Patent Application
20110158218
Transmit beamforming, which may improve wireless communications, requires the feedback of beamforming matrixes in a frequency division duplexing (FDD) mode. The feedback can be differential with respect to the previous feedback. Differential feedback exploits the correlation between the ideal beamforming matrixes across time in order to reduce feedback overhead and increase beamforming accuracy. A quantization codebook may be used to quantize the differential matrix for the feedback. Previously, quantization codebook is constant across time. This is not optimal.
Thus, a strong need exists for improvements in providing differential feedback used in transmit beamforming.
The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:
It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate corresponding or analogous elements.
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the preset invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.
Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, “processing,” “computing,” “calculating,” “determining,” “establishing”, “analyzing”, “checking”, or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulate and/or transform data represented as physical (e.g., electronic) quantities within the computer's registers and/or memories into other data similarly represented as physical quantities within the computer's registers and/or memories or other information storage medium that may store instructions to perform operations and/or processes.
Although embodiments of the invention are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. For example, “a plurality of stations” may include two or more stations.
As mentioned above, in the prior art of differential feedback, a constant differential codebook is used across feedbacks. For the example as shown as 100 of
However, this is not optimal. Embodiments of the present invention provide varying the differential codebook across a plurality of feedbacks. In practice, it is desirable to use the same number of feedback bits across frames. For the same number of bits, the initial feedback has an error greater than the latter differential feedbacks, because the initial feedback can not exploit any correlation (in time or frequency). To compensate for the large error, the differential codebook for frame 1120 should have a span greater than the differential codebook for the latter frames, i.e. frame 2 and 3. The span can be quantified by polar cap size in angle for a given codebook. As illustrated generally as 200 of
Looking now at 300 of
While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
