WCDMA OVSF Code Tree

Implements WCDMA code tree according to Figure 4 of 3GPP TS 25.213

Orthogonal Variable Spreading Factor (OVSF) code tree generation. Only input value is spreading factor (must be power of 2), and only output is cell array for orthogonal codes that is SF x SF in size.

Code Tree Reference:
3GPP TS 25.213 V10.0.0, "3rd Generation Partnership Project;
Technical Specification Group Radio Access Network; Spreading and modulation (FDD) (Release 10)