Methods and apparatus for downlink diversity in CDMA using Walsh codes
US6515978B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 19, 1999 |
| Grant date | Feb 4, 2003 |
| Priority date | — |
| Expiry date | Apr 19, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B2201/709709
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Downlink diversity in a CDMA system is provided by employing Walsh codes in conjunction with M transmit antennas at a common base station serving K mobiles, where M may or may not be to equal to K. The present invention provides methods and apparatus for improving downlink diversity in a CDMA system. Each transmit antenna transmits a signal representing the result of the modulation of Walsh codes by data signals for each of the K mobiles, assuming there is data pertaining to a particular mobile. The assignment of Walsh codes is accomplished in accordance with a transmission matrix T. The transmission matrix maps the user data symbols onto the Walsh codes for each antenna and is preferably designed such that its columns are representative of the transmit antennas and orthogonal. Thus, at a given mobile, the mobile need only correlate with M different Walsh codes since each transmit signal received contains a component that is the result of M different Walsh codes having been modulated by a data signal associated with that particular mobile. The set of Walsh codes to select from includes 2┌log2(K)┐ Walsh codes. However, with respect to any given mobile, there is needed on…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.