Impact of code orthogonality, power control error and source activity on the capacity of multicast transmissions in WCDMA

In WCDMA, data transfer to a group may either take place on multiple point-to-point (FTP) channels transmitted to individual group members separately or on a single point-to-multipoint (PTM) channel that is broadcast over the entire cell. We evaluate the capacity of both channel selection strategies for one-to-many multicast over the WCDMA air interface in terms of outage probability. We study the capacity of both schemes by first deriving suitable outage probability expressions and then calculating the overall capacity, i.e., the number of multicast users that can be supported by both schemes. Particular attention is paid to the impact of code orthogonality, power control error and the activity factor of the multicast source on the capacity of both schemes for multicast transmissions.