CDMA subtractive demodulation
US5218619A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 2, 1991 |
| Grant date | Jun 8, 1993 |
| Priority date | — |
| Expiry date | Aug 2, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B2201/70703
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Subtractive CDMA demodulation optimally decodes a coded information signal embedded in many other overlapping signals making up a received, composite signal. A radio receiver correlates a unique code corresponding to the desired signal to be decoded with the composite signal. Moreover, after each information signal is successfully decoded, it is recoded and removed from the composite signal. Subtractive CDMA demodulation is enhanced by decoding the composite signal in the order of strongest to weakest signal strength. The individual information signals are spread using block error correction codes which are correlated with the composite signal using Fast Walsh transforms. Correlated signals identified as the largest transform component are removed from the composite signal and the remaining composite signal is reformulated using an inverted Fast Walsh transform. Any residual error or interference caused during the extraction of a transform component is removed by recorrelating the composite signal using the index of that transform component.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.