| Zusammenfassung: | We derive approximations for the probability of a bit error for a code division multiple access (CDMA) system with one-stage soft decision parallel interference cancellation. More precisely, we derive the exponential rates, J<sub>κ</sub> with cancellation and I<sub>k</sub> without cancellation, of a CDMA system with k users and processing gain equal to n as n → ∞. Whereas the rates I<sub>k</sub> follow explicitly from Cramér's theorem, the rates J<sub>k</sub> are given in terms of an optimization problem that can be evaluated numerically. We prove that <latex>$J_k > I_k$</latex> for k ≥ 3, which shows that interference cancellation is effective. For the case without interference cancellation, we investigate the second order (Bahadur-Rao) asymptotics. For the case with interference cancellation, we can obtain second order asymptotics only for k = 3. Together the limits provide excellent approximations for the probability of a bit error in a wide range of interest.
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