Radio repeater and radio relay transmission method

• US 20050130587A1
• Filed: 11/17/2004
• Published: 06/16/2005
• Est. Priority Date: 12/05/2003
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Asai, Takahiro, Fujii, Hiromasa, Suda, Hirohito, Tanaka, Tetsu
• Granted Patent: US 7,430,397 B2
• Time in Patent Office: Days
• US Class Current: 455/9
• CPC Class Codes: H04B 7/15564 Relay station antennae loop interference reduction

Abstract

A channel capacity is increased by using MIMO (multiple input multiple output) radio relaying system.

A transmission is made from a transmitter 10 using a first antenna 11₁ and a second antenna 11₂ having polarization characteristics which are orthogonalized to each other. A reception is made in a repeater 20₁ using reception antennas 21₁ and 21₂ each having the same polarization characteristic as the first and the second antenna 11₁ and 11₂, respectively. Each signal received by the first and the second reception antenna 21₁ and 21₂, respectively, is passed through loop interference suppressors 27₁ and 27₂, respectively, and through amplifiers 24₁ and 24₂, respectively, to be transmitted from the first and the second transmission antenna 21₁ and 21₂ having the same polarization characteristics as the second and the first antenna 11₂ and 11₁, respectively. A reception is made in a receiver 30 by antennas 31₂ and 31₄ having the same polarization characteristic as the first antenna 11₁, and the reception is also made by antennas 31₁ and 31₃ having the same polarization characteristic as the second antenna 11₂. These received signals are subject to a signal separation processing in MIMO equalizer 32.

Claims

1. A radio repeater comprising

at least one first reception antenna having a first-polarization characteristic;

at least one second reception antenna having a second-polarization characteristic which is orthogonalized with respect to the first-polarization characteristic;

at least two loop interference suppressors connected to each of the reception antennas for suppressing a loop interference signal from a transmitted radio signal from the received radio signal;

at least two amplifiers for amplifying each loop interference-suppressed radio signal from each of the loop interference suppressors;

and at least one each of a first and a second transmission antenna having the second and the first-polarization characteristic, respectively, which are fed with the radio signals which have been received by the first and the second reception antenna and which have passed through the respective loop interference suppressors and the respective amplifier for transmitting the radio signals.

2. A radio repeater according to claim 1 in which denoting a system which transmits the radio signal received by the reception antenna and passed through the loop interference suppressor and the amplifier from the transmission antenna as a relay system, each of the loop interference suppressors comprising

a channel estimator for receiving the radio signal received by the reception antenna of the own relay system as an input for estimating a first transmission path characteristic of a loop interference signal which comes from the transmission antenna of a different relay system to the reception antenna of the own relay system;

an FIR filter for convoluting the estimated first transmission path characteristic with the radio signal received by the reception antenna of the different relay system;

and a subtractor for subtracting an output from the FIR filter from the radio signal received by the reception antenna of the own relay system to feed it to the amplifier of the own relay system.

3. A radio repeater according to claim 2 in which the radio signal received by the reception antenna of the different relay system is also input to the channel estimator for estimating a second transmission path characteristic of a loop interference signal which comes from the transmission antenna of the own relay system to the reception antenna of the own relay system,

the channel estimator comprising a variable delay for causing the radio signal received by the reception antenna of the own relay system to be delayed by an amount corresponding to a detected delay, and a second FIR filter for convoluting the second transmission path characteristic with the received and delayed radio signal,

the subtractor subtracting each output signal from the second FIR filter from the radio signal received by the reception antenna of the own relay system.

4. A radio repeater according to claim 1 in which each of the loop interference suppressors comprises

a channel estimator for estimating the transmission path characteristic of a loop interference signal received by the reception antenna which is connected to the loop interference suppressor;

a channel separator for discriminating and separating the first transmission path characteristic contained in the estimated transmission path characteristic from a delayed second transmission path characteristic;

a delay decision unit for detecting the delay of the second transmission path characteristic with respect to the first transmission path characteristic;

a first FIR filter for convoluting the radio signal received by the reception antenna which is connected to the loop interference suppressor with the first transmission path characteristic;

a variable delay for delaying the radio signal received by the reception antenna which is connected to the loop interference suppressor by the detected delay;

a second FIR filter for convoluting the received and delayed radio signal with the second transmission path characteristic;

and a subtractor for subtracting each output signal from the first FIR filter and the second FIR filter from the radio signal received by the reception antenna which is connected to the loop interference suppressor to feed the amplifier.

5. A radio repeater according to one of claims 1 to 4 in which at least one of the first reception antenna having the first-polarization characteristic and the second reception antenna having the second-polarization characteristic as well as at least one of the first transmission antenna having the second-polarization characteristic and the second transmission antenna having the first-polarization characteristic comprises an array antenna, further comprising

a weight applicator for establishing weights to each antenna element of the array antenna in order to determine a directivity which suppresses a loop interference signal.

6. A radio relay transmission method comprising the steps of transmitting radio signals from a transmitter using at least one of first antennas having a first-polarization characteristic and at least one of second antennas having a second-polarization characteristic which is orthogonalized to the first-polarization characteristic;

receiving the transmitted radio signals by at least one of the reception antennas having a polarization characteristic which is one of the first-polarization characteristic and the second-polarization characteristic;

and amplifying the received radio signal and transmitting it from a transmission antenna having a polarization characteristic which is orthogonalized to the polarization characteristic of the reception antenna for purpose of radio relaying.

7. A radio relay transmission method according to claim 6, further comprising the step of

receiving the radio relayed radio signal by at least one of antennas having the first-polarization characteristic and at least one of the antennas having the second-polarization characteristic in a receiver.