Nonrearrangeable compact assignment of orthogonal variable- spreading factor codes for multi-rate traffic

Abstract

In UTRA systems, orthogonal variable-spreading-factor (OVSF) codes are used to support different transmission rates for different users. In this paper, we first define an index for measuring the flexibility of an assignable code set. Based on this flexibility index, a single-code assignment scheme, namely nonrearrangeable compact assignment (NCA), is proposed for accommodating multi-rate traffic. NCA can offer maximal flexibility to the resulting assignable code set after each code assignment. As a result, it gives better blocking, throughput and fairness performance when compared to random assignment (RA) scheme.