Inter-cell Interference Coordination in Heterogeneous OFDM Networks
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Solution Overview
Problem
In heterogeneous cellular networks, particularly in LTE systems, controlling inter-cell interference on control channels is challenging due to their distributed transmission across the system bandwidth, leading to performance degradation and communication failures, especially in high residence density regions with increased femto cell installations.
Innovation Solution
An inter-cell interference coordination method and apparatus that generate and exchange information using newly defined control channel multiplexing with data channels, employing RNTP IE messages to adjust transmit power and synchronize interference control on both time and frequency axes, allowing efficient cooperation between cells to mitigate interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If control channels are transmitted in a distributed manner across the system bandwidth, then frequency resource utilization is improved, but inter-cell interference control becomes difficult
Solution Approach 1:
The control channel transmission is segmented into two distinct types: eICIC control channels transmitted only in protected subframes, and non-eICIC control channels transmitted in both protected and non-protected subframes. This segmentation allows different interference coordination strategies to be applied to different control channel instances, resolving the contradiction between distributed transmission benefits and interference control difficulty
Solution Approach 2:
Different quality requirements and transmission characteristics are applied to different control channels based on their eICIC properties. EICIC control channels receive enhanced protection and coordinated transmission, while non-eICIC channels use standard transmission. This local differentiation enables effective interference control for critical channels while maintaining overall system efficiency
2Reliability
If transmit power is increased to improve control channel reliability, then communication quality is improved, but inter-cell interference increases
Solution Approach 1:
The system employs periodic eICIC protected subframes where transmit power is coordinated between cells. During these protected subframes, interfering cells reduce or eliminate control channel transmissions, allowing victim cells to transmit control channels at higher power without causing or suffering from inter-cell interference, thus improving reliability while managing interference
Solution Approach 2:
The eICIC mechanism implements feedback-based power coordination where base stations exchange information about their control channel transmissions and adjust their transmit power accordingly. This feedback loop enables dynamic power adjustment that maintains control channel reliability while preventing inter-cell interference escalation
3Object-generated harmful factors
If eICIC control channels are transmitted only in protected subframes, then interference control is improved, but time resource utilization decreases
Solution Approach 1:
The control channel transmission is segmented into two distinct types: eICIC control channels transmitted only in protected subframes, and non-eICIC control channels transmitted in both protected and non-protected subframes. This segmentation allows different interference coordination strategies to be applied to different control channel instances, resolving the contradiction between distributed transmission benefits and interference control difficulty
Solution Approach 2:
The system maintains universality by ensuring that control channel functionality is preserved through multiple transmission opportunities. Even though eICIC control channels are restricted to protected subframes, the system compensates by allowing non-eICIC control channels to transmit in all subframes, ensuring that overall control channel coverage and reliability are maintained without sacrificing excessive time resources
Data Source
AI summary
An inter-cell interference coordination method and apparatus is provided for a heterogeneous network system based on Orthogonal Frequency Division Multiplexing (OFMD) communication. The inter-cell interference coordination method and apparatus exchanges two different types of inter-cell interference coordination messages between base stations to adaptively use the frequency division and time division schemes, thereby coordinating inter-cell interference of control channels transmitted randomly in distributed manner.