E-PDCCH Interference Cancellation via Orthogonal Covering Codes
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Solution Overview
Problem
The enhanced physical downlink control channel (E-PDCCH) faces challenges in predicting and managing inter-cell interference (ICI) and multi-user interference (MUI) due to the instability of these interferences, making it difficult to select an appropriate aggregation level to guarantee a target block error rate (BLER).
Innovation Solution
The method involves allocating different orthogonal covering code (OCC) sequences to different cells and users, and combining control channel elements (CCEs) with cell-specific or user-specific OCC sequences to enable user equipment to cancel interference on the E-PDCCH, using orthogonal or semi-orthogonal OCC sequences to optimize aggregation levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If beamforming and multi-user MIMO are implemented on PDCCH to enhance coverage and capacity, then the PDCCH coverage and capacity are improved, but inter-cell interference and multi-user interference become unstable and difficult to predict
Solution Approach 1:
The patent introduces orthogonal covering codes (OCC) as an intermediary mechanism to separate and manage interference from different cells and users. By multiplying PDCCH sequences with cell-specific and user-specific OCCs, the system creates orthogonal channels that allow interference cancellation at the receiver, thus maintaining reliability while enabling beamforming and MU-MIMO operations
Solution Approach 2:
The patent changes the parameter space by introducing OCC sequences with different orthogonality properties (orthogonal vs. semi-orthogonal) and adjusting the aggregation level N. This allows dynamic adaptation to interference conditions while maintaining the ability to support beamforming and multi-user operations
2Reliability
If multiple aggregation levels are used to guarantee target BLER under unstable interference, then the target block error rate is maintained, but the complexity of selecting appropriate aggregation levels increases
Solution Approach 1:
OCC sequences serve as a mediator that simplifies aggregation level selection. By providing orthogonal separation, the system can use lower aggregation levels while maintaining BLER performance, reducing the complexity of selecting appropriate aggregation levels compared to dealing with unstable interference alone
Solution Approach 2:
The patent applies preliminary action by pre-multiplying PDCCH sequences with OCCs before transmission. This preprocessing step creates predictable interference patterns that can be canceled at the receiver, eliminating the need for complex real-time aggregation level adjustments
3Reliability
If orthogonal covering codes are allocated to different cells and users, then interference cancellation capability is improved, but the complexity of OCC allocation and management increases
Solution Approach 1:
The patent segments the OCC allocation into two independent parts: cell-specific OCCs for inter-cell interference cancellation and user-specific OCCs for multi-user interference cancellation. This segmentation simplifies the allocation management by separating the two interference sources that would otherwise require complex joint management
Solution Approach 2:
Different OCC properties are assigned to different cells and users based on local requirements. Cell-specific OCCs provide orthogonal separation for ICI cancellation, while user-specific OCCs provide additional orthogonal separation for MUI cancellation, optimizing the system for local interference conditions
Data Source
AI summary
Embodiments of the present invention provide an interference cancellation method for an enhanced physical downlink control channel E-PDCCH, comprising steps of: (1) allocating different orthogonal covering code OCC sequences to different cells and/or different users; and (2) combining a plurality of control channel elements CCEs constituting one PDCCH with a cell-specific OCC sequence and/or a user-specific OCC sequence respectively, so as to enable a user equipment to cancel interference on the PDCCH.