DFTS-OFDM PUCCH Transmit Diversity via Frequency-Domain Separation
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Solution Overview
Problem
Current LTE systems face challenges in efficiently utilizing wide carriers for legacy terminals and achieving backward compatibility in LTE Rel-10 deployments, particularly in ensuring efficient resource allocation and transmission diversity for Physical Uplink Control Channel (PUCCH) signals, especially with the introduction of additional transmit antennas.
Innovation Solution
The proposed solution combines DFT precoding and transmit diversity coding for PUCCH transmission, employing frequency-domain separation and time-domain orthogonal spreading separation, using multiple antennas to transmit data and reference signals across different subcarriers, enhancing orthogonality and multiplexing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmit diversity coding is implemented for DFTS-OFDM PUCCH transmission, then link performance is improved by 2-2.5 dB, but device complexity increases due to additional antennas and processing
Solution Approach 1:
The data symbols are divided into two separate blocks, with each block transmitted through a different antenna port using distinct sets of subcarriers. This segmentation enables transmit diversity while maintaining manageable complexity by processing smaller symbol blocks independently through each antenna path.
Solution Approach 2:
The patent introduces frequency-domain separation as an additional dimension for diversity, where different antenna ports transmit on different sets of subcarriers. This complements the time-domain orthogonal spreading already present in DFTS-OFDM, creating a two-dimensional diversity structure that improves reliability without proportionally increasing complexity.
2Adaptability or versatility
If multiple antennas are used for PUCCH transmission, then transmit diversity and multiplexing capacity are enhanced, but resource allocation complexity increases
Solution Approach 1:
The available subcarriers are segmented into different sets assigned to different antenna ports. This segmentation simplifies resource allocation by creating distinct, non-overlapping frequency resources for each antenna, making it easier to manage and track resources compared to a fully shared approach.
Solution Approach 2:
Different sets of subcarriers are allocated to different antenna ports based on their specific transmission requirements. This local quality approach allows optimized resource distribution where each antenna port receives appropriate frequency resources tailored to its function, enhancing multiplexing capacity while maintaining clear resource boundaries.
3Measurement precision
If frequency-domain separation is applied to data symbols from different antenna ports, then orthogonality is improved, but spectrum efficiency may be reduced
Solution Approach 1:
Instead of allocating all subcarriers to each antenna port, the patent uses partial action by assigning specific subsets of subcarriers to each antenna. This partial allocation ensures sufficient orthogonality for reliable detection while avoiding the excessive resource consumption that would occur if all subcarriers were assigned to every antenna port.
Solution Approach 2:
The patent adds frequency-domain separation as another dimension of orthogonality complementing the existing time-domain orthogonal spreading. This multi-dimensional approach achieves robust orthogonality without requiring complete spectral exclusion, as the diversity gains from multiple dimensions allow more efficient overall spectrum utilization.
Data Source
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Figure 3A~3B
AI summary
A transmission method and apparatus that combines the benefits of DFT preceding and transmit diversity coding for PUCCH transmission. In one aspect, the invention provides an improved transmit diversity coding method and apparaius for DFTS-OFDM PUCCH with minimal impact on multiplexing capacity. In one embodiment, the improved transmit diversity method and apparatus has the feature of employing frequency-domain separation for the payload signals.