Cyclically Shifted Sequences for Interference Randomization
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Solution Overview
Problem
Wireless communication systems face challenges in efficiently transmitting control information, particularly in randomizing interference from adjacent cells, which affects the reliability of ACK and CQI channels.
Innovation Solution
The use of cyclically shifted sequences, derived from base sequences with good correlation properties, such as CAZAC or PN sequences, for modulating information and sending using LFDM, where the cyclic shifts are determined by a hopping pattern specific to each cell or user, allowing for interference randomization across different symbol periods or slots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cyclically shifted sequences are used for control information transmission, then interference randomization between adjacent cells is improved, but sequence design and hopping pattern coordination become more complex
Solution Approach 1:
The patent applies parameter changes by systematically varying the cyclic shift amount based on hopping patterns that change over time and differ between cells. This transforms a static sequence into a dynamic one where the shift parameter adapts according to predefined patterns, achieving interference randomization while maintaining manageable complexity through structured parameter variation rather than arbitrary sequence design
Solution Approach 2:
The patent implements periodic action through hopping patterns that periodically change the cyclic shift amounts across different time intervals or subframes. This periodic variation in sequence parameters creates predictable yet diverse transmission characteristics that randomize interference over time while allowing receivers to anticipate and track the pattern, reducing the perceived complexity
2Reliability
If cyclic shifts are determined by cell-specific hopping patterns, then adjacent cell interference randomization is improved, but coordination and synchronization between cells become more difficult
Solution Approach 1:
The patent applies segmentation by dividing the hopping pattern design into cell-specific segments where each cell uses its own predetermined pattern. This allows independent configuration of hopping patterns for different cells without requiring continuous inter-cell coordination, as each cell's pattern is self-contained and does not depend on the state of other cells
Solution Approach 2:
The patent employs disposable short-living objects by using temporary, cell-specific hopping patterns that are predetermined and discarded after use. Each cell uses a specific pattern for a defined period or set of subframes, then transitions to the next pattern in its sequence, eliminating the need for long-term coordination or persistent state maintenance between cells
Data Source
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AI summary
Techniques for transmitting information using cyclically shifted sequences are described. In one design, first and second sequences may be generated by cyclically shifting a base sequence by first and second amounts, respectively. The base sequence may be a CAZAC sequence, a PN sequence, or some other sequence having good correlation properties. The cyclic shifts for the first and second sequences may be determined based on a hopping pattern. A first modulated sequence may be generated based on the first sequence and a first modulation symbol and may be sent in a first time interval. A second modulated sequence may be generated based on the second sequence and a second modulation symbol and may be sent in a second time interval. Each modulated sequence may be sent on K consecutive subcarriers using localized frequency division multiplexing (LFDM)