Multiple antenna processing on transmit for wireless local area networks

An apparatus in a first wireless station, the apparatus comprising:

• a plurality of antennas for communicating with any of a plurality of wireless stations, including a second wireless station, the first and plurality of wireless stations for communicating packets of information using OFDM signals that include a plurality of frequency tones, the plurality of antennas for receiving and transmitting coupled to at least one receive signal path for receiving and to a transmit signal path for transmitting;
• means for determining, for each of the antennas of the first wireless station, corresponding measures of the EVM for signals received from any one of the plurality of wireless stations;
• means for determining a decision, using the determined measures of the EVMs corresponding to the wireless station, the decision being for selecting one or more of the transmit antennas for transmitting to the wireless station, wherein determining includes a combination of maximum ratio combining on a tone-by-tone weighted basis and selecting a subset of antennas by setting corresponding antenna weights to respective ones or zeros;
• storage means for storing the EVMs or the determined decision based thereon, such that after some time, the storage means includes the EVMs or the decisions for communicating with wireless stations, including the second wireless station, with which the first wireless station recently communicated;
• selection means for retrieving from the memory the stored EVMs or decision determined therefrom for communicating with the second wireless station, and for selecting, according to the retrieved EVMs or decision, an antenna for transmitting to the second wireless station;
• and
• means for transmitting to the second station signals for transmission via the selected antenna for the transmit signal path,
• such that the second station can receive packets transmitted from the first wireless station without the second station requiring a plurality of receive antennas and without any first-station-specific calibration required at the second station.

An apparatus comprising:

• a plurality of antennas for receiving and transmitting, the antennas in a first wireless station for communicating with a plurality of wireless stations including a second wireless station, the first and plurality wireless stations for communicating packets of information using OFDM signals that include a plurality of frequency tones, the plurality of antennas coupled to at least one receive signal path for receiving and to a one transmit signal path for transmitting;
• each of the at least one receive signal path comprising:
• a radio receiver coupled to the antenna of the receive signal path;
• an analog-to-digital converter coupled to the radio receiver to produce a received signal for the antenna of the receive signal path;
• and
• an EVM calculator coupled to the analog-to-digital converter, the EVM calculator configured to determine corresponding measures of the EVM of signals received from any one of the wireless stations via each of the antennas of the first station, and further configured to generate a decision, using the determined measures of the EVMs corresponding to the wireless station, the decision being for selecting one or more of the transmit antennas for transmitting to the wireless station, wherein determining includes a combination of maximum ratio combining on a tone-by-tone weighted basis and selecting a subset of antennas by setting corresponding antenna weights to respective ones or zeros;
• a memory coupled to the EVM calculator and operative to store the EVMs or the determined decision based thereon, such that after some time, the memory includes the EVMs or the decisions for communicating with a set of wireless stations, including the second wireless station, with which the first wireless station recently communicated;
• an antenna selector coupled to the memory and to the transmit signal path and operative to retrieve the stored EVMs or decision determined therefrom for communicating with any one of the set of wireless stations, and further operative to select one transmit antenna for transmitting to the one wireless station of the set;
• and
• a radio transmitter accepting a signal for transmitting and coupled to the antenna selector, the radio transmitter configured to transmit via the antenna selected by the selector,
• such that the second station can receive packets transmitted from the first wireless station without the second station requiring a plurality of receive antennas and without any first-station-specific calibration required at the second station.

An apparatus comprising:

• a plurality of antennas for receiving and transmitting, the antennas in a first wireless station for communicating with any of a plurality of wireless stations, including a second wireless station, the first and the plurality of wireless stations for communicating packets of information using OFDM signals that include a plurality of frequency tones, the plurality of antennas coupled to at least one receive signal path for receiving and to a transmit signal path for transmitting;
• each of the at least one receive signal path comprising:
• a radio receiver coupled to the antenna of the receive signal path;
• an analog-to-digital converter coupled to the radio receiver to produce a received signal for the antenna of the receive signal path;
• the transmit signal path comprising:
• an antenna selector coupled to the antennas;
• and
• a radio transmitter for transmitting coupled to the antenna selector for transmitting a signal, the radio transmitter configured to transmit via the antenna selected by the selector,
• the apparatus further comprising:
• a processing system comprising a computer readable storage medium containing computer readable code segments that when executed by one or more processors of the processing system cause:
• determining corresponding measures of the EVM of signals received from the any one of the wireless stations via each of the antennas of the first station using the received signals from the analog-to-digital converter;
• generating a decision, using the determined measures of the EVMs corresponding to the wireless station, the decision being for selecting one or more of the transmit antennas for transmitting to the wireless station, wherein determining includes a combination of maximum ratio combining on a tone-by-tone weighted basis and selecting a subset of antennas by setting corresponding antenna weights to respective ones or zeros;
• storing the EVMs or the determined decision based thereon in the storage medium, such that after some time, the storage medium includes the EVMs or the decisions for communicating with a set of wireless stations, including the second wireless station, with which the first wireless station recently communicated;
• retrieving the stored EVMs or decision determined therefrom for communicating with the second wireless stations;
• and
• causing the antenna selector to select the antenna for transmitting to the second wireless station,
• such that the second wireless station can receive packets transmitted from the first wireless station without the second station requiring a plurality of receive antennas and without any first-station-specific calibration required at the second station.