LTE 8-TX Codebook Subset Restriction Bitmap Segmentation
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Solution Overview
Problem
The existing Codebook Subset Restriction (CSR) signaling method in LTE Rel-10 with 8 transmit antennas is inefficient due to the conventional CSR bitmap signaling, which cannot be reused with the introduction of the dual codebook structure for 8-TX codebooks, leading to increased feedback overhead and reduced array antenna gain.
Innovation Solution
A new CSR bitmap transmission method is introduced for the LTE DownLink (DL) system with 8 transmit antennas, using a dual codebook structure that generates a CSR bitmap with 53 bits for a first codebook and 56 bits for a second codebook, optimizing the precoding matrix and rank indicators to reduce feedback overhead and enhance array antenna gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the conventional CSR bitmap signaling method is used in LTE Rel-10 with 8 transmit antennas, then the system can support basic MIMO operations, but the feedback overhead increases and array antenna gain is reduced due to inefficiency in the dual codebook structure
Solution Approach 1:
The patent segments the dual codebook structure into a first codebook (W1) and a second codebook (W2), where each codebook has its own restricted subset. The CSR bitmap is divided into two separate bitmaps: one for W1 and one for W2. This segmentation allows independent restriction of precoding matrices in each codebook, reducing the total feedback overhead while maintaining PMI feedback accuracy for 8-TX MIMO systems.
2Reliability
If the dual codebook structure is introduced for 8-TX codebooks, then the array antenna gain can be enhanced, but the conventional CSR signaling method becomes incompatible leading to increased complexity
Solution Approach 1:
The patent applies segmentation by dividing the dual codebook structure into two independent codebooks (W1 and W2) with separate CSR bitmaps. This allows the system to maintain the beneficial array antenna gain of the dual codebook structure while reducing signaling complexity through independent, manageable bitmap restrictions for each codebook component.
Solution Approach 2:
The patent introduces dynamic adaptability by allowing the eNB to independently configure restriction bitmaps for both W1 and W2 codebooks based on channel conditions and system requirements. This dynamic configuration enables flexible optimization of feedback overhead and performance without fixed complexity constraints.
3Manufacturing precision
If the CSR bitmap size is increased to cover all precoding matrices in the dual codebook structure, then all PMI options can be restricted, but the feedback overhead increases significantly
Solution Approach 1:
The patent segments the large CSR bitmap into two smaller bitmaps corresponding to W1 and W2 codebooks respectively. This segmentation achieves precise PMI restriction for all precoding matrices in the dual codebook structure while significantly reducing the total feedback overhead compared to a single large bitmap covering all matrices.
Data Source
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AI summary
The invention is directed to a method in a wireless communication system, the method comprising: generating a codebook subset restriction (CSR) bitmap, the CSR bitmap including at least one bit indicating restricted precoding matrix indicators (PMIs) that are not allowed to be reported by a terminal and at least one bit indicating unrestricted PMIs that are allowed to be reported by the terminal; transmitting the CSR bitmap to the terminal, wherein the CSR bitmap includes a af(1)(v)+i1 -th bit corresponding to a codebook index i1 and a layer v and a a53+f(2)(v)+i2 -th bit corresponding to a codebook index i2 and a layer v, and wherein the codebook indices i1 and i2 indicate a precoding index in a codebook, and wherein the f(1)(v) and the f(2)(v) are defined as the following equations, respectively: f1v={0forv=116forv=232forv=336forv=440forv=544forv=648forv=752forv=8andf2v={0forv=116forv=232forv=348forv=4.