Paulo R. B. Gomes Amarilton L. Magalhães André L. F. de Almeida Joint Downlink-Uplink Channel Estimation for Non-Reciprocal RIS-Assisted Communications. 4732-4737 2025 ICC https://doi.org/10.1109/ICC52391.2025.11161229 conf/icc/2025 db/conf/icc/icc2025.html#GomesMA25 streams/conf/icc