Parallel-type coherent multi-stage interference canceller with iterative channel estimation using both pilot and decision-feedback data symbols for W-CDMA mobile radio

In order to increase the link capacity in the wideband direct sequence code division multiple access (W-CDMA) reverse link, employing a parallel-type coherent multistage interference canceller (COMSIC) is more practical than using a serial (successive)-type due to its inherent advantage of a short processing delay, although its interference suppression effect is inferior to the serial-type. Therefore, this paper proposes a parallel-type COMSIC with iterative channel estimation (ICE) using both pilot and decision-feedback data symbols at each canceling stage. Computer simulation results show that the required average transmit E_b/N₀ for obtaining the average BER of 10 ^-3 using the three-stage parallel-type COMSIC with ICE using pilot and decision-feedback data symbols after forward error correction (FEC) decoding (number of iterations was 2 at each stage) was decreased by approximately 2.1 dB compared to a COMSIC with channel estimation using only pilot symbols, with the spreading factor (SF) of 16 and when the number of active users was 20 (thereby the capacity normalized by the processing gain (Pg) becomes 42%). The results also show that the required average transmit E_b/N₀, loss of the parallel-type COMSIC using ICE at the average BER of 10^-3 compared to the serial-type was negligible (i.e., within 0.2 dB) due to the significantly improved channel estimation and decreased data decision error, while achieving a much shorter processing delay irrespective of the number of active users