Symbol rate adaptation and blind rate detection using FOSSIL (forest for OVSF-sequence-set-inducing lineages)
We introduce a forest whose nodes represent orthogonal variable spreading factor (OVSF) code sequences of different lengths used for multi-rate CDMA. These code sequences have properties that facilitate symbol rate adaptation and blind rate detection, which can be used in a fast time-varying environment such as mobile communication systems. The properties of these codes also makes flexible the assignment of code sequences of different lengths to different users who communicates at different constant symbol rates. In particular, certain lineages in the forest have a property that the set of code sequences represented by such a lineage are cyclic orthogonal to each other with unit length being that of the shortest sequence in the set. We present the forest-structured generation of the code sequences and their properties. Then, we present a symbol rate adaptation protocol and a blind rate detection algorithm that use the code properties.