Convolutional despreading method for rapid code phase determination of chipping codes of spread spectrum systems
US6345073B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 8, 1998 |
| Grant date | Feb 5, 2002 |
| Priority date | — |
| Expiry date | Oct 8, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L1/0054
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A convolutional despreading method takes advantage of the algebraic structure of the spreading code and applies convolutional type decoding to received signal chip symbols to rapidly estimate code phase, preferably used for rapid acquisition of direct sequence spread spectrum signals. Modeled reduced-state structures having branchword transitions are used to reduce metric computations. The reduced state structures and algebraic structures provide additive constraints for modifying convolutional sequential metric searching for improved speed of code phase determination. The convolution despreading method preferably uses a modified convolutional sequential search algorithm, such as, a modified Fano Tree convolutional sequential search, or, a modified Viterbi trellis convolutional sequential search. The method can also directly determine a modulated data stream, when present, to provide demodulated data without necessarily performing conventional cross correlation despreading. A metric state processors then functions as an ad hoc despreader. The convolutional despreading method is particularly useful in direct sequence spread spectrum systems where the use of chip spreading codes requ…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.