Multi-User Detection for Coded Multirate OFDM-CDMA Systems

Authors: V. Kühn, M. Feuersänger
Abstract: This paper analyzes the performance of multi-user detection (MUD) for a quasi-synchronous OFDM-CDMA uplink transmission. OFDM-CDMA has been chosen because it offers a great advantage over single carrier systems due to flat fading conditions on each subcarrier. This leads to much lower implementation costs of MUD techniques. In order to allow different data rates for each user, the CDMA spreading factors vary in the range of 4 up to 32. Specifically, we regard linear MUD techniques such as the MMSE approach as well as a combination with the nonlinear parallel interference cancellation (PIC) resulting in a recursive receiver structure. Assuming perfectly known channel impulse responses for each user and a rough synchronization it turns out that decreasing the spreading factors and keeping the number of sub-carriers constant leads to a performance loss due to a smaller diversity gain of each user signal. We will show that the effects of multi-user interference can be mitigated by applying a combination of MMSE and PIC. Thus the performance of the system can be improved.
Document type: Conference Paper
Publication: Berlin, Germany, 28. - 30. January 2002
Conference: 4th International ITG Conference on Source and Channel Coding (SCC 02)
Index: 167
SCC_2002_kühn.pdf354 KBSCC_2002_kü KB
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