Method and apparatus for generating non-recursive variable rate orthogonal spreading codes

摘要

A method for constructing and selecting non-recursive orthogonal variable spreading factor (OVSF) codes is provided. The method includes: defining a variable B=SF_max/SF_min, where SF_max is a maximum desired spreading factor and SF_min is a minimum desired spreading factor; forming B unique base matrices G_k of dimension SF_min×SF_min, where G_iG_i^T=SF_minI_min ∀i, where T denotes a matrix transpose and I_min is an SF_min×SF_min identity matrix; forming a modulation matrix M of dimension B×B such that MM^T=BI_B, where I_B is a B×B identity matrix; forming an SF_max×SF_max orthogonal variable spread factor (OVSF) code matrix C′ as:; $$ C^{\prime }=\left[\begin{array}{cccc}{M}_{1,1}·G_1& M_{1,2}·G_2& \dots & M_{1,B}·G_B\\ M_{2,1}·G_1& M_{2,2}·G_2& \dots & M_{2,B}·G_B\\ ⋮& ⋮& ⋰& ⋮\\ M_{B,1}·G_1& M_{B,2}·G_2& \dots & M_{B,B}·G_B\end{array}\right],$$where M_i,j is a scalar from the i-th row and j-th column of the modulation matrix M, G_l . . . G_B is the k-th base matrix G_k and M_i,j·G_k denotes the multiplication of the elements of G_k by the scalar M_i,j; selecting a row of the OVSF code matrix C′ to use as a pseudo-noise (PN) code; and one of spreading or despreading a signal using the selected PN code.