Ap link channels improve interference handling in dynamic tdd networks
Leveraging Slowly Time-Varying AP-AP Channels for Interference Mitigation in Dynamic TDD
Information Theory
Summary
Dynamic TDD networks face interference when some access points are sending data while others are receiving. The authors noticed that the connections between access points change slowly compared to user connections. By jointly figuring out user data and these stable access point links, they reduce interference better than before. Their method works especially well when access point connections stay nearly constant over time.
What this means in practice
- •For wireless network engineers: Improve signal quality in cellular networks by reducing interference between access points using stable channel information across time.
- •For telecom equipment developers: Design base stations that jointly estimate user data and access point channels to achieve better interference management in TDD systems.
Authors
Martin Andersson, Tung T. Vu, Pål Frenger, Jan Åslund, Erik G. Larsson
Abstract
We address the challenge of cross-link interference in dynamic time-division duplexing (TDD) systems. Specifically, we focus on mitigating the interference caused by access points (APs) operating in downlink to APs operating in uplink. To this end, we exploit that channels between APs typically vary much more slowly over time than channels between users and APs. This observation allows us to jointly estimate the uplink user data and the AP-AP channels using a least-squares formulation over multiple coherence intervals, during which the AP-AP channels stay constant. We derive conditions for unique solvability of this least-squares problem by analyzing the rank of the regression matrix. For cases where a unique solution does not exist, we propose to transform the problem into a uniquely solvable one by sacrificing a subset of the uplink data samples. Numerical results demonstrate that our proposed methods achieve substantial gains over baseline algorithms. Further, we observe that one of our proposed algorithms achieves almost perfect AP-AP interference mitigation when the AP-AP channels vary very slowly over time.