A novel interference resolving algorithm for the TDD TD-CDMA mode in UMTS
Harald Haas, Stephen McLaughlin, G.J.R. Povey · 2002
When comparing UTRA-TDD with UTRA-FDD it can be found that in the UTRA-TDD mode additional interference scenarios exist. Mobile stations (MSs) can interfere with each other and so can base stations (BSs). Since the source and sink of this type of interference are the same we call it same-entity interference. It is shown by a novel interference resolving algorithm that same-entity interference can be constructively exploited to enable asynchronous overlaps in a UTRA-TDD network. Asynchronous overlaps exist when any cell A is transmitting while the neighbour cell B is receiving. It was found that in a network where an asynchronous overlap exists the algorithm proposed reduces outage from 14% to 6%. In contrast, the outage of an ideally synchronised network was found to be 3.5%. In this 'ideal' network asynchronous overlaps are disallowed resulting in a significant drawback. This is that the flexibility of a TDD system to easily adopt different channel asymmetries is significantly limited.