Cell search in WCDMA under large-frequency and clock errors: Algorithms to hardware implementation

Abstract

This paper proposes a complete cell-search solution for real-world handset operations in the wide-band code-division multiple-access system. Large-frequency and clock errors are induced at initial search due to an inaccuracy of crystal oscillators within handsets and could cause fatal performance degradation. In addition to a primary search algorithm for achieving essential pseudo-noise code acquisitions, an enhanced algorithm combining frequency offset compensation, random sample per frame, and sample point reordering is proposed to achieve fast initial search even while an inaccuracy is up to 12 ppm. After a series of trade-off between performance and complexity, two search bins in the first stage are adopted to mitigate possible errors in each bin and make the enhanced schemes become effective. In final, the complete solution is presented with alternative algorithms: a primary one and an enhanced one. The solution is implemented with the flexibility for switching algorithms in different searches and using low-power methods for the sake of handsets' working time. Its core area is 3.8 x 3.8-mm(2) in a 3.3-V 0.35-mm CMOS technology, and the power consumption is 35.6 and 67 mW for the primary and enhanced algorithms, respectively.