PRACH Delay Detection via Preamble Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In 5G wireless communication systems, the estimation of propagation delay between a user equipment (UE) and a radio network node is challenging due to large antenna arrays and coexistence of different signal numerologies, which complicates the detection of delays larger than one OFDM symbol, leading to inefficiencies in timing advance configuration and increased complexity in ASIC implementations.
Innovation Solution
A method involving a radio network node that processes preambles by detecting fractional-symbol delays through early and late arrival energy measurements, using a pseudogap or phase changes within the preamble to improve delay estimation accuracy without reducing signal energy, allowing for more reliable detection of delays up to multiple OFDM symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a special very long OFDM symbol with long CP and large DFT is used for PRACH in LTE, then accurate detection with large delay uncertainty is achieved, but device complexity increases due to the need for large DFT in ASIC for every antenna branch
Solution Approach 1:
The patent segments the PRACH preamble into multiple short sequences transmitted in different time windows. Instead of using a single long OFDM symbol, the preamble is divided into multiple segments that can be processed separately, reducing the DFT size requirement while maintaining delay detection accuracy through the segmented structure.
Solution Approach 2:
The patent introduces a time-domain segmentation dimension by transmitting multiple short sequences at different time windows. This transforms the problem from a single long symbol in time domain to multiple short symbols distributed across time, enabling delay detection without requiring excessively large DFT in the frequency domain.
2Measurement precision
If a special very long OFDM symbol with long CP is used for PRACH, then large propagation delays can be detected, but the solution becomes undesirable in 5G systems with large antenna arrays and multiple signal numerologies
Solution Approach 1:
The patent creates a universal preamble structure using multiple short sequences that can be processed with standard DFT sizes. This segmented approach is adaptable to different signal numerologies and antenna array configurations in 5G systems, as it does not require special long OFDM symbols that are specific to LTE architecture.
Solution Approach 2:
The patent changes the parameter of preamble structure from a single long OFDM symbol to multiple short sequences transmitted in different time windows. This parameter change enables the system to handle large propagation delays while maintaining compatibility with 5G numerologies and reducing the need for large DFT operations.
3Reliability
If the propagation delay is made larger than the cyclic prefix duration, then accurate timing advance estimation becomes difficult, but the UE needs to compensate for these large delays
Solution Approach 1:
The patent segments the preamble into multiple short sequences transmitted at different time windows. This segmentation creates distinct temporal signatures that enable reliable detection even when the total propagation delay exceeds the cyclic prefix duration. The segmented structure provides multiple measurement opportunities within the extended time window.
Solution Approach 2:
The patent maintains continuous transmission of preamble energy across multiple time windows. By transmitting multiple short sequences sequentially, the system ensures continuous useful action for delay estimation, preventing energy loss that would occur with a single long symbol approach when delays exceed the CP duration.
Data Source
AI summary
According to embodiments described herein, a long delay-detector improves delay estimation performance for PRACH for many practical deployment scenarios. This, for example, reduces the risk that the timing advance of the UE is set incorrectly and hence reduces the risk that subsequent communication fails and that the UE spreads unnecessary interference to other communication in the system.