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Harmful Cooperation in Relay-Assisted MIMO Under Imperfect CSI.
Nikolaos Mouziouras1, Constantinos T Angelis1, Andreas Tsormpatzoglou1
1Department of Informatics & Telecommunications, Campus of Arta, University of Ioannina, 47150 Arta, Greece.
Sensors (Basel, Switzerland)
|July 15, 2026
Summary
Cooperative MIMO systems suffer performance loss from imperfect channel information and relay errors. A new relay activation method improves performance by selectively using reliable relays, enhancing system robustness.
Area of Science:
- Wireless Communication Systems
- Information Theory
- Signal Processing
Background:
- Cooperative multiple-input multiple-output (MIMO) systems offer diversity gains under ideal conditions.
- Practical impairments like imperfect channel state information (CSI) and relay decoding errors significantly degrade performance.
- Decode-and-Forward (DF) relaying is susceptible to error propagation, introducing structured interference.
Purpose of the Study:
- Investigate cooperative MIMO performance under practical impairments.
- Analyze the impact of imperfect CSI and relay errors on system performance.
- Propose and evaluate a reliability-aware relay activation mechanism.
Main Methods:
- Theoretical analysis of SINR and BER performance under imperfect CSI and relay errors.
- Introduction of the 'harmful cooperation region' concept.
- Development and simulation of a reliability-aware relay activation strategy.
- Investigation of antenna scaling effects on system robustness.
Main Results:
- Imperfect CSI causes SINR saturation and BER error floors.
- Relay error propagation exacerbates performance degradation.
- Cooperative systems can underperform direct MIMO in certain SNR regimes.
- The proposed relay activation mechanism significantly improves BER performance.
- Larger MIMO configurations show increased resilience to CSI imperfections.
Conclusions:
- Cooperative transmission performance is highly SNR-dependent under imperfect CSI.
- Robust system design requires joint consideration of CSI uncertainty, relay reliability, and system dimensions.
- The reliability-aware relay activation mechanism effectively mitigates performance degradation.
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