Delayed-Decision-Feedback Equalization for Multiuser Systems
Ramon Schlagenhaufer, Brent R. Petersen, Abu B. Sesay · 1999
The topic of this paper is delayeddecision -feedback equalization for wireless multiuser systems consisting of an arbitrary number of portables (users) and one central base station. The multiple users are supported by means of spread spectrum multiple access (SSMA) or CDMA. We consider joint or multiuser detection of all signals. In addition to bandwidth diversity, the system may employ antenna diversity at the receiver. The focus is on the reverse link. The radio channels are considered to be frequency selective. A flexible detection order of the multiple received signals is achieved by placing delay elements after the forward filters of the decisionfeedback equalizer (DFE). This delays the signals of some users longer than those of others and results in di#erent performance improvements for di#erent users. The special cases of parallel and successive DFE result from no delays and infinite delays, respectively. These structures are analyzed and compared to the linear MMSE equalizer/combiner.