I. Introduction
The direct use of a full search vector quantization (VQ)
In this letter, we use VQ and full search VQ interchangeably.
is limited because of its exponential complexity (for example, the full search VQ becomes prohibitively complex if the bit allocation exceeds 12–13 bits/vector). To overcome the complexity limitation, several structured/product code VQ methods [7] have been proposed and used widely.