Interference Avoidance for PRACH and RRC Messages in 5G Sectors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In 4G and 5G mobile networks, the Random Access procedure experiences high failure rates due to interference from nearby cells, particularly in the downlink and uplink directions, affecting PRACH messages and RRC Setup/Release processes, leading to repeated attempts and eventual network access failures.
Innovation Solution
Dividing cells into sectors (Alpha, Beta, Gamma) and assigning distinct Downlink and Uplink Interference Avoidance regions to prevent interference, ensuring each sector transmits PRACH and RRC messages in non-overlapping regions, thereby reducing interference and increasing SINR by at least 3 dB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cells transmit PRACH and RRC messages in the same time-frequency resources, then resource utilization is maximized, but interference from nearby cells increases causing high failure rates
Solution Approach 1:
The patent divides the time-frequency resources into separate Downlink Interference Avoidance regions and Uplink Interference Avoidance regions. PRACH messages and RRC messages are transmitted in these dedicated interference avoidance regions rather than sharing general resources, thereby segmenting the resource space to eliminate inter-cell interference while maintaining efficient utilization of non-reserved resources.
2Productivity
If PRACH msg2, msg3, msg4 and RRC messages are transmitted using available resources, then transmission capacity increases, but interference from PDSCH and PUSCH in nearby cells causes decoding failures
Solution Approach 1:
The patent extracts critical control messages (PRACH msg2, msg3, msg4, and RRC messages) from the general resource pool and assigns them to dedicated Interference Avoidance regions. This extraction removes these messages from the harmful environment of general resource sharing where PDSCH and PUSCH transmissions cause interference, ensuring reliable decoding while maintaining overall system capacity.
Solution Approach 2:
The patent applies local quality by creating specific regions with different interference characteristics. The Downlink and Uplink Interference Avoidance regions have protected quality attributes (reserved for critical messages only), while other regions maintain general resource sharing. This localized differentiation ensures high reliability for control messages without sacrificing overall resource utilization efficiency.
3Reliability
If maximum number of msg1 retransmission attempts are allowed, then access reliability improves, but battery energy is wasted on repeated unsuccessful procedures
Solution Approach 1:
The patent implements preliminary anti-action by pre-configuring Interference Avoidance regions that proactively prevent interference-related decoding failures before they occur. By guaranteeing interference-free transmission resources for critical messages in advance, the system eliminates the root cause of repeated failures, allowing UEs to succeed on first or few attempts rather than exhausting energy on multiple retries caused by persistent interference.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A system for optimizing a 4G or 5G Radio Access Network (RAN) including multiple cell sites each having multiple sectors, and at least one of the cell sites in communication with a user equipment (UE), the system including i) a downlink (DL) medium access control (MAC) layer including a DL MAC Scheduler configured to schedule at least one of Physical Random Access Channel (PRACH) message 2, PRACH message 4, Radio Resource Control (RRC) Release and Physical Downlink Shared Channel (PDSCH) of other traffic, in each sector in at least one of frequency and time, in the downlink direction; and ii) an uplink (UL) MAC layer including a UL MAC scheduler configured to schedule at least one of PRACH message 3, RRC Setup Complete and Physical Uplink Shared Channel (PUSCH) of other traffic, in each sector in at least one of frequency and time, in the uplink direction. For a cell load condition below a specified threshold, the UL MAC is configured to assign a single UL interference avoidance, UL IA, region in physical resource blocks, PRBs, to all the sectors, and wherein the PRB location for the UL IA region is known to all the sectors.