Extending Unlicensed Spectrum Coverage with Distributed Remote Radio Heads
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Solution Overview
Problem
Mismatches in coverage areas between primary carriers in licensed frequency bands and secondary carriers in unlicensed frequency bands limit the performance gains of carrier aggregation in wireless communication systems, as users within the majority of the primary carrier's coverage area cannot benefit from the additional bandwidth provided by secondary carriers operating in unlicensed frequency bands.
Innovation Solution
Connecting remote radio heads (RRHs) to nodes that support both primary and secondary carriers, generating channel activity reports to allocate channels and determine duty cycles, ensuring that the worst channel conditions are met across all RRHs, and implementing schedulers to manage channel sharing among nodes, thereby extending unlicensed spectrum coverage and reducing coverage mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If secondary carriers are allocated in unlicensed frequency bands to provide additional bandwidth, then the bandwidth for downlink communications is improved, but the coverage area of secondary carriers is limited and does not match the primary carrier coverage
Solution Approach 1:
The system segments the coverage area management by introducing multiple Remote Radio Heads (RRHs) that are distributed across different locations. Each RRH serves a specific geographic segment, and channel activity reports are generated independently for each RRH based on local channel conditions. This segmentation allows different parts of the coverage area to use different unlicensed channels optimized for their local conditions, thereby extending the effective coverage while maintaining additional bandwidth.
Solution Approach 2:
The patent implements local quality optimization by allocating unlicensed channels based on local channel conditions at each RRH location. Instead of using a uniform channel allocation across the entire coverage area, the system evaluates channel quality metrics (such as interference levels and signal strength) locally at each RRH and assigns the most appropriate unlicensed channel for that specific location. This ensures that each local area utilizes the best available spectrum resources, extending coverage while providing additional bandwidth.
2Device complexity
If the same unlicensed channels are allocated to all RRHs based on lowest channel quality, then channel allocation simplicity is maintained, but the coverage area and performance are limited by the worst-case conditions
Solution Approach 1:
The system divides the channel allocation process into separate segments for each RRH. Instead of computing a single allocation for all RRHs simultaneously, each RRH independently generates channel activity reports based on its local conditions, and allocations are determined separately for each RRH. This segmentation reduces overall system complexity while enabling coverage extension, as each RRH can be configured independently based on its specific geographic and channel conditions.
3Quantity of substance
If carrier aggregation is implemented with primary carriers in licensed bands and secondary carriers in unlicensed bands, then additional bandwidth is provided, but coverage mismatches limit the performance gains for users in the primary carrier coverage area
Solution Approach 1:
The patent applies local quality optimization to ensure reliable performance gains across the entire primary carrier coverage area. By evaluating channel conditions locally at each RRH and allocating unlicensed channels accordingly, the system ensures that users throughout the coverage area experience consistent performance improvements. Each RRH is configured to provide reliable secondary carrier service in its local area, and the aggregation of these local quality optimizations across multiple RRHs delivers reliable overall performance gains for all users.
Solution Approach 2:
The system extends carrier aggregation performance from a single-point (central base station) to a multi-dimensional distributed architecture. By deploying multiple RRHs across different geographic locations and allocating unlicensed channels based on local conditions at each dimension (location), the system achieves reliable performance gains across the entire coverage volume. This dimensional expansion ensures that users anywhere in the primary carrier coverage area can access secondary carriers with consistent reliability.
Data Source
AI summary
A controller in a wireless communication system includes a transceiver to receive channel activity reports from a first node and a plurality of second nodes that are connected to the first node. The first node supports wireless communication over one or more first channels of a licensed frequency band and second channels of an unlicensed frequency band. The second node supports wireless communication over the second channels of the unlicensed frequency band. The controller also includes a processor to allocate a subset of the second channels to the first node and the plurality of second nodes based on the channel activity reports.