Closed loop feedback system for improved down link performance

• US 20050157684A1
• Filed: 03/02/2005
• Published: 07/21/2005
• Est. Priority Date: 06/02/2000
• Status: Active Grant

• Current Assignee: Intellectual Ventures I LLC (Intellectual Ventures LLC)
• Original Assignee: Nokia Networks (Nokia Corporation)
• Inventors: Ylitalo, Juha, Katz, Marcos
• Granted Patent: US 7,792,206 B2
• Time in Patent Office: Days
• US Class Current: 370/334
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/0652 Feedback error handling
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A method includes receiving at least two space-time coded signals from an antenna system associated with a first station, determining complex channel state information based on the received space-time coded signals, and sending the complex channel state information to the first station. In an alternative embodiment, a method includes transmitting at least two space-time coded signals in respective beams of a multi-beam antenna array, measuring a channel impulse response for each space-time coded signal at a second station, and sending an indicia of a selected set of least attenuated signals from the second station to the first station. The multi-beam antenna array is associated with a first station. The beams transmit a signature code embedded in each respective space-time coded signal, and the signature codes are orthogonal so that the second station can separate and measure the channel impulse response corresponding to each space-time coded signal.

Claims

1. A method comprising steps of:

selecting at least two beams of plural beams formed by a multi-beam antenna array associated with a first station for transmission of a corresponding at least two space-time coded signals produced by a space-time encoder;

determining a time delay associated with each of the at least two space-time coded signals as received in each respective beam; and

setting into a variable delay line the time delay corresponding to each beam, each variable delay line being coupled between the multi-beam antenna array and the space-time encoder.

2. The method of claim 1, further comprising a step of measuring a channel response based on an up link signal from a second station.

3. The method of claim 2, wherein:

the step of measuring includes receiving plural signal components of the up link signal in corresponding plural beams of the multi-beam antenna array;

the step of selecting includes selecting the at least two beams based on the received plural signal components; and

the step of determining includes determining delay spreads for each of the received plural signal components and assigning to each beam the determined delay spread as the time delay to be set into the respective variable delay line.

4. The method of claim 1, further comprising steps of:

encoding each signal of the at least two space-time coded signals with a signature code that is mutually orthogonal to each other signature code encoded in the at least two space-time coded signals so as to form a reference space-time coded signal and at least one remaining space-time coded signal, wherein the step of setting includes delaying each signal of the at least one remaining space-time coded signal in a respective variable delay line to form at least one delayed space-time coded signal; and

transmitting the reference space-time coded signal and the at least one delayed space-time coded signal in respective beams of the at least two beams.

5. The method of claim 4, further comprising steps of:

receiving the reference space-time coded signal and the at least one delayed space-time coded signal from the multi-beam antenna array;

determining complex channel state information based on the received reference space-time coded signal and the received at least one delayed space-time coded signal; and

sending the complex channel state information to the first station.

6. The method of claim 4, further comprising a step of segmenting the complex channel state information into a plurality of channel state information segments, wherein the step of sending the complex channel state information includes sending the plurality of channel state information segments in a sequence.

7. A system comprising a base station, the base station including:

a multi-beam antenna array;

first circuitry to select at least two beams of plural beams formed by the multi-beam antenna array for transmission of a corresponding at least two space-time coded signals produced by a space-time encoder;

second circuitry to determine a time delay associated with each of the at least two space-time coded signals as received in each respective beam;

at least two variable delay lines, each variable delay line being coupled between the multi-beam antenna array and a space-time encoder; and

third circuitry to set the time delay corresponding to each beam of the at least two beams into a corresponding delay line of the at least two variable delay lines.

8. The system of claim 7, wherein the first circuitry includes logic to measure a channel response based on an up link signal from a remote station.

9. The system of claim 8, wherein:

the up link signal includes plural signal components, each signal component being a received signal component in a corresponding beam of the plural beams of the multi-beam antenna array;

the logic to measure the channel response includes logic to receive the plural signal components of the up link signal and logic to select the at least two beams based on the received plural signal components; and

the second circuitry includes logic to determine delay spreads for each of the received plural signal components and logic to assign to each beam the determined delay spread as the time delay to be set into the respective variable delay line.

10. The system of claim 7, wherein:

the base station further includes the space-time encoder;

the space-time encoder encodes each signal of the at least two space-time coded signals with a signature code that is mutually orthogonal to each other signature code encoded in the at least two space-time coded signals so as to form a reference space-time coded signal and at least one remaining space-time coded signal; and

the at least one variable delay line delays each respective signal of the at least one remaining space-time coded signal in a respective variable delay line to form at least one delayed space-time coded signal, the base station transmitting the reference space-time coded signal and the at least one delayed space-time coded signal in respective beams of the at least two beams.

11. The system of claim 10, further comprising a remote station, the remote station including:

a receiver to receive the reference space-time coded signal and the at least one delayed space-time coded signal from the multi-beam antenna array;

a processor to determine complex channel state information based on the received reference space-time coded signal and the received at least one delayed space-time coded signal; and

a transmitter to send the complex channel state information to the base station.

12. The system of claim 11, wherein:

the processor includes a processor module to segment the complex channel state information into a plurality of channel state information segments; and

the transmitter includes circuitry to send the complex channel state information in a sequence of the channel state information segments.