Subframe Truncation for Interference Avoidance in Carrier Aggregation

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Solution Overview

Problem

In heterogeneous wireless networks, the uncoordinated deployment of Home eNode-Bs (HeNBs) leads to significant interference with macro-cell eNBs due to shared bandwidth, degrading the quality of service for user equipment (UEs) as downlink communications from macro-cells can severely interfere with femto-cells, especially when multiple component carriers are used, increasing the risk of interference.

Innovation Solution

A base unit uses signals in the control region of an OFDM subframe on an anchor carrier to indicate a truncated portion of a subframe component transmitted on an additional component carrier, allowing UEs to avoid decoding errors and manage interference by transmitting truncation information via cross-carrier notifications, which can also be repeated on the additional component carrier.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If carrier aggregation with multiple component carriers is used to increase data throughput, then productivity is improved, but the risk of interference between macro-cell and femto-cell transmissions increases

Engineering Contradiction:

Improvedata throughputVSAvoidinterference between macro-cell and femto-cell transmissions

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the subframe transmission by introducing a front-truncation mechanism that divides the subframe into truncated and non-truncated portions. This segmentation allows the system to transmit data on multiple component carriers while preventing control region overlap by truncating the subframe before the interfering control region begins, thus maintaining productivity while reducing interference.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies preliminary action by notifying UEs in advance about the front-truncation time period through control signaling. This notification allows UEs to prepare for the truncated subframe structure before reception, enabling them to correctly decode data on additional component carriers despite the truncation, thereby maintaining high throughput while avoiding interference.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If subframe components are transmitted on additional component carriers to increase capacity, then productivity is improved, but decoding errors increase due to control region overlap with femto-cell subframes

Engineering Contradiction:

Improvenetwork capacityVSAvoiddecoding accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent uses preliminary action by providing advance notification to UEs about the front-truncation time period through control signaling on the anchor carrier. This notification enables UEs to correctly interpret the truncated subframe structure on additional component carriers before decoding begins, preventing decoding errors while maintaining network capacity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary mechanism where control signaling on the anchor carrier acts as a mediator to convey front-truncation information to UEs. This intermediary notification bridge ensures that UEs have the necessary information to correctly decode subframe components on additional component carriers without control region overlap, thus maintaining both capacity and reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If control regions are transmitted on shared component carriers to maintain coordination, then device complexity is reduced, but interference with femto-cell control regions increases

Engineering Contradiction:

Improvecoordination complexityVSAvoidinterference with femto-cell control regions

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the control region transmission from the shared component carrier by implementing front-truncation that removes the truncated portion containing control regions. This extraction eliminates control region overlap and interference with femto-cell control regions while maintaining simplified device operation through cross-carrier notification mechanisms.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8194603B2Subframe component reduction and notification in a heterogeneous wireless communication system

Publication Date: 2012.06.05 GOOGLE TECHNOLOGY HOLDINGS LLC

AI summary

A wireless base unit (102) supporting carrier aggregation determines a truncation time period (159, 169) in order to create a reduced subframe component (154, 164) on an additional component carrier (120) such that the truncated subframe component (154, 164) does not interfere with the control region (171, 172) of a subframe (170, 180) transmitted on an overlapping component carrier (130) by an uncoordinated second base unit (105). The wireless base unit (102) transmits the truncated subframe component (154, 164) and also transmits truncation time period information within a control region (151, 161) of an anchor carrier (110). A remote terminal (104, 108) that supports carrier aggregation searches a control region (151, 161) of a subframe (150, 160) transmitted on the anchor carrier (110) for truncation information and uses the truncation information to determine a boundary of a data region in a subframe component (154, 164) received on the additional component carrier (120).