FIELD: broadband communications. SUBSTANCE: optimal code chains are generated for use in expansion and compression functions for CDMA communication system. For instance, use is made of family of four-phase expansion codes affording maximal quantity of expansion codes to attain high capacity in CDMA communication system at minimal peak cross correlation between any two expansion codes of this family so as to maintain cross correlation of noise at tolerable level or below tolerable levels. Family S(2) of four-phase code chains, L = 2m-1 in length, where m is integer number equal to or greater than 5, is such optimal family of expansion codes. Size of family S(2) of quaternary expansion codes equals (L+2)(L+1)2 and maximal cross correlation is 
. Expansion codes are preferably assigned to base stations using definite subset codes of family S(2) possessing equal properties of cross correlation of code families S(0) and/or S(1).Expansion codes are elongated to advantage by one or mode code characters, as required or for any other reasons. For instance, best expansion codes suited to maintain variable transfer speed services are those whose length can be expressed as integer number which is a multiple of each expansion factor in mobile communication system. As length of some expansion codes is 2m-1, one code character is added to expansion code generated. EFFECT: optimized cross correlation between elongated expansion codes. 46 cl, 10 dwg
