Design of subsets of complex spreading sequences

The performance of a code division multiple access system depends on the correlation properties of the employed spreading code. Low cross-correlation values between spreading sequences are desired to suppress multiple access interference. An autocorrelation function with a distinct peak enables proper synchronization and suppresses intersymbol interference. These requirements, however, contradict each other and a trade-off needs to be established. In this paper, a global two dimensional optimization method is proposed to minimize cross-correlation with auto-correlation allowed to lie within a fixed region. This approach is applied to the design of subsets of complex spreading sequences.