam is formed with the combiner.
9. The method as claimed in claim 1 , wherein the selector provides a smooth transition between a pure common polar diagram and a pure user-specific polar diagram, the smooth transition being provided with the subset of Kc signals.
10. The method as claimed in claim 4 , wherein the subset of Kc signals are passed to an eigen beam former.
11. The method as claimed in claim 10 , wherein the subset of KC signals passed to the eigen beam former:
are used to form an interference covariance matrix with an interference covariance estimation device,
are used to form a signal covariance matrix with a signal covariance estimation device, and
are passed to a despreading device to form despread output signals.
12. The method as claimed in claim 1 , wherein weights are calculated from the individual polar diagrams with a weighting device and with the interference covariance matrix and the signal covariance matrix, using eigen value decompositions, and the weights are passed together with despread output signals to a combiner.
13. The method as claimed in claim 12 , wherein an eigen beam is formed with the combiner.
14. The method as claimed in claim 13 , wherein the selector provides a smooth transition between a pure common polar diagram and a pure user-specific polar diagram, the smooth transition being provided with the subset of Kc signals.