Apparatus and method for providing closed-loop transmit antenna diversity in a mobile communication system

A transmit antenna diversity apparatus in a base station for generating weight vectors for the transmission power of each antenna of at least two antennas at the base station in a mobile communication system, comprising:

• a first switch unit for switching feedback information received at predetermined intervals;
• a fixed weight vector selector having fixed weight vector indexes, for receiving the feedback information from the first switch unit at the end of a predetermined period, and for outputting fixed weight vectors corresponding to an index in the received feedback information;
• an adaptive differential weight generator having previous normalized weight vectors and a look-up table, for receiving the feedback information from the first switch unit at predetermined intervals during a predetermined period, for detecting an index from the feedback information, for reading differential weight vectors corresponding to the index from the look-up table, for calculating normalized weight vectors, and for assigning corresponding weights to the at least two antennas;
• and
• a second switch unit for switching to the adaptive differential weight vector generator during the predetermined period in order to assign normalized weight vectors received from the adaptive differential weight vector generator to the antennas, for switching to the fixed weight vector selector at the end of each predetermined period in order to assign fixed weight vectors to the antennas, and for outputting the fixed weights vector to the adaptive differential weight vector generator.

A method in a mobile terminal of generating weight vectors for the transmission power of each antenna of at least two antennas at a base station using transmit antenna diversity, said mobile terminal having a look-up table and previous normalized weight vectors, in a mobile communication system comprising the steps of:

• receiving a primary common pilot channel and a secondary common pilot channel, both of which are channel-despread;
• estimating downlink channel status based on the received common pilot channels;
• searching for an index corresponding to differential weight vectors that maximize the strength of received signals using the estimated channel status, the normalized weight vectors, and differential weight vectors of the look-up table during a predetermined period;
• transmitting the index found by the searching to a base station;
• and
• calculating new normalized weight vectors by means of the corresponding differential weight vectors and a predetermined value to thereby update the previous normalized weight vectors.

A method in a base station using transmit antenna diversity of generating weight vectors for the transmission power of each of at least two antennas at the base station, said base station having a look-up table and previous normalized weight vectors, in a mobile communication system, comprising the steps of:

• receiving feedback information from a mobile terminal;
• receiving a differential weight vector index corresponding to adaptive differential weight vectors during a predetermined period;
• searching for differential weight vectors corresponding to the received differential weight vector index from the look-up table;
• calculating normalized weight vectors using differential weight vectors found in the searching step;
• assigning the normalized weight vectors to the antennas;
• updating previous normalized weight vectors with the calculated normalized weight vectors;
• receiving a fixed weight vector index corresponding to a fixed weight vectors at the end of the predetermined period;
• and
• assigning fixed weight vectors corresponding to the received fixed weight vector index to the antennas.