Open-loop transmit diversity for CDMA forward link

Open-loop transmit diversity (TD) methods for the third generation (3G) CDMA cellular standards are briefly described. These solutions are based on orthogonal signal transmission from the base station to reduce same-cell interference. The performance enhancement due to this orthogonal signal transmission is studied and it is compared with traditional schemes. Performance bounds based on the Shannon capacity limit are also given to compare and contrast several fundamental differences among the TD methods.