Credit based channel transmission scheduling (CBCTS) of packet data units (PDUs) on a downlink channel is provided based on priority, quantity, and timing efficiency. The CBCTS technique includes initializing a set of credit accounts with a set of credit values. Credit accounts are sorted to determine the account having the highest number of credits. An account is selected from the set having an associated PDU type that is ready for transmission and has a size that fits within a MAC block. The selected PDU is inserted into the MAC block. The cost associated with the inserted PDU is subtracted from the credits. The selected PDU size is subtracted from the MAC block size, and a determination is made as to whether there is free space remaining on the MAC block for insertion of additional PDUs. If so, another sort and search is performed prior to transmission on the downlink channel.