Cyclic Prefix Determination for OFDM Channel Estimation
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Solution Overview
Problem
In OFDM systems, inter-symbol interference (ISI) caused by multipath distortion leads to inaccurate channel estimation and increased bit error rates, especially when the delay spread exceeds the cyclic prefix length, necessitating a method to mitigate ISI without sacrificing data throughput.
Innovation Solution
The implementation of an analytic signal with a digital signature in the frequency domain, converted to a time domain signal and extended with a cyclic prefix, which includes 'zero' data to effectively increase the cyclic prefix length, thereby immunizing channel estimation from ISI effects and improving data decoding accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the cyclic prefix length is increased to mitigate ISI, then channel estimation accuracy is improved, but data throughput is reduced
Solution Approach 1:
The patent segments the cyclic prefix into two functional parts: a first portion used for ISI mitigation and channel estimation, and a second portion containing 'zero' data that extends the effective length without adding harmful interference. This segmentation allows the system to achieve longer effective CP length for better channel estimation while maintaining data throughput by placing zeros in the second portion that do not carry data information.
Solution Approach 2:
The patent changes the parameter of cyclic prefix composition by inserting 'zero' data in the second portion of the cyclic prefix. This parameter change extends the effective cyclic prefix length to better handle long delay spreads and improve channel estimation accuracy, while the zero values ensure that no additional data throughput is lost beyond the necessary overhead.
2Object-affected harmful factors
If the cyclic prefix length is increased to handle long delay spreads, then ISI mitigation is improved, but data throughput is reduced
Solution Approach 1:
The cyclic prefix is segmented into a first portion for active signal transmission and a second portion filled with 'zero' data. This segmentation enables the effective cyclic prefix length to extend into the second portion, providing better ISI mitigation for long delay spreads while the zero values in the second portion do not carry data, thus minimizing throughput impact.
Solution Approach 2:
The patent converts the potentially harmful effect of extended cyclic prefix length (which would normally reduce throughput) into a benefit by filling the extended portion with 'zero' data. The zeros extend the protective coverage against ISI without introducing additional data loss, effectively turning what would be wasted bandwidth into useful ISI mitigation capability.
3Measurement precision
If pilot signals are transmitted for channel estimation, then channel response accuracy is improved, but susceptibility to ISI increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the cyclic prefix with 'zero' data in the second portion before pilot signal transmission. This preliminary configuration ensures that when pilot signals are transmitted for channel estimation, they are protected by the extended cyclic prefix length, reducing ISI susceptibility and improving channel response accuracy.
Data Source
AI summary
A user equipment (UE) performs a transform domain (DFT) based method to detect the cyclic prefix (CP) length that is being used by a base station for cellular communications. The detected CP length is then used to reduce the amount of time required to complete the synchronization and cell search procedures. In particular, the UE uses the detected CP length information to obtain Cell Identification parameters (NID1, NID2) along with information including a Maximum energy Tap location and a reference signal receive power (RSRP) while completing the synchronization and cell search procedures.