Full-Duplex RACH Preamble Lengths for Interference Mitigation
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Solution Overview
Problem
Full-duplex wireless communications face interference issues due to self-interference and cross-link interference, which affect the reliability of random access channel (RACH) procedures, especially in shared radio frequency spectrum where transmit power is constrained by regulatory limits.
Innovation Solution
The use of different RACH preambles based on the full-duplex mode, with longer preambles for full-duplex operations and shorter preambles when full-duplex is not present, and configuring RACH occasions with varying preamble lengths to mitigate interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full-duplex communications are used in shared radio frequency spectrum, then network efficiency and throughput are enhanced, but self-interference and cross-link interference increase affecting RACH reliability
Solution Approach 1:
The RACH preamble is segmented into different length options (short and long preambles) that can be selectively used based on the duplex mode. This segmentation allows the system to divide the RACH procedure into different configurations optimized for half-duplex or full-duplex operations, thereby maintaining reliability while enabling full-duplex communications.
Solution Approach 2:
The patent changes the parameter of preamble length based on the duplex mode configuration. By adjusting this physical parameter (preamble length) according to whether the system operates in half-duplex or full-duplex mode, the reliability of RACH procedures is maintained even when full-duplex operations introduce interference.
2Reliability
If longer RACH preambles are used for full-duplex communications, then interference mitigation is improved, but transmission overhead and power consumption increase
Solution Approach 1:
The system dynamically selects between short and long RACH preambles based on the duplex mode configuration. This dynamic adaptation allows the system to use longer preambles (which provide better interference mitigation) only when full-duplex mode is detected, while using shorter preambles in half-duplex mode to conserve energy and reduce overhead.
Solution Approach 2:
The preamble length parameter is changed based on the duplex mode. By adjusting this parameter dynamically, the system achieves optimal balance between interference mitigation capability and energy efficiency, using longer preambles only when necessary for full-duplex operations.
3Reliability
If different RACH preambles are configured for different duplex modes, then RACH transmission reliability is enhanced, but device complexity increases
Solution Approach 1:
The network entity performs preliminary configuration by indicating the duplex mode (half-duplex or full-duplex) to the UE before the RACH procedure. This preliminary information allows the UE to pre-determine which preamble length to use, simplifying the device complexity while ensuring the correct preamble is selected for the given duplex mode.
Solution Approach 2:
The network entity acts as an intermediary that provides configuration information about the duplex mode. This intermediary role simplifies the UE's decision-making process by providing clear guidance on which preamble type to use, thereby enhancing reliability without significantly increasing device complexity.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described that provide for mitigation of interference related to full-duplex communications for random access channel (RACH) initial access procedures in shared radio frequency spectrum. A user equipment (UE) may send different RACH preambles subsequent to a channel access procedure, based on whether full-duplex communications or half-duplex communications are being used at a corresponding network entity. The different RACH preambles may include a longer RACH preamble that is used when full-duplex is present, and a shorter RACH preamble that is used when full-duplex is not present. The shorter or longer RACH preamble may be used, for example, based at least in part on an open-loop transmit power for the RACH procedure, a RACH occasion configuration that provides different preamble lengths for different RACH occasions, a full-duplexing type that is being used, or any combinations thereof.