TIMING ADJUSTMENT METHOD, RECEIVING STATION, AND TRANSMITTING STATION IN WIRELESS COMMUNICATION SYSTEM, AND WIRELESS COMMUNICATION SYSTEM

• US 20110038249A1
• Filed: 02/16/2009
• Published: 02/17/2011
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kuwahara, Mikio, Fujishima, Kenzaburo, Linwong, Pinai, Tsunehara, Katsuhiko, Tamaki, Satoshi
• Granted Patent: US 8,787,146 B2
• Time in Patent Office: Days
• US Class Current: 370/210
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 27/2675 Pilot or known symbols
• CPC Class Codes: H04W 56/00 Synchronisation arrangements

Abstract

A discontinuous change in a transmission timing in a time domain, which is caused by a transmission timing adjustment processing of an OFDMA uplink or the like, brings about a discontinuous rotation of a signal phase in a frequency domain, resulting in reduced communication quality. A wireless communication system of the present invention allows the signal phase of the frequency domain in a receiving station to be continuous before and after the timing adjustment processings by controlling a signal sequence in a transmission signal after conversion in the time domain in synchronization with the timing adjustment processing.

Claims

1. A wireless communication system, comprising:

a first radio station, the first radio station including;

a unit that measures a difference between a reference timing of the first radio station and a reception timing of a signal transmitted from the second radio station;

a timing adjustment signal generator that generates a signal including data on the difference; and

a transmitter that transmits a signal including data on the difference; and

a second radio station, the second radio station including;

a signal generator that generates a signal in a time domain using an orthogonal transformation;

a timing adjustment signal extraction unit that extracts data on the difference included in a signal including data on the difference transmitted from the first radio station;

a transmission timing controller that determines the correction amount of a signal arrangement phase and that of a transmission timing based on the extracted difference data;

a phase controller that controls a signal arrangement phase of a signal in the time domain based on the correction amount of the signal arrangement phase; and

a timing adjustment unit that controls a transmission timing of a signal in which the signal arrangement phase is controlled based on the correction amount of the transmission timing,

wherein a signal is transmitted and received between the first radio station and the second radio station, and

wherein using the controlled transmission timing, the second radio station transmits a signal to the first radio station.

2. The wireless communication system according to claim 1,

wherein the signal generator is an LEFT unit using a discrete Fourier transformation as an orthogonal transformation.

3. The wireless communication system according to claim 1,

wherein the second radio station further includes a guard interval addition unit that adds a guard interval to a signal in which the signal arrangement phase is controlled;

and

wherein the timing adjustment unit controls a transmission timing of a signal to which the guard interval is added.

4. The wireless communication system according to claim 1,

wherein the correction amount of the signal arrangement phase is equal to that of the transmission timing.

5. The wireless communication system according to claim 1,

wherein the first radio station transmits to the second radio station a signal with a known pattern in which an orthogonal transformation and a change in a signal sequence are not performed.

6. The wireless communication system according to claim 1,

wherein when advancing a transmission timing of the second radio station, the correction amount of the signal arrangement phase for displacing the phase behind is set;

and

wherein when delaying a transmission timing of the second radio station, the correction amount of the transmission timing for displacing the phase in front is set.

7. The wireless communication system according to claim 1,

wherein a unit that measures the difference is a timing error detector, the timing error detector including:

a delay unit that delays an input signal;

a correlation operation unit that performs complex multiplication between one complex conjugate and the other complex conjugate in the input signal and a signal output from the delay unit;

an LPF that averages signals output from the correlation operation unit;

an inter-symbol average unit that performs an electrification operation and an inter-symbol average processing with respect to signals output from the LPF;

a timing detector that detects a desired reception timing from signals output from the inter-symbol average unit; and

a comparator that compares an output timing from the timing detector and the reference timing, and

wherein the timing error detector outputs the comparison results as the difference to the timing adjustment signal generator.

8. The wireless communication system according to claim 1,

wherein a unit that measures the difference is a timing synchronization detector, the timing synchronization detector including:

a matched filter;

an inter-symbol average unit that performs an electrification operation and an inter-symbol average processing with respect to signals output from the matched filter;

a timing detector that detects a desired reception timing from signals output from the inter-symbol average unit; and

a comparator that compares an output timing from the timing detector and the reference timing; and

wherein the timing synchronization detector outputs the comparison results as the difference to the timing adjustment signal generator.

9. A transmitting station for transmitting and receiving a signal to and from a receiving station through wireless communication, comprising:

a signal generator that generates a signal in a time domain using an orthogonal transformation;

a timing adjustment signal extraction unit that extracts difference data included in a signal including the difference data transmitted from the receiving station;

a transmission timing controller that determines the correction amount of a signal arrangement phase and that of a transmission timing based on the extracted difference data;

a phase controller that controls a signal arrangement phase of a signal in the time domain based on the correction amount of the signal arrangement phase; and

a timing adjustment unit that controls a transmission timing of a signal in which the signal arrangement phase is controlled based on the correction amount of the transmission timing,

wherein the transmitting station transmits a signal to the receiving station at the controlled transmission timing.

10. The transmitting station according to claim 9,

wherein the receiving station transmits to the transmitting station a signal with a known pattern in which the orthogonal transformation and a change in a signal sequence are not performed.

11. The transmitting station according to claim 9,

wherein the correction amount of the signal arrangement phase is equal to that of the transmission timing.

12. The transmitting station according to claim 9,

wherein the signal generator is an IFFT unit that uses a discrete Fourier transformation as the orthogonal transformation.

13. The transmitting station according to claim 9, further comprising:

a guard interval addition unit that adds a guard interval to a signal in which the signal arrangement phase is controlled,

wherein the timing adjustment unit controls a transmission timing of a signal to which the guard interval is added.

14. A receiving station for transmitting and receiving a signal to and from a transmitting station through wireless communication, comprising:

a unit that measures a difference between a reference timing of the receiving station and a reception timing of a signal transmitted from the transmitting station;

a timing adjustment signal generator that generates a signal including the difference data; and

a transmitter that transmits a signal including the difference data.

15. The receiving station according to claim 14,

wherein a unit that measures the difference is a timing error detector, the timing error detector including:

a delay unit that delays an input signal;

a correlation operation unit that performs complex multiplication between one complex conjugate and the other complex conjugate in the input signal and a signal output from the delay unit;

an LPF that averages signals output from the correlation operation unit;

an inter-symbol average unit that performs an electrification operation and an inter-symbol average processing with respect to signals output from the LPF;

a timing detector that detects a desired reception timing from signals output from the inter-symbol average unit; and

a comparator that compares an output timing from the timing detector and the reference timing, and

wherein the timing error detector outputs the comparison results as the difference to the timing adjustment signal generator.

16. A method for adjusting a timing for synchronizing a reception signal in a wireless communication system for transmitting and receiving a signal between a first radio station and a second radio station, the method comprising causing:

the first radio station to execute the steps of

measuring a difference between a reference timing of the first radio station and a reception timing of a signal transmitted from the second radio station;

generating a signal including the difference data; and

transmitting a signal including the difference data, and

the second radio station to execute the steps of;

generating a signal in a time domain using an orthogonal transformation;

extracting difference data included in a signal including the difference data transmitted from the first radio station;

determining the correction amount of a signal arrangement phase and that of a transmission timing based on the extracted difference data;

controlling a signal arrangement phase of a signal in the time domain based on the correction amount of the signal arrangement phase; and

controlling a transmission timing of a signal in which the signal arrangement phase is controlled based on the correction amount of the transmission timing.