# US 7,613,423 B2 · Method of creating active multipaths for mimo wireless systems

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- Number: US 7,613,423 B2
- Document ID: US7613423B2
- Status: Granted
- Kind: B2
- Application number: 10/938,374
- Filed: 2004-09-10
- Published: 2006-03-16
- Granted: 2009-11-03
- Earliest claimed: 2004-09-10
- Assignees: Samsung Electronics Co., Ltd.
- Inventors: Chiu Ngo; Jun Shen
- Web page: https://patentgrep.com/patent/US7613423B2

## CPC

- H04B 7/15592: {Adapting at the relay station communication parameters for supporting cooperative relaying, i.e. transmission of the same data via direct - and relayed path (cooperative diversity H04B7/024)}
- H04B: TRANSMISSION

## Abstract

A method of transmission in a wireless communication system including a transmitter, a transceiver and a receiver. The transmitter transmits a first signal to the receiver. The transceiver also receives the first signal and retransmits the first signal to the receiver by modifying the signal characteristics, such that the first signal and the retransmitted signal are received substantially uncorrelated at the receiver.

## Claims

### Claim 1

A method of transmission in a wireless communication system, the method comprising:
transmitting a first signal from a first signal source to a receiver via a first signal path; and
modifying characteristics of the first signal and retransmitting the modified first signal from a second signal source via a second signal path, such that the first signal and the modified first signal are received substantially uncorrelated at the receiver, via the first and second signal paths, respectively,
wherein the characteristics are modified based on correlation quality feedback from the receiver in a first mode and randomly assigned in a second mode.

### Claim 2 (depends on 1)

The method of claim 1, wherein the second signal source comprises a transceiver, and wherein modifying the signal characteristics includes selectively introducing a time delay in retransmission of the modified first signal from the transceiver such that the retransmitted modified first signal via the second signal path is received by the receiver after the first signal via the first signal path, whereby the first signal via the first signal path and the retransmitted modified first signal via the second signal path are received substantially uncorrelated at the receiver.

### Claim 3 (depends on 1)

The method of claim 1, wherein modifying the signal characteristics includes selectively changing a magnitude of the first signal before retransmission, such that the first signal via the first signal path and the retransmitted modified first signal via the second signal path are received substantially uncorrelated at the receiver.

### Claim 4 (depends on 1)

The method of claim 1, wherein the first signal source comprises a transmitter and the second signal source comprises a transceiver, and wherein the wireless communication system comprises a multiple-input multiple-output (MIMO) system, such that the transmissions from the transmitter and the transceiver form multipaths.

### Claim 5 (depends on 1)

The method of claim 1, wherein:
the wireless communication system comprises a multiple-input multiple-output (MIMO) communication system.

### Claim 6 (depends on 1)

The method of claim 1, wherein modifying the signal characteristics further includes determining a modification such that first signal via the first signal path and the retransmitted modified first signal via the second signal path are received substantially uncorrelated at the receiver.

### Claim 7 (depends on 6)

The method of claim 6, further comprising determining at the receiver a relative correlation between the first signal via the first signal path and the modified first signal from the second signal path, wherein the second signal source comprises a transceiver, and wherein determining the modification further includes receiving a feedback from the receiver at the transceiver indicating the relative correlation, and if the first signal and the retransmitted modified first signal are indicated as not sufficiently uncorrelated, further modifying and retransmitting the further modified first signal from the transceiver such that the first signal and the further modified first signal are received substantially uncorrelated at the receiver.

### Claim 8 (depends on 6)

The method of claim 6, wherein modifying the signal characteristics includes randomly changing a magnitude of the first signal before retransmission, such that the first signal and the retransmitted modified first signal are received as essentially statistically independent signals at the receiver.

### Claim 9 (depends on 6)

The method of claim 6, wherein modifying the signal characteristics includes randomly modifying the signal characteristics, whereby the first signal and the retransmitted modified first signal are received as essentially statistically independent signals at the receiver.

### Claim 10 (depends on 6)

The method of claim 6, wherein the second signal source comprises a transceiver, and wherein modifying the signal characteristics includes randomly introducing a time delay in retransmission of the modified first signal from the transceiver such that the retransmitted modified first signal via the second signal source is received by the receiver after the first signal via the first signal source, whereby the first signal and the retransmitted modified first signal are received as essentially statistically independent signals at the receiver.

### Claim 11 (depends on 6)

The method of claim 6, wherein the communication system includes multiple transceivers, the method further comprising:
receiving the first signal at the multiple transceivers and from each transceiver retransmitting modified first signal with modified signal characteristics, such that the first signal and the retransmitted modified first signals are received substantially uncorrelated at the receiver.

### Claim 12 (depends on 11)

The method of claim 11, wherein modifying the signal characteristics in each transceiver includes introducing a time delay in retransmission of the modified first signal from that transceiver such that the retransmitted modified first signals are received by the receiver after the first signal, whereby the first signal and the retransmitted modified first signals are received substantially uncorrelated at the receiver.

### Claim 13 (depends on 11)

The method of claim 11, wherein modifying the signal characteristics in each transceiver includes changing a magnitude of the first signal before retransmission, such that the first signal and the retransmitted modified first signal are received substantially uncorrelated at the receiver.

### Claim 14 (depends on 11)

The method of claim 11, wherein the first signal source comprises a transmitter, and wherein the wireless communication system comprises a multiple-input multiple-output (MIMO) system, such that the transmissions from the transmitter and the transceivers form multipaths.

### Claim 15 (depends on 11)

The method of claim 11, wherein modifying the signal characteristics in each transceiver further includes determining a modification such that the first signal and the retransmitted modified first signals are received substantially uncorrelated at the receiver.

### Claim 16 (depends on 15)

The method of claim 15, further comprising determining at the receiver a relative correlation among the received signals, wherein determining the modification in each transceiver further includes receiving feedback from the receiver at that transceiver indicating the relative correlation, and if the first signal and the retransmitted modified first signal are indicated as not sufficiently uncorrelated, farther modifying and retransmitting the further modified first signal from that transceiver such that the first signal and the second retransmission signal are received substantially uncorrelated at the receiver.

### Claim 17 (depends on 15)

The method of claim 15, wherein modifying the signal characteristics in each transceiver includes randomly changing a magnitude of the first signal before retransmission, such that the first signal and the retransmitted signals are received as essentially statistically independent signals at the receiver.

### Claim 18 (depends on 15)

The method of claim 15, wherein modifying the signal characteristics in each transceiver includes randomly introducing a time delay in retransmission of the modified first signal from the transceiver such that the retransmitted modified first signal is received by the receiver after the first signal, whereby the first signal and the retransmitted modified first signal are received as essentially statistically independent signals at the receiver.

### Claim 19 (depends on 11)

The method of claim 11, further including coordinating modification of the signal characteristics of the first signal in the transceivers, such that the first signal and the retransmitted signals are received substantially uncorrelated at the receiver.

### Claim 20 (depends on 1)

The method of claim 1, wherein:
the wireless communication system comprises a multiple-input multiple-output (MIMO) communication system; and
the first signal and the retransmitted modified signals comprise a plurality of data streams, such that the plurality of data streams are transmitted over a plurality of transmit antennas in the MIMO communication system.

### Claim 21 (depends on 1)

The method of claim 1, wherein the first signal source comprises a transmitter, the second signal source comprises a transceiver, the method further comprising:
determining at the receiver a correlation between the first signal via the first signal path and the modified first signal via the second signal path.

### Claim 22 (depends on 21)

The method of claim 21, wherein the first signal path does not include the transceiver.

### Claim 23 (depends on 22)

The method of claim 22, wherein the first signal path is a direct line of sight (LOS) path.

### Claim 24 (depends on 1)

The method of claim 1, wherein the characteristics include signal delay modifications and signal gain modifications.

### Claim 25 (depends on 1)

The method of claim 1, wherein the first mode is a controlled mode, and the second mode is a random mode.

### Claim 26 (depends on 25)

The method of claim 25, wherein in the controlled mode, only one signal is delayed, and in the random mode only one random repeated signal is used.

### Claim 27

A wireless communication system, comprising:
a first signal source, a second signal source, and a receiver,
wherein the transmitter is configured to transmit a first signal from the first signal source to the receiver via a first signal path, and
wherein the second signal source is configured to receive the first signal, modify characteristics of the first signal, and retransmit the modified first signal to the receiver via a second signal path, such that the first signal and the retransmitted modified first signal are received substantially uncorrelated at the receiver,
wherein the characteristics are modified based on correlation quality feedback from the receiver in a first mode and randomly assigned in a second mode.

### Claim 28 (depends on 27)

The system of claim 27, wherein the second signal source comprises a transceiver, and wherein the transceiver modifies the first signal received at the transceiver by introducing a time delay in retransmission of the modified first signal from the transceiver such that the retransmitted modified first signal is received via the second signal path by the receiver after the first signal via the first signal path, whereby the first signal and the retransmitted modified first signal are received substantially uncorrelated at the receiver.

### Claim 29 (depends on 27)

The system of claim 27, wherein the transceiver modifies by selectively changing a magnitude of the first signal before retransmission, such that the first signal and the retransmitted modified first signal are received substantially uncorrelated at the receiver. signal and the retransmitted signals are received substantially uncorrelated at the receiver.

### Claim 30 (depends on 27)

The system of claim 27, wherein the first signal source comprises a transmitter, the second signal source comprises a transceiver, and wherein the wireless-communication system comprises a multiple-input multiple-output (MIMO) system, such that the transmissions from the transmitter and the transceiver form multipaths.

### Claim 31 (depends on 27)

The system of claim 27, wherein:
the wireless communication system comprises a multiple-input multiple-output (MIMO) communication system.

### Claim 32 (depends on 27)

The system of claim 27, wherein the second signal source comprises a transceiver, and wherein the transceiver modifies the signal characteristics by determining a modification such that first signal via the first signal path and the retransmitted modified first signal via the second signal path are received substantially uncorrelated at the receiver.

### Claim 33 (depends on 32)

The system of claim 32, wherein:
the receiver transmits a feedback to the transceiver indicating a relative correlation of the first signal and the retransmitted modified first signal received at the receiver via the first and second signal paths, respectively; and
the transceiver determines the modification based on the feedback from the receiver, wherein if the first signal and the retransmitted modified first signal are indicated as not sufficiently uncorrelated, the transceiver farther modifies and retransmits the further modified first signal from the transceiver such that the first signal and the further modified first signal are received substantially uncorrelated at the receiver, and
wherein the relative correlation is determined at the receiver.

### Claim 34 (depends on 32)

The system of claim 32, wherein the transceiver modifies the signal characteristics by randomly changing a magnitude of the first signal before retransmission of the modified first signal, such that the first signal and the retransmitted modified first signal are received as essentially statistically independent signals at the receiver.

### Claim 35 (depends on 32)

The system of claim 32, wherein transceiver modifies the signal characteristics by randomly modifying the signal characteristics, whereby the first signal and the retransmitted modified first signal are received as essentially statistically independent signals at the receiver.

### Claim 36 (depends on 32)

The system of claim 32, wherein the transceiver modifies the signal characteristics by randomly introducing a time delay in retransmission of the modified first signal from the transceiver such that the retransmitted modified first signal is received by the receiver via the second signal path after the first signal via the first signal path, whereby the first signal and the retransmitted modified first signal are received as essentially statistically independent signals at the receiver.

### Claim 37 (depends on 32)

The system of claim 32, further comprising multiple transceivers, wherein each transceiver receives the first signal and retransmits the modified first signal to the receiver by modifying the signal characteristics, such that the first signal and the retransmitted modified first signals are received substantially uncorrelated at the receiver.

### Claim 38 (depends on 37)

The system of claim 37, wherein each transceiver modifies the signal characteristics by selectively introducing a time delay in retransmission of the modified first signal from that transceiver such that the retransmitted signals are received by the receiver after the first signal, whereby the first signal and the retransmitted signals are received substantially uncorrelated at the receiver.

### Claim 39 (depends on 37)

The system of claim 37, wherein each transceiver modifies the signal characteristics by selectively changing a magnitude of the first signal before retransmission, such that the first signal and the retransmitted modified first signal are received substantially uncorrelated at the receiver.

### Claim 40 (depends on 37)

The system of claim 37, wherein the wireless communication system comprises a multiple-input multiple-output (MIMO) system, such that the transmissions from the transmitter and the transceivers form multipaths.

### Claim 41 (depends on 37)

The system of claim 37, wherein:
the wireless communication system comprises a multiple-input multiple-output (MIMO) communication system; and
the first signal and retransmitted modified signals comprise a plurality of data streams, such that the plurality of data streams are transmitted over a plurality of transmit antennas in the MIMO communication system.

### Claim 42 (depends on 37)

The system of claim 37, wherein each transceiver modifies the signal characteristics by determining a modification such that first signal and the retransmitted modified signals are received substantially uncorrelated at the receiver.

### Claim 43 (depends on 42)

The system of claim 42, wherein:
the receiver transmits feedback to the transceivers indicating a relative correlation of the first signal and the retransmitted modified signals received at the receiver; and
each transceiver determines the modification based on the feedback from the receiver, wherein if the signals received at the receiver are indicated as not sufficiently uncorrelated, that transceiver further modifies and retransmits the further modified first signal from the transceiver such that the first signal and the further modified signals are received substantially uncorrelated at the receiver, and
wherein the relative correlation is determined at the receiver.

### Claim 44 (depends on 42)

The system of claim 42, wherein each transceiver modifies the signal characteristics by randomly changing a magnitude of the first signal before retransmission, such that the first signal and the retransmitted modified signals are received as essentially statistically independent signals at the receiver.

### Claim 45 (depends on 42)

The system of claim 42, wherein each transceiver modifies the signal characteristics by randomly introducing a time delay in retransmission of the modified first signal from the transceiver such that the retransmitted modified first signal is received by the receiver after the first signal, whereby the first signal and the retransmitted modified first signal are received as essentially statistically independent signals at the receiver.

### Claim 46 (depends on 37)

The system of claim 37, wherein the transceivers coordinate modification of the signal characteristics of the first signal in the transceivers, such that the first signal and the retransmitted modified signals are received substantially uncorrelated at the receiver.

### Claim 47 (depends on 27)

The system of claim 27, further comprising multiple transceivers, wherein each transceiver modifies the signal characteristics differently such that the retransmitted modified signals are substantially uncorrelated at the receiver.

### Claim 48 (depends on 47)

The system of claim 47, wherein the signal characteristics include at least one of a delay, a signal gain, and a signal strength.

### Claim 49 (depends on 27)

The system of claim 27, wherein the first signal source comprises a transmitter, the second signal source comprises a transceiver, and wherein the receiver is further configured to determine a correlation between the first signal via the first signal path and the modified first signal via the second signal path.

### Claim 50 (depends on 49)

The system of claim 49, wherein the first signal path does not include the transceiver.

### Claim 51 (depends on 50)

The system of claim 50, wherein the first signal path is a direct line of sight (LOS) path.