Communication system and method using transmit diversity

• US 20060148415A1
• Filed: 03/06/2006
• Published: 07/06/2006
• Est. Priority Date: 05/21/2001
• Status: Active Grant

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Wichman, Risto, Hamalainen, Jyri
• Granted Patent: US 7,599,666 B2
• Time in Patent Office: Days
• US Class Current: 455/69
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/065 Variable contents, e.g. long-term or short-short
• CPC Class Codes: H04B 7/0656 at the transmitter, e.g. error detection at base station
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04B 7/0862 receiver computing weights based on information from the transmitter

Abstract

Influencing the transmission of signals from a transmitting device to a receiving device in a communication system comprising at least one transmitting device and at least one receiving device is disclosed. In a receiving station received transmission signals are processed and a feedback signal to be transmitted to a transmitting device is generated on the basis of the processed signals. Then, transmit weights to be applied to transmission signals are determined in accordance with the feedback signal.

Claims

1. A transmitting device in a communication system for influencing the transmission of signals from a transmitting device to a receiving device, said communication system comprising at least one transmitting device and at least one receiving device, wherein

the transmitting device is arranged to receive a feedback signal transmitted from a receiving device, process already existing feedback information from the receiving device, select a feedback mode and a corresponding feedback word length on the basis of the already existing feedback information, determine transmit weights in accordance with the feedback signal and apply the determined transmit weights to transmission signals.

2. A transmitting device according to claim 1, wherein the transmitting device transmits transmission signals from two or more transmitting elements to the receiving device for transmission using transmit diversity technique.

3. A transmitting device according to claim 2, being arranged to adapt channel coefficients between the transmitting elements and the receiving device in accordance with the received feedback signal, form an ordered covariance matrix C of the adapted channel coefficients, evaluate the largest eigenvalue of C, and calculate the eigenvector corresponding to the largest eigenvalue, the eigentvector corresponding to the transmit weights.

4. A transmitting device according to claim 1, wherein the received feedback signal comprises a feedback word which is generated according to one of two ore more feedback modes.

5. A transmitting device according to claim 4, wherein the different feedback modes correspond to different feedback word lengths.

6. A transmitting device according to claim 5, comprising means for controlling the length of the feedback word in accordance with temporal properties of a channel between the transmitting device and the receiving device, wherein said transmitting device is arranged to transmit determined feedback control information to the receiving device.

7. A transmitting device according to claim 3, wherein the feedback signal comprises two or more feedback words of different lengths, and said transmitting device is arranged to form an ordered covariance matrix C for each received feedback word, evaluate the largest eigenvalue for each ordered covariance matrix C, compare the largest eigenvalues, and determine the feedback word corresponding to the matrix C with the largest eigenvalue of the largest eigenvalues as best feedback mode.