Frequency-Coded Symbol Mapping for LTE Subcarrier Gaps
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Solution Overview
Problem
In 3GPP LTE systems, the allocation of SFBC blocks to non-contiguous subcarriers due to the presence of CSI-RS and muted reference symbols leads to frequency gaps within SFBC codes, compromising channel conditions and transmission reliability.
Innovation Solution
A method and device that determine which subcarrier frequency bands to mute based on the number and configuration of muted reference symbols, forming pairs of adjacent bands for data transmission to avoid frequency gaps and ensure constant channel conditions, with rules to either mute all bands or selectively pair unpaired bands to minimize overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference symbols or muted reference symbols are designated in specific subcarrier frequency bands, then channel state information can be obtained, but frequency gaps appear in SFBC codes and channel conditions become non-constant
Solution Approach 1:
The patent extracts and identifies the specific subcarrier frequency bands occupied by reference symbols and muted reference symbols, then excludes these bands from SFBC data symbol allocation. This separation ensures that SFBC codes are only formed in contiguous bands without frequency gaps, maintaining constant channel conditions while preserving channel state information measurement capability in the reference symbol bands.
Solution Approach 2:
The patent segments the available subcarrier frequency bands into three categories: bands occupied by reference symbols, bands occupied by muted reference symbols, and bands available for data transmission. By this segmentation, SFBC codes are allocated only in the available bands, ensuring contiguity and eliminating frequency gaps that would otherwise compromise transmission reliability.
2Reliability
If all subcarrier frequency bands are muted to eliminate frequency gaps, then transmission reliability is improved, but data transmission capacity is reduced
Solution Approach 1:
The patent applies local quality by muting only the specific subcarrier frequency bands that would create frequency gaps in SFBC codes, rather than muting all bands. The muting decision is made locally for each band based on the presence and configuration of reference symbols, preserving data transmission capacity in bands where muting is not required while ensuring reliability in bands where it is necessary.
3Reliability
If selective muting of subcarrier frequency bands is implemented, then frequency gaps are eliminated and channel conditions remain constant, but system complexity increases
Solution Approach 1:
The patent implements preliminary action by determining the configuration of reference symbols and muted reference symbols before allocating SFBC blocks to data symbols. The system pre-identifies which subcarrier frequency bands are occupied by reference symbols and plans the SFBC allocations accordingly, ensuring contiguous band assignment without frequency gaps before transmission begins, thereby simplifying the overall system operation.
Data Source
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AI summary
A device and method for communicating frequency-coded symbols that include data elements and reference symbols are disclosed. In one aspect, a carrier frequency band includes a plurality of subcarrier frequency bands (421-432; 621-632; 651-662). Data elements (s1-s22) are transmitted (730; 825) and received (930; 1025) on respective pairs of adjacent subcarrier frequency bands to provide diversity. Reference symbols are transmitted and received on predetermined subcarrier frequency bands. Muting is applied to selected subcarrier frequency bands based on the number and frequency configuration of the reference symbols (705-755; 805-850; 905-955; 1005-1050).