Two-Tier Cell Group Identifiers for Inter-eNB Carrier Aggregation
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Solution Overview
Problem
Current LTE systems face challenges in maintaining uplink time alignment and radio resource management for inter-eNB carrier aggregation, particularly due to differences in propagation delays and path losses across multiple base stations, leading to inter-symbol interference and inefficient resource utilization.
Innovation Solution
The implementation of two-tier identifiers for serving cells, where each serving cell is configured with an uplink group identifier and associated with a cell group identifier based on the originating base station or co-located antennas, enables optimized uplink alignment, radio link monitoring, and radio resource management procedures, allowing for independent timing advance adjustments and seamless handover between base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple timing advance groups are used for different propagation paths, then uplink alignment accuracy is improved, but device complexity increases due to multiple TAG configurations
Solution Approach 1:
The patent segments the timing advance management into multiple independent TAGs (first TAG for first CC, second TAG for second CC). Each TAG maintains its own timing advance value and alignment timer independently, allowing precise uplink alignment for each propagation path without requiring a single complex configuration system.
Solution Approach 2:
The patent introduces a new dimension of management by associating each TAG with a specific component carrier and propagation path. This dimensional separation allows the system to handle multiple timing advance values simultaneously, each tied to a specific carrier frequency and path, rather than using a single unified timing advance mechanism.
2Reliability
If independent timing advance values are applied to different CCs, then uplink synchronization is improved, but device complexity increases due to multiple timing advance groups
Solution Approach 1:
The patent segments uplink synchronization management into separate TAGs for each CC. The first TAG manages timing for the first CC while the second TAG manages timing for the second CC independently. This segmentation ensures that synchronization issues in one CC do not affect the other, improving overall reliability.
Solution Approach 2:
The patent introduces cell group identifiers as intermediaries that link serving cells to their corresponding TAGs. This intermediary mechanism simplifies the management of multiple TAGs by providing a clear mapping relationship between cells and timing advance groups, reducing the complexity of tracking which TAG applies to which CC.
3Device complexity
If a single TAG is used for all CCs, then device complexity is reduced, but uplink alignment fails when propagation delays differ significantly
Solution Approach 1:
The patent segments the TAG configuration based on propagation path characteristics. When propagation delays differ significantly, the system creates separate TAGs for affected CCs rather than forcing a single TAG configuration. This segmentation preserves uplink alignment precision while keeping each individual TAG configuration relatively simple.
Solution Approach 2:
The patent applies local quality by configuring TAGs according to the specific propagation characteristics of each CC. Each TAG is optimized for its local propagation conditions rather than using a uniform configuration for all CCs. This allows precise uplink alignment for each local path while maintaining overall system simplicity.
4Reliability
If multiple MAC entities are established for inter-eNB CA, then uplink alignment management is improved, but device complexity increases
Solution Approach 1:
The patent segments MAC entity responsibilities by establishing separate MAC entities for different cell groups. Each MAC entity manages the TAGs associated with its cell group independently. This segmentation improves uplink alignment management for inter-eNB CA by ensuring that each eNB's timing requirements are handled by a dedicated MAC entity.
Solution Approach 2:
The patent makes each MAC entity universal by enabling it to manage multiple TAGs within its cell group. Rather than creating a separate MAC entity for each TAG, a single MAC entity can handle multiple TAGs, reducing the overall number of MAC entities needed while still providing dedicated management for each cell group.
Data Source
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AI summary
An apparatus and a method are provided to configure two-tier identifiers for serving cells of a user equipment (UE) configured with inter-eNB carrier aggregation (CA). In one novel aspect, cell group identifiers are configured. The cell group identifier is a super set of one or more uplink group identifiers which are associated with serving cells served by the same base station. In one embodiment, different MAC entities are associated with different cell group identifiers. The UE performs uplink alignment, monitoring and management procedures linking to the cell group identifier. In another novel aspect, a group timing advance group (TAG), which is a super set identifier of one or more cell TAGs associated with serving cells served by the same base station, is configured. In another embodiment, the UE performs uplink alignment procedure based on the status of the group TAG, which is determined based on the status of the cell TAGs associated with the group TAG.