Kd-tree codebook for limited feedback CDMA

Abstract

We propose a quantization scheme based on a Kd (K dimensional)-tree algorithm for signature sequence in a reverselink direct sequence (DS)- code division multiple access (CDMA). With a few feedback bits, a receiver quantizes the optimal signature that minimizes interference for a desired user, and relays it to the user via an error-free feedback channel. A user performance depends on the quantization codebook and a number of feedback bits. We show the performance of the proposed Kd-tree codebook with a nearest neighbor criterion and derive the performance approximation. Also we modify the Kd-tree scheme to search for the entry in the codebook, which gives the least interference. Numerical examples show that the Kd-tree codebook performs close to the optimal codebook with only fraction of computational complexity.