Inter-cell interference coordination in heterogeneous LTE networks
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Solution Overview
Problem
In heterogeneous LTE networks, inter-cell interference between macro and small cells is severe, particularly due to asymmetric UL-DL subframe configurations in TDD systems, leading to potential link failures if protected subframes are allocated arbitrarily, especially in cases of UL-dominant, DL-dominant, or bidirectional interference scenarios.
Innovation Solution
The allocation of protected subframes is tailored based on the type of interference and the relationship between the number of uplink and downlink subframes, using specific subsets of HARQ processes to minimize interference, ensuring normal data transmission and reception in small cells without link failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If protected subframes are allocated arbitrarily in HetNet, then interference coordination is simplified, but link failures occur due to asymmetric UL-DL subframe configurations
Solution Approach 1:
The patent changes the parameter of subframe configuration by introducing specific timing relationships between protected subframes in macro cells and small cells. It defines that protected subframes in small cells must correspond to protected subframes in macro cells, and establishes timing constraints based on HARQ process durations. This parameter adjustment resolves the contradiction by ensuring reliable link operation while maintaining manageable coordination complexity through standardized timing rules.
2Area of stationary object
If Cell Range Expansion (CRE) is applied to expand small cell coverage, then coverage enhancement is achieved, but downlink interference to small cell UEs increases
Solution Approach 1:
The patent applies periodic action by configuring periodic protected subframes in both macro cells and small cells. These protected subframes occur at regular intervals and create interference-free windows for small cell UEs. The periodic structure allows the system to maintain expanded coverage through CRE while periodically eliminating downlink interference impacts on small cell users.
3Productivity
If macro cell UEs are scheduled on protected subframes to maintain macro cell throughput, then macro cell productivity is maintained, but small cell UEs experience strong uplink interference
Solution Approach 1:
The patent implements preliminary action by pre-configuring protected subframes before data transmission occurs. The network预先 determines which subframes will be protected in both macro and small cells based on HARQ timing relationships. This advance configuration ensures that when small cell UEs need to transmit uplink data, the corresponding macro cell subframes are already designated as protected, preventing strong uplink interference while maintaining macro cell productivity through alternative resource allocation.
Data Source
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AI summary
Embodiments of the present disclosure provide a method for coordinating inter-cell interference in a heterogeneous network comprising a macro cell and at least one small cell.The method comprises obtaining,with regard to a terminal device in a small cell,a type of interference from the macro cell to the small cell;and determining a relationship between a number of uplink subframes and a number of downlink subframes in a current subframe configuration used in the macro cell.The method also comprises allocating protected subframes for the terminal device according to the obtained type of interference and the determined relationship;and scheduling transmission in relation to the allocated protected subframes in the macro cell.