An improved multicarrier modulation system and method is introduced which has the advantages of both isotropic orthogonal transfer algorithm orthogonal frequency division multiplexing (IOTA OFDM) and scalable advanced modulation (SAM). The invention reduces adjacent channel interference (ACI) in the multicarrier modulation system used in multicast systems by generating (2601) a spectrally efficient modified pulse for multicarrier modulation and then adapting (2605) the pulse at the edge of the subchannel for reducing the ACI product by the total multicarrier signal (2607). This BTRRC OFDM (2607) is an Offset OFDM with BTRRC pulse (2605) while the prior art RRC OFDM (604) is an Offset OFDM with RRC pulse (603). BTRRC OFDM has characteristics similar to RRC OFDM and has better power efficiency in simulcast or Nakagami fading environments where there is a timing error. Thus, BTRRC OFDM is desirable to substitute SAM in a simulcast environment.