Impact of Link Adaptation Strategies in Ray-Traced 5G Scenarios

Year 2025, Volume: 1 Issue: 2, 29 - 35, 29.09.2025

Önem Yıldız

Abstract

Efficient link adaptation is critical for maintaining reliable and high-throughput wireless communication, especially in 5G networks where dense deployments and diverse mobility patterns increase the complexity of radio conditions. This study evaluates the performance of Inner-Loop Link Adaptation (ILLA) and Outer-Loop Link Adaptation (OLLA) mechanisms under realistic scenarios involving imperfect channel estimates and noisy CQI feedback. A ray tracing-based simulation environment was developed using Sionna to model the effects of multipath propagation, shadowing, and geometric obstructions in an actual urban area. Results show that while ILLA reacts quickly to instantaneous SINR variations, it struggles to maintain the target BLER under feedback uncertainty. In contrast, the OLLA-enhanced system achieves more stable BLER control and higher spectral efficiency by compensating for non-idealities of noisy channel through HARQ-based offset tuning. The findings highlight the importance of robust and adaptive link control mechanisms in 5G and beyond wireless systems, particularly under unreliable feedback conditions

Keywords

5G , Link Adaptation , Ray Tracing , Spectral Efficiency , BLER

Işın İzlemeli 5G Senaryolarında Bağlantı Uyarlama Stratejilerinin Etkisi

Abstract

Verimli bağlantı adaptasyonu, özellikle yoğun dağıtımların ve çeşitli mobilite modellerinin radyo koşullarının karmaşıklığını artırdığı 5G ağlarında, güvenilir ve yüksek verimli kablosuz iletişimin sürdürülmesi için kritik öneme sahiptir. Bu çalışma, kusurlu kanal tahminleri ve gürültülü CQI geri bildirimi içeren gerçekçi senaryolar altında İç Döngü Bağlantı Uyarlaması (ILLA) ve Dış Döngü Bağlantı Uyarlaması (OLLA) mekanizmalarının performansını değerlendirmektedir. Gerçek bir kentsel alanda çoklu yol yayılımının, gölgelemenin ve geometrik engellerin etkilerini modellemek için Sionna kullanılarak ışın izleme tabanlı bir simülasyon ortamı geliştirilmiştir. Sonuçlar, ILLA'nın anlık SINR değişimlerine hızlı tepki verirken, geri bildirim belirsizliği altında hedef BLER'i korumakta zorlandığını göstermektedir. Buna karşılık, OLLA ile geliştirilmiş sistem, HARQ tabanlı ofset ayarı yoluyla gürültülü kanalın ideal olmayan özelliklerini telafi ederek daha kararlı BLER kontrolü ve daha yüksek spektral verimlilik elde etmektedir. Bulgular, özellikle güvenilmez geri bildirim koşulları altında, 5G ve ötesi kablosuz sistemlerde sağlam ve adaptif bağlantı kontrol mekanizmalarının önemini vurgulamaktadır.

Keywords

5G , Bağlantı Adaptasyonu , Işın İzleme , Spektral Verimlilik , BLER

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