Method and apparatus for reducing amplitude variations and interference in communication signals, such as in wireless communication signals employing inserted pilot symbols
US6310869A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 31, 1998 |
| Grant date | Oct 30, 2001 |
| Priority date | — |
| Expiry date | Aug 31, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2025/03777
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Several methods and corresponding apparatus reduce peak to average power in signals transmitted in a wireless communications system, particularly with respect to pilot symbols transmitted from a base station to several user stations. A large peak to average amplitude of inserted pilot symbols has been found to result from a common sign chip position that exists in orthogonal codes, such as Walsh codes. In a first embodiment, the Walsh codes are multiplied by a random value of .+-.1. Under a second embodiment, the common sign chip position is eliminated in each Walsh code. The user station then inserts the missing chip position to regain orthogonality. In a third embodiment, the base station transmits pilot symbols, on a separate pilot channel, in only symbol positions that user stations expect to find pilot symbols. Under a fourth embodiment, each Walsh code is randomly shifted.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.