Root Sequence Determiner for LTE Cell Conflict Resolution
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Solution Overview
Problem
In mobile communication networks, particularly in LTE systems, neighboring cells using the same root sequences for random access can lead to unnecessary load and increased risk of false preamble detection, affecting communication delay and signaling congestion due to limited simultaneous preamble handling capacity.
Innovation Solution
A method for a base station to determine and manage root sequence conflicts by prioritizing cells based on properties such as speed configuration, cyclic shift values, and configuration dates, allowing lower priority cells to reconfigure automatically and avoid oscillations in root sequence usage without requiring new communication messages between base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If neighboring cells use the same root sequences for random access, then the system complexity is reduced and configuration is simplified, but this causes unnecessary random access load and increases the risk of false preamble detection
Solution Approach 1:
The patent applies local quality by allowing different root sequence configurations in different spatial locations (neighboring cells). Each cell is assigned specific root sequences based on its geographical location and neighboring relationships, creating spatial differentiation in the random access domain. This resolves the contradiction by maintaining configuration simplicity at the system level while ensuring local differentiation to prevent conflicts.
Solution Approach 2:
The patent segments the set of available root sequences into distinct groups assigned to different cells. Instead of using a single shared pool of root sequences, the system divides them into cell-specific subsets, ensuring that neighboring cells use disjoint sets. This segmentation eliminates false detection while maintaining overall system simplicity through structured allocation.
2Reliability
If root sequence conflicts are detected and reconfiguration is triggered, then random access performance is improved, but new communication between base stations is required and conflict resolution between multilevel neighbours becomes complex
Solution Approach 1:
The patent applies preliminary action by pre-configuring root sequences during network planning and deployment, rather than dynamically resolving conflicts through inter-base station communication. Root sequences are assigned in advance based on predicted neighboring relationships, eliminating the need for runtime conflict detection and resolution protocols. This improves reliability while avoiding the complexity of dynamic negotiation.
Solution Approach 2:
The system implements self-service through autonomous root sequence assignment based on pre-stored neighboring cell information. Each base station independently determines its root sequence configuration using locally available data about neighboring cells, without requiring coordination or communication with those neighbors. This resolves conflicts automatically while minimizing signaling overhead.
3Productivity
If the number of preambles that can be handled simultaneously is limited, then the system remains manageable, but this increases the average delay before communication establishment and can increase signaling congestion
Solution Approach 1:
The patent applies parameter changes by varying the root sequence parameters (specifically the root index and cyclic shift values) across neighboring cells to maximize the number of usable preambles. By optimizing these parameters, the system effectively increases the capacity for simultaneous random access attempts without adding more physical resources, thereby reducing delay while maintaining manageability.
Data Source
AI summary
It is presented a method, executed in a root sequence determiner for a base station controlling a first cell, the first cell being associated with at least one root sequence used for cell differentiation on a random access channel. The method comprises the steps of: obtaining information on root sequences of neighboring cells; when a root sequence conflict is found between the first cell and a neighboring cell, here denoted a conflict cell, determining if the conflict cell is of a higher priority than the first cell, the priorities of the first cell and the conflict cell being based on properties of the respective cells; and when the conflict cell is of a higher priority than the first cell, finding a new root sequence for the first cell, avoiding the root sequences of the neighboring cells.