E-PDCCH Interference Management in Heterogeneous Networks
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Solution Overview
Problem
Heterogeneous networks face challenges in managing interference between macro eNBs and low power nodes due to the spread of control channels across the system bandwidth, which affects the robust reception of PDCCH and PHICH, leading to reduced service area and increased interference for low power cells.
Innovation Solution
Implementing a solution that reduces the transmit power of the control region on specific carriers while maintaining the Common Reference Signal (CRS) power, and using extended PDCCH (E-PDCCH) regions within the PDSCH region to manage interference, allowing for inter-cell interference coordination and supporting both legacy and LTE-A UEs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If control channels are spread across the system bandwidth in heterogeneous networks, then coverage area is expanded, but interference to low power nodes increases and reception robustness deteriorates
Solution Approach 1:
The control channel transmission is segmented into two distinct regions: the traditional PDCCH region in the control region and the extended E-PDCCH region in the data region. This segmentation allows different transmission strategies to be applied to each region, reducing mutual interference between macro eNB and low power node control channels while maintaining comprehensive coverage.
Solution Approach 2:
The control channel is extended from the traditional control region into the data region, utilizing the time-frequency resources in a new dimension. This dimensional extension allows the control channel to be transmitted in regions where low power nodes do not transmit control channels, thereby reducing interference while maintaining coverage.
2Object-affected harmful factors
If control channel transmit power is reduced on specific carriers, then interference to low power nodes decreases, but reception reliability for legacy UEs deteriorates
Solution Approach 1:
Different transmit power levels are applied to different control channel regions and different carrier types. The PDCCH in the control region maintains high power for legacy UE reliability, while the E-PDCCH in the data region uses reduced power to minimize interference to low power nodes, achieving local optimization of power distribution.
Solution Approach 2:
The E-PDCCH acts as an intermediary control channel that bridges the gap between legacy and LTE-A UEs. It provides control information to LTE-A UEs using reduced power in the data region, while legacy UEs continue to receive control information from the traditional PDCCH in the control region, thus mediating the interference-reliability trade-off.
3Productivity
If E-PDCCH region is extended within the PDSCH region, then scheduling efficiency for LTE-A UEs improves, but device complexity increases
Solution Approach 1:
The E-PDCCH region in the data region serves multiple functions: it provides control information to LTE-A UEs, enables flexible resource allocation, and maintains backward compatibility with legacy UEs through cross-carrier scheduling. This multi-functionality improves scheduling efficiency without requiring completely separate control mechanisms.
Solution Approach 2:
The system dynamically adjusts parameters such as the number of resource blocks allocated to E-PDCCH, the aggregation level of control channel elements, and the mapping pattern between CCEs and physical resources. These parameter changes allow the system to optimize scheduling efficiency for LTE-A UEs while managing device complexity through configurable rather than fixed structures.
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A method is provided for managing control channel interference. The method includes a first access node transmitting an E-PDCCH, wherein a DM-RS for the E-PDCCH supports channel estimation of the E-PDCCH.