OFDM Resource Partitioning for Inter-Cell Interference Mitigation

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Solution Overview

Problem

Existing OFDM-based cellular networks face challenges in mitigating inter-cell interference, particularly in frequency re-use-1 schemes, which reduce network capacity and introduce complexity with techniques like orthogonal frequency code division multiplexing, frequency hopping, and inter-cell interference cancellation.

Innovation Solution

The method involves partitioning a time-frequency transmission resource into a first zone used by all cells and a second zone used by less than all cells, with specific sub-carriers and transmission powers allocated differently in each zone to minimize interference, employing techniques like time division multiplexing (TDM), frequency division multiplexing (FDM), or combined TDM/FDM.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a fractional frequency re-use scheme is used to mitigate inter-cell interference, then inter-cell interference is reduced, but network capacity is dramatically reduced

Engineering Contradiction:

Improveinter-cell interferenceVSAvoidnetwork capacity

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The transmission resource is divided into multiple zones (first zone and second zone) within the same frequency band. The first zone uses frequency re-use-1 for high capacity, while the second zone uses frequency re-use-N for low interference, allowing both objectives to be achieved simultaneously without sacrificing overall network capacity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different frequency re-use patterns are applied to different spatial zones within the same cell. The first zone (higher capacity requirement) uses frequency re-use-1, while the second zone (lower interference requirement) uses frequency re-use-N, optimizing the solution locally for different needs

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If orthogonal frequency code division multiplexing is used to achieve spreading gain, then frequency diversity is improved, but orthogonality loss causes performance degradation and increased hardware complexity

Engineering Contradiction:

Improvefrequency diversityVSAvoiddecoding hardware complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The transmission resource is segmented into multiple zones with different frequency re-use patterns, eliminating the need for complex OFCDM spreading and decoding operations while maintaining frequency diversity benefits through the zone-based approach

Inventive Principle:

Principle #1Segmentation

3Object-affected harmful factors

If frequency hopping is used to mitigate inter-cell interference, then interference is reduced, but implementation complexity increases

Engineering Contradiction:

Improveinter-cell interferenceVSAvoidimplementation complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

Instead of implementing complex frequency hopping across the entire spectrum, the solution segments the transmission resource into zones and applies simplified frequency re-use patterns, reducing implementation complexity while maintaining interference mitigation benefits

Inventive Principle:

Principle #1Segmentation

4Reliability

If macro diversity techniques including fast cell selection or soft handoff are used to mitigate inter-cell interference, then coverage is improved, but network complexity increases

Engineering Contradiction:

ImprovecoverageVSAvoidnetwork complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The transmission resource is segmented into zones that can be independently configured, allowing simplified zone-based interference mitigation without requiring complex macro diversity techniques like fast cell selection or soft handoff, thus maintaining coverage while reducing network complexity

Inventive Principle:

Principle #1Segmentation

5Object-affected harmful factors

If inter-cell interference cancellation techniques are used, then inter-cell interference is reduced, but receiver complexity increases making practical implementation difficult

Engineering Contradiction:

Improveinter-cell interferenceVSAvoidreceiver complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The solution segments the transmission resource into zones with different frequency re-use patterns, providing interference mitigation at the transmission level rather than requiring complex receiver-based interference cancellation techniques, thus reducing receiver complexity while maintaining practical implementability

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9258102B2Methods and systems to mitigate inter-cell interference

Publication Date: 2016.02.09 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

The present invention provides methods and devices for mitigating inter-cell interference in communication environments having a plurality of cells. In some embodiments, a time-frequency transmission resource that includes multiple sub-carriers over multiple OFDM symbol intervals is partitioned into a first zone and a second zone. In the first zone, transmissions are transmitted on at least one frequency sub-band which is common to all of the plurality of cells. In the second zone, transmissions are transmitted on at least one frequency sub-band which is used by less than all of the plurality of cells, so as to mitigate inter-cell interference. In some embodiments, in the first zone transmissions are transmitted using a transmission power which is common to all of the plurality of cells and in the second zone transmissions are transmitted using a transmission power which is used by less than all of the plurality of cells so as to mitigate inter-cell interference.