Channel calibration for a time division duplexed communication system

An apparatus in a wireless time division duplexed (TDD) communication system, comprising:

• means for deriving a channel response estimate for a downlink channel from a second station to a first station;
• means for receiving, from the second station, a channel response estimate for an uplink channel from the first station to the second station;
• and
• means for determining correction factors for the second station and correction factors for the first station based on the channel response estimates for the downlink and uplink channels, the correction factors for the second station and the correction factors for the first station being used to obtain a calibrated downlink channel response and a calibrated uplink channel response.

A method of calibrating communication links in a wireless time division duplexed (TDD) multiple-input multiple-output (MIMO) communication system, comprising:

• transmitting a pilot on a first communication link from a first station to a second station;
• obtaining a channel response estimate for the first communication link derived based on the pilot transmitted on the first communication link;
• receiving a pilot on a second communication link from the second station;
• deriving a channel response estimate for the second communication link based on the pilot received on the second communication link;
• and
• determining correction factors for the first station and correction factors for the second station based on the channel response estimates for the first and second communication links, the correction factors for the first station and the correction factors for the second station being used to obtain a calibrated channel response for the first communication link and a calibrated channel response for the second communication link.

An apparatus in a wireless time division duplexed (TDD) communication system, comprising:

• a transmit spatial processor to transmit a first pilot on a first communication link from a first station to a second station;
• a receive spatial processor to receive a second pilot on a second communication link from the second station, to derive a channel response estimate for the second communication link based on the received second pilot, and to receive a channel response estimate for the first communication link derived based on the transmitted first pilot;
• and
• a controller to determine correction factors for the first station and correction factors for the second station based on the channel response estimates for the first and second communication links, the correction factors for the first station and the correction factors for the second station being used to obtain a calibrated channel response for the first communication link and a calibrated channel response for the second communication link.

A method of calibrating communication links in a wireless time division duplexed (TDD) communication system, comprising:

• deriving a channel response estimate for a downlink channel from an access point to a user terminal;
• receiving from the access point a channel response estimate for an uplink channel from the user terminal to the access point;
• and
• determining first correction factors for the access point and second correction factors for the user terminal based on the channel response estimates for the downlink and uplink channels, the first correction factors and the second correction factors being used to obtain a calibrated downlink channel response and a calibrated uplink channel response,
• wherein the first correction factors are different than the second correction factors.