Adjacent channel interference is one of the major impairments that reduces achievable capacity in communication satellites, especially in high capacity throughput satellites (HTS) with densely packed spot beams. Adjacent channel interference (ACI) arises due to leakages in channel filters in any satellite repeaters. Because all filters are finite response filters, adjacent channel interference is always present. The most common technique to suppress ACI is to design multi-pole Butterworth filters with very steep roll-offs and thus very low leakages. However, the steeper the filter is, the higher its insertion loss will be, and the more expensive it will get. A very simple and low cost technique to suppress ACI is presented here. The technique is based on optimizing carrier assignment scheme to users in a ground system. The proposed technique allows maximum bandwidth usage without ACI impairment thus maximizing the achievable capacity throughput in any communication satellite system.