Scheduling on uplink of CDMA packet data network with successive interference cancellation

Abstract

Uplink scheduling in wireless systems is gaining importance due to arising uplink intensive data services, which could be hampered by the currently in-built asymmetry in favor of the downlink. In prior work, (K. Kumaran and L. Qian, 2002, Apr. 2003), we proposed optimal algorithms for uplink scheduling in a CDMA cell that does not employ any form of interference cancellation. In this work, we modify the approach to incorporate successive interference cancellation (SIC), which has been shown to be optimal in an information theoretic sense (G. Caire and S. Shamai, 2000). As in K. Kumaran and L. Qian ( 2002, Apr. 2003), no statistical assumptions are made about channel or traffic behavior, but feedback to communicate current channel state and queue state is assumed. Our results demonstrate that the throughput optimal scheduling strategy takes a particularly simple form with SIC as compared to without, (K. Kumaran and L. Qian, 2002, Apr. 2003), apart from providing some level of performance improvement. A reasonable alternative algorithm based purely on received power can be constructed based on early work on SIC (P. Patel and J. Holtzman, June 1994). Considering decoding errors, only strongly received users can benefit from SIC. Our simulation experiments suggest that our throughput optimal scheduling improves performance over the alternative when users have similar received power. Combining the above observation, we also propose a hybrid scheduling algorithm that performs SIC for strong users and simultaneous transmission for weak users.