Method of searching code space

Abstract

A code space is divided into three windows of different sizes. The position of the strongest ray in the code space is called the 'normal'. Two search correlators are allocated to window (1), four search correlators to window (2), and two search correlators to window (3). This allocation of the search correlators is based on an estimation of the probability of a new ray appearing in the relevant portions of the code space, relative to the normal. To begin with, the four search correlators allocated to the window (2) are controlled to occupy the normal, 0.5 chips, 1.0 chips and 1.5 chips respectively. After dwelling at their positions for 512 chips (the dwell time) each search correlator is moved four steps (two chips) along the code space. Each of the search correlators dwells at its new position for 512 chips, before again moving two chips further along the code space. Whilst the search correlators are dwelling at a position in the code space, the signal power at that position is calculated, and a signal detector acts according to the signal power so detected. When the search correlators reach the end of a window, they are moved back to the start of that window, and the search of the window is repeated. Due to the relative sizes of the windows and to the numbers of correlators assigned to those windows, the frequency of searching is different for each window.

Description

technical field [0001] The invention relates to a method for finding a signal code space. Background technique [0002] Rake receivers are generally used in wideband code division multiple access (W-CDMA) wireless receivers to process received signals. A rake receiver consists of a parallel arrangement of correlators, typically four correlators, whose outputs are fed to a summer. The result of the adder output is the output signal of the Rake receiver. Each correlator is called a "finger" and each finger is independently controllable. Since it is necessary to generate a pseudorandom noise (PN) code of the same frequency and phase as the code modulated onto the received signal to correlate with the line-of-sight (LOS) signal, by mixing the received signal and the delayed signal of the corresponding code the It is possible to separate delayed multipath signals. The code delay must be the same as the delay between the line-of-sight and multipath signals used to obtain the c...

AI Technical Summary

Problems solved by technology

However, in general the signal strength of the line-of-sight beam 10 is not high enough so that each tap follows a different multipath beam

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