Linear M-ary Modulation for PDCCH Interference Mitigation
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Solution Overview
Problem
Current wireless communication systems face interference issues, particularly in LTE-A networks, which can lead to incorrect reception of resource allocation information in PDCCH or EPDCCH, affecting overall system performance and reliability.
Innovation Solution
The implementation of a system that uses linear m-ary modulation constellations, such as 4-PAM and 4-PAM rotated constellations, for PDCCH and EPDCCH, allowing for interference mitigation through zero-forcing and MMSE receiver techniques, and flexible resource allocation in EPDCCH to enhance interference resilience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional QPSK modulation is used for PDCCH and EPDCCH, then the system maintains compatibility with existing standards, but interference from co-channel and coscheduled communications degrades reliability
Solution Approach 1:
The patent changes the modulation parameter from conventional QPSK to linear m-ary modulation (such as 4-PAM with rotated constellations). This parameter change transforms the signal structure so that interfering signals map to different constellation points, enabling the receiver to distinguish between serving and interfering signals and thereby mitigate interference while improving reliability
Solution Approach 2:
The patent applies different modulation schemes to different signal components: linear m-ary modulation is applied specifically to the control channel signals (PDCCH/EPDCCH) that are susceptible to interference, while other signals can maintain their conventional modulation. This localized application optimizes interference mitigation for the most vulnerable channels without unnecessarily complicating the entire system
2Reliability
If linear m-ary modulation with zero-forcing receiver is used, then interference mitigation is improved, but receiver complexity increases
Solution Approach 1:
The patent segments the received signal into serving signal components and interfering signal components based on their distinct linear modulation characteristics. By exploiting the structured nature of linear m-ary modulation, the receiver can separately process and decode control channel signals from data signals, even in the presence of interference, without requiring full-blown MIMO detection algorithms
Solution Approach 2:
The patent employs adaptive receiver techniques that dynamically adjust processing based on detected interference conditions. The zero-forcing receiver selectively nulls interfering signals based on channel state information and modulation type detection, providing high interference mitigation when needed while allowing simpler processing when interference is minimal
3Reliability
If EPDCCH with flexible resource allocation is implemented, then interference resilience is enhanced, but system complexity and implementation difficulty increase
Solution Approach 1:
The patent extends resource allocation flexibility to the frequency domain by allowing EPDCCH to be transmitted in both control region and data region across multiple resource blocks. This dimensional extension in resource allocation space provides additional degrees of freedom to avoid interfering resources and enhance interference resilience through frequency-domain diversity
Solution Approach 2:
The patent makes the EPDCCH channel multi-functional by enabling it to serve both control information transmission and interference mitigation functions simultaneously. The same EPDCCH structure can be adaptively allocated to different UEs with different interference conditions, providing universal interference resilience across multiple users and scenarios
Data Source
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AI summary
Embodiments can relate to an apparatus for interference mitigation in a wireless communication. The apparatus can comprise at least one processing element arranged to extract, from a received PDCCH or EPDCCH signal, modulated symbols; the modulated symbols having been modulated using a linear m-ary modulation constellation. The apparatus also comprises a demodulator to demodulate the extracted PDCCH or EPDCCH modulated symbols; the demodulator being operable to demodulate the extracted symbols according to the linear m-ary modulation constellation.