In order to exploit the benefits of soft handoff, finding good values of handoff control parameters is important. In cellular system specifications such as IS-95C and WCDMA, handoff decision algorithm includes signal strength averaging and drop timer in addition to hysteresis. This paper analyzes the effects of signal strength averaging and drop timer and their performance tradeoffs. Because averaging and drop timer are both based on time delay, one may expect that they have similar impact on soft handoff performance. The results show that the effects of averaging and drop timer are rather similar and closely connected in terms of reducing the signaling overhead. However, they have different impacts on resource usage and diversity gain of the system.

The capacity of multiuser OFDM systems can be maximized by allocating resources (subcarrier and power) to the user with the highest instantaneous channel gain. This assumes complete channel state information (CSI) at the transmitter, which is achieved by every user reporting its CSI for all subcarriers to the transmitter via feedback channel. In practice, due to the limited capacity of the feedback channel, the completeness of CSI may be severely restricted especially with a large number of users transmitting a large amount of feedback information. In order to reduce the amount of feedback information while preserving the maximal capacity, quality based CSI feedback (QCF) is proposed in this letter. The system capacity is derived with QCF and compared with that of full CSI feedback. The results show that QCF successfully reduces the amount of feedback information with little capacity loss.