Multi-Band Carrier Phase Positioning Toward 6G: Performance Bounds and Efficient Estimators. - Ehsan Shourezari; Ossi Kaltiokallio; Mehmet Cagri Ilter; Jukka Talvitie; Gonzalo Seco-Granados; Henk Wymeersch; Mikko Valkama (IEEE Trans. Wirel. Commun., 2026)