OFDM Reference Signal Sequence Generation for Time Diversity
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Solution Overview
Problem
Current OFDM systems face challenges in generating reference signals that are both random and unique to each transmitter, leading to inadequate time diversity and inability to differentiate between cells, resulting in interference rejection limitations.
Innovation Solution
A transmitter and receiver system that generates reference signal sequences as an inseparable function of cell identification, cyclic prefix mode, and time indices, using nonlinear initialization and fast-forward duration hopping, ensuring the sequences are not linearly separable into components based on cell ID and time indices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reference signal sequences are generated as separable functions of cell ID and time indices, then the sequences can be uniquely identified by cell ID, but the sequences lack time diversity and cannot effectively differentiate between synchronous cells
Solution Approach 1:
The patent merges the cell ID parameter with time indices (symbol index l and slot index ns) into a single inseparable initialization function cinit. This combination ensures that the reference signal sequence cannot be uniquely identified by cell ID alone, but requires both cell ID and time information, thereby providing time diversity while maintaining cell differentiation capability.
Solution Approach 2:
The patent introduces time indices as an additional dimension to the traditional cell ID-based sequence generation. By making the sequence initialization dependent on both cell ID and time indices (symbol and slot indices), the system transforms a one-dimensional cell identification problem into a multi-dimensional problem that inherently provides time diversity.
2Ease of manufacture
If reference signal sequences use fixed pre-determined values, then the sequences are simple to generate, but the sequences provide insufficient randomness and peak-to-average-power ratio performance
Solution Approach 1:
The patent changes the initialization parameters of the pseudo-random sequence generator from fixed values to dynamically calculated values based on cell ID and time indices. This parameter change introduces randomness while maintaining a systematic generation process that ensures desirable peak-to-average-power ratio properties.
3Measurement precision
If reference signal sequences are made unique to each transmitter using cell ID, then cell identification is improved, but the sequences become separable and lose time diversity
Solution Approach 1:
The patent combines cell ID with time indices in the initialization function, creating an inseparable relationship. This merging ensures that the sequence maintains its unique identification capability (since cell ID is still part of the initialization) while simultaneously providing time diversity (since time indices are also required to fully specify the sequence).
Data Source
AI summary
In one embodiment, a transmitter includes a binary sequence generator unit configured to provide a sequence of reference signal bits, wherein the sequence is an inseparable function of a cell identification parameter, a cyclic prefix mode corresponding to the transmitter and one or more time indices of the sequence. The transmitter also include a mapping unit that transforms the sequence of reference signal bits into a complex reference signal, and a transmit unit configured to transmit the complex reference signal. In another embodiment, a receiver includes a receive unit configured to receive a complex reference signal and a reference signal decoder unit configured to detect a sequence of reference signal bits from the complex reference signal, wherein the sequence is an inseparable function of a cell identification parameter, a cyclic prefix mode corresponding to a transmitter and one or more time indices of the sequence.