Random Access Sub-Carrier Segmentation for Interference Coordination
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Solution Overview
Problem
In orthogonal frequency division multiplexing systems, inter-cell interference occurs due to the use of the same sub-carrier frequency in adjacent cells, which affects the correct detection and minimizes the false detection of random access sequences in radio communication systems.
Innovation Solution
The method involves assigning sub-carrier frequencies to RACH communications links based on interference coordination techniques, where mobile terminals receive information on available resources, measure signal quality, and derive allowed resources based on these measurements to maximize correct detection and minimize false detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the same sub-carrier frequency is used in adjacent cells, then spectral efficiency is improved, but inter-cell interference increases causing false detection of random access sequences
Solution Approach 1:
The patent segments the available sub-carrier frequencies into multiple RACH channel groups. Each group is assigned to different cells or sectors, allowing adjacent cells to use different frequency segments for random access. This segmentation eliminates inter-cell interference while maintaining spectral efficiency by ensuring that the entire frequency spectrum is still utilized across the network.
Solution Approach 2:
The patent implements local quality by assigning different sub-carrier frequency characteristics to different locations (cells or sectors). Each cell or sector is configured with specific RACH channel groups that have distinct frequency assignments tailored to its local interference environment. This allows optimal detection performance in each local area while coordinating with neighboring cells to minimize overall interference.
2Reliability
If sub-carrier frequencies are coordinated between cells, then false detection is minimized, but system complexity increases due to additional signaling and coordination
Solution Approach 1:
The patent applies preliminary action by pre-configuring RACH channel groups with specific sub-carrier frequency assignments during network planning and deployment. The network side determines and broadcasts the mapping between RACH channels and sub-carrier frequencies in advance through system information messages. This eliminates the need for real-time coordination and complex dynamic signaling, as the frequency coordination is established beforehand.
Solution Approach 2:
The patent enables self-service by allowing user equipment to autonomously select appropriate RACH channels from the available groups based on downlink signal quality measurements. The UE measures the quality of downlink signals from different cells and autonomously determines which RACH channel group to use for uplink random access, without requiring complex network coordination or additional signaling exchanges.
Data Source
AI summary
A method of determining random access resources performed by a mobile terminal, the method comprising: receiving information on available random access resources from a network; deciding how to derive the random access resources to be allowed based on default values or information received from the network; measuring received signal quality of at least one of a cell to be accessed and a neighboring cell; and deriving the allowed random access resources based on the deciding and the measuring.