Control Channel Interference Management in Heterogeneous Networks
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Solution Overview
Problem
Heterogeneous networks face interference management challenges due to the significantly lower transmit power of low power nodes compared to macro eNBs, particularly in the control channels (PCFICH, PDCCH, PHICH) which affects the service area and attachment of User Equipment (UE) to low power cells, leading to reduced coverage and increased interference.
Innovation Solution
Implementing a solution that reduces the transmit power of the control region on macro eNBs while maintaining the Common Reference Signal (CRS) power, allowing for reduced interference with low power nodes and supporting both LTE Release 8 and LTE-A UEs, along with configuring UE measurement reporting to adapt to the reduced control channel power, and using extended PDCCH (E-PDCCH) within the PDSCH region for interference management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmit power of control channels on macro eNBs is maintained at high levels, then the coverage area and reliability of control channels are improved, but the interference to low power nodes increases significantly
Solution Approach 1:
The patent applies local quality by differentiating transmit power levels across different channels and frequency resources. Specifically, the macro eNB transmits control channels (PCFICH, PDCCH, PHICH) at reduced power levels on certain frequency resources while maintaining normal power on other resources, allowing low power nodes to experience less interference in specific local frequency-time regions while overall system performance is maintained
Solution Approach 2:
The patent changes the transmit power parameter dynamically based on the serving cell type and channel type. The macro eNB adjusts control channel transmit power from high levels to reduced levels on specific frequency resources, creating a parameter variation that allows coexistence with low power nodes while maintaining control channel functionality
2Object-affected harmful factors
If the transmit power of control channels on macro eNBs is reduced to decrease interference, then the interference to low power nodes is reduced, but the service area and coverage of control channels deteriorate
Solution Approach 1:
The patent segments the control channel transmission resources into different frequency regions and time slots. By dividing the spectrum into multiple component carriers and allocating reduced power only to control channels on specific carriers while maintaining data channel power, the system preserves coverage area through distributed resource allocation rather than uniform power reduction
Solution Approach 2:
The patent moves control channel transmissions to additional frequency dimensions by utilizing multiple component carriers. Control channels are transmitted on specific carriers at reduced power while data channels occupy other frequency resources, effectively expanding the dimensional space available for communication and maintaining coverage through frequency diversity
3Object-affected harmful factors
If the transmit power of control channels is reduced, then the interference with low power nodes decreases, but the number of UEs that can be served by low power cells decreases
Solution Approach 1:
The patent creates a universal power management scheme that serves multiple functions simultaneously: it reduces interference to low power nodes, maintains macro eNB control channel coverage, and enables low power nodes to serve their attached UEs effectively. The differentiated power strategy works across different cell types and channel types, achieving multi-objective optimization
4Object-affected harmful factors
If the Common Reference Signal power is maintained while control channel power is reduced, then the interference coordination between macro and low power nodes is improved, but the complexity of UE measurement and reporting increases
Solution Approach 1:
The patent uses the Common Reference Signal as an intermediary reference that remains at normal power levels while control channels are reduced. The CRS serves as a stable measurement reference for UEs to assess channel conditions and report measurements, mediating between the reduced control channel power and the need for accurate UE measurements without requiring complex power adjustment mechanisms
Data Source
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Figure 3a~3b
AI summary
A method is provided for managing control channel interference. The method includes an access node transmitting a first control channel at a lower nominal transmit power on a first component carrier than the nominal transmit power of a second control channel on a second component carrier, and the access node transmitting a data channel at the same nominal transmit power on the first and second component carriers.