Method and apparatus for obtaining transmit diversity using switched antennas

摘要

A method and apparatus for providing diversity transmissions to a mobile unit from a transmitting station having at least first and second antennas by repeatedly switching between the two antennas during the transmission of information to the receiving unit. Message information is transmitted from the first antenna in the transmitting station to the receiving unit. After the start of the transmission of the message information from the first antenna, transmission of the message information from the first antenna to the receiving unit terminates and transmission of the message information from the second antenna in the transmitting station to the receiving unit is initiated. Some time after transmission of the message information from second antenna is initiated, the transmission of the message information from the second antenna to the receiving unit terminates and transmission of the message information from the first antenna in the transmitting station to the receiving unit is initiated. Repeated switching between the first and second antennas is achieved by repeating the process. The switching results in diversity transmissions that improve the ability of a receiving unit to receive the coded and interleaved transmitted message information from the transmitting station. The interleaver disperses the encoded symbols in each antenna dwell period such that the decoder decisions are based on a mix of symbols form each antenna. Therefore the decoder decisions are unreliable only when the mix of symbols from the different antennas, with different fading characteristics, are unreliable over the span of symbols the decoder uses in its decision process.