NR PRACH Transmission With Repeated Preambles for mmWave Coverage
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Solution Overview
Problem
In wireless communication systems operating at high millimeter wave (mmWave) bands, transmitting random access preamble signals with large subcarrier spacing (SCS) reduces signal coverage due to shorter symbol durations, while using smaller SCS limits transmit power, posing challenges in maintaining effective communication efficiency.
Innovation Solution
Compensate for reduced PRACH coverage by transmitting random access preamble signals with multiple repetitions in time or frequency, adjusting the length of the signal to maintain coverage and power within regulatory limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the UE transmits the random access preamble signal using a large subcarrier spacing (SCS), then the time duration of the symbols is smaller, but the signal coverage is reduced
Solution Approach 1:
The patent divides the random access preamble signal into multiple repetitions transmitted in time. Each repetition is a copy of the preamble sequence, and by transmitting multiple repetitions sequentially, the total time duration is extended to compensate for the shorter symbol duration caused by large SCS, thereby maintaining signal coverage while enabling faster symbol transmission.
Solution Approach 2:
The patent employs periodic transmission of the preamble sequence by repeating it multiple times in the time domain. This periodic action allows the system to maintain adequate signal coverage through extended transmission duration while utilizing large subcarrier spacing for faster symbol processing and transmission.
2Reliability
If the UE transmits the random access preamble signal using a smaller subcarrier spacing (SCS), then the signal coverage is improved, but the UE is unable to transmit at full transmit power due to power limits
Solution Approach 1:
The patent segments the transmission into multiple repetitions of the preamble signal. By distributing the total energy across multiple repetitions, the system can use smaller subcarrier spacing to maintain signal coverage while transmitting at full power through the repeated structure, effectively overcoming the power spectral density limits that would otherwise restrict full power transmission.
3Reliability
If the time duration of the random access preamble signal is extended to improve coverage, then signal coverage is improved, but the transmission time is increased
Solution Approach 1:
The patent uses periodic repetition of the preamble sequence to extend coverage. The repetitions are transmitted in a structured periodic manner, allowing the system to achieve extended coverage through multiple copies while maintaining efficient time utilization through the regular, predictable transmission pattern that enables the base station to process and respond to the random access request effectively.
Data Source
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AI summary
Wireless communications systems and methods related to random access signaling are provided. A user equipment (UE) may transmit to a base station (BS) in a frequency band, a random access signal including at least one of a length in time or a length in frequency that is based on a subcarrier spacing (SCS) in the frequency band. The BS may receive the random access signal and transmit a response to the random access signal.