Design of High-Speed Preamble Searcher for RACH Preamble Structure in WCDMA Reverse Link Receiver

Eun-Sun JUNG
Hyung-Jin CHOI

Publication
IEICE TRANSACTIONS on Communications   Vol.E89-B    No.11    pp.2990-2997
Publication Date: 2006/11/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e89-b.11.2990
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Transmission Systems and Transmission Equipment for Communications
Keyword: 
acquisition,  FHT,  RACH,  Searcher,  WCDMA,  

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Summary: 
In this paper, we propose a high speed Preamble Searcher suitable for the RACH (Random Access Channel) structure in WCDMA reverse link receivers. Unlike IS-95, WCDMA system uses the AISMA (Acquisition Indication Sense Multiple Access) scheme. Because of the time limit between RACH preamble transmission and AI (Acquisition Indicators), and the restriction on the number of RACH signatures assigned to RACH preamble, fast acquisition is required for efficient operation. The Preamble Searcher proposed in this paper is designed for 2-antenna systems; it adopts the FHT (Fast Hadamard Transform) algorithm that has the radix-2 16 point FFT (Fast Fourier Transform) structure. The acquisition speed using FHT is 32 times faster than the conventional method that correlates each signature. Based on this fast acquisition scheme, we improved the acquisition performance by calculating correlation up to 4096 chips of the total preamble length.