Assignment of multiple OVSF codes at the downlink in WCDMA

We examine the problem of assigning multiple orthogonal variable spreading factor (OVSF) codes to serve calls at the downlink in WCDMA. In contrast to previously published approaches, we propose algorithms that fully exploit any additional hardware available at the user equipment. Depending on the requested rate and the number of available transceivers, our schemes support a call by as many OVSF codes as possible. Compared to previous multiple code assignment schemes, our approach significantly lowers code blocking. Different ways to calculate the most appropriate combination of codes result in different variations of our schemes. It turns out that if we attempt to minimize the highest rate among the codes used, instead of minimizing the excess bandwidth wasted, we get better results in terms of code blocking, and the number of reassignments to support the call.