1. A method for simplified computation of metrics of cross-correlations of binary codes and for using the metrics for signal processing applications, the method comprising: in a receiver including an outer product matrix calculator, a metric of cross correlations calculator, a single user decoder, and a despreader: computing, by the outer product matrix calculator, an outer product matrix based on a first code vector, wherein the first code vector comprises a code vector for spreading code for a first single user and wherein computing the outer product matrix includes computing a first outer product matrix by multiplying the first code vector by a transpose of the first code vector; computing, by the outer product matrix calculator, at least one second outer product matrix based on at least one second code vector, wherein the at least one second code vector comprises at least one second code vector for a spreading code for at least one second single user different from the first single user and wherein computing the outer product matrix based on the at least one second code vector includes computing the at least one second outer product matrix by multiplying the at least one second code vector by a transpose of the at least one second code vector; computing, by the metric of cross correlations calculator, a metric of cross-correlations between the first code vector and the at least one second code vector using the first and the at least one second outer product matrices, wherein computing a metric of the cross-correlations includes computing a square or sum of squares of the cross-correlations by element-wise combination of the first and the at least one second outer product matrices and summing elements of the combination; receiving, by the despreader, the code vector for the spreading code for the first single user and a multi-user signal and despreading the multi-user signal using the code vector for the spreading code of the first single user to produce, as output, a despread output signal; and decoding, by the single user decoder, from the despread output signal, and using the square or sum of squares of the cross correlations, a signal for the first single user.