8-TX Codebook Feedback Signaling With PMI2 and CQI Co-Transmission
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Solution Overview
Problem
There is a need for improved methods and devices in Release 10 of 3GPP wireless networks to reduce feedback overhead related to Channel Quality Indicator (CQI), Precoder Matrix Indicator (PMI), and Rank Indicator (RI) feedback, making it similar to the efficiency of Release 8 feedback mechanisms.
Innovation Solution
A mobile station transmits a second precoder matrix indicator (PMI2) value alongside the channel quality indicator (CQI) in the same subframe, reducing the need for separate subframes and enhancing feedback efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Release 10 uses implicit feedback with two codebook indices (PMI1 and PMI2) to specify precoders, then the precision of channel state information feedback is improved, but the feedback overhead increases compared to Release 8
Solution Approach 1:
The precoder matrix indicator feedback is segmented into two separate codebook indices: PMI1 for wideband/long-term channel properties and PMI2 for frequency-selective/short-term channel properties. This segmentation allows the feedback to be distributed across different subframes, reducing the instantaneous feedback overhead while maintaining comprehensive channel state information precision
Solution Approach 2:
The feedback mechanism uses periodic transmission where PMI1 and PMI2 are sent in different subframes according to a predetermined pattern. This periodic distribution of feedback information reduces the peak feedback overhead in any single subframe while ensuring complete channel state information is conveyed over time
2Quantity of substance
If PMI1 and PMI2 are transmitted in different subframes, then the feedback overhead per subframe is reduced, but the time required to complete feedback transmission increases
Solution Approach 1:
PMI1 feedback is transmitted in advance in earlier subframes, allowing the base station to prepare for receiving PMI2 in subsequent subframes. This preliminary transmission of the first codebook index optimizes the timing and reduces the overall feedback completion time while maintaining reduced per-subframe overhead
3Adaptability or versatility
If the codebook size is increased to provide more precise precoder selection, then the adaptability to different channel conditions is improved, but the complexity of the feedback mechanism increases
Solution Approach 1:
The large codebook is segmented into two smaller codebooks (C1 for PMI1 and C2 for PMI2), where each codebook handles specific aspects of channel characteristics. This segmentation reduces the complexity of selecting from a single large codebook while maintaining the ability to adapt to diverse channel conditions through the combination of both codebook indices
Solution Approach 2:
Different codebooks are designed with different properties: C1 is optimized for wideband/long-term channel characteristics while C2 is optimized for frequency-selective/short-term characteristics. This local optimization of each codebook for specific channel aspects improves overall adaptability while keeping each individual codebook manageable in size
Data Source
AI summary
A mobile station for use in a wireless network. The mobile station is operable to transmit feedback values to a base station of the wireless network. The feedback values include a first precoder matrix indicator (PMI1) value and a second precoder matrix indicator (PMI2) value. The mobile station transmits the PMI2 value to the base station in the same subframe as a channel quality indicator (CQI) value. The CQI value may be either a wideband CQI value or a subband CQI value.