CDM-8 CSI-RS Aggregation for MIMO Port Capacity
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Solution Overview
Problem
Current CDM-8 designs in wireless communications suffer from performance losses due to channel variations over 9 OFDM symbols and have higher CSI-RS overhead, particularly for 24 and 32 ports, leading to orthogonality loss and increased CSI-RS overhead.
Innovation Solution
The solution involves aggregating two length 4 orthogonal cover code groups from legacy LTE CSI-RS resources to form a length 8 orthogonal cover code, minimizing orthogonality loss by selecting pairs that maximize time and frequency separations within the CDM-8 groups, thus reducing channel variation impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If CDM-8 designs are used for 24 and 32 ports, then port capacity is increased, but orthogonality is lost due to channel variations over 9 OFDM symbols
Solution Approach 1:
The patent divides the CDM-8 group into multiple CDM-4 subgroups and further segments them into individual port groups. This segmentation allows each subgroup to be evaluated separately for orthogonality maintenance, enabling the system to support 24 and 32 ports while identifying and excluding configurations that would lose orthogonality due to channel variations.
Solution Approach 2:
The patent introduces dynamic evaluation of CDM aggregation configurations based on channel conditions. By assessing orthogonality maintenance capability for each possible aggregation configuration and selecting only those that maintain orthogonality under varying channel conditions, the system adaptively maintains reliability while supporting high port capacity.
2Adaptability or versatility
If CDM-8 designs are used for 24 and 32 ports, then port capacity is increased, but CSI-RS overhead increases
Solution Approach 1:
The patent segments the 24 or 32 ports into multiple CDM-8 groups, where each group is further divided into CDM-4 subgroups. This hierarchical segmentation allows efficient resource element allocation and reduces the total number of CSI-RS resources needed compared to non-segmented approaches, as each segment can be optimized independently for resource usage.
Solution Approach 2:
The patent organizes ports into a hierarchical structure with multiple dimensions: CDM-8 groups containing CDM-4 subgroups containing individual ports. This multi-dimensional organization allows more efficient packing of reference signals into available resource elements, reducing overhead while maintaining full port capacity.
3Adaptability or versatility
If arbitrary CDM-4 aggregation is performed to form CDM-8 groups, then configuration flexibility is increased, but performance losses occur due to channel variations
Solution Approach 1:
The patent performs preliminary evaluation of all possible CDM-4 aggregation configurations to determine which ones maintain orthogonality under channel variations. By pre-identifying valid aggregation configurations before actual transmission, the system maintains both flexibility in configuration selection and reliability in performance, avoiding arbitrary aggregations that would cause performance loss.
Data Source
AI summary
A network node, wireless device, base station, user equipment and corresponding methods are provided. The network node includes processing circuitry configured to: select a first set and second set of reference signal resources in a subframe and aggregate the first set and second set of reference signal resources in the subframe to form a code division multiplexing, CDM, aggregation configuration. The first set and second set of reference signal resources in the subframe satisfy a temporal criterion such that any two resource elements in the first set and second set of reference signal resources have up to a maximum time separation of six OFDM symbols. The first set and second set of reference signal resources in the subframe satisfy a frequency criterion such that any two resource elements in the first set and second set of reference signal resources have up to a maximum frequency separation of six subcarriers.