Dynamic Preamble Group Assignment for Random Access Interference
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Solution Overview
Problem
Existing cellular mobile communication systems face challenges in reducing intra-cell interference during the random access procedure due to the limited number of orthogonal preamble sequences, which increases collision probability at high RACH loads and results in unnecessary intra-cell interference at low loads.
Innovation Solution
A method where groups of orthogonal preamble sequences are assigned to cells based on RACH or traffic load thresholds, with additional sequence groups added as load increases to reduce collision probability while allowing intra-cell interference to rise, thereby optimizing resource usage and system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of orthogonal preamble sequences is increased to reduce collision probability at high RACH loads, then collision probability decreases, but intra-cell interference increases due to the limited availability of orthogonal sequences
Solution Approach 1:
The system dynamically adjusts the number of available preamble sequences based on RACH load conditions. At low loads, only orthogonal sequences are used to avoid interference. At high loads, additional non-orthogonal sequences are activated to reduce collisions, accepting increased interference as necessary to maintain access reliability.
Solution Approach 2:
The invention changes the parameter of sequence orthogonality based on system conditions. When RACH load exceeds a threshold, the system transitions from using only orthogonal sequences to including non-orthogonal sequences, effectively changing the correlation properties of the preamble set to balance collision probability and interference levels.
2Reliability
If additional non-orthogonal preamble sequences are assigned to increase the number of available sequences, then collision probability is reduced, but intra-cell interference occurs between sequences
Solution Approach 1:
The system dynamically adjusts the number of available preamble sequences based on RACH load conditions. At low loads, only orthogonal sequences are used to avoid interference. At high loads, additional non-orthogonal sequences are activated to reduce collisions, accepting increased interference as necessary to maintain access reliability.
Solution Approach 2:
The invention changes the parameter of sequence orthogonality based on system conditions. When RACH load exceeds a threshold, the system transitions from using only orthogonal sequences to including non-orthogonal sequences, effectively changing the correlation properties of the preamble set to balance collision probability and interference levels.
3Object-generated harmful factors
If the number of orthogonal preambles is kept small to avoid intra-cell interference, then intra-cell interference is minimized, but collision probability increases at high RACH loads
Solution Approach 1:
The system dynamically adjusts the number of available preamble sequences based on RACH load conditions. At low loads, only orthogonal sequences are used to avoid interference. At high loads, additional non-orthogonal sequences are activated to reduce collisions, accepting increased interference as necessary to maintain access reliability.
Solution Approach 2:
The invention changes the parameter of sequence orthogonality based on system conditions. When RACH load exceeds a threshold, the system transitions from using only orthogonal sequences to including non-orthogonal sequences, effectively changing the correlation properties of the preamble set to balance collision probability and interference levels.
Data Source
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AI summary
The invention relates to a method in a network node in control of a cell in a cellular telecommunication network for reducing intra-cell interference between user equipments (UE) (10) residing in said cell and performing random access (RA). The method comprises the steps of arranging groups (12, 12a, 12b) of preamble sequences where the sequences within each group are orthogonal to each other, - assigning one such group (12) to the cell (11), from which group the UEs performing RA randomly selects a preamble, and - assigning one or more additional group (s) (12a, 12b) of preamble sequences to said cell if the RACH or traffic load exceeds a certain threshold. The invention further relates to a radio network node in a cellular telecommunication system, capable of carrying out said method.