Performance analysis of active handoff in CDMA2000 femtocells

Cellular operators are developing femtocells to improve network coverage for indoor users. But in current CDMA systems, heavy reuse of PN codes among femtocells causes ambiguity in choosing the target for handoff. To resolve the ambiguity, a method which uses reverse link (RL) sensing at femtocells has been proposed. This method uses RL measurements of the mobile's signal to choose the femtocell with the best forward link channel, as the handoff target. The robustness of this method to fast fading and shadowing is demonstrated in this work. By making multiple RL measurements, the error in handoff due to fading can be reduced, but at the cost of increased delay. The tradeoff between probability of error in handoff and RL measurement duration is demonstrated. It is also shown that unsynchronized measurements by femtocells cause a only marginal increase in the probability of handoff error.