A satellite communication system for a mesh type network must support many multi-point connections simultaneously, and allocate satellite channels with the required data rates to support each connection independently. The conventional approach is excessively expensive since it forces the earth station to have one single carrier modem for each connection. To eliminate this problem, we introduce the Multicarrier/Multirate Group MODEM for earth stations. This new MODEM is implemented as a single LSI chip. The current version supports up to 128 communication channels simultaneously, and the bandwidth of each communication channel can be set individually. This paper describes the architecture and processing method of the modem and proposes an algorithm that decreases buffer circuit so as to reduce circuit size. Performance evaluation results are shown.