Multi-User Detector Intercell Interference Mitigation
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Solution Overview
Problem
In CDMA cellular communication systems, mitigating intercell interference is challenging due to the lack of timely and accurate information from surrounding cells, which is typically carried in higher layer messaging and is inaccessible, leading to performance degradation when only intracell interference is considered.
Innovation Solution
A method and arrangement for mitigating intercell interference by acquiring and estimating the transfer function matrix for all cells, including cell-specific scrambling codes, channel impulse responses, and channelization codes, using information available within the current cell, such as cell identifiers and midamble sequences, to construct the transfer function matrix for multi-user detection (MUD) across all cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher layer messaging is used to carry information from surrounding cells, then intercell interference mitigation can be achieved, but the complexity of information exchange and system implementation increases significantly
Solution Approach 1:
The patent extracts only the essential information elements needed for interference mitigation (scrambling codes, channel impulse responses, channelization codes) from the complex higher layer messaging structure. By selecting and using only these specific parameters, the system achieves intercell interference mitigation without requiring access to the complete higher layer message set, thereby reducing implementation complexity while maintaining reliability.
2Measurement precision
If higher layer messaging is accessed for intercell information, then accurate interference mitigation is possible, but accessibility and ease of operation deteriorate due to cell-specific constraints
Solution Approach 1:
The patent enables each cell to serve itself by extracting the necessary interference mitigation information (scrambling codes, channel impulse responses, channelization codes) from its own available signal observations and local knowledge. This self-service approach eliminates the need for complex inter-cell information exchange mechanisms, making the system easier to operate while maintaining accurate interference estimation through local signal processing.
3Device complexity
If only intracell interference is considered, then system complexity is reduced, but overall performance deteriorates due to unmitigated intercell interference
Solution Approach 1:
The patent applies partial action by implementing interference mitigation for a selected subset of surrounding cells rather than attempting to mitigate interference from all cells in the network. The multi-user detector is configured to process signals from specific neighboring cells based on available information, achieving partial intercell interference mitigation that improves system performance without requiring the excessive complexity of complete network-wide interference cancellation.
Data Source
AI summary
A method (400) and arrangement (200) for mitigation of intercell and intracell interference in a 3GPP cellular communication system (100) by, in a receiver in a cell of the system, deriving for a first channel in the cell a signal, representative of first channel transfer function (A(1)); deriving for at least a second channel originating in a different cell a signal (A(2 . . . M)), representative of second channel transfer function, based on: deriving a cell specific scrambling code (s), deriving a channel impulse response (h), and deriving a channelisation code (c); and performing multi-user detection using the first and second signals. Where the channelisation code is unknown, a substitute channelisation code is preferably substituted. It will be appreciated that the technique can be applied to both downlink and uplink. This provides the advantage that both intra-cell interference and intercell interference are mitigated.