On dually almost MRD codes

Abstract: In this paper we define and study a family of codes which come close to be MRD codes, so we call them AMRD codes (almost MRD). An AMRD code is a code with rank defect equal to 1. AMRD codes whose duals are AMRD are called dually AMRD. Dually AMRD codes are the closest to the MRD codes given that both they and their dual codes are almost optimal. Necessary and sufficient conditions for the codes to be dually AMRD are given. Furthermore we show that dually AMRD codes and codes of rank defect one and maximum 2-generalized weight coincide when the size of the matrix divides the dimension.