Variable Cyclic Prefix Configuration for mmWave OFDM
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Solution Overview
Problem
In wireless communication systems operating at high millimeter wave (mmWave) bands, the fixed cyclic prefix (CP) lengths used in OFDM-based transmissions lead to a tradeoff between performance and spectral efficiency, as they are required to be greater than the channel delay spread to mitigate inter-symbol interference (ISI), but result in increased overhead and reduced bandwidth efficiency.
Innovation Solution
Implementing variable CP lengths within a transmission period, where each symbol can have an individually configurable CP length based on channel conditions, target operating signal-to-noise ratio (SNR), modulation coding scheme (MCS), and whether the symbol carries data or a reference signal, allowing for longer CPs for reference signals to ensure good channel estimation without increasing overhead for all symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed cyclic prefix (CP) lengths are used in OFDM-based transmissions to mitigate inter-symbol interference (ISI), then performance is improved, but spectral efficiency deteriorates due to increased overhead
Solution Approach 1:
The patent applies dynamics by transitioning from fixed CP lengths to variable CP lengths that can be individually configured for each symbol within a transmission period. This allows the system to adapt CP duration to specific channel conditions and symbol requirements, optimizing both ISI mitigation performance and spectral efficiency by using longer CPs only when necessary and shorter CPs when the channel allows
Solution Approach 2:
The patent implements local quality by allowing different CP lengths for different symbols within the same transmission period. Specifically, reference signal symbols can have longer CPs to ensure good channel estimation, while data symbols can have shorter CPs to improve spectral efficiency. This localized optimization resolves the contradiction by applying longer CPs only where performance requires them rather than uniformly across all symbols
2Measurement precision
If longer cyclic prefix (CP) lengths are used to ensure good channel estimation for reference signals, then measurement precision is improved, but overhead increases and spectral efficiency decreases
Solution Approach 1:
The patent applies local quality by differentiating CP length requirements between reference signal symbols and data symbols. Reference signal symbols, which require accurate channel estimation, are assigned longer CPs to ensure measurement precision. Data symbols, which have less stringent requirements, use shorter CPs to minimize overhead. This selective approach resolves the contradiction by localizing longer CPs only to symbols where measurement precision is critical
Data Source
AI summary
Wireless communications systems and methods related to applying variable cyclic prefix (CP) lengths to symbols within a transmission period in a wireless network are provided. A first wireless communication device identifies a first cyclic prefix (CP) configuration for a transmission period. The first wireless communication device communicates, with a second wireless communication device during the transmission period, a first communication signal including a first plurality of symbols, wherein each of the first plurality of symbols include an individually configurable CP length configured based on the first CP configuration. A first symbol of the first plurality of symbols includes a first CP length. A second symbol of the first plurality of symbols includes a second CP length that is longer than the first CP length.