Rank- -Optimal Adaptive Design of Binary
George N. Karystinos, Dimitris A. Pados · 2007
Over the real/complex field, the spreading code that maximizes the signal-to-interference-plus-noise ratio (SINR) at the output of the maximum-SINR linear filter is the minimum-eigen- value eigenvector of the interference autocovariance matrix. In the context of binary spreading codes, the maximization problem is NP-hard with complexity exponential in the code length. A new method for the optimization of binary spreading codes under a rank- approximation of the inverse interference autocovariance matrix is presented where the rank- -optimal binary code is ob- tained in lower than quadratic complexity. Significant SINR per- formance improvement is demonstrated over the common binary hard-limited eigenvector design which is shown to be equivalent to the rank- -optimal solution. Index Terms—Binary sequences, code-division multiple-access (CDMA), code-division multiplexing, signal waveform design, signal-to-interference-plus-noise ratio (SINR), signature sets, spread-spectrum communications.